52 results on '"Jianguo Wen"'
Search Results
2. Visualizing the Effect of Oxidation on Magnetic Domain Behavior of Nanoscale Fe3GeTe2 for Applications in Spintronics
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Yue Li, Xiaobing Hu, Arash Fereidouni, Rabindra Basnet, Krishna Pandey, Jianguo Wen, Yuzi Liu, Hong Zheng, Hugh O. H. Churchill, Jin Hu, Amanda K. Petford-Long, and Charudatta Phatak
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General Materials Science - Published
- 2023
3. Stabilizing a Li–Mn–O Cathode by Blocking Lattice O Migration through a Nanoscale Phase Complex
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Weiyuan Huang, Mingjian Zhang, Mingyuan Ge, Shunning Li, Lin Xie, Zhefeng Chen, Gang Wang, Junhao Lin, Jimin Qiu, Lei Yu, Jianguo Wen, Guo-Xi Ren, Cong Lin, Wenguang Zhao, Haibiao Chen, and Feng Pan
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Fuel Technology ,Renewable Energy, Sustainability and the Environment ,Chemistry (miscellaneous) ,Materials Chemistry ,Energy Engineering and Power Technology - Published
- 2023
4. Effect of Siderophore DFOB on U(VI) Adsorption to Clay Mineral and Its Subsequent Reduction by an Iron-Reducing Bacterium
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Limin Zhang, Hailiang Dong, Runjie Li, Dong Liu, Liang Bian, Yu Chen, Zezhen Pan, Maxim I. Boyanov, Kenneth M. Kemner, Jianguo Wen, Qingyin Xia, Hongyu Chen, Edward J. O’Loughlin, Guanyu Wang, Ying Huang, Qingyin Xia, Jianguo Wen, and Zezhen Pan
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siderophore DFOB ,Minerals ,Iron ,Siderophores ,Fe(III) reduction ,General Chemistry ,Ferric Compounds ,U(VI) reduction ,Clay ,Uranium ,Environmental Chemistry ,Adsorption ,Ferrous Compounds ,nontronite ,Shewanella putrefaciens CN32 ,Oxidation-Reduction - Abstract
Uranium mining and nuclear fuel production have led to significant U contamination. Past studies have focused on the bioreduction of soluble U(VI) to insoluble U(IV) as a remediation method. However, U(IV) is susceptible to reoxidation and remobilization when conditions change. Here, we demonstrate that a combination of adsorption and bioreduction of U(VI) in the presence of an organic ligand (siderophore desferrioxamine B, DFOB) and the Fe-rich clay mineral nontronite partially alleviated this problem. DFOB greatly facilitated U(VI) adsorption into the interlayer of nontronite as a stable U(VI)-DFOB complex. This complex was likely reduced by bioreduction intermediates such as the Fe(II)-DFOB complex and/or through electron transfer within a ternary Fe(II)-DFOB-U(VI) complex. Bioreduction with DFOB alone resulted in a mobile aqueous U(IV)-DFOB complex, but in the presence of both DFOB and nontronite U(IV) was sequestered into a solid. These results provide novel insights into the mechanisms of U(VI) bioreduction and the stability of U and have important implications for understanding U biogeochemistry in the environment and for developing a sustainable U remediation approach.
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- 2022
5. A New Cathode Material for a Li–O2 Battery Based on Lithium Superoxide
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Samuel T. Plunkett, Alireza Kondori, Duck Young Chung, Jianguo Wen, Mark Wolfman, Saul H. Lapidus, Yang Ren, Rachid Amine, Khalil Amine, Anil U. Mane, Mohammad Asadi, Said Al-Hallaj, Brian P. Chaplin, Kah Chun Lau, Hsien-Hau Wang, and Larry A. Curtiss
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Fuel Technology ,Renewable Energy, Sustainability and the Environment ,Chemistry (miscellaneous) ,Materials Chemistry ,Energy Engineering and Power Technology - Published
- 2022
6. Lithium-Ion Battery Materials as Tunable, 'Redox Non-Innocent' Catalyst Supports
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Alon Chapovetsky, Robert M. Kennedy, Ryan Witzke, Evan C. Wegener, Fulya Dogan, Prajay Patel, Magali Ferrandon, Jens Niklas, Oleg G. Poluektov, Ning Rui, Sanjaya D. Senanayake, José A. Rodriguez, Nestor J. Zaluzec, Lei Yu, Jianguo Wen, Christopher Johnson, Cynthia J. Jenks, A. Jeremy Kropf, Cong Liu, Massimiliano Delferro, and David M. Kaphan
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General Chemistry ,Catalysis - Abstract
The development of general strategies for the electronic tuning of a catalyst’s active site is an ongoing challenge in heterogeneous catalysis. To this end, herein we describe the application of Li-ion battery cathode and anode materials as redox non-innocent catalyst supports that can be continuously modulated as a function of lithium intercalation. A zero-valent nickel complex was oxidatively grafted onto the surface of lithium manganese oxide (LixMn2O4) to yield isolated Ni(II) occupying the vacant interstitial octahedral site in the Li diffusion channel on the surface and subsurface of the spinel structure (Ni/LixMn2O4). The activity of Ni/LixMn2O4 for olefin hydrogenation, as a representative probe reaction, was found to increase monotonically as a function of support reductive lithiation. Simulation of Ni/LixMn2O4 reveals the dramatic impact of surface redox states on the viability of the homolytic oxidative addition mechanism for H2 activation. Catalyst control through support lithiation was extended to an organotantalum complex on LixTiO2, demonstrating the generality of this phenomenon.
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- 2022
7. Magnetic Effect of Dopants on Bright and Dark Excitons in Strongly Confined Mn-Doped CsPbI3 Quantum Dots
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Yulin Lin, Xiaohan Liu, Jinwoo Cheon, Tian Qiao, Dong Hee Son, Jianguo Wen, Mohit Khurana, Alexey V. Akimov, and Daniel Rossi
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Materials science ,Dopant ,Condensed matter physics ,Condensed Matter::Other ,Mechanical Engineering ,Exciton ,Relaxation (NMR) ,Bioengineering ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Polaron ,Magnetic field ,Ion ,Photoexcitation ,Condensed Matter::Materials Science ,Quantum dot ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science - Abstract
We investigated the magnetic effect of Mn2+ ions on an exciton of Mn-doped CsPbI3 quantum dots (QDs), where we looked for the signatures of an exciton magnetic polaron known to produce a large effective magnetic field in Mn-doped CdSe QDs. In contrast to Mn-doped CdSe QDs that can produce ∼100 T of magnetic field upon photoexcitation, manifested as a large change in the energy and relaxation dynamics of a bright exciton, Mn-doped CsPbI3 QDs exhibited little influence of a magnetic dopant on the behavior of a bright exciton. However, a μs-lived dark exciton in CsPbI3 QDs showed 40% faster decay in the presence of Mn2+, equivalent to the effect of ∼3 T of an external magnetic field. While further study is necessary to fully understand the origin of the large difference in the magneto-optic property of an exciton in two systems, we consider that the difference in antiferromagnetic coupling of the dopants is an important contributing factor.
