Publications | Core Facilities

Welcome to the Publications page of the ASU Core Research Facilities. Here, we proudly showcase a curated collection of scholarly articles and research findings that have been made possible through the use of our state-of-the-art facilities and instruments. This page serves as a testament to the innovative and impactful research conducted by our community of scientists, engineers and scholars across various disciplines.

Please note that some of these research projects have utilized multiple facilities within our Core Research Facilities, leading to certain articles being listed in more than one section. This overlap highlights the interdisciplinary and collaborative nature of the work being conducted here.

Explore the links below to see how our facilities have contributed to advancing knowledge and solving some of the world's most pressing challenges.

Eyring Materials Center
METAL
Advanced Electronics & Photonics
NanoFab
Research Computing
Instrument Design & Fabrication
Biosciences

Eyring Materials Center

Fe-single-atom catalyst nanocages linked by bacterial cellulose-derived carbon nanofiber aerogel for Li-S batteries
- Abstract: Li-S battery (LSB) is promising for achieving high capacity. Still, its development is hindered by the complex redox process with sluggish kinetics and particularly the resulting lithium polysulfides (LiPS) shuttle effects. Single-atom catalysts (SACs), with their maximized atom utilization, could effectively chemisorb soluble LiPSs and expedite the sulfide conversion reaction kinetics. Here we report incorporating Fe single metal atom catalyst (Fe-SAC) in the sulfur cathode design and its electrocatalytic effects. Fe-doped ZIF-8 nanocages were introduced into a cheap biomass bacteria cellulose. A pyrolysis process converted them into an aerogel structure with Fe-SAC-functionalized N-doped carbon nanocages linked by a carbon nanofiber network (FeSA-NC@CBC), which was applied as a scaffold to fabricate freestanding and binder-free sulfur cathodes. We conducted electrochemical measurements to reveal Fe-SAC functions including lowering energy barriers for S₈ reduction to liquid-phase LiPSs and further to solid-phase Li₂S₂/Li₂S and accelerating Li₂S₂/Li₂S nucleation and deposition, as corroborated by our theoretical calculation results. Benefiting from the synergistic effects of highly active Fe-SAC and three-dimensional conductive network, the sulfide reaction kinetics is improved, which can diminish LiPS shuttle effects and therefore improve LBS rate performance and cycling stability. Accordingly, the fabricated FeSA-NC@CBC composite cathode delivers an excellent rate capability at 2C with a reversible capacity of 840 mAh/g and a long-term cyclic stability of 800 mAh/g at 1C after 500 cycles.
Calorimetric Measurement of the Surface Energy of Enstatite, MgSiO₃
- Abstract: Surface thermodynamics of minerals influence their properties and occurrence in both terrestrial and planetary systems. Using high-temperature oxide melt solution calorimetry, we report the first direct measurement of the surface energy of enstatite, MgSiO₃. Enstatite nanoparticles of different sizes were synthesized using the sol–gel method, characterized with X-ray diffraction, thermal analysis, infrared spectroscopy, surface area measurements, and electron microscopy. The materials consist of crystallites with sizes of ∼10–20 nm, which are agglomerated into larger nanoparticles. Thus, both surface and interface terms contribute to the measured enthalpies. Analysis based on calorimetry and calculated surface and interface areas gives the surface enthalpy of enstatite as 4.79 ± 0.45 J m^–2. This value is comparable to that of forsterite (Mg₂SiO₄) and larger than those of many nonsilicate oxide materials. This large surface energy may present a barrier to the nucleation of enstatite in planetary atmospheres and other geochemical and planetary environments. The interfacial energy of enstatite appears to be close to zero. The transition enthalpy from bulk orthoenstatite to bulk clinoenstatite is 0.34 ± 0.93 kJ mol^–1, which is in agreement with earlier reports. The methodology developed here can be extended to other materials having complex structures and morphologies to separate surface and interfacial contributions to energetics.
Dynamic structure of active sites in ceria-supported Pt catalysts for the water gas shift reaction
- Abstract: Oxide-supported noble metal catalysts have been extensively studied for decades for the water gas shift (WGS) reaction, a catalytic transformation central to a host of large volume processes that variously utilize or produce hydrogen. There remains considerable uncertainty as to how the specific features of the active metal-support interfacial bonding—perhaps most importantly the temporal dynamic changes occurring therein—serve to enable high activity and selectivity. Here we report the dynamic characteristics of a Pt/CeO₂ system at the atomic level for the WGS reaction and specifically reveal the synergistic effects of metal-support bonding at the perimeter region. We find that the perimeter Pt⁰ − O vacancy−Ce³⁺ sites are formed in the active structure, transformed at working temperatures and their appearance regulates the adsorbate behaviors. We find that the dynamic nature of this site is a key mechanistic step for the WGS reaction.
Strong Ferromagnetism Achieved via Breathing Lattices in Atomically Thin Cobaltites
- Abstract: Low-dimensional quantum materials that remain strongly ferromagnetic down to monolayer thickness are highly desired for spintronic applications. Although oxide materials are important candidates for the next generation of spintronics, ferromagnetism decays severely when the thickness is scaled to the nanometer regime, leading to deterioration of device performance. Here, a methodology is reported for maintaining strong ferromagnetism in insulating LaCoO₃ (LCO) layers down to the thickness of a single unit cell. It is found that the magnetic and electronic states of LCO are linked intimately to the structural parameters of adjacent “breathing lattice” SrCuO₂ (SCO). As the dimensionality of SCO is reduced, the lattice constant elongates over 10% along the growth direction, leading to a significant distortion of the CoO₆ octahedra, and promoting a higher spin state and long-range spin ordering. For atomically thin LCO layers, surprisingly large magnetic moment (0.5 μ_B/Co) and Curie temperature (75 K), values larger than previously reported for any monolayer oxides are observed. The results demonstrate a strategy for creating ultrathin ferromagnetic oxides by exploiting atomic heterointerface engineering, confinement-driven structural transformation, and spin-lattice entanglement in strongly correlated materials.
Chip-integrated metasurface full-Stokes polarimetric imaging sensor
- Abstract: Polarimetric imaging has a wide range of applications for uncovering features invisible to human eyes and conventional imaging sensors. Chip-integrated, fast, cost-effective, and accurate full-Stokes polarimetric imaging sensors are highly desirable in many applications, which, however, remain elusive due to fundamental material limitations. Here we present a chip-integrated Metasurface-based Full-Stokes Polarimetric Imaging sensor (MetaPolarIm) realized by integrating an ultrathin (~600 nm) metasurface polarization filter array (MPFA) onto a visible imaging sensor with CMOS compatible fabrication processes. The MPFA is featured with broadband dielectric-metal hybrid chiral metasurfaces and double-layer nanograting polarizers. This chip-integrated polarimetric imaging sensor enables single-shot full-Stokes imaging (speed limited by the CMOS imager) with the most compact form factor, records high measurement accuracy, dual-color operation (green and red) and a field of view up to 40 degrees. MetaPolarIm holds great promise to enable transformative applications in autonomous vision, industry inspection, space exploration, medical imaging and diagnosis.
Large volume multianvil cell assembly for hydrothermal synthesis and conversions up to 6.5 GPa and 400°C
- Abstract: A multianvil cell assembly with octahedral edge length 25 mm has been adapted for high pressure investigations involving water-rich environments up to 6.5 GPa and 400°C. Water-rich samples are confined in Teflon containers with a volume up to 300 mm3. Applicability tests were performed between 250 and 400°C by investigating the transformation of amorphous titania particles close to the rutile–TiO2-II (∼5 GPa) phase boundary, and the transformation of amorphous silica particles close to the quartz–coesite (∼2.5 GPa) and coesite–stishovite (∼7 GPa) phase boundaries. The performed experiments employed 25.4 mm tungsten carbide anvils with a truncation edge length of 15 mm. The sample pressure at loads approaching 820 t was estimated to be around 6.5 GPa. The large volume multianvil cell is expected to have broad and varied application areas, ranging from the simulation of geofluids to hydrothermal synthesis and conversion/crystal growth in aqueous environments at gigapascal pressures.
Quantifying and Reducing Ion Migration in Metal Halide Perovskites through Control of Mobile Ions
- Abstract: The presence of intrinsic ion migration in metal halide perovskites (MHPs) is one of the main reasons that perovskite solar cells (PSCs) are not stable under operation. In this work, we quantify the ion migration of PSCs and MHP thin films in terms of mobile ion concentration (N_o) and ionic mobility (µ) and demonstrate that No has a larger impact on device stability. We study the effect of small alkali metal A-site cation additives (e.g., Na⁺, K⁺, and Rb⁺) on ion migration. We show that the influence of moisture and cation additive on N_o is less significant than the choice of top electrode in PSCs. We also show that N_o in PSCs remains constant with an increase in temperature but μ increases with temperature because the activation energy is lower than that of ion formation. This work gives design principles regarding the importance of passivation and the effects of operational conditions on ion migration.
Strain Anisotropy Driven Spontaneous Formation of Nanoscrolls from 2D Janus Layers
- Abstract: 2D Janus transition metal dichalcogenides (TMDs) have attracted attention due to their emergent properties arising from broken mirror symmetry and self-driven polarization fields. While it has been proposed that their vdW superlattices hold the key to achieving superior properties in piezoelectricity and photovoltaic, available synthesis has ultimately limited their realization. Here, the first packed vdW nanoscrolls made from Janus TMDs through a simple one-drop solution technique are reported. The results, including ab initio simulations, show that the Bohr radius difference between the top sulfur and the bottom selenium atoms within Janus ${\rm{M}}_{{\rm{Se}}}^{\rm{S}}$ (M = Mo, W) results in a permanent compressive surface strain that acts as a nanoscroll formation catalyst after small liquid interaction. Unlike classical 2D layers, the surface strain in Janus TMDs can be engineered from compressive to tensile by placing larger Bohr radius atoms on top ( ${\rm{M}}_{{\rm{Se}}}^{\rm{S}}$ ) to yield inverted C scrolls. Detailed microscopy studies offer the first insights into their morphology and readily formed Moiré lattices. In contrast, spectroscopy and FETs studies establish their excitonic and device properties and highlight significant differences compared to 2D flat Janus TMDs. These results introduce the first polar Janus TMD nanoscrolls and introduce inherent strain-driven scrolling dynamics as a catalyst to create superlattices.
Inflammasome modulation with P2X7 inhibitor A438079-loaded dressings for diabetic wound healing
- Abstract: The inflammasome is a multiprotein complex critical for the innate immune response to injury. Inflammasome activation initiates healthy wound healing, but comorbidities with poor healing, including diabetes, exhibit pathologic, sustained activation with delayed resolution that prevents healing progression. In prior work, we reported the allosteric P2X7 antagonist A438079 inhibits extracellular ATP-evoked NLRP3 signaling by preventing ion flux, mitochondrial reactive oxygen species generation, NLRP3 assembly, mature IL-1β release, and pyroptosis. However, the short half-life in vivo limits clinical translation of this promising molecule. Here, we develop a controlled release scaffold to deliver A438079 as an inflammasome-modulating wound dressing for applications in poorly healing wounds. We fabricated and characterized tunable thickness, long-lasting silk fibroin dressings and evaluated A438079 loading and release kinetics. We characterized A438079-loaded silk dressings in vitro by measuring IL-1β release and inflammasome assembly by perinuclear ASC speck formation. We further evaluated the performance of A438079-loaded silk dressings in a full-thickness model of wound healing in genetically diabetic mice and observed acceleration of wound closure by 10 days post-wounding with reduced levels of IL-1β at the wound edge. This work provides a proof-of-principle for translating pharmacologic inhibition of ATP-induced inflammation in diabetic wounds and represents a novel approach to therapeutically targeting a dysregulated mechanism in diabetic wound impairment.
Thermo-Mechanical behavior of hypoeutectic Ni-Y-Zr alloys
- Abstract: Microstructure refinement and optimized alloying can improve metallic alloy performance: stable nanocrystalline (NC) alloys with immiscible second phases, e.g., Cu-Ta, are stronger than unstable NC alloys and their coarse-grained (CG) counterparts, but higher melting point matrices are needed. Hypoeutectic, CG Ni-Y-Zr alloys were produced via arc-melting to explore their potential as high-performance materials. Microstructures were studied to determine phases present, local composition and length scales, while heat treatments allowed investigating microstructural stability. Alloys had a stable, hierarchical microstructure with ~250 nm ultrafine eutectic, ~10 µm dendritic arm spacing and ~1 mm grain size. Hardness and uniaxial compression tests revealed that mechanical properties of Ni-0.5Y-1.8Zr (in wt%) were comparable to Inconel 617 despite the small alloying additions, due to its hierarchical microstructure. Uniaxial compression at 600 °C showed that ternary alloys outperformed Ni-Zr and Ni-Y binary alloys in flow stress and hardening rates, which indicates that the Ni₁₇Y₂ phase was an effective reinforcement for the eutectic, which supplemented the matrix hardening due to increased solubility of Zr. Results suggest that ternary Ni-Y-Zr alloys hold significant promise for high temperature applications.
