Yecun Wu

All Publications

• Quadruple the rate capability of high-energy batteries through a porous current collector design NATURE ENERGY Ye, Y., Xu, R., Huang, W., Ai, H., Zhang, W., Affeld, J., Cui, A., Liu, F., Gao, X., Chen, Z., Li, T., Xiao, X., Zhang, Z., Peng, Y., Vila, R. A., Wu, Y., Oyakhire, S. T., Kuwajima, H., Suzuki, Y., Matsumoto, R., Masuda, Y., Yuuki, T., Nakayama, Y., Cui, Y. 2024

  View details for DOI 10.1038/s41560-024-01473-2

  View details for Web of Science ID 001177787600002

• Interlayer engineering of Fe3GeTe2: From 3D superlattice to 2D monolayer. Proceedings of the National Academy of Sciences of the United States of America Wu, Y., Wang, B. Y., Yu, Y., Li, Y., Ribeiro, H. B., Wang, J., Xu, R., Liu, Y., Ye, Y., Zhou, J., Ke, F., Harbola, V., Heinz, T. F., Hwang, H. Y., Cui, Y. 2024; 121 (4): e2314454121

  Abstract

  The discoveries of ferromagnetism down to the atomically thin limit in van der Waals (vdW) crystals by mechanical exfoliation have enriched the family of magnetic thin films [C. Gong et al., Nature 546, 265-269 (2017) and B. Huang et al., Nature 546, 270-273 (2017)]. However, compared to the study of traditional magnetic thin films by physical deposition methods, the toolbox of the vdW crystals based on mechanical exfoliation and transfer suffers from low yield and ambient corrosion problem and now is facing new challenges to study magnetism. For example, the formation of magnetic superlattice is difficult in vdW crystals, which limits the study of the interlayer interaction in vdW crystals [M. Gibertini, M. Koperski, A. F. Morpurgo, K. S. Novoselov, Nat. Nanotechnol. 14, 408-419 (2019)]. Here, we report a strategy of interlayer engineering of the magnetic vdW crystal Fe3GeTe2 (FGT) by intercalating quaternary ammonium cations into the vdW spacing. Both three-dimensional (3D) vdW superlattice and two-dimensional (2D) vdW monolayer can be formed by using this method based on the amount of intercalant. On the one hand, the FGT superlattice shows a strong 3D critical behavior with a decreased coercivity and increased domain wall size, attributed to the co-engineering of the anisotropy, exchange interaction, and electron doping by intercalation. On the other hand, the 2D vdW few layers obtained by over-intercalation are capped with organic molecules from the bulk crystal, which not only enhances the ferromagnetic transition temperature (TC), but also substantially protects the thin samples from degradation, thus allowing the preparation of large-scale FGT ink in ambient environment.

  View details for DOI 10.1073/pnas.2314454121

  View details for PubMedID 38232283

• Twisted epitaxy of gold nanodisks grown between twisted substrate layers of molybdenum disulfide. Science (New York, N.Y.) Cui, Y., Wang, J., Li, Y., Wu, Y., Been, E., Zhang, Z., Zhou, J., Zhang, W., Hwang, H. Y., Sinclair, R., Cui, Y. 2024; 383 (6679): 212-219

  Abstract

  We expand the concept of epitaxy to a regime of "twisted epitaxy" with the epilayer crystal orientation between two substrates influenced by their relative orientation. We annealed nanometer-thick gold (Au) nanoparticles between two substrates of exfoliated hexagonal molybdenum disulfide (MoS2) with varying orientation of their basal planes with a mutual twist angle ranging from 0° to 60°. Transmission electron microscopy studies show that Au aligns midway between the top and bottom MoS2 when the twist angle of the bilayer is small (<~7°). For larger twist angles, Au has only a small misorientation with the bottom MoS2 that varies approximately sinusoidally with twist angle of the bilayer MoS2. Four-dimensional scanning transmission electron microscopy analysis further reveals a periodic strain variation (<|±0.5%|) in the Au nanodisks associated with the twisted epitaxy, consistent with the Moiré registry of the two MoS2 twisted layers.