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- 2021
8. Superconductivity in Y4RuGe8 with a Vacancy-Ordered CeNiSi2-Type Superstructure
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Jianguo Wen, Jin-Ke Bao, Jidong Samuel Jiang, Sander van Smaalen, Mercouri G. Kanatzidis, Duck Young Chung, Daniel E. Bugaris, Sitaram Ramakrishnan, Huihuo Zheng, Gang Cao, and Hao Zheng
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Superconductivity ,Materials science ,Condensed matter physics ,General Chemical Engineering ,Vacancy defect ,Materials Chemistry ,General Chemistry ,Type (model theory) ,Superstructure (condensed matter) - Published
- 2021
9. Valence Effects of Fe Impurity for Recovered LiNi0.6Co0.2Mn0.2O2 Cathode Materials
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Yan Wang, Jianguo Wen, Yangtao Liu, Yulin Lin, Yadong Zheng, Panawan Vanaphuti, Jinzhao Fu, Xiaotu Ma, Mengyuan Chen, Zhenzhen Yang, Ruihan Zhang, and Zeyi Yao
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Valence (chemistry) ,Materials science ,Condensed matter physics ,Impurity ,law ,Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,Cathode ,law.invention - Published
- 2021
10. Identifying Support Effects in Au-Catalyzed CO Oxidation
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Scott M. Tatro, Louisa Savereide, Zachary R. Mansley, Emily Cheng, Ryan J. Paull, Kenneth R. Poeppelmeier, Laurence D. Marks, Jianguo Wen, Justin M. Notestein, Emily P. Greenstein, and Abha Gosavi
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Materials science ,General Chemistry ,Electronic structure ,Photochemistry ,Catalysis - Published
- 2021
11. New Compounds and Phase Selection of Nickel Sulfides via Oxidation State Control in Molten Hydroxides
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Duck Young Chung, Hyowon Park, David J. Mandia, Xiuquan Zhou, Lei Yu, Andrey A. Yakovenko, Mahalingam Balasubramanian, Mercouri G. Kanatzidis, and Jianguo Wen
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Absorption spectroscopy ,Chemistry ,Intercalation (chemistry) ,General Chemistry ,Antibonding molecular orbital ,Biochemistry ,Catalysis ,symbols.namesake ,Colloid and Surface Chemistry ,X-ray photoelectron spectroscopy ,Oxidation state ,symbols ,Physical chemistry ,Density functional theory ,van der Waals force ,Ternary operation - Abstract
Molten salts are promising reaction media candidates for the discovery of novel materials; however, they offer little control over oxidation state compared to aqueous solutions. Here, we demonstrated that when two hydroxides are mixed, their melts become fluxes with tunable solubility, which are surprisingly powerful solvents for ternary chalcogenides and offer effective paths for crystal growth to new compounds. We report that precise control of the oxidation state of Ni is achievable in mixed molten LiOH/KOH to grow single crystals of all known ternary K-Ni-S compounds. It is also possible to access several new phases, including a new polytope of β-K2Ni3S4, as well as low-valence KNi4S2 and K4Ni9S11. KNi4S2 is a two-dimensional low-valence nickel-rich sulfide, and β-K2Ni3S4 has a hexagonal lattice. Moreover, using KNi4S2 as a template, we obtained a new layered binary Ni2S by topotactic deintercalation of K. The new binary Ni2S has a van der Waals gap and can function as a new host layer for intercalation chemistry, as demonstrated by the intercalation of LiOH between its layers. The oxidation states of low-valence KNi4S2 and Ni2S were studied using X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. Density functional theory calculations showed large antibonding interactions at the Fermi level for both KNi4S2 and Ni2S, corresponding to the flat-bands with large Ni-dx2-y2 character.
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- 2021
12. Stabilized Lithium, Manganese-Rich Layered Cathode Materials Enabled by Integrating Co-Doping and Nanocoating
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Jinzhao Fu, Yan Wang, Xiaotu Ma, Panawan Vanaphuti, Jianguo Wen, Yulin Lin, Yangtao Liu, and Zhenzhen Yang
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Materials science ,chemistry.chemical_element ,02 engineering and technology ,Manganese ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,Atomic layer deposition ,Chemical engineering ,chemistry ,Coating ,law ,engineering ,Ionic conductivity ,General Materials Science ,Lithium ,0210 nano-technology ,Dissolution - Abstract
While lithium, manganese-rich (LMR) layered oxide cathode materials offer high energy density (>900 Wh kg-1) and low cost, LMR is susceptible to continuous capacity and voltage decay from the oxygen migration and side reaction with aqueous electrolyte at high voltage. Herein, the integration of Na/F co-doping (CD) and AlF3 coating on LMR is achieved without the need of complex atomic layer deposition. Akin to pristine and CD samples, CD with 1 wt % AlF3 (CD-1.0 wt %) shows excellent electrochemical performance with the capacity and voltage retentions of 93 and 91% after 150 cycles at 0.5C, respectively, and increased ionic conductivity. Spectroscopic analysis indicates that the coating mainly influences the Co distribution, where Co is enriched on the surface, and partial diffusion of Al3+ ions toward the bulk, leading to a slight change of transition-metal (TM) valence states at the nanometer scale and the formation of a stable Lix(CoAl)Oy phase. Post-cycling analysis reveals that CD-1.0 wt % can alleviate the formation of rock-salt structure and Mn dissolution. Besides, little to no metal segregation is detected for the cycled CD-1.0 wt % sample. This finding presents the first instance to apply co-doping and AlF3 coating as a new strategy to enhance the structural homogeneity and takes another step toward their commercial viability.
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- 2021
13. Process Engineering to Increase the Layered Phase Concentration in the Immediate Products of Flame Spray Pyrolysis
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Yulin Lin, Jianguo Wen, Jun Lu, Joseph A. Libera, Lei Yu, Kyojin Ku, Yujia Liang, and Eungje Lee
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Materials science ,020209 energy ,Nucleation ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Combustion ,Cathode ,Adiabatic flame temperature ,law.invention ,Chemical engineering ,chemistry ,law ,Phase (matter) ,0202 electrical engineering, electronic engineering, information engineering ,Degradation (geology) ,General Materials Science ,Lithium ,0210 nano-technology ,Thermal spraying - Abstract
Flame-spray-pyrolysis (FSP) is a robust and scalable process to synthesize particles at the commodity-scale. FSP has been used to produce the precursor powders which were converted to the layered structure (R3m phase) by a postannealing step in making nickel-rich cathode materials (NCMs). Theoretically, the high flame temperature (normally >1500 K) in FSP can provide adequate energy for the phase conversion from rock-salt to layered structures and potentially enables one-step synthesis. However, the high flame temperature is a critical issue to cause lithium loss and structural degradation, preventing the formation of the layered phase. In this work, guided by the gaseous nucleation theory, we implemented several FSP processes with different solution recipes. The layered phase concentration in the as-burned products can be increased with the solution enthalpies. By adding a rapid quench step to suppress the lithium loss and phase degradation, the layered phase can be further increased. This work contributes new ideas to innovating process regarding the process efficiency and throughput of manufacturing cathode materials at a large scale.
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- 2021
14. Plasmon-enhanced Catalytic Ozonation for Efficient Removal of Recalcitrant Water Pollutants
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Lei Yu, Steve M. Heald, Muntaseer Bunian, Wenwen Yang, Tingting Wu, Jianguo Wen, Yu Lei, and Xiankun Chen
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Spinel ferrite ,Catalytic ozonation ,Materials science ,Chemical engineering ,Water pollutants ,General Medicine ,Surface plasmon resonance ,Plasmon ,Catalysis - Abstract
Ag-Doped MnFe2O4 catalyst (Ag/MnFe2O4) was synthesized by a simple sol–gel method followed by H2 reduction. Utilizing the localized surface plasmon resonance (LSPR) of Ag, ∼35-fold and ∼7-fold degr...
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- 2021
15. Intermediate Sr2Co1.5Fe0.5O6−δ Tetragonal Structure between Perovskite and Brownmillerite as a Model Catalyst with Layered Oxygen Deficiency for Enhanced Electrochemical Water Oxidation
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Gibin George, Yulin Lin, Carlos D. Posada, Sivasankara Rao Ede, William Ratcliff, Jianguo Wen, Candyce N. Collins, Hui Wu, Shubo Han, and Zhiping Luo
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Materials science ,Hydrogen ,010405 organic chemistry ,Oxide ,Oxygen evolution ,chemistry.chemical_element ,General Chemistry ,engineering.material ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Tetragonal crystal system ,Chemical engineering ,chemistry ,engineering ,Brownmillerite ,Water splitting ,Perovskite (structure) - Abstract
The generation of hydrogen in an environmentally benign way is highly essential to meet future energy demands. However, in the process of splitting water electrochemically, sluggish kinetics of the...