Heat capacity of microgram oxide samples by fast scanning calorimetry
- Abstract: Quantitative scanning calorimetry on microgram-sized samples opens a broad, new range of opportunities for studying the thermodynamic properties of quantity-limited materials, including those produced under extreme conditions or found as rare accessory minerals in nature. We calibrated the Mettler Toledo Flash DSC 2+ calorimeter to obtain quantitative heat capacities in the range 200–350 °C, using samples weighing between 2 and 11.5 μg. Our technique is applied to a new set of oxide materials to which it has never been used before, without the need for melting, glass transitions, or phase transformations. Heat capacity data were obtained for silica in the high pressure stishovite (rutile) structure, dense post-stishovite glass, standard fused quartz, and for TiO₂ rutile. These heat capacities agree within 5%–15% with the literature values reported for rutile, stishovite, and fused SiO₂ glass. The heat capacity of post-stishovite glass, made by heating stishovite to 1000 °C, is a newly reported value. After accurate calibrations, measured heat capacities were then used to calculate masses for samples in the microgram range, a substantial improvement over measurement in conventional microbalances, which have uncertainties approaching 50%–100% for such small samples. Since the typical uncertainty of heat capacities measured on 10–100 mg samples in conventional differential scanning calorimetry is typically 7% (1%–5% with careful work), flash differential scanning calorimetry, using samples a factor of 1000 smaller, increases the uncertainty of heat capacity measurements by a factor of <3, opening the door for meaningful measurements on ultra-small, high-pressure samples and other quantity-limited materials.
Memory-dictated dynamics of single-atom Pt on CeO₂ for CO oxidation
- Abstract: Single atoms of platinum group metals on CeO₂ represent a potential approach to lower precious metal requirements for automobile exhaust treatment catalysts. Here we show the dynamic evolution of two types of single-atom Pt (Pt₁) on CeO₂, i.e., adsorbed Pt₁ in Pt/CeO₂ and square planar Pt1 in Pt_ATCeO₂, fabricated at 500 °C and by atom-trapping method at 800 °C, respectively. Adsorbed Pt1 in Pt/CeO₂ is mobile with the in situ formation of few-atom Pt clusters during CO oxidation, contributing to high reactivity with near-zero reaction order in CO. In contrast, square planar Pt₁ in Pt_ATCeO₂ is strongly anchored to the support during CO oxidation leading to relatively low reactivity with a positive reaction order in CO. Reduction of both Pt/CeO₂ and PtATCeO₂ in CO transforms Pt₁ to Pt nanoparticles. However, both catalysts retain the memory of their initial Pt₁ state after reoxidative treatments, which illustrates the importance of the initial single-atom structure in practical applications.
Energetics and structure of SiC(N)(O) polymer-derived ceramics
- Abstract: This study presents new experimental data on the thermodynamic stability of SiC(O) and SCN(O) ceramics derived from the pyrolysis of polymeric precursors: SMP-10 (polycarbosilane), PSZ-20 (polysilazane), and Durazane-1800 (polysilazane) at 1200°C. There are close similarities in the structure of the polysilazanes, but they differ in crosslinking temperature. High-resolution X-ray photoelectron spectroscopy shows notable differences in the microstructure of all polymer-derived ceramics (PDCs). The enthalpies of formation (∆H°_{f, elem}) of SiC(O) (from SMP-10), SCN(O) (from PSZ-20), and SCN(O) (from Durazane-1800) are −20 ± 4.63, −78.55 ± 2.32, and −85.09 ± 2.18 kJ/mol, respectively. The PDC derived from Durazane-1800 displays greatest thermodynamic stability. The results point to increased thermodynamic stabilization with addition of nitrogen to the microstructure of PDCs. Thermodynamic analysis suggests increased thermodynamic drive for forming SiCN(O) microstructures with an increase in the relative amount of SiN_xC₄₋_x mixed bonds and a decrease in silica. Overall, enthalpies of formation suggest superior stabilizing effect of SiN_xC₄₋_x compared to SiO_xC₄₋_x mixed bonds. The results indicate systematic stabilization of SiCN(O) structures with decrease in silicon and oxygen content. The destabilization of PDCs resulting from higher silicon content may reach a plateau at higher concentrations.
Mechanistic Study of Arsenate Adsorption onto Different Amorphous Grades of Titanium (Hydr)Oxides Impregnated into a Point-of-Use Activated Carbon Block
- Abstract: Millions of households still rely on drinking water from private wells or municipal systems with arsenic levels approaching or exceeding regulatory limits. Arsenic is a potent carcinogen, and there is no safe level of it in drinking water. Point-of-use (POU) treatment systems are a promising option to mitigate arsenic exposure. However, the most commonly used POU technology, an activated carbon block filter, is ineffective at removing arsenic. Our study aimed to explore the potential of impregnating carbon blocks with amorphous titanium (hydr)oxide (THO) to improve arsenic removal without introducing titanium (Ti) into the treated water. Four synthesis methods achieved 8–16 wt % Ti-loading within the carbon block with a 58–97% amorphous THO content. The THO-modified carbon block could adsorb both oxidation states of arsenic (arsenate and arsenite) in batch or column tests. Modified carbon block with higher Ti and amorphous content always led to better arsenate removal, achieving arsenic loadings up to 31 mg As/mg Ti after 70,000 bed volumes in continuous-flow tests. Impregnating carbon block with amorphous THO consistently outperformed impregnation using crystalline TiO₂. The best-performing system (TTIP-EtOH carbon block) was an amorphous THO derived using titanium isopropoxide, ethanol, and acetic acid via the sol–gel technique, aged at 80 °C for 18 h and dried overnight at 60 °C. Comparable pore-size distribution and surface area of the impregnated carbon blocks suggested that chemical properties play a more crucial role than physical and textural properties in removing arsenate via the amorphous Ti-impregnated carbon block. Freundlich isotherms indicated energetically favorable adsorption for amorphous chemically synthesized adsorbents. The mass transport coefficients for the amorphous TTIP-EtOH carbon block were fitted using a pore-surface diffusion model, resulting in D_surface = 3.1 × 10^–12 and D_pore = 3.2 × 10^–6 cm²/s. Impregnating the carbon block with THO enabled effective arsenic removal from water without adversely affecting the pressure drop across the unit or the carbon block’s ability to remove polar organic chemical pollutants efficiently.
Significance of Secondary Fe-Oxide and Fe-Sulfide Minerals in Upper Peak Ring Suevite from the Chicxulub Impact Structure
- Abstract: The suevite (polymict melt rock-bearing breccia) composing the upper peak ring of the Chicxulub impact crater is extremely heterogeneous, containing a combination of relict clasts and secondary minerals. Using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS) and electron probe microanalysis (EPMA), we investigated the nature and occurrence of primary and secondary Fe-oxide and Fe-sulfide minerals to better understand hydrothermal trends such as mineral precipitation and dissolution, and to document the remobilization of Fe and associated siderophile elements within suevites. Large primary Fe-oxides (~20–100 µm) reveal decomposition and dissolution patterns, forming sub-micrometer to micrometer Fe-oxide phases. Secondary sub-micrometer Fe-oxide crystals are also visibly concentrated within clay. The occurrence of Fe-oxide crystals within clay suggests that these likely formed at temperatures ≤100 °C, near the formation temperature of smectite. The formation of Fe-oxide minerals on clay surfaces is of interest as it may form a micro-setting, where free electrons (from the oxidation of Fe^2+>) and the adsorption of simple organic molecules on the surface of clay could generate reactive conditions favorable to microbial communities. Primary and secondary Fe-sulfide minerals exhibiting a variety of morphologies are present within samples, representing different formation mechanisms. Secondary Fe-sulfide minerals occur within rims of clasts and vesicles and in fractures and voids. Some secondary Fe-sulfide grains are associated with Ni- and Co-rich phases, potentially reflecting the post-impact migration of siderophile elements within the suevite of the Chicxulub crater.
Intracytoplasmic membranes develop in Geobacter sulfurreducens under thermodynamically limiting conditions
- Abstract: Geobacter sulfurreducens is an electroactive bacterium capable of reducing metal oxides in the environment and electrodes in engineered systems^1,2. Geobacter sp. are the keystone organisms in electrogenic biofilms, as their respiration consumes fermentation products produced by other organisms and reduces a terminal electron acceptor e.g. iron oxide or an electrode. To respire extracellular electron acceptors with a wide range of redox potentials, G. sulfurreducens has a complex network of respiratory proteins, many of which are membrane-bound^3,4,5. We have identified intracytoplasmic membrane (ICM) structures in G. sulfurreducens. This ICM is an invagination of the inner membrane that has folded and organized by an unknown mechanism, often but not always located near the tip of a cell. Using confocal microscopy, we can identify that at least half of the cells contain an ICM when grown on low potential anode surfaces, whereas cells grown at higher potential anode surfaces or using fumarate as electron acceptor had significantly lower ICM frequency. 3D models developed from cryo-electron tomograms show the ICM to be a continuous extension of the inner membrane in contact with the cytoplasmic and periplasmic space. The differential abundance of ICM in cells grown under different thermodynamic conditions supports the hypothesis that it is an adaptation to limited energy availability, as an increase in membrane-bound respiratory proteins could increase electron flux. Thus, the ICM provides extra inner-membrane surface to increase the abundance of these proteins. G. sulfurreducens is the first Thermodesulfobacterium or metal-oxide reducer found to produce ICMs.
Plasma enhanced atomic layer deposition and atomic layer etching of gallium oxide using trimethylgallium
- Atomic layer etching driven by self-limiting thermal reactions has recently been developed as a highly conformal and isotropic technique for low damage atomic scale material removal by sequential exposures of vapor phase reactants. Gallium oxide (Ga₂O₃) is currently among the materials of interest due to a large variety of applications including power electronics, solar cells, gas sensors, and photon detectors. In this study, Ga2O3 was deposited by plasma enhanced atomic layer deposition using trimethylgallium [TMG, Ga(CH3)3] and O2 plasma at a substrate temperature of 200 °C. We report a newly developed method for Ga2O3 thermal atomic layer etching, in which surface modification is achieved through HF exposure resulting in a gallium fluoride surface layer, and then removed through volatile product formation via ligand exchange with TMG. Saturation of the precursor exposure at a substrate temperature of 300 °C resulted in an etch rate of 1.0 ± 0.1 Å/cycle for amorphous Ga₂O₃. Uniformity and conformality of the atomic layer etching process were confirmed via atomic force microscopy with a measured surface roughness of 0.55 ± 0.05 nm that remains unchanged after etching. The use of TMG for etching may expand available precursors for atomic layer etching processes, while allowing for both etching and deposition of Ga2O3 using the same metalorganic precursor.
Comparison of AlF₃ thin films grown by thermal and plasma enhanced atomic layer deposition
- Abstract: Films of aluminum fluoride (AlF₃) deposited by thermal and plasma enhanced atomic layer deposition (PEALD) have been compared using in situ multiwavelength ellipsometry (MWE) and monochromatic x-ray photoelectron spectroscopy (XPS). The AlF₃ films were grown using cyclic exposures of trimethylaluminum, hydrogen fluoride, and H radicals from a remote H2 inductively coupled plasma. Films were characterized in situ using MWE and XPS for growth rate, film composition, and impurity incorporation. The MWE showed a growth rate of 1.1 and 0.7 Å per cycle, at 100 °C, for thermal and plasma enhanced ALD AlF3 films, respectively. Carbon incorporation was below the XPS detection limit. The plasma enhanced ALD AlF₃ film showed the presence of Al-Al chemical states, in the Al 2p scans, suggesting the presence of Al-rich clusters with a concentration of 14%. The Al-rich clusters are thought to originate during the hydrogen plasma step of the PEALD process. The Al-rich clusters were not detected in thermal ALD AlF₃ films using the same precursors and substrate temperature.
Short term, low dose alpha-ketoglutarate based polymeric nanoparticles with methotrexate reverse rheumatoid arthritis symptoms in mice and modulate T helper cell responses
- Abstract: Activated effector T cells induce pro-inflammatory responses in rheumatoid arthritis (RA) which then lead to inflammation of the joints. In this report, we demonstrate that polymeric nanoparticles with alpha keto-glutarate (aKG) in their polymer backbone (termed as paKG NPs) modulate T cell responses in vitro and in vivo. Impressively, a low dose of only three administrations of methotrexate, a clinically and chronically administered drug for RA, in conjunction with two doses of paKG NPs, reversed arthritis symptoms in collagen-induced arthritis (CIA) mice. This was further followed by significant decreases in pro-inflammatory antigen-specific T helper type 17 (T_H17) responses and a significant increase in anti-inflammatory regulatory T cell (T_REG) responses when CIA treated splenic cells were isolated and re-exposed to the CIA self-antigen. Overall, this study supports the concurrent and short term, low dose of paKG NPs and methotrexate for the reversal of RA symptoms.
