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Israel E Wachs - One of the best experts on this subject based on the ideXlab platform.
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Molecular Design of Supported Metal Oxide Catalysts
Studies in Surface Science and Catalysis, 2008Co-Authors: Israel E Wachs, Goutam Deo, Du Soung Kim, M. A. VuurmanAbstract:Abstract This study demonstrates that molecular design of supported Metal Oxide catalysts is possible from molecular level information obtained from combined Raman spectroscopy and the methanol oxidation reaction. The important factors that influence the molecular design of the supported Metal Oxide catalysts are the specific Oxide support (factor of ∼10 3 ) and the specific surface Metal Oxide (factor of ∼10 1 ). The synthesis method is not critical since it does not influence the surface Metal Oxide structure or reactivity. Calcination temperature is not important as long as moderate temperatures (350–500°C) are used.
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recent conceptual advances in the catalysis science of mixed Metal Oxide catalytic materials
Catalysis Today, 2005Co-Authors: Israel E WachsAbstract:The catalysis science of mixed Metal Oxides (supported Metal Oxides, molecular sieves and bulk mixed Metal Oxides) has undergone dramatic paradigm changes over the past 25 years as new characterization techniques became available (X-ray absorption spectroscopy (EXAFS/XANES/soft XANES), Raman, solid-state NMR, HR-TEM, UV–vis DRS and LEISS) to catalysis researchers. The major advantages offered by these spectroscopic improvements are that (1) they can detect XRD inactive amorphous surface Metal Oxide phases as well as crystalline nanophases and (2) their ability to collect information under various environmental conditions. Application of these spectroscopic techniques to the investigation of mixed Metal Oxide catalysts have provided new fundamental insights into the electronic and molecular structures of mixed Metal Oxide catalytic active sites and how they control the catalytic activity and selectivity characteristics. The most significant discovery has been that amorphous Metal Oxide phases are always present and are the catalytic active sites for many applications of mixed Metal Oxide catalysts. This has resulted in a significant paradigm shift as to how mixed Metal Oxide catalytic materials function for different applications. This article reviews the instrumental advances and the resulting conceptual advances that have evolved over the past 25 years in the catalysis science of mixed Metal Oxide catalysts. # 2004 Elsevier B.V. All rights reserved.
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recent conceptual advances in the catalysis science of mixed Metal Oxide catalytic materials
Catalysis Today, 2005Co-Authors: Israel E WachsAbstract:Abstract The catalysis science of mixed Metal Oxides (supported Metal Oxides, molecular sieves and bulk mixed Metal Oxides) has undergone dramatic paradigm changes over the past 25 years as new characterization techniques became available (X-ray absorption spectroscopy (EXAFS/XANES/soft XANES), Raman, solid-state NMR, HR-TEM, UV–vis DRS and LEISS) to catalysis researchers. The major advantages offered by these spectroscopic improvements are that (1) they can detect XRD inactive amorphous surface Metal Oxide phases as well as crystalline nanophases and (2) their ability to collect information under various environmental conditions. Application of these spectroscopic techniques to the investigation of mixed Metal Oxide catalysts have provided new fundamental insights into the electronic and molecular structures of mixed Metal Oxide catalytic active sites and how they control the catalytic activity and selectivity characteristics. The most significant discovery has been that amorphous Metal Oxide phases are always present and are the catalytic active sites for many applications of mixed Metal Oxide catalysts. This has resulted in a significant paradigm shift as to how mixed Metal Oxide catalytic materials function for different applications. This article reviews the instrumental advances and the resulting conceptual advances that have evolved over the past 25 years in the catalysis science of mixed Metal Oxide catalysts.
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Surface Aspects of Bismuth–Metal Oxide Catalysts
Journal of Catalysis, 1996Co-Authors: N. Arora, Israel E Wachs, Goutam Deo, Andrew M. HirtAbstract:A series of conventional and model bismuth–Metal Oxidecatalysts (vanadates, molybdates, tungstates, and niobates) werephysically and chemically characterzied (Raman spectroscopy,BET, XPS, and methanol oxidation) to obtain additional insightsinto the structure-reactivity relationships of such catalyticmaterials. The reactivity for methanol oxidation over theconventional bismuth–Metal Oxide catalysts was found to beprimarily related to the surface area of the Oxide catalysts andwas essentially independent of the near surface composition andthe bulk structure. The selectivity for methanol oxidation overthe conventional bismuth–Metal Oxide catalysts was essentiallyfound not to be a function of the surface area, the near surfacecomposition, and the bulk structure. A series of modelbismuth–Metal Oxide catalysts was synthesized by depositingMetal Oxides on the surface of a bismuth Oxide support. Themodel studies demonstrated that two-dimensional Metal Oxideoverlayers are not stable on the bismuth Oxide support andreadily react to form bulk bismuth–Metal Oxide compounds uponheating. Furthermore, the model studies revealed that these bulkbismuth–Metal Oxide compounds are related to the active sitesfor the partial oxidation reaction.In situRamanspectroscopy in methanol/oxygen, methanol, and oxygen reactionenvironments with helium as the diluent revealed no additionalinformation regarding the nature of the active site. It wasfound that only highly crystalline bismuth–Metal Oxide phasesare selective for the partial oxidation of methanol toformaldehyde. Thus, selective bismuth–Metal Oxide catalystswill always possess highly crystalline Metal Oxide phasescontaining extremely low surface areas which make it difficultto obtain fundamental surface information about the outermost layers.
