Southeast University

About: Southeast University is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Computer science & MIMO. The organization has 66363 authors who have published 79434 publications receiving 1170576 citations. The organization is also known as: SEU.

MoS2/ZnO van der Waals heterostructure as a high-efficiency water splitting photocatalyst: a first-principles study

Abstract: Previous investigations [H. L. Zhuang and R. G. Hennig, J. Phys. Chem. C, 2013, 117, 20440-20445; J. Kang, S. Tongay, J. Zhou, J. Li and J. Wu, Appl. Phys. Lett., 2013, 102, 012111] demonstrated that molybdenum disulfide (MoS2) is a potential photocatalyst for water splitting. However, the photogenerated electron-hole pairs in MoS2 remain in the same spatial regions, resulting in a high rate of recombination. Using first-principles calculations, we designed a MoS2-based heterostructure by stacking MoS2 on two-dimensional zinc oxide (ZnO) and investigated its structural, electronic, and optical properties. The interaction at the MoS2/ZnO interface was found to be dominated by van der Waals (vdW) forces. The energy levels of both water oxidation and reduction lie within the bandgap of the MoS2/ZnO vdW heterostructure, which guarantee their occurrence for water splitting. Moreover, a type-II band alignment and a large built-in electric field are formed at the MoS2/ZnO interface, which ensure the enhanced separation of the photogenerated electron-hole pairs. In addition, strong optical absorption in the visible region was also found in the MoS2/ZnO vdW heterostructure, indicating that it has potential for application in photovoltaic and photocatalytic devices.

Analysis and Comparison of Medium Voltage High Power DC/DC Converters for Offshore Wind Energy Systems

Abstract: Offshore wind farm with an internal medium-voltage dc (MVDC)-grid collection connected HVDC transmission may be an option to harvest offshore wind energy. High-power MV dc/dc converters with high-step-up conversion ratios are the key components for the internal MVDC grid. In this paper, a high-efficiency step-up resonant switched-capacitor converter for offshore wind energy system is studied, which is characterized by the soft-switching condition for all switches and diodes. This significantly reduces switching losses and higher switching frequency is feasible to reduce the overall system volume and weight. The comparisons with other two kinds of topologies are also presented; moreover, the possible specification requirements of high power MV dc/dc converters are analyzed and set. The operation principle of the proposed converter has been successfully verified by simulation and experiment results.

Gold Nanoclusters and Graphene Nanocomposites for Drug Delivery and Imaging of Cancer Cells

Abstract: Gold nanoclusters (GNCs) have attracted wide attention owing to their outstanding surface and physical properties (for example, near-infrared photoluminescence, optical chirality, and ferromagnetism), which has led to a wide range of applications, such as for single-molecule photonics, sensing, and biological labeling. In contrast to organic dyes and quantum dots, GNCs do not contain chemical functions and toxic heavy metals. Their near-infrared range of emission avoids interference from many biological moieties, making GNCs ideal for biological assays and cell imaging so that they may become a powerful alternative to usual fluorescence labels. On the other hand, two dimensional graphene has attracted considerable interest owing to its long-range p conjugation, yielding extraordinary thermal, mechanical, and electrical properties. To date, the chemistry of graphene that has been reported mainly concerns the chemistry of graphene oxide (GO), which has chemically reactive oxygen-containing groups, including carboxylic acid groups at the edges of GO and epoxy and hydroxy groups on the basal planes. Because electrical conductivity, a large specific Brunauer–Emmett–Teller surface area, and high fracture strength can be recovered by restoring the p network, one of the most important reactions of GO is its reduction. Previous studies have established that graphene, including GO and its reduced form, reduced graphene oxide (RGO), is biocompatible and is a perfect support for a variety of metal and metal oxide nanoparticles, such as Pt, Au, TiO2, [9] fluorescent molecules, and drugs with potential biochemical applications. Functionalized graphene sheets are thus prone to act as drug delivery platforms, while their nearinfrared thermal properties make them attractive multimodal cancer therapeutic agents. Furthermore, RGO could also allow a facile attachment of many molecular drugs and nanomaterials. RGO has been frequently modified by noncovalent physisorption of polymers, small aromatic molecules, and metal nanoparticles with higher electron affinity, such as gold, onto their basal planes by p–p stacking, cation–p, or van der Waals interactions. For GNC-RGO nanocomposites, it may not only offer new and efficient entries in the current search for multimodal therapeutic materials that are prone to targeting/detecting and treating specifically altered tissues, but also offer attractive alternatives to existing cancer therapeutic techniques. Herein, we explore the biological properties of newly prepared GNC-RGO nanocomposites. This material could cause inhibition of HepG2 cells at high concentration, but more interestingly for oncotherapy it could carry anticancer agents such as doxorubicin (DOX) inside the cells while leading to some synergy in inducing karyopyknosis. It is observed that GNCs anchored on RGO retain their nearinfrared fluorescent property so that Raman spectroscopy could be used to investigate the performance of DOX-loaded GNC-RGO nanocomposites against hepatocarcinoma and provide important mechanistic clues about their interactions with proteins and DNA. GNCs were prepared in the organic phase following a conventional Brust–Schiffrin procedure and transferred into an aqueous phase. Simple mixing of the dodecanethiolCTAB-capped GNCs with RGO in aqueous solution followed by separation afforded water-soluble GNC-RGO nanocomposites in excellent yields. TEM analysis (Figure 1a) established that 95% of the water-soluble GNCs ranged between 2–3 nm in diameter with a distribution peak at 2.5 nm. They maintained their size distribution and morphology upon attachment to RGO (Figure 1b). HRTEM (Figure 1b, inset) showed that the GNCs kept their interplanar Au–Au spacing at 0.215 nm after attachment onto RGO. Though common gold nanoparticle sols exhibit a surface plasmon band (SPB), creating a broad absorption band in the visible region around 520 nm and thus their characteristic deep-red color, the color of GNCs and GNC-RGO was faint, in agreement with the fact that no obvious UV/Vis absorbance could be observed in Figure 1c. It is known that Au nanoparticles less than 3 nm in size do not exhibit the surface plasmon resonance characteristic peak at around 520 nm. This result is in good agreement with our observation (Figure 1 c) in which the absorption originating [*] C. Wang, J. Li, Dr. H. Jiang, Prof. X.-M. Wang State Key Lab of Bioelectronics (Chien-Shiung Wu Laboratory) Southeast University, No. 2 Sipailou, Nanjing 210096 (China) E-mail: xuewang@seu.edu.cn