Reactive sintering of garnet-type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) from pyrochlore precursors prepared using a non-aqueous sol–gel method
- Abstract: Garnet-type solid-state electrolytes such as Ta-doped Li₇La₃Zr₂O₁₂ (LLZTO) are promising ceramic electrolytes for all-solid-state batteries because of their high (electro)chemical stability and ionic conductivity. LLZTO is typically synthesized from oxide precursors via solid-state reaction, but use of other precursors such as pyrochlores has also received recent interest. Here, a Ta-doped pyrochlore was prepared using non-aqueous sol–gel methods to serve as precursor for LLZTO. The dense LLZTO ceramic was directly obtained via a reactive sintering method with ionic conductivity ~ 0.4 mS/cm, which is comparable to LLZTO prepared by solid-state reaction, using only 2 h sintering at 1100 ℃. Investigation of the synthesis parameters shows that liquid phase sintering is important for achieving high pellet densities and phase purity. The grain size of LLZTO is less than 2 μm, indicating that fine-grained garnet ceramics are accessible with this approach. This work reveals an alternate method for the synthesis and processing of LLZTO materials.
In Situ TEM under Optical Excitation for Catalysis Research
- Abstract: In situ characterization of materials in their operational state is a highly active field of research. Investigating the structure and response of materials under stimuli that simulate real working environments for technological applications can provide new insight and unique input to the synthesis and design of novel materials. Over recent decades, experimental setups that allow different stimuli to be applied to a sample inside an electron microscope have been devised, built, and commercialized. In this review, we focus on the in situ investigation of optically active materials using transmission electron microscopy. We illustrate two different approaches for exposing samples to light inside the microscope column, explaining the importance of different aspects of their mechanical construction and choice of light source and materials. We focus on the technical challenges of the setups and provide details of the construction, providing the reader with input on deciding which setup will be more useful for a specific experiment. The use of these setups is illustrated using examples from the literature of relevance to photocatalysis and nanoparticle synthesis.
Exploring Blob Detection to Determine Atomic Column Positions and Intensities in Time-Resolved TEM Images with Ultra-Low Signal-to-Noise
- Abstract: Spatially resolved in situ transmission electron microscopy (TEM), equipped with direct electron detection systems, is a suitable technique to record information about the atom-scale dynamics with millisecond temporal resolution from materials. However, characterizing dynamics or fluxional behavior requires processing short time exposure images which usually have severely degraded signal-to-noise ratios. The poor signal-to-noise associated with high temporal resolution makes it challenging to determine the position and intensity of atomic columns in materials undergoing structural dynamics. To address this challenge, we propose a noise-robust, processing approach based on blob detection, which has been previously established for identifying objects in images in the community of computer vision. In particular, a blob detection algorithm has been tailored to deal with noisy TEM image series from nanoparticle systems. In the presence of high noise content, our blob detection approach is demonstrated to outperform the results of other algorithms, enabling the determination of atomic column position and its intensity with a higher degree of precision.
Deep Denoising for Scientific Discovery: A Case Study in Electron Microscopy
- Abstract: Denoising is a fundamental challenge in scientific imaging. Deep convolutional neural networks (CNNs) provide the current state of the art in denoising photographic images. However, their potential has been inadequately explored for scientific imaging. Denoising CNNs are typically trained on clean images corrupted with artificial noise, but in scientific applications, noiseless ground-truth images are usually not available. To address this, we propose a simulation-based denoising (SBD) framework, in which CNNs are trained on simulated images. We test the framework on transmission electron microscopy (TEM) data, showing that it outperforms existing techniques on a simulated benchmark dataset, and on real data. We analyze the generalization capability of SBD, demonstrating that the trained networks are robust to variations of imaging parameters and of the underlying signal structure. Our results reveal that state-of-the-art architectures for denoising photographic images may not be well adapted to scientific-imaging data. For instance, substantially increasing their field-of-view dramatically improves their performance on TEM images acquired at low signal-to-noise ratios. We also demonstrate that standard performance metrics for photographs (such as peak signal-to-noise ratio) may not be scientifically meaningful, and propose several metrics to remedy this issue in the case of TEM images. In addition, we propose a technique, based on likelihood computations, to visualize the agreement between the structure of the denoised images and the observed data. Finally, we release a publicly available benchmark dataset containing 18,000 simulated TEM images.
Probing Response and Functionality in Active Materials Systems with In Situ Electron Microscopy
- Introduction: The response of a materials system to an applied stimulus is often critical to many technological applications. While fundamental materials properties govern how a material system will respond, complex electronic, mechanical, magnetic, catalytic or optical behaviors may take place in composite systems with different geometric configurations. Static observations provide no direct information about stimuli-response behavior in a material. For example, although materials properties are governed by atomic structure, knowing the coordinates of every atom in an oxide nanoparticle does not directly reveal its electronic, optical, chemical or transport properties. While computational materials science has made great progress, ab initio prediction of the dynamic responses of a system is often a formidable task even with contemporary high-performance computers. Dynamic in situ electron microscopy is able to directly provide information on the response of materials to applied stimuli.
Atomic Scale Visualization of Cation Point Defects in Gadolinium Doped Ceria
- Introduction: Ceria and ceria-based materials are well known for their unique ability of reversibly exchange lattice oxygen with the surrounding environment favoring their use in areas such as catalysis, energy and sensing technologies. Because of the high-level of tolerance to oxygen vacancies in these materials, they have been commonly doped with aliovalent point defects, such as Pr³⁺, Gd³⁺ and Ca²⁺, to increase extrinsic oxygen vacancies resulting in enhanced ionic and electronic conductivity [1]. Gadolinium doped ceria (GDC) is known to be one of the most promising possible anode materials for operation of solid oxide fuel cells (SOFC) below 600 °C [2]. However, the association between atomic level point defect location/configuration and the performance for oxygen exchange is not well understood. To understand the effect of point defect structure and locations relating to active oxygen exchange sites, it’s necessarily developed atomic level imaging and spectroscopic techniques to visualize them.
In Situ Engineering and Characterization of Photonic Modes in Dielectric Nanocubes
- Introduction: Photonic devices rely on materials having high refractive index difference between the photonic structure and the surrounding medium. In sub-micron-sized dielectric particles, which can be considered as cavities, electromagnetic waves with specific wavelengths can be trapped in the form of photonic modes, providing opportunities for energy harvesting and information transfer. To further understand this phenomenon and provide guidance for mode engineering, a systematical experimental study on photonic modes under varying conditions is necessary. Monochromated electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) has proved to be a powerful technique to study photonic modes by providing both high energy and spatial resolution [1]. According to the simulation data, photonic modes are strongly dependent on the dielectric properties and the geometry of the material [2]. In situ capability grants us the ability to easily modify the morphology inside the microscope enabling the observation of the variation in the photonic mode.
Convolutional Neural Network as a Solution to Segment and Classify High Resolution TEM Images to Obtain 3D Information
- Introduction: Analysis of nanoparticles has enjoyed a continuously increasing interest, with applications in catalysis, medicine or optoelectronics, to name a few. The physical and chemical properties of these particles rely on their exact 3D structure, and multiple approaches have been developed to extract this information. The most accurate and reliable procedure for retrieving the nanoparticle morphology is through scanning transmission electron microscopy (STEM) tomography, which performs well even at the atomic scale [1]. However, tomographic techniques require acquiring at least two different image projections from different zone axes, demanding a stable and stationary system. This limits the temporal resolution necessary to capture dynamics, which are critical to understanding the underlying functionality of interest. Other approaches use the intensity of a single STEM or TEM image, combined with very precise image simulations to extract 3D structure information [2]. Here too, temporal resolution is limited by the signal-to-noise ratios required in order to reliably measure the intensity of each atomic column. Deep neural networks have shown tremendous results in applications involving processing and analyzing high dimensional data. Specifically, convolutional neural networks (CNNs) were used in applications involving natural image data such as: image classification, segmentation, and object detection [3]. More recently, machine learning based algorithms have shown great success in processing other kinds of images, applied to medical imaging data, and images encountered in biology, chemistry and physics. Pioneering work on 3D shape reconstruction of gold nanoparticles using machine learning was first done on simulated TEM images [4], followed by experimental data [5]. Still, in the presence of low doses, i.e., poor signal-to-noise ratios, the reported results are not accurate.
Revealing Photonic Properties with High Spatial Resolution: An EELS Study on Ceria Nanocubes
- Introduction: Nanoscale optics can be applied to various fields, e.g., sensor, energy harvesting, and communication [1]. A fundamental understanding of their properties is necessary to fulfill the potential of nano optics. However, the relatively low spatial resolution of traditional optical measurement methods, e.g., Raman spectroscopy and infrared spectroscopy, set an obstacle to study the photonic properties for nanoscale optical structures. By the Weizsäcker-Williams approximation [2–4], the electromagnetic field generated by high-speed charged particles (e.g., electron in transmission electron microscope (TEM)) can be approximated as virtual quanta, e.g. virtual photons. In other words, in TEM, electrons can be used as a light source with a higher spatial resolution. Another unmatched advantage of using TEM to detect optic properties is that it can simultaneously excite and detect energy loss process in a large range of energy, from infrared [5] to ultraviolet [6], through electron energy-loss spectroscopy (EELS) in a scanning TEM (STEM). In sub-micron-sized dielectric particles e.g., CeO₂ (ceria), light can be trapped in the form of photonic modes, providing opportunities for energy harvesting and information transfer. Here, we applied monochromated STEM EELS to study the photonic modes in a ceria cube
How to Get Something Out of Nothing (Almost!): Extracting Information from Noisy Data
- Introduction: The availability of high readout-rate, high sensitivity, direct electron detectors will have a major impact on our ability to understand not only the spatial but also the temporal structure of materials systems. Areas where spatiotemporal information is essential for fundamental understanding of functionality include phase changes, transport and chemical conversion processes. For example, in heterogeneous catalysis, reactant molecules chemisorb onto nanoparticles surfaces and are transformed into product molecules. The breaking and making of chemical bonds is associated with structural dynamics in the particles such as fluxionalities in strain as well as atomic diffusion processes. Understanding this fluxionality and how it relates to functionality will be key to designing new and improved catalysts. However, extracting subtle structural information from time-resolved electron microscopy images is not straightforward. The short exposure times needed for high temporal resolution, usually results in very low signal-to-noise (SNR) in individual frames and new data processing approaches must be developed to extract scientifically useful information.
Harnessing High Temporal Resolutions to Explore Fluxional Behavior on CeO₂ Nanoparticles under Reducing Conditions
- Introduction: State-of-the-art, commercially available, direct electron detectors can acquire TEM image series at up to 1000 frames per second (fps), capturing 1 ms snapshots of a materials system undergoing dynamic structural re-arrangement. In materials science in general, and catalysis in particular, this time regime may provide information on reaction paths, mechanisms or intermediate and metastable states of an evolving system. For example, fast structural re-arrangements at the atomic level under reaction conditions, known as fluxional behavior, are of increasing interest in catalysis [1]. Unfortunately, characterizing these dynamic events in the presence of gases and external stimuli without sacrificing either temporal or spatial resolutions is still a major challenge due to signal-to-noise (SNR) limitations.