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- 2021
16. Effects of Superparamagnetic Iron Nanoparticles on Electrocatalysts for the Reduction of Oxygen
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Wei Gao, Charles E. Schulz, Talha Al-Zoubi, Duan Luo, Jianguo Wen, Andrew A. Gewirth, Angela M. DiAscro, and Hong Yang
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Nanostructure ,010405 organic chemistry ,fungi ,Nanoparticle ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Oxygen ,0104 chemical sciences ,Inorganic Chemistry ,Metal ,chemistry ,Chemical engineering ,visual_art ,visual_art.visual_art_medium ,Density functional theory ,Physical and Theoretical Chemistry ,Pyrolysis ,Carbon ,Superparamagnetism - Abstract
It is of great research interest to understand the nanostructures contributing to the activity observed in the reduction of oxygen by non-platinum group metal (PGM) electrocatalysts in acidic media. Iron- and nitrogen-containing carbon networks are often the most studied structures, among which single-atom iron-coordinated nitrogen (FeNx) moieties have often been proposed to be the structures leading to the high activity in these non-PGM electrocatalysts. Iron nanoparticles embedded within a carbon support are also formed under certain conditions as a result of the synthetic processes in making non-PGM electrocatalysts. In this study, we present a study to understand the oxygen reduction reaction (ORR) activity of prepared iron- and nitrogen-containing non-PGM electrocatalysts obtained through the pyrolysis of metal-organic framework (MOF) precursors. We studied the structure-property relationship among nanostructures made from the MOF precursor ZIF-8 under different pyrolysis conditions. Density functional theory calculations were used to explain the effect of structural moieties on the ORR activity. Our results suggest that iron-coordinated C-N structures and iron nanoparticles act synergistically to catalyze the ORR.
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- 2021
17. Discovery of Gold Nanoparticles in Marcellus Shale
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Seungyeol Lee, Hongwu Xu, Huifang Xu, Jianguo Wen, and Jenelle Wempner
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Atmospheric Science ,Colloid ,Materials science ,Chemical engineering ,Space and Planetary Science ,Geochemistry and Petrology ,Colloidal gold ,Marcellus shale ,Nanoparticle ,Oil shale - Abstract
A high density of gold (Au) nanoparticles has been observed on the surfaces of the coexisting opal nanospheres in kerogen-bearing shales from the Marcellus Formation. Our analyses of the Au nanopar...
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- 2021
18. Complex Fluorine Chemical Potential Effects on the Shape and Compositional Heterogeneity of KTa1–xNbxO3 Nanoparticles
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Tiffany Ly, Laurence D. Marks, and Jianguo Wen
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General Energy ,Chemical engineering ,chemistry ,Fluorine ,Nanoparticle ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
When kinetic conditions dominate and dictate the growth in a nanoparticle synthesis, properties of the synthesis environment can have considerable effects on the properties of the products. Such ef...
- Published
- 2020
19. Predicting Morphological Evolution during Coprecipitation of MnCO3 Battery Cathode Precursors Using Multiscale Simulations Aided by Targeted Synthesis
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Xiaoping Wang, Jiajun Chen, Juan C. Garcia, Venkat Srinivasan, Arturo Gutierrez, Ilke Arslan, Jianguo Wen, Hakim Iddir, Pallab Barai, and Timothy T. Fister
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Battery (electricity) ,Materials science ,Coprecipitation ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,Chemical engineering ,Cathode material ,law ,Materials Chemistry ,0210 nano-technology - Abstract
The performance of lithium-ion batteries is intimately linked to both the structure and the morphology of the cathode material, which in turn is critically linked to the synthesis conditions. Howev...
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- 2020
20. Chemisorption-Driven Roughening of Hydrothermally Grown KTa1–xNbxO3 Nanoparticles
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Laurence D. Marks, Tiffany Ly, and Jianguo Wen
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General Energy ,Morphology (linguistics) ,Materials science ,Chemical engineering ,Chemisorption ,Nanoparticle ,Physical and Theoretical Chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
The chemical and physical properties of nanoparticle surfaces have significant effects on their growth processes and resulting morphology. Hydrothermally grown KNbO3, KTaO3, and KTa1-xNbxO3 were st...
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- 2020
21. Activation of Low-Valent, Multiply M–M Bonded Group VI Dimers toward Catalytic Olefin Metathesis via Surface Organometallic Chemistry
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David M. Kaphan, Gokhan Celik, Jacob White, Prachi Sharma, A. Jeremy Kropf, Magali Ferrandon, Hacksung Kim, Alon Chapovetsky, Navneet Singh Khetrapal, Marek Pruski, Massimiliano Delferro, Alfred P. Sattelberger, Evan C. Wegener, Frédéric A. Perras, Jianguo Wen, Fulya Dogan, and Ryan R. Langeslay
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Olefin metathesis ,010405 organic chemistry ,Organic Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Petrochemical ,chemistry ,Group (periodic table) ,Polymer chemistry ,Physical and Theoretical Chemistry ,Organometallic chemistry - Abstract
Olefin metathesis is a broadly employed reaction with applications that range from fine chemicals to materials and petrochemicals. The design and investigation of olefin metathesis catalysts have b...
- Published
- 2020
22. Catalytically Active Oil-Based Lubricant Additives Enabled by Calcining Ni–Al Layered Double Hydroxides
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Jianbin Luo, Fangmin Guo, Huaping Sheng, Yijun Shi, Yuhong Liu, Ali Erdemir, Hongdong Wang, Jianguo Wen, Wenrui Liu, and Kailun Xia
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Materials science ,Nickel oxide ,Layered double hydroxides ,chemistry.chemical_element ,02 engineering and technology ,Tribology ,engineering.material ,021001 nanoscience & nanotechnology ,law.invention ,Nanomaterials ,Nickel ,020303 mechanical engineering & transports ,0203 mechanical engineering ,chemistry ,Chemical engineering ,law ,engineering ,General Materials Science ,Calcination ,Physical and Theoretical Chemistry ,Lubricant ,0210 nano-technology ,Carbon - Abstract
Layered double hydroxides (LDHs) have lately been hailed as robust lubricant additives for improving tribological properties and as ideal catalysts for synthesizing carbon-based nanomaterials. In this paper, in situ analytical tools are used to track the evolution of the crystal structure and chemical composition of LDHs during calcination. Nickel oxide and elemental nickel can be produced by calcining NiAl-LDH in air (LDH-C-Air) and argon (LDH-C-Ar), respectively. For the base oil with 1 wt % LDH-C-Air, negligible wear can be detected even after a 2 h friction test under a severe contact pressure (∼637 MPa). A relatively thick tribofilm (∼60 nm) with a better mechanical property is formed, which protects the solid surface from severe wear. In addition, the possible formed carbon debris may also prevent the direct collision of asperities and effectively improve the wear resistance. This work provides a unique vision for the application of calcined LDHs with the combination of catalysis and tribology.
- Published
- 2019
23. In Situ Formed Ir3Li Nanoparticles as Active Cathode Material in Li–Oxygen Batteries
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Paul C. Redfern, Kah Chun Lau, Larry A. Curtiss, Mohammad Asadi, Chengji Zhang, Khalil Amine, Dongzhou Zhang, Hsien-Hau Wang, Avik Halder, Jun Lu, Dean J. Miller, Rajeev S. Assary, Xiangyi Luo, Anh T. Ngo, Rachid Amine, Jianguo Wen, Stefan Vajda, Amin Salehi-Khojin, Yun Jung Lee, and Pedram Abbasi
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In situ ,010304 chemical physics ,Chemistry ,Nanoparticle ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Oxygen ,0104 chemical sciences ,Chemical engineering ,Cathode material ,0103 physical sciences ,Energy density ,Physical and Theoretical Chemistry - Abstract
Lithium–oxygen (Li–O2) batteries are a promising class of rechargeable Li batteries with a potentially very high achievable energy density. One of the major challenges for Li–O2 batteries is the hi...
- Published
- 2019
24. Selective Growth of a Discontinuous Subnanometer Pd Film on Carbon Defects for Li–O2 Batteries
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Fengwei Huo, Jianguo Wen, Tao Zhang, Jun Lu, Khalil Amine, Matthew Li, Binghua Zou, and Xuanxuan Bi
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Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,Limiting ,Overpotential ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Fuel Technology ,chemistry ,Chemical engineering ,Chemistry (miscellaneous) ,Materials Chemistry ,0210 nano-technology ,human activities ,Carbon - Abstract
A high charge overpotential and poor cycle stability are the limiting factors in lithium–oxygen (Li–O2) batteries, causing poor round-trip efficiency and cell failure. Many types of electrocatalyst...
