@article{smith_sawant_zeng_eldred_wu_greeley_gao_2024, title={Disproportionation chemistry in K<sub>2</sub>PtCl<sub>4</sub> visualized at atomic resolution using scanning transmission electron microscopy}, volume={10}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.adi0175}, abstractNote={
            The direct observation of a solid-state chemical reaction can reveal otherwise hidden mechanisms that control the reaction kinetics. However, probing the chemical bond breaking and formation at the molecular level remains challenging because of the insufficient spatial-temporal resolution and composition analysis of available characterization methods. Using atomic-resolution differential phase-contrast imaging in scanning transmission electron microscopy, we have visualized the decomposition chemistry of K
            2
            PtCl
            4
            to identify its transient intermediate phases and their interfaces that characterize the chemical reduction process. The crystalline structure of K
            2
            PtCl
            4
            is found to undergo a disproportionation reaction to form K
            2
            PtCl
            6
            , followed by gradual reduction to crystalline Pt metal and KCl. By directly imaging different Pt─Cl bond configurations and comparing them to models predicted via density functional theory calculations, a causal connection between the initial and final states of a chemical reaction is established, showcasing new opportunities to resolve reaction pathways through atomistic experimental visualization.
          }, number={6}, journal={SCIENCE ADVANCES}, author={Smith, Jacob G. and Sawant, Kaustubh J. and Zeng, Zhenhua and Eldred, Tim B. and Wu, Jianbo and Greeley, Jeffrey P. and Gao, Wenpei}, year={2024}, month={Feb} }
 @misc{chao_venkatraman_moniri_jiang_tang_dai_gao_miao_chi_2023, title={<i>In Situ</i> and Emerging Transmission Electron Microscopy for Catalysis Research}, volume={123}, ISSN={["1520-6890"]}, DOI={10.1021/acs.chemrev.2c00880}, abstractNote={Catalysts are the primary facilitator in many dynamic processes. Therefore, a thorough understanding of these processes has vast implications for a myriad of energy systems. The scanning/transmission electron microscope (S/TEM) is a powerful tool not only for atomic-scale characterization but also in situ catalytic experimentation. Techniques such as liquid and gas phase electron microscopy allow the observation of catalysts in an environment conducive to catalytic reactions. Correlated algorithms can greatly improve microscopy data processing and expand multidimensional data handling. Furthermore, new techniques including 4D-STEM, atomic electron tomography, cryogenic electron microscopy, and monochromated electron energy loss spectroscopy (EELS) push the boundaries of our comprehension of catalyst behavior. In this review, we discuss the existing and emergent techniques for observing catalysts using S/TEM. Challenges and opportunities highlighted aim to inspire and accelerate the use of electron microscopy to further investigate the complex interplay of catalytic systems.}, number={13}, journal={CHEMICAL REVIEWS}, author={Chao, Hsin-Yun and Venkatraman, Kartik and Moniri, Saman and Jiang, Yongjun and Tang, Xuan and Dai, Sheng and Gao, Wenpei and Miao, Jianwei and Chi, Miaofang}, year={2023}, month={Jul}, pages={8347–8394} }
 @article{smith_huang_gao_zhang_chi_2023, title={Atomic Resolution Cryogenic 4D-STEM Imaging via Robust Distortion Correction}, ISSN={["1936-086X"]}, DOI={10.1021/acsnano.2c12777}, abstractNote={Cryogenic four-dimensional scanning transmission electron microscopy (4D-STEM) imaging is a useful technique for studying quantum materials and their interfaces by simultaneously probing charge, lattice, spin, and chemistry on the atomic scale with the sample held at temperatures ranging from room to cryogenic. However, its applications are currently limited by the instabilities of cryo-stages and electronics. To overcome this challenge, we develop an algorithm to