Detecting and Characterizing the Fluxionality in Pt Nanoparticles
- Introduction: Platinum on ceria support is a technologically important and highly active catalyst for CO oxidation [1-3]. Past studies have shown that the functioning of this catalyst is influenced by structural rearrangements (fluxionality) occurring under reaction conditions [4]. Our latest in situ TEM results on this catalyst show significant fluxionality exhibited by Pt nanoparticles even at room temperature in a CO atmosphere. Correlating fluxionality and catalytic activity will provide fundamental insights into the reaction pathways and help in the design of better catalysts. The fluxionality is often stochastic with the particles showing periods of structural stability punctuated with periods of intense structural rearrangement. In this work we discuss an approach to detect the onset of unstable behavior of Pt nanoparticles on ceria exposed to CO gas of different partial pressures at room temperature.
Rhodium Doping of Strontium Titanate for Enhanced Visible Light Absorption
- Introduction: Ever since the discovery of electrochemical photolysis of water using anatase [1], a lot of attraction has been focused on the development of materials that can harvest the energy from photons and generate solar fuels. For example, photocatalytic water splitting using semiconductor-based materials is one way of harvesting solar energy to generate H₂. Absorbed the solar energy (photons) is converted to electronhole pairs which act as charge carriers and reduce and oxidize the water respectively [2]. Most used materials with high structural stability under the reaction are oxides but they suffer from poor efficiency due to their bandgaps being in UV part of the spectrum which constitutes 3-4% of the solar spectrum [3]. Tuning the bandgap by doping has gained a lot of interest and proven to be quite successful in making these oxides that absorb in the visible part of the spectrum. In this work, we aim to investigate the effects of rhodium (Rh) doping in strontium titanate (STO) and associated visible light absorption properties. We have chosen a model photocatalyst consisting of Ni/NiO core-shell co-catalyst loaded on a Rh doped STO, since this type of core-shell structure loaded on semiconductor has previously shown overall water splitting [4].
Detection of Adsorbates Induced Changes on Pt/CeO₂ Catalyst using In situ Electron Holography
- Introduction: Heterogeneous catalysis is an important approach to control chemical transformations in which a set of reactants are converted to products on a catalyst surface. Detection of surface species upon exposure to reactants is important to understand catalytic functionalities of the nanoparticles e.g., active site determination. Exposure to various gases changes the surface chemistry and electronic properties of the nanoparticle [1]. Off-axis electron holography could be used as a technique in which these adsorbateinduced changes would be detected by measuring the phase change of the fast electron as it interacts with the modified nanoparticle surface [2] Recent work has shown the possibility of doing electron holography in the presence of gas inside the microscope without a significant drop in fringe visibility [3]. In this work, we aim to detect the presence of surface species on Pt nanoparticles supported on CeO₂ upon interaction with CO. This reaction was chosen for this investigation because CO binds strongly with Pt even at room temperature giving a significant surface coverage.
Epitaxial Heusler Superlattice Co₂MnAl/Fe₂MnAl with Perpendicular Magnetic Anisotropy and Termination-Dependent Half-Metallicity
- Abstract: Single-crystal Heusler atomic-scale superlattices that have been predicted to exhibit perpendicular magnetic anisotropy and half-metallicity have been successfully grown by molecular beam epitaxy. Superlattices consisting of full-Heusler Co₂MnAl and Fe₂MnAl with one to three unit cell periodicity were grown on GaAs (001), MgO (001), and Cr (001)/MgO (001). Electron energy loss spectroscopy maps confirmed clearly segregated epitaxial Heusler layers with high cobalt or high iron concentrations for samples grown near room temperature on GaAs (001). Superlattice structures grown with an excess of aluminum had significantly lower thin film shape anisotropy and resulted in an out-ofplane spin reorientation transition at temperatures below 200 K for samples grown on GaAs (001). Synchrotron-based spin resolved photoemission spectroscopy found that the superlattice structure improves the Fermi level spin polarization near the X point in the bulk Brillouin zone. Stoichiometric Co₂MnAl terminated superlattice grown on MgO (001) had a spin polarization of 95%, while a pure Co₂MnAl film had a spin polarization of only 65%.
Carbon as a key driver of super-reduced explosive volcanism on Mercury: Evidence from graphite-melt smelting experiments
- Abstract: Here we present the results of experiments designed to reproduce the interaction between super-solidus mercurian magmas and graphite at high temperatures (ramped up from ambient temperature to 1195–1390 °C) and low pressure (10 mbar). The compositions of resultant gases were measured in situ with a thermal gravimeter/differential scanning calorimeter connected to a mass spectrometer configured to operate under low pressures and reducing conditions. Solid run products were analyzed by electron microprobe and Raman spectroscopy. Three magma starting compositions were based on the composition of the Borealis Planitia region (termed NVP for the Northern Volcanic Plains) on Mercury ± alkali metals, sulfur, and transition metal oxides. Smelting between FeO_melt and graphite was observed above 1100 °C, evidenced by the generation of CO and CO₂ gas and the formation of Fe-Si metal alloys, which were found in contact with residual graphite grains. Experiments with transition metal oxide-free starting compositions did not produce metal alloys and showed no significant gas production. In all runs that produced gas, C-O-H±S species dominated the degassing vapor. Our results suggest that the consideration of graphite smelting processes can significantly increase calculated eruption velocities and that gas produced by smelting alone can account for >75% of the pyroclastic deposits identified on Mercury. A combination of S-H-degassing and CO-CO₂ production from smelting can explain all but the single largest pyroclastic deposit on Mercury.
Structural analysis of the basal state of the Artemis:DNA-PKcs complex
- Abstract: Artemis nuclease and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) are key components in nonhomologous DNA end joining (NHEJ), the major repair mechanism for double-strand DNA breaks. Artemis activation by DNA-PKcs resolves hairpin DNA ends formed during V(D)J recombination. Artemis deficiency disrupts development of adaptive immunity and leads to radiosensitive T- B- severe combined immunodeficiency (RS-SCID). An activated state of Artemis in complex with DNA-PK was solved by cryo-EM recently, which showed Artemis bound to the DNA. Here, we report that the pre-activated form (basal state) of the Artemis:DNA-PKcs complex is stable on an agarose-acrylamide gel system, and suitable for cryo-EM structural analysis. Structures show that the Artemis catalytic domain is dynamically positioned externally to DNA-PKcs prior to ABCDE autophosphorylation and show how both the catalytic and regulatory domains of Artemis interact with the N-HEAT and FAT domains of DNA-PKcs. We define a mutually exclusive binding site for Artemis and XRCC4 on DNA-PKcs and show that an XRCC4 peptide disrupts the Artemis:DNA-PKcs complex. All of the findings are useful in explaining how a hypomorphic L3062R missense mutation of DNA-PKcs could lead to insufficient Artemis activation, hence RS-SCID. Our results provide various target site candidates to design disruptors for Artemis:DNA-PKcs complex formation.
Coarse-Grained Simulations for the Characterization and Optimization of Hybrid Protein–DNA Nanostructures
- Abstract: We present here the combination of experimental and computational modeling tools for the design and characterization of protein–DNA hybrid nanostructures. Our work incorporates several features in the design of these nanostructures: (1) modeling of the protein–DNA linker identity and length; (2) optimizing the design of protein–DNA cages to account for mechanical stresses; (3) probing the incorporation efficiency of protein–DNA conjugates into DNA nanostructures. The modeling tools were experimentally validated using structural characterization methods like cryo-TEM and AFM. Our method can be used for fitting low-resolution electron density maps when structural insights cannot be deciphered from experiments, as well as enable in-silico validation of nanostructured systems before their experimental realization. These tools will facilitate the design of complex hybrid protein–DNA nanostructures that seamlessly integrate the two different biomolecules.
The structural basis for regulation of the glutathione transporter Ycf1 by regulatory domain phosphorylation
- Abstract: Yeast Cadmium Factor 1 (Ycf1) sequesters heavy metals and glutathione into the vacuole to counter cell stress. Ycf1 belongs to the ATP binding cassette C-subfamily (ABCC) of transporters, many of which are regulated by phosphorylation on intrinsically-disordered domains. The regulatory mechanism of phosphorylation is still poorly understood. Here, we report two cryo-EM structures of Ycf1 at 3.4 Å and 4.0 Å resolution in inward-facing open conformations that capture previously unobserved ordered states of the intrinsically disordered regulatory domain (R-domain). R-domain phosphorylation is clearly evident and induces a topology promoting electrostatic and hydrophobic interactions with Nucleotide Binding Domain 1 (NBD1) and the Lasso motif. These interactions stay constant between the structures and are related by rigid body movements of the NBD1/R-domain complex. Biochemical data further show R-domain phosphorylation reorganizes the Ycf1 architecture and is required for maximal ATPase activity. Together, we provide insights into how R-domains control ABCC transporter activity.
Seasonal formation of ikaite in slime flux jelly on an infected tree (Populus fremontii) wound from the Sonoran Desert
- Abstract: Ikaite is the calcium carbonate hexahydrate (CaCO₃·6H₂O), which precipitates below ~ 7 °C, first identified from Ikka Fjord in southwest Greenland and subsequently more widely reported. Here is described the serendipitous discovery of ikaite on a tree (Populus fremontii) wound from the hot Sonoran Desert, which precipitates during short cold periods in the winter, whereas monohydrocalcite forms through most of the year. The tree wound consists of infected wood, called wetwood that exudes a nutrient-rich water on which a jelly-like slime flux forms. Ikaite, along with alpha sulfur, precipitates in and on the bacterial slime flux jelly. Each tree wound occurs as an island of mineralization: all the elements for the mineral formation are supplied through the xylem sap expressed from the wetwood infection. The P. fremontii wetwood is capped and surrounded by a hard mineralized zone dominated by ikaite/monohydrocalcite, alpha sulfur, and a range of carbonates and sulfates, on which the slime flux jelly occurs. Water oozing from the wetwood is modestly alkaline (pH = 8.34), with elevated concentrations of K⁺ (5554.7 ppm) and S as SO₄²⁻ (1662.9 ppm), with Ca²⁺ (151.9 ppm) and Mg²⁺ (270.3 ppm). This water chemistry favors the precipitation of ikaite/monohydrocalcite, both within and below the jelly. The ikaite is temperature sensitive, though the laboratory results show that it can persist for several days at room temperature in the sulfur-rich jelly. The ikaite, and associated mineralization within and around the slime flux jelly, illustrates a new, and likely, global form of bio-mediated mineralization.
Compositional Analysis of SiOC(H) Powders: A Comparison of X-ray Photoelectron Spectroscopy (XPS) and Combustion Analysis
- Abstract: Accurate chemical analysis of small samples of fine powders in the Si–O–C–H system is challenging. We present a comparison of analysis by X-ray photoelectron spectroscopy (XPS) and combustion analysis, validating XPS as an accurate and simple methodology for Si, C, and O analysis to give bulk and not just surface compositions. The XPS analyses are supported by showing consistency in thermochemical calculations of heats of formation based on high temperature oxide melt solution calorimetry. However, because XPS is not suitable for quantitation of hydrogen, it must be combined with other techniques for samples with substantial H content.
Ultrasonication-Induced Strong Metal-Support Interaction Construction in Water Towards Enhanced Catalysis
- Abstract: The development of facile methodologies to afford robust supported metal nanocatalysts under mild conditions is highly desirable yet challenging, particularly via strong metal-support interactions (SMSI) construction. State-of-the-art approaches capable of generating SMSI encapsulation mainly focus on high temperature annealing in reductive/oxidative atmosphere. Herein, ultra-stable metal nanocatalysts based on SMSI construction were produced by leveraging the instantaneous high-energy input from ultrasonication under ambient conditions in H₂O, which could rapidly afford abundant active intermediates, Ti³⁺ ions, and oxygen vacancies within the scaffolds to induce the SMSI overlayer formation. The encapsulation degree could be tuned and controlled via the reducibility of the solvents and the ultrasonication parameters. This facile and efficient approach could be further extended to diverse metal oxide supports and noble metal NPs leading to enhanced performance in hydrogenation reactions and CO₂ conversion.
Decadal transition from quiescence to supereruption: petrologic investigation of the Lava Creek Tuff, Yellowstone Caldera, WY