  View details for DOI 10.1126/science.adk5947

  View details for PubMedID 38207038

• Angle-selective thermal emitter for directional radiative cooling and heating JOULE Zhou, J., Chen, T. G., Tsurimaki, Y., Hajj-Ahmad, A., Fan, L., Peng, Y., Xu, R., Wu, Y., Assawaworrarit, S., Fan, S., Cutkosky, M. R., Cui, Y. 2023; 7 (12)

  View details for DOI 10.1016/j.joule.2023.10.013

  View details for Web of Science ID 001142770900001

• Ultrahigh-loading Manganese-based Electrode for Aqueous Battery via Polymorph Tuning. Advanced materials (Deerfield Beach, Fla.) Xiao, X., Zhang, Z., Wu, Y., Xu, J., Gao, X., Xu, R., Huang, W., Ye, Y., Oyakhire, S. T., Zhang, P., Chen, B., Cevik, E., Asiri, S. M., Bozkurt, A., Amine, K., Cui, Y. 2023: e2211555

  Abstract

  Manganese-based aqueous batteries utilizing Mn2+ /MnO2 redox reactions are promising choices for grid-scale energy storage due to their high theoretical specific capacity, high power capability, low-cost, and intrinsic safety with water-based electrolytes. However, the application of such systems is hindered by the insulating nature of deposited MnO2 , resulting in low normalized areal loading (0.0050.05 mAh cm-2 ) during charge/discharge cycle. In this work, we investigated the electrochemical performance of various MnO2 polymorphs in Mn2+ /MnO2 redox reactions and determined ɛ-MnO2 with low conductivity to be the primary electrochemically deposited phase in normal acidic aqueous electrolyte. We found that increasing the temperature can change the deposited phase from ɛ-MnO2 with low conductivity to gamma-MnO2 with two orders of magnitude increase in conductivity. We demonstrated that the highly conductive gamma-MnO2 could be effectively exploited for ultrahigh areal loading electrode, and a normalized areal loading of 33 mAh cm-2 was achieved. At a mild temperature of 50 °C, cells were cycled with an ultrahigh areal loading of 20 mAh cm-2 (1-2 orders of magnitude higher than previous studies) for over 200 cycles with only 13% capacity loss. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/adma.202211555

  View details for PubMedID 37149287

• Onboard early detection and mitigation of lithium plating in fast-charging batteries. Nature communications Huang, W., Ye, Y., Chen, H., Vilá, R. A., Xiang, A., Wang, H., Liu, F., Yu, Z., Xu, J., Zhang, Z., Xu, R., Wu, Y., Chou, L. Y., Wang, H., Xu, J., Boyle, D. T., Li, Y., Cui, Y. 2022; 13 (1): 7091

  Abstract

  Fast-charging is considered as one of the most desired features needed for lithium-ion batteries to accelerate the mainstream adoption of electric vehicles. However, current battery charging protocols mainly consist of conservative rate steps to avoid potential hazardous lithium plating and its associated parasitic reactions. A highly sensitive onboard detection method could enable battery fast-charging without reaching the lithium plating regime. Here, we demonstrate a novel differential pressure sensing method to precisely detect the lithium plating event. By measuring the real-time change of cell pressure per unit of charge (dP/dQ) and comparing it with the threshold defined by the maximum of dP/dQ during lithium-ion intercalation into the negative electrode, the onset of lithium plating before its extensive growth can be detected with high precision. In addition, we show that by integrating this differential pressure sensing into the battery management system (BMS), a dynamic self-regulated charging protocol can be realized to effectively extinguish the lithium plating triggered by low temperature (0 °C) while the conventional static charging protocol leads to catastrophic lithium plating at the same condition. We propose that differential pressure sensing could serve as an early nondestructive diagnosis method to guide the development of fast-charging battery technologies.

  View details for DOI 10.1038/s41467-022-33486-4

  View details for PubMedID 36402759

• Vacuum insulation arrays as damage-resilient thermal superinsulation materials for energy saving JOULE Zhou, J., Peng, Y., Xu, J., Wu, Y., Huang, Z., Xiao, X., Cui, Y. 2022; 6 (10): 2358-2371

  View details for DOI 10.1016/j.joule.2022.07.015

  View details for Web of Science ID 000880294900015

• Electrostatic gating and intercalation in 2D materials NATURE REVIEWS MATERIALS Wu, Y., Li, D., Wu, C., Hwang, H. Y., Cui, Y. 2022