- Published
- 2019
25. Enhanced Electrochemical Performance of Sodium Manganese Ferrocyanide by Na3(VOPO4)2F Coating for Sodium-Ion Batteries
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Siqi Yuan, Guoqiang Tan, Fangwei Peng, Jianguo Wen, Zi-Feng Ma, Fan Feng, Xiao-Zhen Liao, and Lei Yu
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Materials science ,Coprecipitation ,Sodium ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,Manganese ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Surface coating ,chemistry ,Coating ,Cathode material ,engineering ,General Materials Science ,Ferrocyanide ,0210 nano-technology - Abstract
Sodium manganese ferrocyanide NaxMn[Fe(CN)6]y is an attractive cathode material for sodium-ion batteries. However, NaxMn[Fe(CN)6]y prepared by simple coprecipitation of Mn2+ and [Fe(CN)6]4– usually...
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- 2019
26. Rapid Detection of Mycoplasma-Infected Cells by an ssDNA Aptamer Probe
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Ling Xu, Youli Zu, Jianjun Qi, Wenqi Jiang, Hongguang Sun, Wei Han, Haijun Zhou, Shuanghui Yang, Yanting Liu, Jianguo Wen, Zihua Zeng, Jianzhong Hu, and Hongbin Lu
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Aptamer ,Cell ,DNA, Single-Stranded ,Bioengineering ,Biosensing Techniques ,02 engineering and technology ,medicine.disease_cause ,01 natural sciences ,Flow cytometry ,law.invention ,Confocal microscopy ,law ,Tumor Cells, Cultured ,Fluorescence microscope ,medicine ,Humans ,Mycoplasma Infections ,Lymphocytes ,Instrumentation ,Fluid Flow and Transfer Processes ,medicine.diagnostic_test ,Chemistry ,Process Chemistry and Technology ,010401 analytical chemistry ,Mycoplasma ,Aptamers, Nucleotide ,021001 nanoscience & nanotechnology ,Molecular biology ,In vitro ,0104 chemical sciences ,medicine.anatomical_structure ,Cell culture ,DNA Probes ,0210 nano-technology - Abstract
Mycoplasmas are unique cell wall-free bacteria. Because they lack a cell wall and have resistance to β-lactam antibiotics, mycoplasma is the major pathogen that infects cultured cells in research laboratories. For rapid detection of mycoplasma-infected cells, we developed an ssDNA aptamer sequence composed of 40 nucleotides. Flow cytometry analysis showed that the synthetic aptamer probe selectively targeted mycoplasma-infected culture cells with high specificity identical to commercially available PCR-based assays. Additionally, fluorescent microscopy studies revealed that the aptamer probe rapidly stained mycoplasma-infected cells with higher sensitivity compared to Hoechst dye-mediated cellular DNA content stains. Moreover, confocal microscopy studies of trypsin-treated cells validated that the aptamer probes selectively targeted mycoplasma components on the surface of infected cells. Finally, preclinical studies of peripheral blood cells demonstrated that the aptamer probe was able to detect in vitro mycoplasma infection of primary lymphocytes. Taken together, these findings indicate that the aptamer probe will not only allow rapid detection of mycoplasma-infected culture cells for research purposes but also provide a simple method to monitor mycoplasma infection in primary cell products for clinical use.
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- 2019
27. Semi-artificial Photosynthetic CO2 Reduction through Purple Membrane Re-engineering with Semiconductor
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Philip D. Laible, Tijana Rajh, Peijun Guo, Oleg G. Poluektov, Jens Niklas, Yimin A. Wu, Zhaowei Chen, Yuzi Liu, Jianguo Wen, Jingjing Zhang, Elena A. Rozhkova, Yu Jin Kim, Gregory A. Tira, and He Zhang
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Colloid and Surface Chemistry ,Membrane ,Chemistry ,General Chemistry ,Biochemical engineering ,010402 general chemistry ,Re engineering ,Photosynthesis ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Cellular engineering - Abstract
The engineering of biological pathways with man-made materials provides inspiring blueprints for sustainable fuel production. Here, we leverage a top-down cellular engineering strategy to develop a...
- Published
- 2019
28. Electrophilic Organoiridium(III) Pincer Complexes on Sulfated Zirconia for Hydrocarbon Activation and Functionalization
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Frédéric A. Perras, Marek Pruski, Fulya Dogan, Cong Liu, Massimiliano Delferro, Evan C. Wegener, Karen I. Goldberg, David M. Kaphan, Magali Ferrandon, Zoha H. Syed, Jianguo Wen, and Gokhan Celik
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X-ray absorption spectroscopy ,Absorption spectroscopy ,Cationic polymerization ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Heterogeneous catalysis ,Photochemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,chemistry ,Surface modification ,Iridium ,Spectroscopy - Abstract
Single-site supported organometallic catalysts bring together the favorable aspects of homogeneous and heterogeneous catalysis while offering opportunities to investigate the impact of metal–support interactions on reactivity. We report a (dmPhebox)Ir(III) (dmPhebox = 2,6-bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl) complex chemisorbed on sulfated zirconia, the molecular precursor for which was previously applied to hydrocarbon functionalization. Spectroscopic methods such as diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS), dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy, and X-ray absorption spectroscopy (XAS) were used to characterize the supported species. Tetrabutylammonium acetate was found to remove the organometallic species from the surface, enabling solution-phase analytical techniques in conjunction with traditional surface methods. Cationic character was imparted to the iridium center by its grafting onto sulfa...
- Published
- 2019
29. Annealing Temperature-Dependent Terahertz Thermal–Electrical Conversion Characteristics of Three-Dimensional Microporous Graphene
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Fei Fan, Yi Huang, Zhao Ziran, Yingxin Wang, Honghui Chen, Wenle Ma, Meng Chen, and Jianguo Wen
- Subjects
Materials science ,Annealing (metallurgy) ,Terahertz radiation ,Graphene ,business.industry ,02 engineering and technology ,Carbon nanotube ,Photodetection ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Responsivity ,law ,Seebeck coefficient ,Optoelectronics ,General Materials Science ,Charge carrier ,0210 nano-technology ,business - Abstract
Three-dimensional microporous graphene (3DMG) possesses ultrahigh photon absorptivity and excellent photothermal conversion ability and shows great potential in energy storage and photodetection, especially for the not well-explored terahertz (THz) frequency range. Here, we report on the characterization of the THz thermal-electrical conversion properties of 3DMG with different annealing treatments. We observe distinct behavior of bolometric and photothermoelectric responses varying with annealing temperature. Resistance-temperature characteristics and thermoelectric power measurements reveal that marked charge carrier reversal occurs in 3DMG as the annealing temperature changes between 600 and 800 °C, which can be well explained by Fermi-level tuning associated with oxygen functional group evolution. Benefiting from the large specific surface area of 3DMG, it has an extraordinary capability of reaching thermal equilibrium quickly and exhibits a fast photothermal conversion with a time constant of 23 ms. In addition, 3DMG can serve as an ideal absorber to improve the sensitivity of THz detectors and we demonstrate that the responsivity of a carbon nanotube device could be enhanced by 12 times through 3DMG. Our work provides new insight into the physical characteristics of carrier transport and THz thermal-electrical conversion in 3DMG controlled by annealing temperature and opens an avenue for the development of highly efficient graphene-based THz devices.
- Published
- 2019
30. Ultrabroadband, Sensitive, and Fast Photodetection with Needle-Like EuBiSe3 Single Crystal
- Author
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Yingying Niu, Weidong Wu, Yingkang Jin, Dong Wu, Jianguo Wen, Yingxin Wang, Meng Chen, and Zhao Ziran
- Subjects
Materials science ,business.industry ,Photodetector ,02 engineering and technology ,Photodetection ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,010309 optics ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Single crystal ,Biotechnology - Abstract
Ultrabroadband photodetection has been a hot topic with the rapid development of materials science and the application requirements for communication, imaging, and sensing. Photodetectors based on ...