- Abstract: The magmatic processes responsible for triggering nature’s most destructive eruptions and their associated timescales remain poorly understood. Yellowstone Caldera is a large silicic volcanic system that has had three supereruptions in its 2.1-Ma history, the most recent of which produced the Lava Creek Tuff (LCT) ca. 631 ka. Here we present a petrologic study of the phenocrysts, specifically feldspar and quartz, in LCT ash in order to investigate the timing and potential trigger leading to the LCT eruption. The LCT phenocrysts have resorbed cores, with crystal rims that record slightly elevated temperatures and enrichments in magmaphile elements, such as Ba and Sr in sanidine and Ti in quartz, compared to their crystal cores. Chemical data in conjunction with mineral thermometry, geobarometry, and rhyolite-MELTS modeling suggest the chemical signatures observed in crystal rims were most likely created by the injection of more juvenile silicic magma into the LCT sub-volcanic reservoir, followed by decompression-driven crystal growth. Geothermometry and barometry suggest post-rejuvenation, pre-eruptive temperatures and pressures of 790–815 °C and 80–150 MPa for the LCT magma source. Diffusion modeling utilizing Ba and Sr in sanidine and Ti in quartz in conjunction with crystal growth rates yield conservative estimates of decades to years between rejuvenation and eruption. Thus, we propose rejuvenation as the most likely mechanism to produce the overpressure required to trigger the LCT supereruption in less than a decade.z
New Evidence for Wet Accretion of Inner Solar System Planetesimals from Meteorites Chelyabinsk and Benenitra
- Abstract: We investigated the hydrogen isotopic compositions and water contents of pyroxenes in two recent ordinary chondrite falls, namely, Chelyabinsk (2013 fall) and Benenitra (2018 fall), and compared them to three ordinary chondrite Antarctic finds, namely, Graves Nunataks GRA 06179, Larkman Nunatak LAR 12241, and Dominion Range DOM 10035. The pyroxene minerals in Benenitra and Chelyabinsk are hydrated (∼0.018–0.087 wt.% H₂O) and show D-poor isotopic signatures (δDSMOW from −444‰ to −49‰). On the contrary, the ordinary chondrite finds exhibit evidence of terrestrial contamination with elevated water contents (∼0.039–0.174 wt.%) and δD_SMOW values (from −199‰ to −14‰). We evaluated several small parent-body processes that are likely to alter the measured compositions in Benenitra and Chelyabinsk and inferred that water loss in S-type planetesimals is minimal during thermal metamorphism. Benenitra and Chelyabinsk hydrogen compositions reflect a mixed component of D-poor nebular hydrogen and water from the D-rich mesostases. A total of 45%–95% of water in the minerals characterized by low δD_SMOW values was contributed by nebular hydrogen. S-type asteroids dominantly composed of nominally anhydrous minerals can hold 254–518 ppm of water. Addition of a nebular water component to nominally dry inner solar system bodies during accretion suggests a reduced need of volatile delivery to the terrestrial planets during late accretion.
Energetics and structure of SiC(N)(O) polymer-derived ceramics
- Abstract: This study presents new experimental data on the thermodynamic stability of SiC(O) and SCN(O) ceramics derived from the pyrolysis of polymeric precursors: SMP-10 (polycarbosilane), PSZ-20 (polysilazane), and Durazane-1800 (polysilazane) at 1200°C. There are close similarities in the structure of the polysilazanes, but they differ in crosslinking temperature. High-resolution X-ray photoelectron spectroscopy shows notable differences in the microstructure of all polymer-derived ceramics (PDCs). The enthalpies of formation (∆H°_{f, elem}) of SiC(O) (from SMP-10), SCN(O) (from PSZ-20), and SCN(O) (from Durazane-1800) are −20 ± 4.63, −78.55 ± 2.32, and −85.09 ± 2.18 kJ/mol, respectively. The PDC derived from Durazane-1800 displays greatest thermodynamic stability. The results point to increased thermodynamic stabilization with addition of nitrogen to the microstructure of PDCs. Thermodynamic analysis suggests increased thermodynamic drive for forming SiCN(O) microstructures with an increase in the relative amount of SiN_xC_4−x mixed bonds and a decrease in silica. Overall, enthalpies of formation suggest superior stabilizing effect of SiN_xC_4−x compared to SiO_xC_4−x mixed bonds. The results indicate systematic stabilization of SiCN(O) structures with decrease in silicon and oxygen content. The destabilization of PDCs resulting from higher silicon content may reach a plateau at higher concentrations.
Development of nano boron-doped diamond electrodes for environmental applications
- Abstract: Boron doped diamond (BDD) is an outstanding electrode material with unique electrocatalytic properties and excellent stability, relevant to electrochemical advanced oxidation processes and electroanalytical techniques. From an environmental sustainability viewpoint, BDD electrodes are comprised only of earth abundant elements (carbon, boron, oxygen). However, a major drawback is the high manufacturing costs per unit surface area for BDD electrodes when fabricated using chemical vapor deposition or comparable surface deposition processes. BDD nanoparticles can provide an alternative manufacturing process that reduces costs by over 1000-fold while also improving catalytic activity. Herein, we demonstrate that nano-BDD electrodes can be fabricated by depositing BDD nanoparticles on a silicon substrate using a Nafion® ink-casting method. Scanning electron microscopy (SEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) were used to investigate the electrode structural and morphological properties, which were compared to BDD electrodes manufactured using standard methods. Cyclic voltammetry measurements revealed similar electrochemical properties for both electrodes, with a broad “electrochemical window”, essential for effective production of ∙OH radicals without oxygen generation, providing an energy-efficient approach to degradation of pollutants in water. The electrocatalytic properties of the nano-BDD enabled electrodes were investigated using a [Fe(CN)₆]^3-/4- redox probe. The sensing properties of as-prepared nano-BDD electrodes was studied using Dopamine.
Towards the design of mechanical flexible electrodes for sensing: Self-standing polypyrrole-copper nanocomposites
- Abstract: Self-standing electrodes with intrinsic conductivity and high electrocatalytic activity emerge as an alternative to existing sensors given their promising flexibility and wearability. Herein we demonstrate the fabrication of flexible sensors based on a hybrid nanocomposite of self-supported polypyrrole electrodes modified with copper nanoparticles (PPy-Cu) for the electrochemical detection of dopamine. The surface morphology and composition of flexible nanocomposite electrodes was studied using scanning electron microscopy (SEM), in combination with elemental mapping through energy dispersive X-ray spectroscopy (EDS). Surface characterization by X-ray photoelectron spectroscopy (XPS) revealed that copper exists in both Cu(0) and Cu(II) forms. The incorporation of copper nanoparticles in the self-standing polypyrrole matrix introduced additional electroactive sites, further enhancing charge transfer, and improving the device's sensitivity. The sensing capability of self-standing PPy-Cu electrodes was evaluated using chronoamperometric measurements and optimized at various copper electrodeposition times. PPy-Cu 120s showed great performance for dopamine sensing with a low limit of detection of 1.19 μM and a linear range of 2.5 μM–250 μM. Additionally, the self-standing sensor is comprised entirely of Polypyrrole, a biocompatible polymer, and Copper nanoparticles, making it sustainable and environmentally friendly. These encouraging results pave the way for the development of next-generation flexible sensors for the detection of neurotransmitters and environmentally relevant analytes.
Ultra-small gold particles via Citrus × sinensis: Theoretical and experimental SERS study
- Abstract: In this study, we have addressed the green synthesis of sub-nanostructured gold species using Citrus × sinensis. Absorption bands in the ultraviolet region (338 nm) were observed. Analysis by atomic resolution microscopy revealed the identification of sub-nanostructured Au species with particle sizes of about 0.9 nm. With favorable results, these systems were tested as substrates for surface-enhanced Raman spectroscopy (SERS) using pyridine. The chemical enhancement mechanism was studied as the source of the SERS effect. Complementarily, the interaction between gold clusters (Au_2n, with n = 1–5) and pyridine was modeled using Density Functional at the Becke-3-parameter-Lee-Yang-Parr level of approximation in combination with the LANL2DZ basis set. A correlation between the adsorption energy and the SERS enhancement factor was analyzed as a function of the Au-N interaction distance.
Robust and Manufacturable Lithium Lanthanum Titanate-Based Solid-State Electrolyte Thin Films Deposited in Open Air
- Abstract: State-of-the-art solid-state electrolytes (SSEs) are limited in their energy density and processability based on thick, brittle pellets, which are generally hot pressed in vacuum over the course of several hours. We report on a high-throughput, open-air process for printable thin-film ceramic SSEs in a remarkable one-minute time frame using a lithium lanthanum titanium oxide (LLTO)-based SSE that we refer to as robust LLTO (R-LLTO). Powder XRD analysis revealed that the main phase of R-LLTO is polycrystalline LLTO, accompanied by selectively retained crystalline precursor phases. R-LLTO is highly dense and closely matched to the stoichiometry of LLTO with some heterogeneity throughout the film. A minimal presence of lithium carbonate is identified despite processing fully in ambient conditions. The LLTO films exhibit remarkable mechanical properties, demonstrating both flexibility with a low modulus of ∼35 GPa and a high fracture toughness of >2.0 $MPa \sqrt{m}$ . We attribute this mechanical robustness to several factors, including grain boundary strengthening, the presence of precursor crystalline phases, and a decrease in crystallinity or ordering caused by ultrafast processing. The creation of R-LLTO─a ceramic material with elastic properties that are closer to polymers with higher fracture toughness─enables new possibilities for the design of robust solid-state batteries.
Nickel-Based Single-Molecule Catalysts with Synergistic Geometric Transition and Magnetic Field-Assisted Spin Selection Outperform RuO₂ for Oxygen Evolution
- Abstract: Overcoming slow kinetics and high overpotential in electrocatalytic oxygen evolution reaction (OER) requires innovative catalysts and approaches that transcend the scaling relationship between binding energies for intermediates and catalyst surfaces. Inorganic complexes provide unique, customizable geometries, which can help enhance their efficiencies. However, they are unstable and susceptible to chemical reaction under extreme pH conditions. Immobilizing complexes on substrates creates single-molecule catalysts (SMCs) with functional similarities to single-atom catalysts (SACs). Here, an efficient SMC, composed of dichloro(1,3-bis(diphenylphosphino)propane) nickel [NiCl₂dppp] anchored to a graphene acid (GA), is presented. This SMC surpasses ruthenium-based OER benchmarks, exhibiting an ultra-low onset and overpotential at 10 mAcm^-2 when exposed to a static magnetic field. Comprehensive experimental and theoretical analyses imply that an interfacial charge transfer from the Ni center in NiCl₂dppp to GA enhances the OER activity. Spectroscopic investigations reveal an in situ geometrical transformation of the complex and the formation of a paramagnetic Ni center, which under a magnetic field, enables spin-selective electron transfer, resulting in enhanced OER performance. The results highlight the significance of in situ geometric transformations in SMCs and underline the potential of an external magnetic field to enhance OER performance at a single-molecule level.
Tuning Film Stresses for Open-Air Processing of Stable Metal Halide Perovskites
- Abstract: Challenges to upscaling metal halide perovskites (MHPs) include mechanical film stresses that accelerate degradation, dominate at the module scale, and can lead to delamination or fracture. In this work, we demonstrate open-air blade coating of single-step coated perovskite as a scalable method to control residual film stress after processing and introduce beneficial compression in the thin film with the use of polymer additives such as gellan gum and corn starch. The optoelectronic properties of MHP films with compression are improved with higher photoluminescence yields. MHP film stability is significantly improved under compression, under humidity, heat, and thermal cycling. By measuring the evolution of film stresses, we demonstrate for the first time that stress relaxation occurs in MHP films with tensile stress that correlates with film degradation. This discovery of a new mechanism underpinning MHP degradation shows that film stress can be used as a parameter to screen MHP devices and modules for quality control before deployment as a design for reliability criterion.
A hydrogen-enriched layer in the topmost outer core sourced from deeply subducted water
- Abstract: The Earth’s core–mantle boundary presents a dramatic change in materials, from silicate to metal. While little is known about chemical interactions between them, a thin layer with a lower velocity has been proposed at the topmost outer core (Eʹ layer) that is difficult to explain with a change in concentration of a single light element. Here we perform high-temperature and -pressure laser-heated diamond-anvil cell experiments and report the formation of SiO₂ and FeH_x from a reaction between water from hydrous minerals and Fe–Si alloys at the pressure–temperature conditions relevant to the Earth’s core–mantle boundary. We suggest that, if water has been delivered to the core–mantle boundary by subduction, this reaction could enable exchange of hydrogen and silicon between the mantle and the core. The resulting H-rich, Si-deficient layer formed at the topmost core would have a lower density, stabilizing chemical stratification at the top of the core, and a lower velocity. We suggest that such chemical exchange between the core and mantle over gigayears of deep transport of water may have contributed to the formation of the putative Eʹ layer.

