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Shuit-Tong Lee

Bio: Shuit-Tong Lee is an academic researcher from Soochow University (Suzhou). The author has contributed to research in topics: Silicon & Nanowire. The author has an hindex of 138, co-authored 1121 publications receiving 77112 citations. Previous affiliations of Shuit-Tong Lee include University of British Columbia & Hong Kong University of Science and Technology.
Topics: Silicon, Nanowire, OLED, Electroluminescence, Diamond


Papers
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Journal ArticleDOI
TL;DR: By varying the process temperatures, the DAPMP nanostructures can be controllably prepared as either nanoribbons, nanotubes, or nanowires with high morphological and chemical purities.
Abstract: Single-crystal one-dimensional (1-D) nanostructures of [2-(p-dimethyl-aminophenyl)ethenyl]-phenyl-methylene-propanedinitrile (DAPMP) have been prepared by a simple solution process without the assistance of added surfactant, catalyst, or template under ambient condition. The approach exploits the directional supramolecular interaction induced by strong donor-acceptor dipole-dipole supramolecular interaction in the growth of 1-D nanostructures. By varying the process temperatures, the DAPMP nanostructures can be controllably prepared as either nanoribbons, nanotubes, or nanowires with high morphological and chemical purities. Significant changes in optical properties were observed for nanostructures of different morphology.

186 citations

Journal ArticleDOI
TL;DR: In this article, Si-containing products with different colors and appearances were formed on the surfaces of the Si wafers over a wide temperature range of 890-1320 °C and a long distance of 85 mm.
Abstract: Silicon-based nanostructures with different morphologies, sizes, compositions, and microstructures were grown on Si wafers by thermal evaporation of SiO powders at 1350 °C for 5 h under 300 Torr of a flowing gas mixture of 5% H2-Ar at a flow rate of 50 standard cubic centimeters per minute (sccm). The SiO powders and Si wafers were placed inside an alumina tube, which was heated by a tube furnace. The local temperature inside the tube was carefully calibrated by a thermal couple. After evaporation, Si-containing products with different colors and appearances were formed on the surfaces of the Si wafers over a wide temperature range of 890-1320 °C and a long distance of 85 mm. Basing on the colors and appearances of the products, five distinct zones, which corresponding to different temperature ranges, were clearly identified from the highest temperature of 1320 °C to the lowest temperature of 890 °C. They are zone I (1250-1320 °C), zone II (1230-1250 °C), zone III (1180-1230 °C), zone IV (930-1180 °C), and zone V (890-930 °C). The deposited products were systematically studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results show that, besides Si nanowires, many other kinds of Si-based nanostructures such as octopuslike, pinlike, tadpolelike, and chainlike structures were also formed. The temperature distribution inside the alumina tube was found to play a dominant role on the formation of these structures. It is demonstrated that a control over the growth temperature can precisely control the morphologies and intrinsic structures of the silicon-based nanomaterials. This is an important step toward design and control of nanostructures. The growth mechanisms of these products were briefly discussed.

182 citations

Journal ArticleDOI
TL;DR: In this article, a hole-transporting material, 1,3,4,5,6,7-hexaphenyl-2-{3‘-(9-ethylcarbazolyl)}-isoindole (HPCzI), has been synthesized.
Abstract: A new hole-transporting material, 1,3,4,5,6,7-hexaphenyl-2-{3‘-(9-ethylcarbazolyl)}-isoindole (HPCzI), has been synthesized. The new compound is a highly phenylated isoindole with good thermal and chemical stabilities. Thermal analysis using scanning calorimetry shows the compound to have a high melting point at 311.5 °C. Its bulky structure leads to good film-forming properties of the compound via thermal evaporation. Aside from the high hole mobility, the compound possesses other important attributes required for a good hole-transporting host material for applications in organic electroluminescence. The photophysical property of HPCzI and its performance as a hole-transporting material in a double-layered electroluminescent device were investigated. At a drive voltage of 8.8 V and a current density of 20 mA/cm2, the device with a configuration of ITO/HPCzI/AlQ3/MgAg (30 Ω/□:700 A:700 A:2000 A) showed a green AlQ3 emission with a current efficiency of 3.5 cd/A.

180 citations

Journal ArticleDOI
TL;DR: Cux Co1-x O nanoparticles (NPs) facilely deposited on graphene oxide (GO) is reported as a low-cost and high-performance catalyst for the hydrolysis of AB, which exhibits an initial total turnover frequency (TOF) value of 70.0 mol/(Cat-metal) mol⋅min, which is the highest TOF ever reported for noble metal-free catalysts.
Abstract: Ammonia-borane (AB) is an excellent material for chemical storage of hydrogen. However, the practical utilization of AB for production of hydrogen is hindered by the need of expensive noble metal-based catalysts. Here, we report Cux Co1-x O nanoparticles (NPs) facilely deposited on graphene oxide (GO) as a low-cost and high-performance catalyst for the hydrolysis of AB. This hybrid catalyst exhibits an initial total turnover frequency (TOF) value of 70.0 (H2 ) mol/(Cat-metal) mol⋅min, which is the highest TOF ever reported for noble metal-free catalysts, and a good stability keeping 94 % activity after 5 cycles. Synchrotron radiation-based X-ray absorption spectroscopy (XAS) investigations suggested that the high catalytic performance could be attributed to the interfacial interaction between Cux Co1-x O NPs and GO. Moreover, the catalytic hydrolysis mechanism was studied by in situ XAS experiments for the first time, which reveal a significant water adsorption on the catalyst and clearly confirm the interaction between AB and the catalyst during hydrolysis.