- Published
- 2019
31. Tuning the Performance of Single-Atom Electrocatalysts: Support-Induced Structural Reconstruction
- Author
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Wanpeng Zhao, Jianlin Shi, Xiao-Min Lin, Hangrong Chen, Tao Li, Jun Tian, Jianguo Wen, Pan Linyu, and Gang Wan
- Subjects
inorganic chemicals ,Materials science ,General Chemical Engineering ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Heterogeneous catalysis ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Metal ,Chemical engineering ,chemistry ,Yield (chemistry) ,visual_art ,Atom ,Materials Chemistry ,visual_art.visual_art_medium ,0210 nano-technology ,Pyrolysis ,Cobalt - Abstract
Creating active and stable electrocatalysts remains a highly desirable and critical goal in the fields of catalysis and clean energy conversion. Single-atom catalyst (SAC), as a new research frontier in heterogeneous catalysis, has demonstrated emerging prospects for many electrocatalytic reactions. Support-assisted pyrolysis approaches are widely used in the synthesis of single-atom electrocatalysts. While extensive efforts have been devoted to increase the loading of the atomically dispersed metal sites, the role of the support in creating these active metal sites remains largely unexplored. Herein, we compare catalysts created by support-free and support-assisted pyrolysis of vitamin B12 and cobalt tetramethoxyphenylporphyrin, respectively, and demonstrate an important effect of support-induced structural reconstruction that directly controls the activation of SAC. Electrochemical studies show support-free catalysts are inactive for oxygen reduction reaction whereas the support-assisted pyrolysis yield...
- Published
- 2018
32. Atomically Precise Strategy to a PtZn Alloy Nanocluster Catalyst for the Deep Dehydrogenation of n-Butane to 1,3-Butadiene
- Author
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A. Jeremy Kropf, Jeffrey Camacho-Bunquin, Cong Liu, Christopher L. Marshall, Massimiliano Delferro, Hyuntae Sohn, Magali Ferrandon, Peter C. Stair, Ce Yang, Gokhan Celik, Ryan A. Hackler, and Jianguo Wen
- Subjects
X-ray absorption spectroscopy ,Materials science ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Atomic layer deposition ,chemistry ,X-ray photoelectron spectroscopy ,Chemical engineering ,Chemisorption ,Scanning transmission electron microscopy ,Dehydrogenation ,0210 nano-technology ,Platinum - Abstract
The development of on-purpose 1,3-butadiene (BDE) technologies remains an active area in catalysis research due to the importance of BDE in industrial polymer production. Here, we report on a non-oxidative dehydrogenation catalyst for the production of BDE prepared by atomically precise installation of platinum sites on a Zn-modified SiO2 sup-port via Atomic Layer Deposition (ALD). In situ reduction x-ray adsorption spectroscopy (XAS) experiments, X-ray photoelectron spectroscopy (XPS), CO chemisorption, and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging of activated PtZn/SiO2 material, revealed the formation of a uniform, well-distributed sub-nano to nanometer PtZn (1.2 ± 0.3 nm) alloy as the active catalytic species.
- Published
- 2018
33. Morphology and CO Oxidation Activity of Pd Nanoparticles on SrTiO3 Nanopolyhedra
- Author
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Cassandra George, Lawrence A. Crosby, Peter C. Stair, Laurence D. Marks, Michael J. Bedzyk, Kenneth R. Poeppelmeier, Neil M. Schweitzer, Richard P. Van Duyne, Jianguo Wen, Robert M. Kennedy, and Bor-Rong Chen
- Subjects
Materials science ,Diffuse reflectance infrared fourier transform ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Atomic layer deposition ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Transmission electron microscopy ,Strontium titanate ,Hydrothermal synthesis ,0210 nano-technology ,Single crystal ,Palladium - Abstract
Single crystal SrTiO3 nanocuboids having primarily TiO2-(001) surfaces and nanododecahedra having primarily (110) surfaces were created by two separate hydrothermal synthesis processes. Pd nanoparticles grown on the two sets of STO nanopolyhedra by atomic layer deposition show different morphologies and CO oxidation performance. Transmission electron microscopy and small-angle X-ray scattering show that 2–3 nm Pd nanoparticles with 3–5 nm interparticle distances decorate the STO surfaces. When the number of ALD cycles increases, the growth of the Pd nanoparticles is more significant in size on TiO2-(001)-STO surfaces, while that on (110)-STO surfaces is more predominant in number. High resolution electron microscopy images show that single crystal and multiply twinned Pd nanoparticles coexist on both types of the STO nanopolyhedra and exhibit different degrees of adhesion. The CO oxidation reaction, which was employed to determine the dependence of catalytic activity, showed that the Pd catalytic performa...
- Published
- 2018
34. All Roads Lead to TiO2: TiO2-Rich Surfaces of Barium and Strontium Titanate Prepared by Hydrothermal Synthesis
- Author
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Michael J. Bedzyk, Laurence D. Marks, Robert M. Kennedy, Jianguo Wen, Lawrence A. Crosby, Bor-Rong Chen, and Kenneth R. Poeppelmeier
- Subjects
Strontium ,Materials science ,General Chemical Engineering ,chemistry.chemical_element ,Nanoparticle ,Barium ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Isotropic etching ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Nanocrystal ,Chemical engineering ,Barium titanate ,Materials Chemistry ,Strontium titanate ,Hydrothermal synthesis ,0210 nano-technology - Abstract
Through high-resolution electron microscopy, the surface structure of barium titanate and strontium titanate nanoparticles are found to be terminated by a TiO2 double layer. These results confirm prior observations of TiO2-rich surface reconstructions on strontium titanate nanoparticles made hydrothermally at high pH and single crystals prepared with wet chemical etching. Of all the reconstructions observed on single crystals for these two materials, we report for first time the √13 × √13R33.7° structure on the {001} facets of hydrothermally prepared barium titanate and strontium titanate nanocrystals. The aqueous environment common to the two preparation methods preferentially leaves strontium and barium depleted from the A-sites near the surface and leads to TiO2-terminated surfaces for both materials. Analysis indicates that the observed structures are the thermodynamic lowest energy structures in aqueous conditions.
- Published
- 2018
35. Toward Highly Efficient Electrocatalyst for Li–O2 Batteries Using Biphasic N-Doping Cobalt@Graphene Multiple-Capsule Heterostructures
- Author
-
Kun He, Lina Chong, Said Al Hallaj, Khalil Amine, Guoqiang Tan, Jianguo Wen, Rachid Amine, Reza Shahbazian-Yassar, Yifei Yuan, Hsien-Hau Wang, Jun Lu, Dean J. Miller, Di-Jia Liu, Cong Liu, Yuanyuan Guo, and Xuanxuan Bi
- Subjects
Materials science ,Inorganic chemistry ,Ionic bonding ,chemistry.chemical_element ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,Electrocatalyst ,01 natural sciences ,law.invention ,Catalysis ,law ,General Materials Science ,Graphene ,Mechanical Engineering ,Doping ,technology, industry, and agriculture ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Cathode ,0104 chemical sciences ,chemistry ,Chemical engineering ,Electrode ,0210 nano-technology ,Cobalt - Abstract
For the promotion of lithium–oxygen batteries available for practical applications, the development of advanced cathode catalysts with low-cost, high activity, and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@graphene multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium–oxygen cells. The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electroactive zones possible; furthermore, the colander-like porous electrode facilitates the oxygen diffusion, catalytic reaction, and stable deposition of discharge products. As a result, the electrode exhibits much improved electrocatalytic prope...