  View details for DOI 10.1038/s41578-022-00473-6

  View details for Web of Science ID 000847996800001

• Cold-Starting All-Solid-State Batteries from Room Temperature by Thermally Modulated Current Collector in Sub-Minute. Advanced materials (Deerfield Beach, Fla.) Ye, Y., Huang, W., Xu, R., Xiao, X., Zhang, W., Chen, H., Wan, J., Liu, F., Lee, H. K., Xu, J., Zhang, Z., Peng, Y., Wang, H., Gao, X., Wu, Y., Zhou, G., Cui, Y. 2022: e2202848

  Abstract

  All-solid-state batteries (ASSBs) show great potential as high-energy and high-power energy storage devices but their attainable energy/power density at room temperature is severely reduced because of the sluggish kinetics of lithium-ion transport. Here we first reported a thermally modulated current collector (TMCC), which can rapidly cold-start ASSBs from room temperature to operating temperatures (70∼90 °C) in less than one minute, and simultaneously enhance the transient peak power density by 15-fold compared to one without heating. This TMCC is prepared by integrating a uniform, ultrathin (∼200 nm) nickel layer as a thermal modulator within an ultralight polymer-based current collector. By isolating the thermal modulator from the ion/electron pathway of ASSBs, it can provide fast, stable heat control yet does not interfere with regular battery operation. Moreover, this ultrathin (13.2 μm) TMCC effectively shortens the heat transfer pathway, minimizes heat losses, and mitigates the formation of local hot spots. The simulated heating energy consumption can be as low as ∼3.94% of total battery energy. This TMCC design with good tunability opens new frontiers towards smart energy storage devices in the future from the current collector perspective. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/adma.202202848

  View details for PubMedID 35762033

• Heat Conductor-Insulator Transition in Electrochemically Controlled Hybrid Superlattices. Nano letters Zhou, J., Wu, Y., Kwon, H., Li, Y., Xiao, X., Ye, Y., Ma, Y., Goodson, K. E., Hwang, H. Y., Cui, Y. 2022

  Abstract

  Designing materials with ultralow thermal conductivity has broad technological impact, from thermal protection to energy harvesting. Low thermal conductivity is commonly observed in anharmonic and strongly disordered materials, yet a microscopic understanding of the correlation to atomic motion is often lacking. Here we report that molecular insertion into an existing two-dimensional layered lattice structure creates a hybrid superlattice with extremely low thermal conductivity. Vibrational characterization and ab initio molecular dynamics simulations reveal strong damping of transverse acoustic waves and significant softening of longitudinal vibrations. Together with spectral correlation analysis, we demonstrate that the molecular insertion creates liquid-like atomic motion in the existing lattice framework, causing a large suppression of heat conduction. The hybrid materials can be transformed into solution-processable coatings and used for thermal protection in wearable electronics. Our work provides a generic mechanism for the design of heat insulators and may further facilitate the engineering of heat conduction based on understanding atomic correlations.

  View details for DOI 10.1021/acs.nanolett.2c01407

  View details for PubMedID 35715219

• Observation of an intermediate state during lithium intercalation of twisted bilayer MoS2. Nature communications Wu, Y., Wang, J., Li, Y., Zhou, J., Wang, B. Y., Yang, A., Wang, L., Hwang, H. Y., Cui, Y. 2022; 13 (1): 3008

  Abstract

  Lithium intercalation of MoS2 is generally believed to introduce a phase transition from H phase (semiconducting) to T phase (metallic). However, during the intercalation process, a spatially sharp boundary is usually formed between the fully intercalated T phase MoS2 and non-intercalated H phase MoS2. The intermediate state, i.e., lightly intercalated H phase MoS2 without a phase transition, is difficult to investigate by optical-microscope-based spectroscopy due to the narrow size. Here, we report the stabilization of the intermediate state across the whole flake of twisted bilayer MoS2. The twisted bilayer system allows the lithium to intercalate from the top surface and enables fast Li-ion diffusion by the reduced interlayer interaction. The E2g Raman mode of the intermediate state shows a peak splitting behavior. Our simulation results indicate that the intermediate state is stabilized by lithium-induced symmetry breaking of the H phase MoS2. Our results provide an insight into the non-uniform intercalation during battery charging and discharging, and also open a new opportunity to modulate the properties of twisted 2D systems with guest species doping in the Moire structures.

  View details for DOI 10.1038/s41467-022-30516-z

  View details for PubMedID 35637182

• Capturing the swelling of solid-electrolyte interphase in lithium metal batteries. Science (New York, N.Y.) Zhang, Z., Li, Y., Xu, R., Zhou, W., Li, Y., Oyakhire, S. T., Wu, Y., Xu, J., Wang, H., Yu, Z., Boyle, D. T., Huang, W., Ye, Y., Chen, H., Wan, J., Bao, Z., Chiu, W., Cui, Y. 1800; 375 (6576): 66-70

  Abstract

  [Figure: see text].