Back to top.

METAL

Fe-single-atom catalyst nanocages linked by bacterial cellulose-derived carbon nanofiber aerogel for Li-S batteries
- Abstract: Li-S battery (LSB) is promising for achieving high capacity. Still, its development is hindered by the complex redox process with sluggish kinetics and particularly the resulting lithium polysulfides (LiPS) shuttle effects. Single-atom catalysts (SACs), with their maximized atom utilization, could effectively chemisorb soluble LiPSs and expedite the sulfide conversion reaction kinetics. Here we report incorporating Fe single metal atom catalyst (Fe-SAC) in the sulfur cathode design and its electrocatalytic effects. Fe-doped ZIF-8 nanocages were introduced into a cheap biomass bacteria cellulose. A pyrolysis process converted them into an aerogel structure with Fe-SAC-functionalized N-doped carbon nanocages linked by a carbon nanofiber network (FeSA-NC@CBC), which was applied as a scaffold to fabricate freestanding and binder-free sulfur cathodes. We conducted electrochemical measurements to reveal Fe-SAC functions including lowering energy barriers for S₈ reduction to liquid-phase LiPSs and further to solid-phase Li₂S₂/Li₂S and accelerating Li₂S₂/Li₂S nucleation and deposition, as corroborated by our theoretical calculation results. Benefiting from the synergistic effects of highly active Fe-SAC and three-dimensional conductive network, the sulfide reaction kinetics is improved, which can diminish LiPS shuttle effects and therefore improve LBS rate performance and cycling stability. Accordingly, the fabricated FeSA-NC@CBC composite cathode delivers an excellent rate capability at 2C with a reversible capacity of 840 mAh/g and a long-term cyclic stability of 800 mAh/g at 1C after 500 cycles.
Trace element concentrations as proxies for diagenetic alteration in the African archaeofaunal record: Implications for isotope analysis
- Abstract: Isotope ratio analyses of trace elements are applied to tooth enamel, ostrich eggshell, and other archaeological hard tissues to infer mobility and other aspects of hominin and animal paleoecology. It has been assumed that these highly mineralized tissues are resistant to diagenetic alteration, but this is seldom tested and some studies document diagenetic alteration over brief time spans. Here, we build on existing research on Maximum Threshold Concentrations (MTCs) to develop screening tools for diagenesis that can inform heavy isotopic analyses. The premise of the MTC approach is that archaeological tissues are likely contaminated and unsuitable for isotope ratio analysis when they exceed characteristic modern concentration ranges of trace elements. Furthermore, we propose a new metric called the Maximum Threshold Ratio (MTR) of 85Rb/88Sr or whole element Rb/Sr, which can be measured simultaneously with 87Sr/86Sr during laser ablation (LA) MC-ICP-MS or applied during post hoc screening of specimens. We analyzed 56 enamel samples from modern Kenyan mammals and 34 modern ostrich eggshells from South Africa, Namibia, and the United States by solution ICP-MS, as well as a subset of shells using LA-MC-ICP-MS. Our results indicate that thresholds are consistent across taxa at a single location, but likely vary across locations. Therefore, MTCs and MTRs need to be tissue and locality specific, but not necessarily taxon-specific. Other important differences are observed between the inner and outer surfaces of the eggshells and between LA and solution ICP-MS. This exploratory study provides guidelines for building reference thresholds to screen enamel and eggshell for diagenesis potentially impacting biogenic isotope ratios.
Environmental harshness mediates the relationship between aboveground and belowground communities in Antarctica
- Abstract: Linkages between aboveground and belowground communities are a key but globally under-researched component of responses to environmental change. Given the logistical complications to studying these relationships, much of our knowledge derives from laboratory experiments and localized field studies which have so far yielded inconsistent results. Because environmental factors may alter relationships between above- and belowground communities, there is a need for broad-scale field studies testing these interactions. The Antarctic Peninsula provides an ideal test setting, given the relatively simple communities both above- and belowground. The Peninsula is also experiencing rapid environmental changes, including alterations in species diversity and distribution both above- and belowground. Thus, an improved understanding of the broad-scale consequences of altered environments and vegetation communities for the soil microbiome is of high priority. To determine the nature and strength of the relationship between in situ plant and soil communities across a broad spatial scale and range of environmental conditions, we sampled soil communities at 9 locations (spanning 60–72°S along the Scotia Arc and Antarctic Peninsula) beneath the major aboveground habitats (moss, grass, lichen, algae and bare soil). We measured a comprehensive suite of soil physicochemical properties, microbial (bacterial and fungal) diversity and composition, and invertebrate abundance and community composition to determine the relationships between plant and soil communities. Our results suggest that, with increased environmental severity, plant cover types become more important for influencing the physicochemical soil environment, and therefore the soil microbial communities. Although we found site-specific relationships, broad-scale patterns reveal significant differences among bare soils and vegetated soils, particularly soils beneath grass and moss. This suggests that expansion of vegetation communities under current climate warming projections will be accompanied by shifts in the soil microbiome, with important implications for the ecosystem functioning with which they are associated.
The Role of Primary Producer Traits in Moderating Community Structure and Ecosystem Function
- Abstract: Primary producers, from algae to trees, play a pivotal role in community structure and ecosystem function. Primary producers vary broadly in their functional traits (i.e., morphological, physiological, biochemical, and behavioral characteristics), which determine how they respond to stimuli and affect ecosystem properties. Functional traits provide a mechanistic link between environmental conditions, community structure, and ecosystem function. With climate change altering environmental conditions, understanding this mechanistic link is essential for predicting future community structure and ecosystem function. Competitive interactions and trait values in primary producers are often context dependent, whereby changes in environmental conditions and resources alter relationships between species and ecosystem processes. Well-established paradigms concerning how species in a community respond to each other and to environmental conditions may need to be re-evaluated in light of these environmental changes, particularly in highly variable systems. In this dissertation, I examine the role of primary producer functional traits on community structure and ecosystem function. Specifically, I test a conceptual framework that incorporates response traits, effect traits, and their interaction, in affecting primary producer communities and ecosystem function across different aquatic systems. First, I identified species specific responses to intensifying hydrologic stressors important in controlling wetland plant community composition over time in an aridland stream. Second, I found that effect traits of submerged and emergent vegetation explained differences in ecosystem metabolism and carbon dynamics among permafrost mire thaw ponds. Next, I examined response-effect trait interactions by comparing two dominant wetland plant species over a water-stress gradient, finding that responses to changes in hydrology (i.e., altered tissue chemistry) in turn affect ecosystem processes (i.e., subsurface CO₂ concentration). Finally, I demonstrate how indirect effects of diatom functional traits on water chemistry and ecosystem metabolism help explain disconnects between resource availability and productivity in the Colorado River. By expanding my understanding of how metabolic processes and carbon cycling in aquatic ecosystems vary across gradients in hydrology, vegetation, and organic matter, I contributed to my understanding of how communities influence ecosystem processes. A response-effect trait approach to understanding communities and ecosystems undergoing change may aid in predicting and mitigating the repercussions of future climate change.
The effects of burning on isotope ratio values in modern bone: Importance of experimental design for forensic applications
- Abstract: This study examined preservation of isotope ratio values by comparing isotope composition of bones before and after burning. We analyzed common geoprofiling isotope systems (δ¹³C, δ¹⁵N, δ¹⁸O, and ⁸⁷Sr/⁸⁶Sr) and lesser studied systems (δ³⁴S and δ⁸⁸/⁸⁶Sr) to evaluate if inferences about diet and residence history were altered by the burning process. We used two burn methods: one to simulate previous academic studies using a muffle furnace and one to more closely resemble a house fire or body disposal attempt using open flame. To mimic previous burn studies, ribs and femora from four dry modern human skeletons were heated in a muffle furnace. To resemble a forensic burn situation, fleshed pig ribs from a single geographic location were burned on an open fire both with and without use of a diesel accelerant. Isotope ratios from bone collagen, carbonate, phosphate, and strontium were analyzed. Fleshed pig samples burned in an open fire maintained unaltered isotope ratio values. Dry human samples burned in a muffle furnace maintained unaltered isotope ratio values in most isotope systems, except for δ¹⁸O values in carbonate and phosphate, which showed a depletion of ¹⁸O at higher temperatures. This research suggests that the isotope composition of fleshed burned bone retains the geoprofiling inferences of unburned bone, at least within the parameters of the open fire burn used in this study. However, oxygen isotopes of carbonate and phosphate from dry bone burned in a muffle furnace do not retain the geoprofiling inferences. This research demonstrates the need for research using an experimental design relevant to a specific burn situation.
Seasonal formation of ikaite in slime flux jelly on an infected tree (Populus fremontii) wound from the Sonoran Desert
- Abstract: Ikaite is the calcium carbonate hexahydrate (CaCO₃·6H₂O), which precipitates below ~ 7 °C, first identified from Ikka Fjord in southwest Greenland and subsequently more widely reported. Here is described the serendipitous discovery of ikaite on a tree (Populus fremontii) wound from the hot Sonoran Desert, which precipitates during short cold periods in the winter, whereas monohydrocalcite forms through most of the year. The tree wound consists of infected wood, called wetwood that exudes a nutrient-rich water on which a jelly-like slime flux forms. Ikaite, along with alpha sulfur, precipitates in and on the bacterial slime flux jelly. Each tree wound occurs as an island of mineralization: all the elements for the mineral formation are supplied through the xylem sap expressed from the wetwood infection. The P. fremontii wetwood is capped and surrounded by a hard mineralized zone dominated by ikaite/monohydrocalcite, alpha sulfur, and a range of carbonates and sulfates, on which the slime flux jelly occurs. Water oozing from the wetwood is modestly alkaline (pH = 8.34), with elevated concentrations of K⁺ (5554.7 ppm) and S as SO₄²⁻ (1662.9 ppm), with Ca²⁺ (151.9 ppm) and Mg²⁺ (270.3 ppm). This water chemistry favors the precipitation of ikaite/monohydrocalcite, both within and below the jelly. The ikaite is temperature sensitive, though the laboratory results show that it can persist for several days at room temperature in the sulfur-rich jelly. The ikaite, and associated mineralization within and around the slime flux jelly, illustrates a new, and likely, global form of bio-mediated mineralization.