- Published
- 2017
36. Insight into the Capacity Fading Mechanism of Amorphous Se2S5 Confined in Micro/Mesoporous Carbon Matrix in Ether-Based Electrolytes
- Author
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Chunsheng Wang, Khalil Amine, Xiaobing Zuo, Cheng-Jun Sun, Gui-Liang Xu, Tao Li, Larry A. Curtiss, Zonghai Chen, Chao Luo, Jianguo Wen, Lei Cheng, Dean J. Miller, Tianyuan Ma, Yang Ren, Valeri Petkov, and Steve M. Heald
- Subjects
Materials science ,Absorption spectroscopy ,Binding energy ,Analytical chemistry ,Bioengineering ,Ether ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,Ab initio quantum chemistry methods ,law ,General Materials Science ,Mechanical Engineering ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,XANES ,Cathode ,0104 chemical sciences ,Amorphous solid ,chemistry ,Chemical engineering ,0210 nano-technology - Abstract
In contrast to the stable cycle performance of space confined Se-based cathodes for lithium batteries in carbonate-based electrolytes, their common capacity fading in ether-based electrolytes has been paid less attention and not yet well-addressed so far. In this work, the lithiation/delithiation of amorphous Se2S5 confined in micro/mesoporous carbon (Se2S5/MPC) cathode was investigated by in situ X-ray near edge absorption spectroscopy (XANES) and theoretical calculations. The Se2S5/MPC composite was synthesized by a modified vaporization-condensation method to ensure a good encapsulation of Se2S5 into the pores of MPC host. In situ XANES results illustrated that the lithiation/delithiation reversibility of Se component was gradually decreased in ether-based electrolytes, leading to an aggravated formation of long-chain polyselenides during cycling and further capacity decay. Moreover, ab initio calculations revealed that the binding energy of polyselenides (Li2Sen) with carbon host is in an order of Li2Se6Li2Se4Li2Se. The insights into the failure mechanism of Se-based cathode gain in this work are expected to serve as a guide for future design on high performance Se-based cathodes.
- Published
- 2016
37. Tuning of Photoluminescence by Cation Nanosegregation in the (CaMg)x(NaSc)1–xSi2O6 Solid Solution
- Author
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Guokui Liu, Licong Peng, Maxim S. Molokeev, Zhiguo Xia, Kenneth R. Poeppelmeier, Mahalingam Balasubramanian, Zhi-Gang Mei, Lin Gu, Quanlin Liu, Jianguo Wen, and Dean J. Miller
- Subjects
Photoluminescence ,Chemistry ,Analytical chemistry ,Nanotechnology ,Phosphor ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Ion ,Color rendering index ,Colloid and Surface Chemistry ,Homogeneous ,Density functional theory ,Isostructural ,0210 nano-technology ,Solid solution - Abstract
Controlled photoluminescence tuning is important for the optimization and modification of phosphor materials. Herein we report an isostructural solid solution of (CaMg)x(NaSc)1–xSi2O6 (0 < x < 1) in which cation nanosegregation leads to the presence of two dilute Eu2+ centers. The distinct nanodomains of isostructural (CaMg)Si2O6 and (NaSc)Si2O6 contain a proportional number of Eu2+ ions with unique, independent spectroscopic signatures. Density functional theory calculations provided a theoretical understanding of the nanosegregation and indicated that the homogeneous solid solution is energetically unstable. It is shown that nanosegregation allows predictive control of color rendering and therefore provides a new method of phosphor development.
- Published
- 2016
38. Insight into the Catalytic Mechanism of Bimetallic Platinum–Copper Core–Shell Nanostructures for Nonaqueous Oxygen Evolution Reactions
- Author
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A. Jeremy Kropf, Sungsik Lee, Tianpin Wu, Xiangyi Luo, Xiaoping Wang, Jianguo Wen, Jun Lu, Dean J. Miller, Deborah J. Myers, Khalil Amine, and Lu Ma
- Subjects
Nanostructure ,Materials science ,Mechanical Engineering ,Oxygen evolution ,chemistry.chemical_element ,Bioengineering ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Overpotential ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Electrochemical cell ,chemistry ,General Materials Science ,0210 nano-technology ,Polarization (electrochemistry) ,Platinum ,Bimetallic strip - Abstract
The oxygen evolution reaction (OER) plays a critical role in multiple energy conversion and storage applications. However, its sluggish kinetics usually results in large voltage polarization and unnecessary energy loss. Therefore, designing efficient catalysts that could facilitate this process has become an emerging topic. Here, we present a unique Pt–Cu core–shell nanostructure for catalyzing the nonaqueous OER. The catalysts were systematically investigated with comprehensive spectroscopic techniques, and applied in nonaqueous Li–O2 electrochemical cells, which exhibited dramatically reduced charging overpotential (
- Published
- 2015
39. Direct Observation of Interfacial Au Atoms on TiO2 in Three Dimensions
- Author
-
Jianguo Wen, Jian-Min Zuo, Shankar Sivaramakrishnan, and Wenpei Gao
- Subjects
Materials science ,Annealing (metallurgy) ,Mechanical Engineering ,Direct observation ,Nanoparticle ,Bioengineering ,General Chemistry ,Condensed Matter Physics ,Catalysis ,Crystallography ,Nanocrystal ,Rutile ,Chemical physics ,Scanning transmission electron microscopy ,General Materials Science ,Lack of knowledge - Abstract
Interfacial atoms, which result from interactions between the metal nanoparticles and support, have a large impact on the physical and chemical properties of nanoparticles. However, they are difficult to observe; the lack of knowledge has been a major obstacle toward unraveling their role in chemical transformations. Here we report conclusive evidence of interfacial Au atoms formed on the rutile (TiO2) (110) surfaces by activation using high-temperature (∼500 °C) annealing in air. Three-dimensional imaging was performed using depth-sectioning enabled by aberration-corrected scanning transmission electron microscopy. Results show that the interface between Au nanocrystals and TiO2 (110) surfaces consists of a single atomic layer with Au atoms embedded inside Ti–O. The number of interfacial Au atoms is estimated from ∼1–8 in an interfacial atomic column. Direct impact of interfacial Au atoms is observed on an enhanced Au-TiO2 interaction and the reduction of surface TiO2; both are critical to Au catalysis.
- Published
- 2015
40. Growth of Au on Pt Icosahedral Nanoparticles Revealed by Low-Dose In Situ TEM
- Author
-
Jianguo Wen, Ping Lu, Jian-Min Zuo, Dean J. Miller, Wenpei Gao, Hong Yang, and Jianbo Wu
- Subjects
In situ ,Nanostructure ,Materials science ,Icosahedral symmetry ,Mechanical Engineering ,Diffusion ,Nucleation ,Metal Nanoparticles ,chemistry.chemical_element ,Nanoparticle ,Bioengineering ,General Chemistry ,Radiation Dosage ,Condensed Matter Physics ,Molecular Imprinting ,Crystallography ,Microscopy, Electron, Transmission ,chemistry ,Materials Testing ,General Materials Science ,Gold ,Crystallization ,Platinum ,Deposition (law) - Abstract
A growth mode was revealed by an in situ TEM study of nucleation and growth of Au on Pt icosahedral nanoparticles. Quantitative analysis of growth kinetics was carried out based on real-time TEM data, which shows the process involves: (1) deposition of Au on corner sites of Pt icosahedral nanoparticles, (2) diffusion of Au from corners to terraces and edges, and (3) subsequent layer-by-layer growth of Au on Au surfaces to form Pt@Au core-shell nanoparticles. The in situ TEM results indicate diffusion of Au from corner islands to terraces and edges is a kinetically controlled growth, as evidenced by a measurement of diffusion coefficients for these growth processes. We demonstrated that in situ electron microscopy is a valuable tool for quantitative study of nucleation and growth kinetics and can provide new insight into the design and precise control of heterogeneous nanostructures.