  View details for DOI 10.1126/science.abi8703

  View details for PubMedID 34990230

• Dynamic spatial progression of isolated lithium during battery operations. Nature Liu, F., Xu, R., Wu, Y., Boyle, D. T., Yang, A., Xu, J., Zhu, Y., Ye, Y., Yu, Z., Zhang, Z., Xiao, X., Huang, W., Wang, H., Chen, H., Cui, Y. 1800; 600 (7890): 659-663

  Abstract

  The increasing demand for next-generation energy storage systems necessitates the development of high-performance lithium batteries1-3. Unfortunately, current Li anodes exhibit rapid capacity decay and a short cycle life4-6, owing to the continuous generation of solid electrolyte interface7,8 and isolated Li (i-Li)9-11. The formation of i-Li during the nonuniform dissolution of Li dendrites12 leads to a substantial capacity loss in lithium batteries under most testing conditions13. Because i-Li loses electrical connection with the current collector, it has been considered electrochemically inactive or 'dead' in batteries14,15. Contradicting this commonly accepted presumption, here we show that i-Li is highly responsive to battery operations, owing to its dynamic polarization to the electric field in the electrolyte. Simultaneous Li deposition and dissolution occurs on two ends of the i-Li, leading to its spatial progression toward the cathode (anode) during charge (discharge). Revealed by our simulation results, the progression rate of i-Li is mainly affected by its length, orientation and the applied current density. Moreover, we successfully demonstrate the recovery of i-Li in Cu-Li cells with >100% Coulombic efficiency and realize LiNi0.5Mn0.3Co0.2O2 (NMC)-Li full cells with extended cycle life.

  View details for DOI 10.1038/s41586-021-04168-w

  View details for PubMedID 34937896

• Designing a Nanoscale Three-phase Electrochemical Pathway to Promote Pt-catalyzed Formaldehyde Oxidation. Nano letters Xu, J., Xiao, X., Zhang, Z., Wu, Y., Boyle, D. T., Lee, H. K., Huang, W., Li, Y., Wang, H., Li, J., Zhu, Y., Chen, B., Mitch, W., Cui, Y. 2020

  Abstract

  Gas-phase heterogeneous catalysis is a process spatially constrained on the two-dimensional surface of a solid catalyst. Here, we introduce a new toolkit to open up the third dimension. We discovered that the activity of a solid catalyst can be dramatically promoted by covering its surface with a nanoscale-thin layer of liquid electrolyte while maintaining efficient delivery of gas reactants, a strategy we call three-phase catalysis. Introducing the liquid electrolyte converts the original surface catalytic reaction into an electrochemical pathway with mass transfer facilitated by free ions in a three-dimensional space. We chose the oxidation of formaldehyde as a model reaction and observed a 25000-times enhancement in the turnover frequency of Pt in three-phase catalysis as compared to conventional heterogeneous catalysis. We envision three-phase catalysis as a new dimension for catalyst design and anticipate its applications in more chemical reactions from pollution control to the petrochemical industry.

  View details for DOI 10.1021/acs.nanolett.0c03560

  View details for PubMedID 33201720

• Revealing and Elucidating ALD-Derived Control of Lithium Plating Microstructure ADVANCED ENERGY MATERIALS Oyakhire, S. T., Huang, W., Wang, H., Boyle, D. T., Schneider, J. R., de Paula, C., Wu, Y., Cui, Y., Bent, S. F. 2020

  View details for DOI 10.1002/aenm.202002736

  View details for Web of Science ID 000578514900001

• Supercooled liquid sulfur maintained in three-dimensional current collector for high-performance Li-S batteries. Science advances Zhou, G., Yang, A., Gao, G., Yu, X., Xu, J., Liu, C., Ye, Y., Pei, A., Wu, Y., Peng, Y., Li, Y., Liang, Z., Liu, K., Wang, L. W., Cui, Y. 2020; 6 (21)