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Raman and IR studies of surface Metal Oxide species on Oxide supports: Supported Metal Oxide catalysts
Catalysis Today, 1996Co-Authors: Israel E WachsAbstract:Raman and infrared spectroscopy provide complementary information about the nature of the surface Metal Oxide species present in supported Metal Oxide catalysts. This paper reviews the type of fundamental information that is typically obtained in Raman and IR characterization studies of supported Metal Oxide catalysts. The molecular structures of the surface Metal Oxide species are reflected in the terminal M=O and bridging M-O-M vibrations. The location of the surface Metal Oxide species on the Oxide supports is determined by directly monitoring the specific surface hydroxyls of the support that are being titrated. The surface coverage of the surface Metal Oxide species on the Oxide supports can be quantitatively obtained since at monolayer coverage all the reactive surface hydroxyls are titrated and additional Metal Oxide results in the formation of crystalline Metal Oxide particles. The nature of surface Lewis and Brønsted acid sites present in supported Metal Oxide catalysts are determined by adsorbing basic probe molecules like pyridine. Information about the behavior of the surface Metal Oxide species during catalytic reactions are provided by in situ characterization studies. Such fundamental information is critical for the development of molecular structure-reactivity relationships for supported Metal Oxide catalysts. This paper will be limited to supported Metal Oxide catalysts containing group V-VII transition Metal Oxides (e.g., V, Nb, Cr, Mo, W and Re) on several different Oxide supports (alumina, titania, zirconia, niobia and silica).
Guozhen Shen - One of the best experts on this subject based on the ideXlab platform.
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Transparent Metal Oxide nanowire transistors
Nanoscale, 2012Co-Authors: Di Chen, Xianfu Wang, Bo Liang, Zhe Liu, Guozhen ShenAbstract:With the features of high mobility, a high electric on/off ratio and excellent transparency, Metal Oxide nanowires are excellent candidates for transparent thin-film transistors, which is one of the key technologies to realize transparent electronics. This article provides a comprehensive review of the state-of-the-art research activities that focus on transparent Metal Oxide nanowire transistors. It begins with the brief introduction to the synthetic methods for high quality Metal Oxide nanowires, and the typical nanowire transfer and printing techniques with emphasis on the simple contact printing methodology. High performance transparent transistors built on both single nanowires and nanowire thin films are then highlighted. The final section deals with the applications of transparent Metal Oxide nanowire transistors in the field of transparent displays and concludes with an outlook on the current perspectives and future directions of transparent Metal Oxide nanowire transistors.
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Metal Oxide nanowire transistors
Journal of Materials Chemistry, 2012Co-Authors: Hongtao Huang, Xianfu Wang, Bo Liang, Zhe Liu, Di Chen, Guozhen ShenAbstract:Metal Oxide nanowires are promising building blocks for thin film transistors due to their one-dimensional geometry in nanoscale, high crystalline nature, and excellent optical and electrical properties. In the past decade, intensive research interest has been drawn to Metal Oxide nanowire transistors, and various Metal Oxide nanowires like ZnO, In2O3, and SnO2 have been fabricated into thin film transistors to study their electrical properties and the characteristics as transistor active channels. Much effort has been paid to promote the performance of Metal Oxide nanowire transistors, and expand the application areas covering from sensing devices, transparent and flexible electronics, to memories and integrated logic circuits. In this review, we highlight the state-of-art progress in Metal Oxide nanowire transistors, with an emphasis on basic properties and performances. We summarize the characteristics of transistors based on different Metal Oxide nanowires, the strategies to improve the performance, and various application fields. Finally we present an outlook on the future development of Metal Oxide nanowire transistors, including the study of material properties, the design of device structures and the development of applications.
Hongtao Huang - One of the best experts on this subject based on the ideXlab platform.
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Metal Oxide nanowire transistors
Journal of Materials Chemistry, 2012Co-Authors: Hongtao Huang, Xianfu Wang, Bo Liang, Zhe Liu, Di Chen, Guozhen ShenAbstract:Metal Oxide nanowires are promising building blocks for thin film transistors due to their one-dimensional geometry in nanoscale, high crystalline nature, and excellent optical and electrical properties. In the past decade, intensive research interest has been drawn to Metal Oxide nanowire transistors, and various Metal Oxide nanowires like ZnO, In2O3, and SnO2 have been fabricated into thin film transistors to study their electrical properties and the characteristics as transistor active channels. Much effort has been paid to promote the performance of Metal Oxide nanowire transistors, and expand the application areas covering from sensing devices, transparent and flexible electronics, to memories and integrated logic circuits. In this review, we highlight the state-of-art progress in Metal Oxide nanowire transistors, with an emphasis on basic properties and performances. We summarize the characteristics of transistors based on different Metal Oxide nanowires, the strategies to improve the performance, and various application fields. Finally we present an outlook on the future development of Metal Oxide nanowire transistors, including the study of material properties, the design of device structures and the development of applications.