- Published
- 2015
41. Interfacial Effects on Lithium Superoxide Disproportionation in Li-O2 Batteries
- Author
-
Ernesto Indacochea, Hsien-Hau Wang, Baohua Li, Dean J. Miller, Feiyu Kang, Larry A. Curtiss, Dengyun Zhai, Jun Lu, Jing Gao, Kah Chun Lau, Jianguo Wen, Khalil Amine, and Wenge Yang
- Subjects
Battery (electricity) ,Chemistry ,Mechanical Engineering ,Analytical chemistry ,Bioengineering ,Disproportionation ,General Chemistry ,Electrolyte ,Condensed Matter Physics ,Cathode ,law.invention ,Amorphous solid ,chemistry.chemical_compound ,symbols.namesake ,Transmission electron microscopy ,law ,Lithium superoxide ,symbols ,General Materials Science ,Raman spectroscopy - Abstract
During the cycling of Li-O2 batteries the discharge process gives rise to dynamically evolving agglomerates composed of lithium–oxygen nanostructures; however, little is known about their composition. In this paper, we present results for a Li-O2 battery based on an activated carbon cathode that indicate interfacial effects can suppress disproportionation of a LiO2 component in the discharge product. High-intensity X-ray diffraction and transmission electron microscopy measurements are first used to show that there is a LiO2 component along with Li2O2 in the discharge product. The stability of the discharge product was then probed by investigating the dependence of the charge potential and Raman intensity of the superoxide peak with time. The results indicate that the LiO2 component can be stable for possibly up to days when an electrolyte is left on the surface of the discharged cathode. Density functional calculations on amorphous LiO2 reveal that the disproportionation process will be slower at an elec...
- Published
- 2015
42. Determining the Resolution Limits of Electron-Beam Lithography: Direct Measurement of the Point-Spread Function
- Author
-
Dmitri N. Zakharov, Jianguo Wen, Richard G. Hobbs, Karl K. Berggren, Bowen Baker, Nestor J. Zaluzec, Dong Su, Eric A. Stach, Lihua Zhang, Dean J. Miller, Yujia Yang, and Vitor R. Manfrinato
- Subjects
Point spread function ,Materials science ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Mechanical Engineering ,Electron energy loss spectroscopy ,Resolution (electron density) ,Astrophysics::Instrumentation and Methods for Astrophysics ,Bioengineering ,Astrophysics::Cosmology and Extragalactic Astrophysics ,General Chemistry ,Condensed Matter Physics ,Secondary electrons ,Optics ,Resist ,General Materials Science ,business ,Lithography ,Electron-beam lithography ,Plasmon - Abstract
One challenge existing since the invention of electron-beam lithography (EBL) is understanding the exposure mechanisms that limit the resolution of EBL. To overcome this challenge, we need to understand the spatial distribution of energy density deposited in the resist, that is, the point-spread function (PSF). During EBL exposure, the processes of electron scattering, phonon, photon, plasmon, and electron emission in the resist are combined, which complicates the analysis of the EBL PSF. Here, we show the measurement of delocalized energy transfer in EBL exposure by using chromatic aberration-corrected energy-filtered transmission electron microscopy (EFTEM) at the sub-10 nm scale. We have defined the role of spot size, electron scattering, secondary electrons, and volume plasmons in the lithographic PSF by performing EFTEM, momentum-resolved electron energy loss spectroscopy (EELS), sub-10 nm EBL, and Monte Carlo simulations. We expect that these results will enable alternative ways to improve the resolution limit of EBL. Furthermore, our approach to study the resolution limits of EBL may be applied to other lithographic techniques where electrons also play a key role in resist exposure, such as ion-beam-, X-ray-, and extreme-ultraviolet lithography.
- Published
- 2014
43. Effect of Cooling Rates on Phase Separation in 0.5Li2MnO3·0.5LiCoO2 Electrode Materials for Li-Ion Batteries
- Author
-
Dean J. Miller, Michael M. Thackeray, Matthew R. Suchomel, Baris Key, Mahalingam Balasubramanian, Brandon R. Long, Jason R. Croy, Fulya Dogan, and Jianguo Wen
- Subjects
Diffraction ,Materials science ,General Chemical Engineering ,Analytical chemistry ,General Chemistry ,Cathode ,Synchrotron ,law.invention ,Ion ,X-ray absorption fine structure ,Transmission electron microscopy ,law ,Lattice (order) ,Materials Chemistry ,Spectroscopy - Abstract
The results of a detailed structural investigation on the influence of cooling rates in the synthesis of lithium- and manganese-rich 0.5Li2MnO3·0.5LiCoO2 composite electrode materials, which are of interest for Li-ion battery applications, are presented. It is shown that a low-temperature, intermediate firing step, often employed in cathode synthesis, yields a minor secondary component representing a polydisperse distribution of lattice parameters, not found in the absence of low-temperature treatments. However, regardless of the heating and cooling conditions employed, all samples present two distinctly different local environments as evidenced by X-ray absorption fine structure spectroscopy (XAFS) and nuclear magnetic resonance (NMR) analysis. Transmission electron microscopy (TEM) data show discrete domain structures that are consistent with the XAFS and NMR findings. Furthermore, high resolution synchrotron X-ray diffraction (HR-XRD), as well as the XAFS and NMR data show no discernible differences be...
- Published
- 2014
44. Self-Assembly of Monotethered Single-Chain Nanoparticle Shape Amphiphiles
- Author
-
Jianguo Wen, Liang Yuan, Li Liu, Hanying Zhao, and Yongfang Yang
- Subjects
Materials science ,Polymers and Plastics ,Organic Chemistry ,Nanoparticle ,Chain transfer ,Raft ,Methacrylate ,Micelle ,Inorganic Chemistry ,Polymerization ,Amphiphile ,Polymer chemistry ,Materials Chemistry ,Self-assembly - Abstract
Shape amphiphiles with distinct shapes and amphiphilic properties can be used as fundamental building blocks in the fabrication of novel structures and advanced materials. In this research synthesis and self-assembly of monotethered single-chain nanoparticle shape amphiphiles are reported. Poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS) was synthesized by two-step reversible addition–fragmentation chain transfer (RAFT) polymerization. The PDMAEMA blocks were intramolecularly cross-linked by 1,4-diiodobutane (DIB) at significantly low concentrations, and PS-tethered PDMAEMA single-chain nanoparticles were prepared. Gel permeation chromatograph, 1H NMR and transmission electron microscopy results all indicated successful synthesis of the structures. The controlled self-assembly of the shape amphiphiles in selective solvents was investigated. Depending on the size of the single-chain nanoparticles, the shape amphiphiles self-assemble into strawberry-like micelles, a structure with ...
- Published
- 2013
45. Vacuum-Deposited Small-Molecule Organic Solar Cells with High Power Conversion Efficiencies by Judicious Molecular Design and Device Optimization
- Author
-
Yi-Hong Chen, Chih-Wei Lu, Francis Lin, Li-Yen Lin, Hao-Wu Lin, Ken-Tsung Wong, Dean J. Miller, Seth B. Darling, Jianguo Wen, Po-Han Wang, Yi-Hung Liu, and Zheng-Yu Huang
- Subjects
Photocurrent ,Organic solar cell ,Chemistry ,Nanotechnology ,General Chemistry ,Electrochemistry ,Biochemistry ,Acceptor ,Small molecule ,Catalysis ,Crystal ,Colloid and Surface Chemistry ,Chemical engineering ,Moiety ,Molecule - Abstract
Three new tailor-made molecules (DPDCTB, DPDCPB, and DTDCPB) were strategically designed and convergently synthesized as donor materials for small-molecule organic solar cells. These compounds possess a donor-acceptor-acceptor molecular architecture, in which various electron-donating moieties are connected to an electron-withdrawing dicyanovinylene moiety through another electron-accepting 2,1,3-benzothiadiazole block. The molecular structures and crystal packings of DTDCPB and the previously reported DTDCTB were characterized by single-crystal X-ray crystallography. Photophysical and electrochemical properties as well as energy levels of this series of donor molecules were thoroughly investigated, affording clear structure-property relationships. By delicate manipulation of the trade-off between the photovoltage and the photocurrent via molecular structure engineering together with device optimizations, which included fine-tuning the layer thicknesses and the donor:acceptor blended ratio in the bulk heterojunction layer, vacuum-deposited hybrid planar-mixed heterojunction devices utilizing DTDCPB as the donor and C(70) as the acceptor showed the best performance with a power conversion efficiency (PCE) of 6.6 ± 0.2% (the highest PCE of 6.8%), along with an open-circuit voltage (V(oc)) of 0.93 ± 0.02 V, a short-circuit current density (J(sc)) of 13.48 ± 0.27 mA/cm(2), and a fill factor (FF) of 0.53 ± 0.02, under 1 sun (100 mW/cm(2)) AM 1.5G simulated solar illumination.