180 citations

Journal ArticleDOI
TL;DR: In this article, the oxide-assisted nanowire growth has been studied and shown that oxides play a dominant role in the nucleation and growth of high-quality semiconductor nanowires.
Abstract: Semiconductor wires with nanometer widths have attracted much attention in recent years for their potential applications in mesoscopic research and nanodevices. Since the 1960s, Si whiskers grown from the vapor-liquid-solid (VLS) reaction have been extensively studied. In the VLS reaction, Au particles are generally used as the mediating solvent on a Si substrate since Au and Si form a molten alloy at a relatively low temperature. Si in the vapor phase diffuses into the liquid-alloy droplet and bonds to the solid Si at the liquid-solid interface, which results in the growth of Si whiskers. The diameter of the whisker is determined by the diameter of the liquid-alloy droplet at its tip. Si whiskers generally grow along ⟨111⟩ directions epitaxially on Si(111) substrates in the form of single crystals by the VLS reaction.In different materials systems, however, a variety of whisker forms can be obtained. For example, GaP whiskers display rotational twins around their ⟨111⟩ growth axes, while GaAs whiskers grow in the form of the wurtzite structure.Thus far, the synthesis of one-dimensional nanostructured materials on a large scale remains a challenge. In recent years, many efforts have been made to synthesize Si nanowires by employing different methods such as photolithography and etching techniques and scanning tunneling microscopy. One method of particular interest is a recently developed laser ablation of metal-containing semiconductor targets, by which bulk quantities of semiconductor nanowires can be readily obtained. Our recent studies show that oxides play a dominant role in the nucleation and growth of high-quality semiconductor nanowires in bulk quantities by laser ablation, thermal evaporation, or chemical vapor deposition. A new growth mechanism called oxide-assisted nanowire growth has therefore been established. The ability to synthesize large quantities of high-purity (no contamination), ultra-long (in millimeters), and uniform-sized semiconductor nanowires (a few nanometers to tens of nanometers in diameter) from this new technique offers exciting possibilities in fundamental and applied research.

179 citations


Cited by
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Journal ArticleDOI
11 Oct 2012-Nature
TL;DR: This work reviews recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.
Abstract: Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

7,987 citations

Journal ArticleDOI
TL;DR: The theoretical charge capacity for silicon nanowire battery electrodes is achieved and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.
Abstract: There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices. Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g(-1); ref. 2). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials, silicon anodes have limited applications because silicon's volume changes by 400% upon insertion and extraction of lithium which results in pulverization and capacity fading. Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.

6,104 citations

Journal ArticleDOI
09 Mar 2001-Science
TL;DR: The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures, which could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides.
Abstract: Ultralong beltlike (or ribbonlike) nanostructures (so-called nanobelts) were successfully synthesized for semiconducting oxides of zinc, tin, indium, cadmium, and gallium by simply evaporating the desired commercial metal oxide powders at high temperatures. The as-synthesized oxide nanobelts are pure, structurally uniform, and single crystalline, and most of them are free from defects and dislocations. They have a rectanglelike cross section with typical widths of 30 to 300 nanometers, width-to-thickness ratios of 5 to 10, and lengths of up to a few millimeters. The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures. The nanobelts could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides and building functional devices along individual nanobelts.

5,677 citations

Journal ArticleDOI
TL;DR: The state of the art, future directions and open questions in Raman spectroscopy of graphene are reviewed, and essential physical processes whose importance has only recently been recognized are described.
Abstract: Raman spectroscopy is an integral part of graphene research. It is used to determine the number and orientation of layers, the quality and types of edge, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups. This, in turn, provides insight into all sp(2)-bonded carbon allotropes, because graphene is their fundamental building block. Here we review the state of the art, future directions and open questions in Raman spectroscopy of graphene. We describe essential physical processes whose importance has only recently been recognized, such as the various types of resonance at play, and the role of quantum interference. We update all basic concepts and notations, and propose a terminology that is able to describe any result in literature. We finally highlight the potential of Raman spectroscopy for layered materials other than graphene.

5,673 citations

Journal ArticleDOI
TL;DR: This paper presents a meta-analysis of the chiral stationary phase transition of Na6(CO3)(SO4)2, a major component of the response of the immune system to Na2CO3.
Abstract: Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

5,658 citations