Di Chen - One of the best experts on this subject based on the ideXlab platform.
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Transparent Metal Oxide nanowire transistors
Nanoscale, 2012Co-Authors: Di Chen, Xianfu Wang, Bo Liang, Zhe Liu, Guozhen ShenAbstract:With the features of high mobility, a high electric on/off ratio and excellent transparency, Metal Oxide nanowires are excellent candidates for transparent thin-film transistors, which is one of the key technologies to realize transparent electronics. This article provides a comprehensive review of the state-of-the-art research activities that focus on transparent Metal Oxide nanowire transistors. It begins with the brief introduction to the synthetic methods for high quality Metal Oxide nanowires, and the typical nanowire transfer and printing techniques with emphasis on the simple contact printing methodology. High performance transparent transistors built on both single nanowires and nanowire thin films are then highlighted. The final section deals with the applications of transparent Metal Oxide nanowire transistors in the field of transparent displays and concludes with an outlook on the current perspectives and future directions of transparent Metal Oxide nanowire transistors.
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Metal Oxide nanowire transistors
Journal of Materials Chemistry, 2012Co-Authors: Hongtao Huang, Xianfu Wang, Bo Liang, Zhe Liu, Di Chen, Guozhen ShenAbstract:Metal Oxide nanowires are promising building blocks for thin film transistors due to their one-dimensional geometry in nanoscale, high crystalline nature, and excellent optical and electrical properties. In the past decade, intensive research interest has been drawn to Metal Oxide nanowire transistors, and various Metal Oxide nanowires like ZnO, In2O3, and SnO2 have been fabricated into thin film transistors to study their electrical properties and the characteristics as transistor active channels. Much effort has been paid to promote the performance of Metal Oxide nanowire transistors, and expand the application areas covering from sensing devices, transparent and flexible electronics, to memories and integrated logic circuits. In this review, we highlight the state-of-art progress in Metal Oxide nanowire transistors, with an emphasis on basic properties and performances. We summarize the characteristics of transistors based on different Metal Oxide nanowires, the strategies to improve the performance, and various application fields. Finally we present an outlook on the future development of Metal Oxide nanowire transistors, including the study of material properties, the design of device structures and the development of applications.
Bo Liang - One of the best experts on this subject based on the ideXlab platform.
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Transparent Metal Oxide nanowire transistors
Nanoscale, 2012Co-Authors: Di Chen, Xianfu Wang, Bo Liang, Zhe Liu, Guozhen ShenAbstract:With the features of high mobility, a high electric on/off ratio and excellent transparency, Metal Oxide nanowires are excellent candidates for transparent thin-film transistors, which is one of the key technologies to realize transparent electronics. This article provides a comprehensive review of the state-of-the-art research activities that focus on transparent Metal Oxide nanowire transistors. It begins with the brief introduction to the synthetic methods for high quality Metal Oxide nanowires, and the typical nanowire transfer and printing techniques with emphasis on the simple contact printing methodology. High performance transparent transistors built on both single nanowires and nanowire thin films are then highlighted. The final section deals with the applications of transparent Metal Oxide nanowire transistors in the field of transparent displays and concludes with an outlook on the current perspectives and future directions of transparent Metal Oxide nanowire transistors.
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Metal Oxide nanowire transistors
Journal of Materials Chemistry, 2012Co-Authors: Hongtao Huang, Xianfu Wang, Bo Liang, Zhe Liu, Di Chen, Guozhen ShenAbstract:Metal Oxide nanowires are promising building blocks for thin film transistors due to their one-dimensional geometry in nanoscale, high crystalline nature, and excellent optical and electrical properties. In the past decade, intensive research interest has been drawn to Metal Oxide nanowire transistors, and various Metal Oxide nanowires like ZnO, In2O3, and SnO2 have been fabricated into thin film transistors to study their electrical properties and the characteristics as transistor active channels. Much effort has been paid to promote the performance of Metal Oxide nanowire transistors, and expand the application areas covering from sensing devices, transparent and flexible electronics, to memories and integrated logic circuits. In this review, we highlight the state-of-art progress in Metal Oxide nanowire transistors, with an emphasis on basic properties and performances. We summarize the characteristics of transistors based on different Metal Oxide nanowires, the strategies to improve the performance, and various application fields. Finally we present an outlook on the future development of Metal Oxide nanowire transistors, including the study of material properties, the design of device structures and the development of applications.