  Abstract

  In lithium-sulfur (Li-S) chemistry, the electrically/ionically insulating nature of sulfur and Li2S leads to sluggish electron/ion transfer kinetics for sulfur species conversion. Sulfur and Li2S are recognized as solid at room temperature, and solid-liquid phase transitions are the limiting steps in Li-S batteries. Here, we visualize the distinct sulfur growth behaviors on Al, carbon, Ni current collectors and demonstrate that (i) liquid sulfur generated on Ni provides higher reversible capacity, faster kinetics, and better cycling life compared to solid sulfur; and (ii) Ni facilitates the phase transition (e.g., Li2S decomposition). Accordingly, light-weight, 3D Ni-based current collector is designed to control the deposition and catalytic conversion of sulfur species toward high-performance Li-S batteries. This work provides insights on the critical role of the current collector in determining the physical state of sulfur and elucidates the correlation between sulfur state and battery performance, which will advance electrode designs in high-energy Li-S batteries.

  View details for DOI 10.1126/sciadv.aay5098

  View details for PubMedID 32937326

• Tortuosity Effects in Lithium-Metal Host Anodes JOULE Chen, H., Pei, A., Wan, J., Lin, D., Vila, R., Wang, H., Mackanic, D., Steinruck, H., Huang, W., Li, Y., Yang, A., Xie, J., Wu, Y., Wang, H., Cui, Y. 2020; 4 (4): 938–52

  View details for DOI 10.1016/j.joule.2020.03.008

  View details for Web of Science ID 000527264500022

• Theoretical Calculation Guided Design of Single-Atom Catalysts toward Fast Kinetic and Long-Life Li-S Batteries. Nano letters Zhou, G. n., Zhao, S. n., Wang, T. n., Yang, S. Z., Johannessen, B. n., Chen, H. n., Liu, C. n., Ye, Y. n., Wu, Y. n., Peng, Y. n., Liu, C. n., Jiang, S. P., Zhang, Q. n., Cui, Y. n. 2020

  Abstract

  Lithium-sulfur (Li-S) batteries are promising next-generation energy storage technologies due to their high theoretical energy density, environmental friendliness, and low cost. However, low conductivity of sulfur species, dissolution of polysulfides, poor conversion from sulfur reduction, and lithium sulfide (Li2S) oxidation reactions during discharge-charge processes hinder their practical applications. Herein, under the guidance of density functional theory calculations, we have successfully synthesized large-scale single atom vanadium catalysts seeded on graphene to achieve high sulfur content (80 wt % sulfur), fast kinetic (a capacity of 645 mAh g-1 at 3 C rate), and long-life Li-S batteries. Both forward (sulfur reduction) and reverse reactions (Li2S oxidation) are significantly improved by the single atom catalysts. This finding is confirmed by experimental results and consistent with theoretical calculations. The ability of single metal atoms to effectively trap the dissolved lithium polysulfides (LiPSs) and catalytically convert the LiPSs/Li2S during cycling significantly improved sulfur utilization, rate capability, and cycling life. Our work demonstrates an efficient design pathway for single atom catalysts and provides solutions for the development of high energy/power density Li-S batteries.

  View details for DOI 10.1021/acs.nanolett.9b04719

  View details for PubMedID 31887051

• Supercooled liquid sulfur maintained in three-dimensional current collector for high-performance Li-S batteries. Science advances Zhou, G. n., Yang, A. n., Gao, G. n., Yu, X. n., Xu, J. n., Liu, C. n., Ye, Y. n., Pei, A. n., Wu, Y. n., Peng, Y. n., Li, Y. n., Liang, Z. n., Liu, K. n., Wang, L. W., Cui, Y. n. 2020; 6 (21): eaay5098

  Abstract

  In lithium-sulfur (Li-S) chemistry, the electrically/ionically insulating nature of sulfur and Li2S leads to sluggish electron/ion transfer kinetics for sulfur species conversion. Sulfur and Li2S are recognized as solid at room temperature, and solid-liquid phase transitions are the limiting steps in Li-S batteries. Here, we visualize the distinct sulfur growth behaviors on Al, carbon, Ni current collectors and demonstrate that (i) liquid sulfur generated on Ni provides higher reversible capacity, faster kinetics, and better cycling life compared to solid sulfur; and (ii) Ni facilitates the phase transition (e.g., Li2S decomposition). Accordingly, light-weight, 3D Ni-based current collector is designed to control the deposition and catalytic conversion of sulfur species toward high-performance Li-S batteries. This work provides insights on the critical role of the current collector in determining the physical state of sulfur and elucidates the correlation between sulfur state and battery performance, which will advance electrode designs in high-energy Li-S batteries.