Back to top.

Advanced Electronics & Photonics

Quantifying and Reducing Ion Migration in Metal Halide Perovskites through Control of Mobile Ions
- Abstract: The presence of intrinsic ion migration in metal halide perovskites (MHPs) is one of the main reasons that perovskite solar cells (PSCs) are not stable under operation. In this work, we quantify the ion migration of PSCs and MHP thin films in terms of mobile ion concentration (N_o) and ionic mobility (µ) and demonstrate that N_o has a larger impact on device stability. We study the effect of small alkali metal A-site cation additives (e.g., Na⁺, K⁺, and Rb⁺) on ion migration. We show that the influence of moisture and cation additive on No is less significant than the choice of top electrode in PSCs. We also show that N_o in PSCs remains constant with an increase in temperature but μ increases with temperature because the activation energy is lower than that of ion formation. This work gives design principles regarding the importance of passivation and the effects of operational conditions on ion migration.

Back to top.

NanoFab

Plasma enhanced atomic layer deposition and atomic layer etching of gallium oxide using trimethylgallium
- Atomic layer etching driven by self-limiting thermal reactions has recently been developed as a highly conformal and isotropic technique for low damage atomic scale material removal by sequential exposures of vapor phase reactants. Gallium oxide (Ga₂O₃) is currently among the materials of interest due to a large variety of applications including power electronics, solar cells, gas sensors, and photon detectors. In this study, Ga2O3 was deposited by plasma enhanced atomic layer deposition using trimethylgallium [TMG, Ga(CH3)3] and O2 plasma at a substrate temperature of 200 °C. We report a newly developed method for Ga2O3 thermal atomic layer etching, in which surface modification is achieved through HF exposure resulting in a gallium fluoride surface layer, and then removed through volatile product formation via ligand exchange with TMG. Saturation of the precursor exposure at a substrate temperature of 300 °C resulted in an etch rate of 1.0 ± 0.1 Å/cycle for amorphous Ga2O3. Uniformity and conformality of the atomic layer etching process were confirmed via atomic force microscopy with a measured surface roughness of 0.55 ± 0.05 nm that remains unchanged after etching. The use of TMG for etching may expand available precursors for atomic layer etching processes, while allowing for both etching and deposition of Ga2O3 using the same metalorganic precursor.
Comparison of AlF₃ thin films grown by thermal and plasma enhanced atomic layer deposition
- Abstract: Films of aluminum fluoride (AlF₃) deposited by thermal and plasma enhanced atomic layer deposition (PEALD) have been compared using in situ multiwavelength ellipsometry (MWE) and monochromatic x-ray photoelectron spectroscopy (XPS). The AlF₃ films were grown using cyclic exposures of trimethylaluminum, hydrogen fluoride, and H radicals from a remote H2 inductively coupled plasma. Films were characterized in situ using MWE and XPS for growth rate, film composition, and impurity incorporation. The MWE showed a growth rate of 1.1 and 0.7 Å per cycle, at 100 °C, for thermal and plasma enhanced ALD AlF3 films, respectively. Carbon incorporation was below the XPS detection limit. The plasma enhanced ALD AlF₃ film showed the presence of Al-Al chemical states, in the Al 2p scans, suggesting the presence of Al-rich clusters with a concentration of 14%. The Al-rich clusters are thought to originate during the hydrogen plasma step of the PEALD process. The Al-rich clusters were not detected in thermal ALD AlF₃ films using the same precursors and substrate temperature.

Back to top.

Research Computing

Quantifying the decrease in heat exposure through adaptation and mitigation in twenty-first-century US cities
- Abstract: The continued increase in the duration, frequency and intensity of heat waves is especially problematic in cities, where more than half of the world’s population lives. Here we combine decadal-scale regional climate modeling simulations with projections of urban expansion, greenhouse gas emissions and population migration to examine the extent to which adaptation and mitigation strategies, in isolation and in tandem, can reduce population heat exposure in US cities at the end of the century. We show that adaptation and mitigation strategies, when deployed in isolation, lead to the largest reduction in population heat exposure for Northeast and Midwest cities compared with Southeast, Great Plains and Southwest cities, relative to a contemporary start-of-century baseline. Our results demonstrate synergistic interactions between adaptation and mitigation strategies when deployed in tandem. This results in an end-of-century decrease in population heat exposure that is greater than the sum of their individual parts for the lowest extreme heat thresholds, but less than the sum of their individual parts for the highest extreme heat thresholds, for US cities across all regions.
Trusted CI webinar: Arizona State's Science DMZ
- Abstract: Drawing upon its mission to enable access to discovery and scholarship, Arizona State University is deploying an advanced research network employing the Science DMZ architecture. While advancing knowledge of managing 21st-century cyberinfrastructure in a large public research university, this project also advances how network cyberinfrastructure supports research and education in science, engineering, and health. Replacing existing edge network equipment and installing an optimized, tuned Data Transfer Node provides a friction-free wide area network path and streamlined research data movement. A strict router access control list and intrusion detection system provide security within the Science DMZ, and end-to-end network performance measurement via perfSONAR guards against issues such as packet loss. Recognizing that the operation of the Science DMZ must not compromise the university’s network security profile, while at the same time avoiding the performance penalty associated with perimeter firewall devices, data access and transfer services will be protected by access control lists on the Science DMZ border router as well as host-level security measures. Additionally, the system architecture employs the anti-IP spoofing tool Spoofer, the Intrusion Detection System (IDS) Zeek, data-sharing honeypot tool STINGAR, traditional honeypot/darknet/tarpit tools, as well as other open-source software. Finally, Science data flows are supported by a process incorporating user engagement, iterative technical improvements, training, documentation, and follow-up. Speaker Bios: Douglas Jennewein is Senior Director for Research Computing in the Research Technology Office at Arizona State University. He has supported computational and data-enabled science since 2003 when he built his first supercomputer from a collection of surplus-bound PCs. He currently architects, funds, and deploys research cyberinfrastructure including advanced networks, supercomputers, and big data archives. He has also served on the NSF XSEDE Campus Champions Leadership Team since 2016 and has chaired that group since 2020. Jennewein is a certified Software Carpentry instructor and has successfully directed cyberinfrastructure projects funded by the National Science Foundation, the National Institutes of Health, and the US Department of Agriculture totaling over $4M. Chris Kurtz is the Senior Systems Architect for the Research Technology Office in the Office of Knowledge Enterprise at Arizona State University. Previously Chris was the Director of Public Cloud Engineering as well as the Splunk System Architect (and Evangelist) at ASU. He has been appointed as Splunk Trust Community MVP since its inception. Chris is a regular speaker on Splunk and Higher Education, including multiple presentations at Educause, Educause Security Professionals, and Splunk’s yearly “.conf"" Conference. Prior to architecting Splunk, he was the Systems Manager of the Mars Space Flight Facility at ASU, a NASA/JPL funded research group, where he supported numerous Mars Missions including TES, THEMIS, and the Spirit and Opportunity Rovers. Chris lives in Mesa, Arizona along with his wife, rescue dogs, and cat.
Employing a Research Community Network to Assess Centralized Computing Impact
- Abstract: We present a study of a university research collaboration network constructed from publication co-authorship and grant co-investigator data. Subsequent analysis of the network’s structural characteristics confirms a small-world network topology. In the aim of providing a quantitative means for centralized computing centers to assess impact, degree and centrality metrics for researcher node cohorts with and without compute cluster accounts are contrasted. Additional assessment of the centralized computing researcher cohort confirms an impact exceeding its proportion of the researcher population. As an input to an agent-based model, the network is then employed in a simulation to measure idea propagation, once again contrasting the two researcher node cohorts as idea initiators. This analysis is extended to peer institutions to see if similar patterns are observed. Finally, the analysis is applied to researchers at all XSEDE participating universities in the United States, divided into cohorts with and without XSEDE allocations.
Preventing H₂S poisoning of dense Pd membranes for H₂ purification using an electric-field: An Ab initio study
- Abstract: High purity (> 99.9%) H₂ is required across a breadth of fields from the energy, chemicals, and semiconductor processing industries and the current multi-step pressure swing adsorption processes are both high cost and inefficient. Dense Pd membranes are highly permeable and selective to H₂, but their deployment after steam methane reformation (SMR) is hampered by their vulnerability to poisoning by S species (e.g., H₂S). Here, we use Density Functional Theory (DFT) to investigate the use of an applied electric field (AEF) to prevent S poisoning by altering the energetics of H₂S adsorption and decomposition on the Pd(111) surface. We find that strong, negative AEFs (<-1.5 V/Å) prevent H₂S adsorption without negatively impacting the adsorption or intercalation of H₂ into the Pd membrane. Microkinetic simulations of the surface with high strength AEF show long-term (> 80 days) stability even under high 1000 ppm H₂S exposure at -1.5 & -2 V/Å E-fields. Although the field strength identified here may be challenging to achieve in operation, these findings suggest that E-fields could provide a pathway for gas phase membrane protection in general and, possibly, more cost-effective H₂ purification via stable Pd membrane systems.
Understanding the Effect of Single Atom Cationic Defect Sites in an Al₂O₃ (012) Surface on Altering Selenate and Sulfate Adsorption: An Ab Initio Study
- Abstract: Adsorption is a promising under-the-sink selenate remediation technique for distributed water systems. Recently it was shown that adsorption induced water network rearrangement control adsorption energetics on the α-Al₂O₃ (012) surface. Here, we aim to elucidate the relative importance of the water network effects and surface cation identity on controlling selenate and sulfate adsorption energy using density functional theory calculations. Density functional theory (DFT) calculations predicted the adsorption energies of selenate and sulfate on nine transition metal cations (Sc–Cu) and two alkali metal cations (Ga and In) in the α-Al_s=2O₃ (012) surface under simulated acidic and neutral pH conditions. We find that the water network effects had a larger impact on the adsorption energy than the cationic identity. However, cation identity secondarily controlled adsorption. Most cations decreased the adsorption energy, weakening the overall performance, the larger Sc and In cations enabled inner-sphere adsorption in acidic conditions because they relaxed outward from the surface, providing more space for adsorption. Additionally, only Ti induced Se selectivity over S by reducing the adsorbing selenate to selenite but not reducing the sulfate. Overall, this study indicates that tuning water network structure will likely have a larger impact than tuning cation–selenate interactions for increasing adsorbate effectiveness.
Deep Denoising for Scientific Discovery: A Case Study in Electron Microscopy
- Abstract: Denoising is a fundamental challenge in scientific imaging. Deep convolutional neural networks (CNNs) provide the current state of the art in denoising photographic images. However, their potential has been inadequately explored for scientific imaging. Denoising CNNs are typically trained on clean images corrupted with artificial noise, but in scientific applications, noiseless ground-truth images are usually not available. To address this, we propose a simulation-based denoising (SBD) framework, in which CNNs are trained on simulated images. We test the framework on transmission electron microscopy (TEM) data, showing that it outperforms existing techniques on a simulated benchmark dataset, and on real data. We analyze the generalization capability of SBD, demonstrating that the trained networks are robust to variations of imaging parameters and of the underlying signal structure. Our results reveal that state-of-the-art architectures for denoising photographic images may not be well adapted to scientific-imaging data. For instance, substantially increasing their field-of-view dramatically improves their performance on TEM images acquired at low signal-to-noise ratios. We also demonstrate that standard performance metrics for photographs (such as peak signal-to-noise ratio) may not be scientifically meaningful, and propose several metrics to remedy this issue in the case of TEM images. In addition, we propose a technique, based on likelihood computations, to visualize the agreement between the structure of the denoised images and the observed data. Finally, we release a publicly available benchmark dataset containing 18,000 simulated TEM images.