effectively correct the complex distortions present in atomic resolution cryogenic 4D-STEM data sets. This method uses nonrigid registration to identify localized distortions in a 4D-STEM and relate them to an undistorted experimental STEM image, followed by a series of affine transformations for distortion corrections. This method allows a minimum loss of information in both reciprocal and real spaces, enabling the reconstruction of sample information from 4D-STEM data sets. This method is computationally cheap, fast, and applicable for on-the-fly data analysis in future in situ cryogenic 4D-STEM experiments.}, journal={ACS NANO}, author={Smith, Jacob and Huang, Zhennan and Gao, Wenpei and Zhang, Guannan and Chi, Miaofang}, year={2023}, month={Jun} }
 @article{johnson_yang_liu_zhou_zuo_dickie_wang_gao_anaclet_perras_et al._2023, title={Nanocluster superstructures assembled via surface ligand switching at high temperature}, volume={2}, ISSN={["2731-0582"]}, DOI={10.1038/s44160-023-00304-8}, abstractNote={Superstructures with nanoscale building blocks, when coupled with precise control of the constituent units, open opportunities in rationally designing and manufacturing desired functional materials. Yet, synthetic strategies for the large-scale production of superstructures are scarce. We report a scalable and generalized approach to synthesizing superstructures assembled from atomically precise Ce24O28(OH)8 and other rare-earth metal-oxide nanoclusters alongside a detailed description of the self-assembly mechanism. Combining operando small-angle X-ray scattering, ex situ molecular and structural characterizations, and molecular dynamics simulations indicates that a high-temperature ligand-switching mechanism, from oleate to benzoate, governs the formation of the nanocluster assembly. The chemical tuning of surface ligands controls superstructure disassembly and reassembly, and furthermore, enables the synthesis of multicomponent superstructures. This synthetic approach, and the accurate mechanistic understanding, are promising for the preparation of superstructures for use in electronics, plasmonics, magnetics and catalysis. Synthesizing superstructures with precisely controlled nanoscale building blocks is challenging. Here the assembly of superstructures is reported from atomically precise Ce24O28(OH)8 and other rare-earth metal-oxide nanoclusters and their multicomponent combinations. A high-temperature ligand-switching mechanism controls the self-assembly.}, number={9}, journal={NATURE SYNTHESIS}, author={Johnson, Grayson and Yang, Moon Young and Liu, Chang and Zhou, Hua and Zuo, Xiaobing and Dickie, Diane A. and Wang, Sihan and Gao, Wenpei and Anaclet, Bukuru and Perras, Frederic A. and et al.}, year={2023}, month={Sep}, pages={828–837} }
 @article{chi_ou_eldred_gao_kwon_murray_dreyer_butera_foucher_ambaye_et al._2023, title={Strain-tunable Berry curvature in quasi-two-dimensional chromium telluride}, volume={14}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-023-38995-4}, abstractNote={Abstract}, number={1}, journal={NATURE COMMUNICATIONS}, author={Chi, Hang and Ou, Yunbo and Eldred, Tim B. and Gao, Wenpei and Kwon, Sohee and Murray, Joseph and Dreyer, Michael and Butera, Robert E. and Foucher, Alexandre C. and Ambaye, Haile and et al.}, year={2023}, month={Jun} }
 @article{wei_johnson_ye_cui_yu_ran_cai_liu_chen_gao_et al._2023, title={Surfactants Used in Colloidal Synthesis Modulate Ni Nanoparticle Surface Evolution for Selective CO2 Hydrogenation}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.3c02739}, abstractNote={Colloidal chemistry holds promise to prepare uniform and size-controllable pre-catalysts; however, it remains a challenge to unveil the atomic-level transition from pre-catalysts to active catalytic surfaces under the reaction conditions to enable the mechanistic design of catalysts. Here, we report an ambient-pressure X-ray photoelectron spectroscopy study, coupled with in situ environmental transmission electron microscopy, infrared spectroscopy, and theoretical