  View details for DOI 10.1126/sciadv.aay5098

  View details for PubMedID 32494732

  View details for PubMedCentralID PMC7244266

• Electrochemical generation of liquid and solid sulfur on two-dimensional layered materials with distinct areal capacities Nature Nanotechnology Yang, A., Zhou, G., et al 2020

  View details for DOI 10.1038/s41565-019-0624-6

• Electrochemical generation of liquid and solid sulfur on two-dimensional layered materials with distinct areal capacities. Nature nanotechnology Yang, A. n., Zhou, G. n., Kong, X. n., Vilá, R. A., Pei, A. n., Wu, Y. n., Yu, X. n., Zheng, X. n., Wu, C. L., Liu, B. n., Chen, H. n., Xu, Y. n., Chen, D. n., Li, Y. n., Fakra, S. n., Hwang, H. Y., Qin, J. n., Chu, S. n., Cui, Y. n. 2020

  Abstract

  It has recently been shown that sulfur, a solid material in its elementary form S8, can stay in a supercooled state as liquid sulfur in an electrochemical cell. We establish that this newly discovered state could have implications for lithium-sulfur batteries. Here, through in situ studies of electrochemical sulfur generation, we show that liquid (supercooled) and solid elementary sulfur possess very different areal capacities over the same charging period. To control the physical state of sulfur, we studied its growth on two-dimensional layered materials. We found that on the basal plane, only liquid sulfur accumulates; by contrast, at the edge sites, liquid sulfur accumulates if the thickness of the two-dimensional material is small, whereas solid sulfur nucleates if the thickness is large (tens of nanometres). Correlating the sulfur states with their respective areal capacities, as well as controlling the growth of sulfur on two-dimensional materials, could provide insights for the design of future lithium-sulfur batteries.

  View details for DOI 10.1038/s41565-019-0624-6

  View details for PubMedID 31988508

• Fast lithium growth and short circuit induced by localized-temperature hotspots in lithium batteries. Nature communications Zhu, Y., Xie, J., Pei, A., Liu, B., Wu, Y., Lin, D., Li, J., Wang, H., Chen, H., Xu, J., Yang, A., Wu, C., Wang, H., Chen, W., Cui, Y. 2019; 10 (1): 2067

  Abstract

  Fast-charging and high-energy-density batteries pose significant safety concerns due to high rates of heat generation. Understanding how localized high temperatures affect the battery is critical but remains challenging, mainly due to the difficulty of probing battery internal temperature with high spatial resolution. Here we introduce a method to induce and sense localized high temperature inside a lithium battery using micro-Raman spectroscopy. We discover that temperature hotspots can induce significant lithium metal growth as compared to the surrounding lower temperature area due to the locally enhanced surface exchange current density. More importantly, localized high temperature can be one of the factors to cause battery internal shorting, which further elevates the temperature and increases the risk of thermal runaway. This work provides important insights on the effects of heterogeneous temperatures within batteries and aids the development of safer batteries, thermal management schemes, and diagnostic tools.

  View details for PubMedID 31061393

• A Two-Dimensional MoS2 Catalysis Transistor by Solid-State Ion Gating Manipulation and Adjustment (SIGMA). Nano letters Wu, Y. n., Ringe, S. n., Wu, C. L., Chen, W. n., Yang, A. n., Chen, H. n., Tang, M. n., Zhou, G. n., Hwang, H. Y., Chan, K. n., Cui, Y. n. 2019

  Abstract

  A variety of methods including tuning chemical compositions, structures, crystallinity, defects and strain, and electrochemical intercalation have been demonstrated to enhance the catalytic activity. However, none of these tuning methods provide direct dynamical control during catalytic reactions. Here we propose a new method to tune the activity of catalysts through solid-state ion gating manipulation and adjustment (SIGMA) using a catalysis transistor. SIGMA can electrostatically dope the surface of catalysts with a high electron concentration over 5 × 1013 cm-2 and thus modulate both the chemical potential of the reaction intermediates and their electrical conductivity. The hydrogen evolution reaction (HER) on both pristine and defective MoS2 were investigated as model reactions. Our theoretical and experimental results show that the overpotential at 10 mA/cm2 and Tafel slope can be in situ, continuously, dynamically, and reversibly tuned over 100 mV and around 100 mV/dec, respectively.

