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.

Zinc Selenide Nanoribbons and Nanowires

Abstract: Zinc selenide nanoribbons and nanowires were obtained using laser ablation of ZnSe pressed powders. Their formation appeared to follow the vapor−solid and vapor−liquid−solid growth mechanisms, resp...

Ultrastable, Highly Fluorescent, and Water‐Dispersed Silicon‐Based Nanospheres as Cellular Probes

Abstract: Fluorescent cellular probes are powerful tools for studying cellular morphology, behavior, and physiological functions. For optimum imaging and tracking of biological cells, these probes should be water-dispersible, antibleaching, luminescent, and biocompatible. In the last century, organic dyes and fluorescent proteins were mostly used as fluorescent probes in biological and biomedical research; however, they suffer from severe photobleaching that restricts their applications for long-term in vitro or in vivo cell imaging. This shortcoming has led to an intense interest in colloidal fluorescent semiconductor quantum dots (QDs) since II/VI QDs were shown to be promising for cell imaging in 1998. Compared to fluorescent dyes, QDs possess unique advantages such as size-tunable emission wavelengths, broad photoexcitation, narrow emission spectra, strong fluorescence, and high resistance to photobleaching. Consequently, QDs have been widely used as a new class of fluorescent probes in cellular research, for example, in vitro imaging, cell labeling, and tracking cell migration. However, recent investigations have shown that these QDs are cytotoxic, especially under harsh conditions (e.g., UV irradiation), because heavy metal ions (such as Cd or Pb ions) are often released in oxidative environments, which leads to severe cytotoxicity by conventional mechanisms of heavy metal toxicity. Surface modification of QDs, such as epitaxial growth of the ZnS shell, silica coating, or polymer coating, has been used to alleviate the cytotoxicity problem. While these techniques are viable to a certain extent, they are relatively complicated and require additional processing steps. Notably, the risk of cytotoxic problems still remains since heavy-metal ions contained in the modified QDs may invariably be released in physiological environments. Consequently, the inherent problems, that is, severe photobleaching and cytotoxicity, associated with the traditional dyes and the fluorescent II/VI QDs remain unsolved, and have fueled a continual and urgent search for new cellular probes that are more photostable and biocompatible. Silicon is the leading semiconductor material for technological applications because of its wide-ranging applications by the electronics industry. Silicon-based nanostructures, such as nanoribbons, nanowires, and nanodots, are being intensely investigated. The quantum confinement phenomenon in silicon QDs (SiQDs) is a particular focus of research since it would increase the probability of irradiative recombination by indirect-to-direct band-gap transitions, which lead to enhanced fluorescent intensity and the prospect of longawaited optical applications. The biocompatibility and noncytotoxic properties of SiQDs are much better than those of traditional II/VI QDs, although their photoluminescence (PL) intensity is weaker. As such, silicon-containing materials may be useful for biological applications such as cellular imaging and labeling because of their favorable biocompatibility, if water-dispersed silicon nanomaterials with adequate stability and strong fluorescence are properly developed. Herein we report a new variety of silicon-based nanospheres for use as cellular probes, which possess excellent water-dispersibility, strong photoluminescence, and robust photostability. Our design of these nanospheres was formulated from calculations performed by using the B3LYP/6-31G method, a classic calculation method based on hybrid density functional theory. Figure 1a shows that the calculated free energy of the products PSi O ( 15.2 kcal mol ) is higher than that of PSi C ( 33.1 kcalmol ), whereas the energy barrier of forming the Si O bond (ESi O = 41.5 kcalmol ) is much lower than that of the Si C bond (ESi C = 59.5 kcal mol ). The energy consideration implies that an acrylic acid monomer (AAc) would react with the surface of the SiQDs via the carbonyl or alkene groups by forming Si O or Si C bonds, as previously reported. Furthermore, the calculations yield the energy relation of ESi O (41.5 kcal mol )

Gold nanoparticles-decorated silicon nanowires as highly efficient near-infrared hyperthermia agents for cancer cells destruction.

Abstract: Near-infrared (NIR) hyperthermia agents are of current interest because they hold great promise as highly efficacious tools for cancer photothermal therapy. Although various agents have been reported, a practical NIR hyperthermia agent is yet unavailable. Here, we present the first demonstration that silicon nanomaterials-based NIR hyperthermia agent, that is, gold nanoparticles-decorated silicon nanowires (AuNPs@SiNWs), is capable of high-efficiency destruction of cancer cells. AuNPs@SiNWs are found to possess strong optical absorbance in the NIR spectral window, producing sufficient heat under NIR irradiation. AuNPs@SiNWs are explored as novel NIR hyperthermia agents for photothermal ablation of tumor cells. In particular, three different cancer cells treated with AuNPs@SiNWs were completely destructed within 3 min of NIR irradiation, demonstrating the exciting potential of AuNPs@SiNWs for NIR hyperthermia agents.

A polyoxometalate-assisted electrochemical method for silicon nanostructures preparation: from quantum dots to nanowires.

Abstract: Si quantum dots, nanoparticles, nanowires, and ordered Si complex micro-/nanostructures can be obtained directly from silicon wafer by a polyoxometalate-assisted electrochemical method.

A roadmap for graphene

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.

High-performance lithium battery anodes using silicon nanowires

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.

Nanobelts of Semiconducting 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.

Raman spectroscopy as a versatile tool for studying the properties of graphene

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.

Aggregation-Induced Emission: Together We Shine, United We Soar!

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