calculations, to elucidate the surface catalytic sites of colloidal Ni nanoparticles for CO2 hydrogenation. We show that Ni nanoparticles with phosphine ligands exhibit a distinct surface evolution compared with amine-capped ones, owing to the diffusion of P under oxidative (air) or reductive (CO2 + H2) gaseous environments at elevated temperatures. The resulting NiPx surface leads to a substantially improved selectivity for CO production, in contrast to the metallic Ni, which favors CH4. The further elimination of surface metallic Ni sites by designing multi-step P incorporation achieves unit selectivity of CO in high-rate CO2 hydrogenation.}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Wei, Xiangru and Johnson, Grayson and Ye, Yifan and Cui, Meiyang and Yu, Shen-Wei and Ran, Yihua and Cai, Jun and Liu, Zhi and Chen, Xi and Gao, Wenpei and et al.}, year={2023}, month={Jun} }
 @article{gao_wang_corolla_eldred_bose_gao_li_2022, title={Alkali metal halide-coated perovskite redox catalysts for anaerobic oxidative dehydrogenation of n-butane}, volume={8}, ISSN={["2375-2548"]}, url={https://doi.org/10.1126/sciadv.abo7343}, DOI={10.1126/sciadv.abo7343}, abstractNote={
            Oxidative dehydrogenation (ODH) of
            n
            -butane has the potential to efficiently produce butadiene without equilibrium limitation or coke formation. Despite extensive research efforts, single-pass butadiene yields are limited to <23% in conventional catalytic ODH with gaseous O
            2
            . This article reports molten LiBr as an effective promoter to modify a redox-active perovskite oxide, i.e., La
            0.8
            Sr
            0.2
            FeO
            3
            (LSF), for chemical looping–oxidative dehydrogenation of
            n
            -butane (CL-ODHB). Under the working state, the redox catalyst is composed of a molten LiBr layer covering the solid LSF substrate. Characterizations and ab initio molecular dynamics (AIMD) simulations indicate that peroxide species formed on LSF react with molten LiBr to form active atomic Br, which act as reaction intermediates for C─H bond activation. Meanwhile, molten LiBr layer inhibits unselective CO
            2
            formation, leading to 42.5% butadiene yield. The redox catalyst design strategy can be extended to CL-ODH of other light alkanes such as
            iso
            -butane conversion to
            iso
            -butylene, providing a generalized approach for olefin production.
          }, number={30}, journal={SCIENCE ADVANCES}, author={Gao, Yunfei and Wang, Xijun and Corolla, Noel and Eldred, Tim and Bose, Arnab and Gao, Wenpei and Li, Fanxing}, year={2022}, month={Jul} }
 @article{wang_eldred_smith_gao_2022, title={AutoDisk: Automated diffraction processing and strain mapping in 4D-STEM}, volume={236}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2022.113513}, abstractNote={Development in lattice strain mapping using four-dimensional scanning transmission electron microscopy (4D-STEM) method now offers improved precision and feasibility. However, automatic and accurate diffraction analysis is still challenging due to noise and the complexity of intensity in diffraction patterns. In this work, we demonstrate an approach, employing the blob detection on cross-correlated diffraction patterns followed by a lattice fitting algorithm, to automate the processing of four-dimensional data, including identifying and locating disks, and extracting local lattice parameters without prior knowledge about the material. The approach is both tested using simulated diffraction patterns and applied on experimental data acquired from a Pd@Pt core-shell nanoparticle. Our method shows robustness against various sample thicknesses and high noise, capability to handle complex patterns, and picometer-scale accuracy in strain measurement, making it a promising tool for high-throughput 4D-STEM data processing.}, journal={ULTRAMICROSCOPY}, author={Wang, Sihan and Eldred, Tim B. and Smith, Jacob G. and Gao, Wenpei}, year={2022}, month={Jun} }