  View details for DOI 10.1021/acs.nanolett.9b02888

  View details for PubMedID 31499003

• Ultra-sensitive graphene based mid-infrared plasmonic bio-chemical sensing using dielectric beads as a medium CARBON Liu, X., Zhang, D., Wu, Y., Yang, M., Wang, Q., Coileain, C. O., Xu, H., Yang, C., Abid, M., Abid, M., Liu, H., Chun, B., Shi, Q., Wu, H. 2017; 122: 404-410

  View details for DOI 10.1016/j.carbon.2017.06.089

  View details for Web of Science ID 000407394200045

• Simultaneous large continuous band gap tunability and photoluminescence enhancement in GaSe nanosheets via elastic strain engineering NANO ENERGY Wu, Y., Fuh, H., Zhang, D., Coileain, C. O., Xu, H., Cho, J., Choi, M., Chung, B., Jiang, X., Abid, M., Abid, M., Liu, H., Wang, J., Shvets, I. V., Chang, C., Wu, H. 2017; 32: 157-164

  View details for DOI 10.1016/j.nanoen.2016.12.034

  View details for Web of Science ID 000397003700018

• Quantum Confinement and Gas Sensing of Mechanically Exfoliated GaSe ADVANCED MATERIALS TECHNOLOGIES Wu, Y., Zhang, D., Lee, K., Duesberg, G. S., Syrlybekov, A., Liu, X., Abid, M., Abid, M., Liu, Y., Zhang, L., Coileain, C. O., Xu, H., Cho, J., Choi, M., Chun, B., Wang, H., Liu, H., Wu, H. 2017; 2 (1)

  View details for DOI 10.1002/admt.201600197

  View details for Web of Science ID 000398998700013

• Pushing the Performance Limit of Sub-100 nm Molybdenum Disulfide Transistors NANO LETTERS Liu, Y., Guo, J., Wu, Y., Zhu, E., Weiss, N. O., He, Q., Wu, H., Cheng, H., Xu, Y., Shakir, I., Huang, Y., Duan, X. 2016; 16 (10): 6337-6342

  Abstract

  Two-dimensional semiconductors (2DSCs) such as molybdenum disulfide (MoS2) have attracted intense interest as an alternative electronic material in the postsilicon era. However, the ON-current density achieved in 2DSC transistors to date is considerably lower than that of silicon devices, and it remains an open question whether 2DSC transistors can offer competitive performance. A high current device requires simultaneous minimization of the contact resistance and channel length, which is a nontrivial challenge for atomically thin 2DSCs, since the typical low contact resistance approaches for 2DSCs either degrade the electronic properties of the channel or are incompatible with the fabrication process for short channel devices. Here, we report a new approach toward high-performance MoS2 transistors by using a physically assembled nanowire as a lift-off mask to create ultrashort channel devices with pristine MoS2 channel and self-aligned low resistance metal/graphene hybrid contact. With the optimized contact in short channel devices, we demonstrate sub-100 nm MoS2 transistor delivering a record high ON-current of 0.83 mA/μm at 300 K and 1.48 mA/μm at 20 K, which compares well with that of silicon devices. Our study, for the first time, demonstrates that the 2DSC transistors can offer comparable performance to the 2017 target for silicon transistors in International Technology Roadmap for Semiconductors (ITRS), marking an important milestone in 2DSC electronics.

  View details for DOI 10.1021/acs.nanolett.6b02713

  View details for Web of Science ID 000385469800050

  View details for PubMedID 27579678

• Filter-based compressed sensing MRI reconstruction INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY Wu, Y., Du, H., Mei, W. 2016; 26 (3): 173-178

  View details for DOI 10.1002/ima.22171

  View details for Web of Science ID 000383475300001

• Surface enhanced Raman scattering of monolayer MX2 with metallic nano particles SCIENTIFIC REPORTS Zhang, D., Wu, Y., Yang, M., Liu, X., Coileain, C. O., Abid, M., Abid, M., Wang, J., Shvets, I., Xu, H., Chun, B., Liu, H., Wu, H. 2016; 6: 30320