Back to top.

Instrument Design & Fabrication

Large volume multianvil cell assembly for hydrothermal synthesis and conversions up to 6.5 GPa and 400°C
- Abstract: A multianvil cell assembly with octahedral edge length 25 mm has been adapted for high pressure investigations involving water-rich environments up to 6.5 GPa and 400°C. Water-rich samples are confined in Teflon containers with a volume up to 300 mm3. Applicability tests were performed between 250 and 400°C by investigating the transformation of amorphous titania particles close to the rutile–TiO2-II (∼5 GPa) phase boundary, and the transformation of amorphous silica particles close to the quartz–coesite (∼2.5 GPa) and coesite–stishovite (∼7 GPa) phase boundaries. The performed experiments employed 25.4 mm tungsten carbide anvils with a truncation edge length of 15 mm. The sample pressure at loads approaching 820 t was estimated to be around 6.5 GPa. The large volume multianvil cell is expected to have broad and varied application areas, ranging from the simulation of geofluids to hydrothermal synthesis and conversion/crystal growth in aqueous environments at gigapascal pressures.

Back to top.

Regenerative Medicine

Inflammasome modulation with P2X7 inhibitor A438079-loaded dressings for diabetic wound healing
- Abstract: The inflammasome is a multiprotein complex critical for the innate immune response to injury. Inflammasome activation initiates healthy wound healing, but comorbidities with poor healing, including diabetes, exhibit pathologic, sustained activation with delayed resolution that prevents healing progression. In prior work, we reported the allosteric P2X7 antagonist A438079 inhibits extracellular ATP-evoked NLRP3 signaling by preventing ion flux, mitochondrial reactive oxygen species generation, NLRP3 assembly, mature IL-1β release, and pyroptosis. However, the short half-life in vivo limits clinical translation of this promising molecule. Here, we develop a controlled release scaffold to deliver A438079 as an inflammasome-modulating wound dressing for applications in poorly healing wounds. We fabricated and characterized tunable thickness, long-lasting silk fibroin dressings and evaluated A438079 loading and release kinetics. We characterized A438079-loaded silk dressings in vitro by measuring IL-1β release and inflammasome assembly by perinuclear ASC speck formation. We further evaluated the performance of A438079-loaded silk dressings in a full-thickness model of wound healing in genetically diabetic mice and observed acceleration of wound closure by 10 days post-wounding with reduced levels of IL-1β at the wound edge. This work provides a proof-of-principle for translating pharmacologic inhibition of ATP-induced inflammation in diabetic wounds and represents a novel approach to therapeutically targeting a dysregulated mechanism in diabetic wound impairment.

Back to top.

Advanced Light Microscopy

Inflammasome modulation with P2X7 inhibitor A438079-loaded dressings for diabetic wound healing
- Abstract: The inflammasome is a multiprotein complex critical for the innate immune response to injury. Inflammasome activation initiates healthy wound healing, but comorbidities with poor healing, including diabetes, exhibit pathologic, sustained activation with delayed resolution that prevents healing progression. In prior work, we reported the allosteric P2X7 antagonist A438079 inhibits extracellular ATP-evoked NLRP3 signaling by preventing ion flux, mitochondrial reactive oxygen species generation, NLRP3 assembly, mature IL-1β release, and pyroptosis. However, the short half-life in vivo limits clinical translation of this promising molecule. Here, we develop a controlled release scaffold to deliver A438079 as an inflammasome-modulating wound dressing for applications in poorly healing wounds. We fabricated and characterized tunable thickness, long-lasting silk fibroin dressings and evaluated A438079 loading and release kinetics. We characterized A438079-loaded silk dressings in vitro by measuring IL-1β release and inflammasome assembly by perinuclear ASC speck formation. We further evaluated the performance of A438079-loaded silk dressings in a full-thickness model of wound healing in genetically diabetic mice and observed acceleration of wound closure by 10 days post-wounding with reduced levels of IL-1β at the wound edge. This work provides a proof-of-principle for translating pharmacologic inhibition of ATP-induced inflammation in diabetic wounds and represents a novel approach to therapeutically targeting a dysregulated mechanism in diabetic wound impairment.
Short term, low dose alpha-ketoglutarate based polymeric nanoparticles with methotrexate reverse rheumatoid arthritis symptoms in mice and modulate T helper cell responses
- Abstract: Activated effector T cells induce pro-inflammatory responses in rheumatoid arthritis (RA) which then lead to inflammation of the joints. In this report, we demonstrate that polymeric nanoparticles with alpha keto-glutarate (aKG) in their polymer backbone (termed as paKG NPs) modulate T cell responses in vitro and in vivo. Impressively, a low dose of only three administrations of methotrexate, a clinically and chronically administered drug for RA, in conjunction with two doses of paKG NPs, reversed arthritis symptoms in collagen-induced arthritis (CIA) mice. This was further followed by significant decreases in pro-inflammatory antigen-specific T helper type 17 (T_H17) responses and a significant increase in anti-inflammatory regulatory T cell (T_REG) responses when CIA treated splenic cells were isolated and re-exposed to the CIA self-antigen. Overall, this study supports the concurrent and short term, low dose of paKG NPs and methotrexate for the reversal of RA symptoms.

Back to top.

Flow Cytometry

BIG-TREE: Base-Edited Isogenic hPSC Line Generation Using a Transient Reporter for Editing Enrichment
- Summary: Current CRISPR-targeted single-nucleotide modifications and subsequent isogenic cell line generation in human pluripotent stem cells (hPSCs) require the introduction of deleterious double-stranded DNA breaks followed by inefficient homology-directed repair (HDR). Here, we utilize Cas9 deaminase base-editing technologies to co-target genomic loci and an episomal reporter to enable single-nucleotide genomic changes in hPSCs without HDR. Together, this method entitled base-edited isogenic hPSC line generation using a transient reporter for editing enrichment (BIG-TREE) allows for single-nucleotide editing efficiencies of >80% across multiple hPSC lines. In addition, we show that BIG-TREE allows for efficient generation of loss-of-function hPSC lines via introduction of premature stop codons. Finally, we use BIG-TREE to achieve efficient multiplex editing of hPSCs at several independent loci. This easily adoptable method will allow for the precise and efficient base editing of hPSCs for use in developmental biology, disease modeling, drug screening, and cell-based therapies.
Short term, low dose alpha-ketoglutarate based polymeric nanoparticles with methotrexate reverse rheumatoid arthritis symptoms in mice and modulate T helper cell responses
- Abstract: Activated effector T cells induce pro-inflammatory responses in rheumatoid arthritis (RA) which then lead to inflammation of the joints. In this report, we demonstrate that polymeric nanoparticles with alpha keto-glutarate (aKG) in their polymer backbone (termed as paKG NPs) modulate T cell responses in vitro and in vivo. Impressively, a low dose of only three administrations of methotrexate, a clinically and chronically administered drug for RA, in conjunction with two doses of paKG NPs, reversed arthritis symptoms in collagen-induced arthritis (CIA) mice. This was further followed by significant decreases in pro-inflammatory antigen-specific T helper type 17 (T_H17) responses and a significant increase in anti-inflammatory regulatory T cell (T_REG) responses when CIA treated splenic cells were isolated and re-exposed to the CIA self-antigen. Overall, this study supports the concurrent and short term, low dose of paKG NPs and methotrexate for the reversal of RA symptoms.

Back to top.

Ultrafast Laser Facility

Uracil-DNA glycosylase efficiency is modulated by substrate rigidity
- Abstract: Uracil DNA-glycosylase (UNG) is a base excision repair enzyme that removes the highly mutagenic uracil lesion from DNA by a base flipping mechanism. UNG excision efficiency depends on DNA sequence, yet the underlying principles that dictate UNG substrate specificity have remained elusive. Here, we show that UNG efficiency is dictated by the intrinsic local deformability of the substrate sequence around the uracil. UNG specificity constants (k_cat/K_M) and DNA flexibilities were measured for an engineered set of DNA substrates containing AUT, TUA, AUA, and TUA motifs. Time-resolved fluorescence spectroscopy, NMR imino proton exchange measurements, and molecular dynamics simulations of the bare DNA indicated significant differences in substrate flexibilities. A strong correlation between UNG efficiency and substrate flexibility was observed, with higher k_cat/K_M values measured for more flexible strands. DNA bending and base flipping were observed in simulations, with more frequent uracil flipping observed for the more bendable sequences. Experiments show that bases immediately adjacent to the uracil are allosterically coupled and have the greatest impact on substrate flexibility and resultant UNG activity. The finding that substrate flexibility controls UNG efficiency has implications in diverse fields, including the genesis of mutation hotspots, molecular evolution, and understanding sequence preferences of emerging base editors.
The PshX subunit of the photochemical reaction center from Heliobacterium modesticaldum acts as a low-energy antenna
- Abstract: The anoxygenic phototrophic bacterium Heliobacterium modesticaldum contains a photochemical reaction center protein complex (called the HbRC) consisting of a homodimer of the PshA polypeptide and two copies of a newly discovered polypeptide called PshX, which is a single transmembrane helix that binds two bacteriochlorophyll g molecules. To assess the function of PshX, we produced a ∆pshX strain of Hbt. modesticaldum by leveraging the endogenous Hbt. modesticaldum Type I-A CRISPR-Cas system to aid in mutant selection. We optimized this system by separating the homologous recombination and CRISPR-based selection steps into two plasmid transformations, allowing for markerless gene replacement. Fluorescence and low-temperature absorbance of the purified HbRC from the wild-type and ∆pshX strains showed that the bacteriochlorophylls bound by PshX have the lowest site energies in the entire HbRC. This indicates that PshX acts as a low-energy antenna subunit, participating in entropy-assisted uphill energy transfer toward the P₈₀₀ special bacteriochlorophyll g pair. We further discuss the role that PshX may play in stability of the HbRC, its conservation in other heliobacterial species, and the evolutionary pressure to produce and maintain single-TMH subunits in similar locations in other reaction centers.

Back to top.

Magnetic Resonance Research Center

Uracil-DNA glycosylase efficiency is modulated by substrate rigidity
- Abstract: Uracil DNA-glycosylase (UNG) is a base excision repair enzyme that removes the highly mutagenic uracil lesion from DNA by a base flipping mechanism. UNG excision efficiency depends on DNA sequence, yet the underlying principles that dictate UNG substrate specificity have remained elusive. Here, we show that UNG efficiency is dictated by the intrinsic local deformability of the substrate sequence around the uracil. UNG specificity constants (k_cat/K_M) and DNA flexibilities were measured for an engineered set of DNA substrates containing AUT, TUA, AUA, and TUA motifs. Time-resolved fluorescence spectroscopy, NMR imino proton exchange measurements, and molecular dynamics simulations of the bare DNA indicated significant differences in substrate flexibilities. A strong correlation between UNG efficiency and substrate flexibility was observed, with higher k_cat/K_M values measured for more flexible strands. DNA bending and base flipping were observed in simulations, with more frequent uracil flipping observed for the more bendable sequences. Experiments show that bases immediately adjacent to the uracil are allosterically coupled and have the greatest impact on substrate flexibility and resultant UNG activity. The finding that substrate flexibility controls UNG efficiency has implications in diverse fields, including the genesis of mutation hotspots, molecular evolution, and understanding sequence preferences of emerging base editors.

Back to top.