 @article{witharamage_christudasjustus_smith_gao_gupta_2022, title={Corrosion behavior of an in situ consolidated nanocrystalline Al-V alloy}, volume={6}, ISSN={["2397-2106"]}, url={https://doi.org/10.1038/s41529-022-00225-5}, DOI={10.1038/s41529-022-00225-5}, abstractNote={Abstract}, number={1}, journal={NPJ MATERIALS DEGRADATION}, author={Witharamage, C. S. and Christudasjustus, J. and Smith, J. and Gao, W. and Gupta, R. K.}, year={2022}, month={Feb} }
 @article{eldred_smith_gao_2022, title={Polarization fluctuation of BaTiO3 at unit cell level mapped by four-dimensional scanning transmission electron microscopy}, volume={40}, ISSN={["1520-8559"]}, DOI={10.1116/6.0001451}, abstractNote={Diffraction analysis in four-dimensional scanning transmission electron microscopy now enables the mapping of local structures including symmetry, strain, and polarization of materials. However, measuring the distribution of these configurations at the unit cell level remains a challenge because most analysis methods require the diffraction disks to be separated, limiting the electron probe sizes to be larger than a unit cell. Here, we show improved spatial resolution in mapping the polarization displacement and phases of BaTiO3 sampled at a rate equivalent to the size of the projected unit cells using 4D-STEM. This improvement in spatial resolution is accomplished by masking out the overlapping regions in partially overlapped convergent beam electron diffraction patterns. By reducing the probe size to the order of single projected unit cells in size, the measurement shows local fluctuation within the nanosized rhombohedral domains in tetragonal phased BaTiO3, indicating the origin of phase transition and evolution across different length scales.}, number={1}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Eldred, Tim B. and Smith, Jacob G. and Gao, Wenpei}, year={2022}, month={Jan} }
 @article{addiego_gao_huyan_pan_2022, title={Probing charge density in materials with atomic resolution in real space}, volume={12}, ISSN={["2522-5820"]}, DOI={10.1038/s42254-022-00541-4}, journal={NATURE REVIEWS PHYSICS}, author={Addiego, Christopher and Gao, Wenpei and Huyan, Huaixun and Pan, Xiaoqing}, year={2022}, month={Dec} }
 @article{narayan_joshi_smith_gao_weber_narayan_2022, title={Q-carbon as a new radiation-resistant material}, volume={186}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2021.10.006}, abstractNote={We have discovered that Q-carbon is extremely resistant to radiation damage under ion irradiations involving extreme atomic displacements and electronic excitations. Using 5 MeV Au + ions, the Q-carbon films on sapphire substrates were irradiated in the dose range 3.3–10 dpa (displacements-per-atom). After the ion irradiations, detailed studies on the atomic structure and bonding characteristics showed that atomic structure and bonding characteristics of amorphous Q-carbon remained essentially unchanged to 10 dpa of radiation damage, which is equivalent to over twenty years of neutron damage in a conventional reactor. There was an ion-beam mixed layer below the Q-carbon layer, whose thickness increased from 5 nm to 10 nm, as the dose increased from 3.3 to 10 dpa. This layer was found to be mostly amorphous with a mixture Al2O3 and Al4C3. This layer, formed as a result of enhanced forward scattering and ballistic ion beam mixing, exhibited composition consistent with detailed TRIM calculations. We also found that nanodiamonds (3 nm average size) embedded in Q-carbon grew to about 60 nm after 6.6 dpa and shrank to about 40 nm after 10 dpa. We discuss the mechanism for the growth and shrinkage of metastable phase of diamond under nonequilibrium ion irradiations.}, journal={CARBON}, author={Narayan, J. and Joshi, P. and Smith, J. and Gao, W. and Weber, W. J. and Narayan, R. J.}, year={2022}, month={Jan}, pages={253–261} }