  Abstract

  Monolayer transition metal dichalcogenides MX2 (M = Mo, W; X = S) exhibit remarkable electronic and optical properties, making them candidates for application within flexible nano-optoelectronics. The ability to achieve a high optical signal, while quantitatively monitoring strain in real-time is the key requirement for applications in flexible sensing and photonics devices. Surface-enhanced Raman scattering (SERS) allows us to achieve both simultaneously. However, the SERS depends crucially on the size and shape of the metallic nanoparticles (NPs), which have a large impact on its detection sensitivity. Here, we investigated the SERS of monolayer MX2, with particular attention paid to the effect of the distribution of the metallic NPs. We show that the SERS depends crucially on the distribution of the metallic NPs and also the phonon mode of the MX2. Moreover, strong coupling between MX2 and metallic NPs, through surface plasmon excitation, results in splitting of the and modes and an additional peak becomes apparent. For a WS2-Ag system the intensity of the additional peak increases exponentially with local strain, which opens another interesting window to quantitatively measure the local strain using SERS. Our experimental study may be useful for the application of monolayer MX2 in flexible nano-optoelectronics.

  View details for DOI 10.1038/srep30320

  View details for Web of Science ID 000380197000001

  View details for PubMedID 27457808

  View details for PubMedCentralID PMC4960528

• Probing thermal expansion coefficients of monolayers using surface enhanced Raman scattering RSC ADVANCES Zhang, D., Wu, Y., Yang, M., Liu, X., Coileain, C. O., Xu, H., Abid, M., Abid, M., Wang, J., Shvets, I. V., Liu, H., Wang, Z., Yin, H., Liu, H., Chun, B., Zhang, X., Wu, H. 2016; 6 (101): 99053-99059

  View details for DOI 10.1039/c6ra20623a

  View details for Web of Science ID 000387427800060

• Enhanced Shubnikov-De Haas Oscillation in Nitrogen-Doped Graphene ACS NANO Wu, H., Abid, M., Wu, Y., Coileain, C. O., Syrlybekov, A., Han, J., Heng, C., Liu, H., Abid, M., Shvets, I. 2015; 9 (7): 7207-7214

  Abstract

  N-doped graphene displays many interesting properties compared with pristine graphene, which makes it a potential candidate in many applications. Here, we report that the Shubnikov-de Haas (SdH) oscillation effect in graphene can be enhanced by N-doping. We show that the amplitude of the SdH oscillation increases with N-doping and reaches around 5k Ω under a field of 14 T at 10 K for highly N-doped graphene, which is over 1 order of magnitude larger than the value found for pristine graphene devices with the same geometry. Moreover, in contrast to the well-established standard Lifshitz-Kosevich theory, the amplitude of the SdH oscillation decreases linearly with increasing temperature and persists up to a temperature of 150 K. Our results also show that the magnetoresistance (MR) in N-doped graphene increases with increasing temperature. Our results may be useful for the application of N-doped graphene in magnetic devices.

  View details for DOI 10.1021/acsnano.5b02020

  View details for Web of Science ID 000358823200057

  View details for PubMedID 26061979

• Electrical-field-driven metal-insulator transition tuned with self-aligned atomic defects NANOSCALE Syrlybekov, A., Wu, H., Mauit, O., Wu, Y., Maguire, P., Khalid, A., Coileain, C. O., Farrell, L., Heng, C., Abid, M., Liu, H., Yang, L., Zhang, H., Shvets, I. V. 2015; 7 (33): 14055-14061

  Abstract

  Recently, significant attention has been paid to the resistance switching (RS) behaviour in Fe3O4 and it was explained through the analogy of the electrically driven metal-insulator transition based on the quantum tunneling theory. Here, we propose a method to experimentally support this explanation and provide a way to tune the critical switching parameter by introducing self-aligned localized impurities through the growth of Fe3O4 thin films on stepped SrTiO3 substrates. Anisotropic behavior in the RS was observed, where a lower switching voltage in the range of 10(4) V cm(-1) is required to switch Fe3O4 from a high conducting state to a low conducting state when the electrical field is applied along the steps. The anisotropic RS behavior is attributed to a high density array of anti-phase boundaries (APBs) formed at the step edges and thus are aligned along the same direction in the film which act as a train of hotspot forming conduits for resonant tunneling. Our experimental studies open an interesting window to tune the electrical-field-driven metal-insulator transition in strongly correlated systems.

  View details for DOI 10.1039/c5nr03251b

  View details for Web of Science ID 000359546900030

  View details for PubMedID 26239065

• Mimicking the effect of gravity using an elastic membrane EUROPEAN JOURNAL OF PHYSICS Wu, Y., Zhu, C., Wang, Y., Shi, Q. 2014; 35 (3)

  View details for DOI 10.1088/0143-0807/35/3/035010

  View details for Web of Science ID 000334662200010