- Published
- 2012
46. Self-Assembly of a Diblock Copolymer with Pendant Disulfide Bonds and Chromophore Groups: A New Platform for Fast Release
- Author
-
Jingchuan Liu, Jianguo Wen, Liang Yuan, and Hanying Zhao
- Subjects
Atom-transfer radical-polymerization ,Surfaces and Interfaces ,Conjugated system ,Chromophore ,Condensed Matter Physics ,Gel permeation chromatography ,chemistry.chemical_compound ,Monomer ,chemistry ,Polymer chemistry ,Electrochemistry ,Copolymer ,Proton NMR ,General Materials Science ,Ethylene glycol ,Spectroscopy - Abstract
An amphiphilic block copolymer comprising poly(ethylene glycol) (PEG) and poly(2-(methacryloyl)oxyethyl-2'-hydroxyethyl disulfide) (PMAOHD) blocks was synthesized by atom transfer radical polymerization (ATRP). Pyrenebutyric acid was conjugated to the block copolymer by esterification, and a block copolymer with pendant disulfide bonds and pyrenyl groups (PEG-b-P(MAOHD-g-Py)) was obtained. (1)H NMR and gel permeation chromatography (GPC) results demonstrated the successful synthesis of the block copolymer. The cleavage of the disulfide bonds and the degrafting of the pyrenyl groups were investigated in THF and a THF/methanol mixture. Fluorescence spectroscopy, GPC, and (1)H NMR results demonstrated fast cleavage of the disulfide bonds by Bu(3)P in THF. Fluorescence results showed the ratio of the intensity of the excimer peak to the monomer peak decreased rapidly within 20 min. GPC traces of the block copolymer moved to a long retention time region after addition of Bu(3)P, indicating the cleavage of the disulfide bonds and the degrafting of the pyrenyl groups. PEG-b-P(MAOHD-g-Py) can self-assemble into micelles with poly(MAOHD-g-Py) cores and PEG coronae in a mixture of methanol and THF (9:1 by volume). The dissociation of the micelles in the presence of Bu(3)P was investigated. After cleavage of the disulfide bonds in the micellar cores, a pyrene-containing small molecular compound and a block copolymer with pendant thiol groups were produced. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and (1)H NMR were employed to track the dissociation of the polymeric micelles. All the techniques demonstrated the dissociation of the micelles and the fast release of pyrenyl groups from the micelles.
- Published
- 2012
47. Long-Range and Local Structure in the Layered Oxide Li1.2Co0.4Mn0.4O2
- Author
-
Javier Bareño, Sun-Ho Kang, Mahalingam Balasubramanian, C. H. Lei, Swati V. Pol, Ivan Petrov, Jianguo Wen, and Daniel P. Abraham
- Subjects
Diffraction ,X-ray absorption spectroscopy ,Materials science ,General Chemical Engineering ,Resolution (electron density) ,Intercalation (chemistry) ,Oxide ,chemistry.chemical_element ,General Chemistry ,Crystal structure ,Crystallography ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Materials Chemistry ,Lithium ,Spectroscopy - Abstract
The layered oxides being considered as intercalation compounds for lithium batteries display significant differences between the long-range crystal structure and local arrangements around individual atoms. These differences are important, because the local atomic environments affect Li-ion transport and, hence, the oxide’s rate capability, by determining activation barrier energies, by blocking or opening Li-diffusion pathways, etc. Traditional diffraction methods provide key information on the average crystal structure. However, no single experimental technique can unequivocally determine the average long-range crystal structure and the distribution of local environments over crystallographic distances while retaining atomic-scale resolution. Therefore, in this study, we have employed a combination of diffraction, microscopy, and spectroscopy techniques to investigate the long-range (∼1 μm) and local structure (≤1 nm) of Li1.2Co0.4Mn0.4O2, which is a model compound for layered oxides being considered for...
- Published
- 2011
48. On the Origin of Increased Phonon Scattering in Nanostructured PbTe Based Thermoelectric Materials
- Author
-
Jin-Cheng Zheng, Joseph R. Sootsman, Jiaqing He, Steven N. Girard, Mercouri G. Kanatzidis, Vinayak P. Dravid, Jianguo Wen, and Yimei Zhu
- Subjects
Range (particle radiation) ,Nanostructure ,Phonon scattering ,Condensed matter physics ,Phonon ,Chemistry ,Scattering ,Nanoparticle ,General Chemistry ,Thermoelectric materials ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,Thermal conductivity - Abstract
We have investigated the possible mechanisms of phonon scattering by nanostructures and defects in PbTe-X (X = 2% Sb, Bi, or Pb) thermoelectric materials systems. We find that among these three compositions, PbTe-2% Sb has the lowest lattice thermal conductivity and exhibits a larger strain and notably more misfit dislocations at the precipitate/PbTe interfaces than the other two compositions. In the PbTe-Bi 2% sample, we infer some weaker phonon scattering BiTe precipitates, in addition to the abundant Bi nanostructures. In the PbTe-Pb 2% sample, we also find that pure Pb nanoparticles exhibit stronger phonon scattering than nanostructures with Te vacancies. Within the accepted error range, the theoretical calculations of the lattice thermal conductivity in the three systems are in close agreement with the experimental measurements, highlighting the important role of misfit dislocations, nanoscale particles, and associated interfacial elastic strain play in phonon scattering. We further propose that such particle-induced local elastic perturbations interfere with the phonon propagation pathway, thereby contributing to further reduction in lattice thermal conductivity, and consequently can enhance the overall thermoelectric figure of merit.
- Published
- 2010
49. Visualizing Materials Chemistry at Atomic Resolution
- Author
-
Sergio I. Sanchez, Jianguo Wen, Matthew W. Small, Shankar Sivaramakrishnan, Ralph G. Nuzzo, and Jian-Min Zuo
- Subjects
Solid-state chemistry ,Index (publishing) ,Atomic resolution ,Chemistry ,Analytical Chemistry (journal) ,Nanotechnology ,Electronic structure ,Analytical Chemistry - Abstract
Analytical electron microscopy--empowered by advances in electron optics and detectors--is poised to radically transform our understanding of the complex phenomena arising from atomic and electronic structure in materials chemistry. (To listen to a podcast about this article, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.).
- Published
- 2010
50. Planar GaAs Nanowires on GaAs (100) Substrates: Self-Aligned, Nearly Twin-Defect Free, and Transfer-Printable
- Author
-
Ik Su Chun, Seth A. Fortuna, Jianguo Wen, and Xiuling Li
- Subjects
Materials science ,Silicon ,business.industry ,Mechanical Engineering ,Nanowire ,chemistry.chemical_element ,Bioengineering ,Nanotechnology ,General Chemistry ,Substrate (electronics) ,Condensed Matter Physics ,Epitaxy ,Semiconductor ,chemistry ,Nanoelectronics ,Optoelectronics ,General Materials Science ,Metalorganic vapour phase epitaxy ,Vapor–liquid–solid method ,business - Abstract
We report the controlled growth of planar GaAs semiconductor nanowires on (100) GaAs substrates using atmospheric pressure metalorganic chemical vapor deposition with Au as catalyst. These nanowires with uniform diameters are self-aligned in110direction in the plane of (100). The dependence of planar nanowire morphology and growth rate as a function of growth temperature provides insights into the growth mechanism and identified an ideal growth window of 470 +/- 10 degrees C for the formation of such planar geometry. Transmission electron microscopy images reveal clear epitaxial relationship with the substrate along the nanowire axial direction, and the reduction of twinning defect density by about 3 orders of magnitude compared to111III-V semiconductor nanowires. In addition, using the concept of sacrificial layers and elevation of Au catalyst modulated by growth condition, we demonstrate for the first time a large area direct transfer process for nanowires formed by a bottom-up approach that can maintain both the position and alignment. The planar geometry and extremely low level of crystal imperfection along with the transferability could potentially lead to highly integrated III-V nanoelectronic and nanophotonic devices on silicon and flexible substrates.
- Published
- 2008
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