 @article{su_chen_xu_eldred_smith_dellarova_wang_gao_2022, title={Visualizing the Formation of High-Entropy Fluorite Oxides from an Amorphous Precursor at Atomic Resolution}, volume={12}, ISSN={["1936-086X"]}, DOI={10.1021/acsnano.2c09760}, abstractNote={High-entropy oxides (HEOs) have a large tuning space in composition and crystal structures, offering the possibility for improved material properties in applications including catalysis, energy storage, and thermal barrier coatings. Understanding the nucleation and growth mechanisms of HEOs at the atomic scale is critical to the design of their structure and functions but remains challenging. Herein, we visualize the entire formation process of a high-entropy fluorite oxide from a polymeric precursor using atomic resolution in situ gas-phase scanning transmission electron microscopy. The results show a four-stage formation mechanism, including nucleation during the oxidation of a polymeric precursor below 400 °C, diffusive grain growth below 900 °C, liquid-phase-assisted compositional homogenization under a "state of supercooling" at 900 °C, and entropy-driven recrystallization and stabilization at higher temperatures. The atomistic insights are critical for the rational synthesis of HEOs with controlled grain sizes and morphologies and thus the related properties.}, journal={ACS NANO}, author={Su, Lei and Chen, Xi and Xu, Liang and Eldred, Tim and Smith, Jacob and DellaRova, Cierra and Wang, Hongjie and Gao, Wenpei}, year={2022}, month={Dec} }
 @article{gao_elnabawy_hood_shi_wang_roling_pan_mavrikakis_xia_chi_2021, title={Atomistic insights into the nucleation and growth of platinum on palladium nanocrystals}, volume={12}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-021-23290-x}, abstractNote={Abstract}, number={1}, journal={NATURE COMMUNICATIONS}, author={Gao, Wenpei and Elnabawy, Ahmed O. and Hood, Zachary D. and Shi, Yifeng and Wang, Xue and Roling, Luke T. and Pan, Xiaoqing and Mavrikakis, Manos and Xia, Younan and Chi, Miaofang}, year={2021}, month={Jun} }
 @article{wang_sun_brady_fleischmann_eldred_gao_wang_jiang_augustyn_2021, title={Fast Proton Insertion in Layered H2W2O7 via Selective Etching of an Aurivillius Phase}, volume={11}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202003335}, abstractNote={Abstract}, number={1}, journal={ADVANCED ENERGY MATERIALS}, author={Wang, Ruocun and Sun, Yangyunli and Brady, Alexander and Fleischmann, Simon and Eldred, Tim B. and Gao, Wenpei and Wang, Hsiu-Wen and Jiang, De-en and Augustyn, Veronica}, year={2021}, month={Jan} }
 @article{morgan_andie m. o'connell_jansson_peterson_mahle_eldred_gao_parsons_2021, title={Stretchable and Multi-Metal-Organic Framework Fabrics Via High-Yield Rapid Sorption-Vapor Synthesis and Their Application in Chemical Warfare Agent Hydrolysis}, volume={13}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.1c07366}, DOI={10.1021/acsami.1c07366}, abstractNote={Protocols to create metal-organic framework (MOF)/polymer composites for separation, chemical capture, and catalytic applications currently rely on relatively slow solution-based processing to form single MOF composites. Here, we report a rapid, high-yield sorption-vapor method for direct simultaneous growth of single and multiple MOF materials onto untreated flexible and stretchable polymer fibers and films. The synthesis utilizes favorable reactant absorption into polymers coupled with rapid vapor-driven MOF crystallization to form high surface area (>250 m2/gcomposite) composites, including UiO-66-NH2, HKUST-1, and MOF-525 on spandex, nylon, and other fabrics. The resulting composites are robust and maintain their functionality even after stretching. Stretchable MOF fabrics enable rapid solid-state hydrolysis of the highly toxic chemical warfare agent soman and paraoxon-methyl simulant. We show that this approach can readily be scaled by solution spray-coating of MOF precursors and to large area substrates.}, number={26}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Morgan, Sarah E. and Andie M. O'Connell and Jansson, Anton and Peterson, Gregory W. and Mahle, John J. and Eldred, Tim B. and Gao, Wenpei and Parsons, Gregory N.}, year={2021}, month={Jul}, pages={31279–31284} }