Default Latest Most Read Please wait a minute... Editorial Two-Dimensional Materials Beyond Graphene: an Emerging Field with Blooming Progress Peng Hailin Acta Chimica Sinica 2015, 73 (9): 861-862. DOI: 10.6023/A1509E001 Published: 20 September 2015 Abstract (628) PDF (482KB)(1040) Knowledge map Reference | Related Articles | Metrics Cited: CSCD(1) Review Electric-double-layer Transistors Based on Two Dimensional Materials He Xuexia, Liu Fucai, Zeng Qingsheng, Liu Zheng Acta Chim. Sinica 2015, 73 (9): 924-935. DOI: 10.6023/A15040280 Published: 15 September 2015 Abstract (1606) PDF (4119KB)(13830) Knowledge map Over the past years, two-dimensional (2D) nanomaterials especially transition metal dichalcogenides (TMDs) have emerged as promising semiconductor materials to complement graphene-based electronics. They grain lots of attention due to their large number of candidates and varieties of physical properties. In this family, there are a wide range of materials exists ranging from Mott insulator semiconductor, metal, even to superconductor. Some of them, e.g. MoS2, MoSe2, WS2 and WSe2 have been widely investigated in these years, and they show unique properties for artificial van der Waals solids, electronics with ultra-low energy consumption, valleytronics, non-linear optics and high performance catalyst for hydrogen evolution reaction, while many of them still await a thorough theoretical and experimental exploration. Scientists in this field have try their best to modify the properties of this unique family. Charge carrier control is a key issue in the development of electronic functions of semiconductive materials. Beyond the simple enhancement of conductivity, high charge carrier accumulation can realize various phenomena, such as chemical reaction, phase transition, magnetic ordering, and superconductivity. In 2007, Hebard et al. reported the first electric-double-layer transistors (EDLT) using ionic liquid as the gate dielectric, the mobility was increased by 3 cm2·V-1·s-1 than the traditional transistor, this was the first demonstration that EDLT can be used to enhance the performance such as the mobility and the operation voltage of the devices. After that work, many works have been done using EDLT method. Very recently, scientists found that EDLT is also applicable for modifying the electronic properties of both organic and inorganic materials by control the charge carriers in the interface of the EDLT. Based on this method, high transistor performance, insulator-metal transitions, superconductivity, and even ferromagnetism have been released. In this review, we introduce and review the recent work for modifying the electronic properties based on 2D TMD materials. Reference | Related Articles | Metrics Cited: Baidu(1) CSCD(4) Communication Fluorescence Quenching Effect of Rhodanmine 6G on Two-Dimensional Bi2Se3 Crystals Wu Jinxiong, Liu Zhongfan, Peng Hailin Acta Chim. Sinica 2015, 73 (9): 944-948. DOI: 10.6023/A15070513 Published: 15 September 2015 Abstract (679) PDF (1884KB)(1732) Knowledge map As a novel quantum material, two-dimensional crystal of Bi2Se3 is a typical topological insulator with an insulating bulk gap and gapless edges or surface states, which has created new opportunities for spintronics and low-dissipation electric transport. For the first time, we studied the fluorescence quenching effect of Rhodanmine 6G molecules on two-dimensional crystals of Bi2Se3 with the thickness ranged from 1 layer to 8 layers. Atomically-thin, high-quality two-dimensional crystals of Bi2Se3 with different thicknesses down to monolayer were firstly grown on mica substrates via van der Waals epitaxy. Typically, its domain size is about tens or several tens micrometers, providing a good platform for studying the thickness-dependent chemical and physical properties of two-dimensional Bi2Se3 crystals. Besides, as fluorescence-probe molecules with high fluorescence quantum yield, a uniform and continuous film of Rhodamine 6G molecules were deposited onto the surface of mica substrate and two-dimensional Bi2Se3 crystals by vacuum evaporation, on which adsorption of almost equal number of Rhodamine 6G molecules was achieved revealed by atomic force microscopy characterization. Subsequently, the measurements of fluorescence spectroscopy were conducted on the Horiba-Jobin Yvon Labram HR800 micro Raman spectrometer with a spatial resolution about 1 μm. Excited by 514.5 nm Ar+ laser, the fluorescence signal from 520 nm to 640 nm of Rhodanmine 6G molecules on different surfaces was collected under the same condition. It was found that the atomically-thin Bi2Se3 crystals can quench the fluorescence of adsorbed Rhodamine 6G molecules. Meanwhile, the thicker Bi2Se3 crystals show more obvious quenching ability to Rhodanmine 6G molecules. In the end, a possible quenching mechanism of fluorescence resonance energy transfer was suggested. According to the UV-Vis spectroscopy of two-dimensional crystals of Bi2Se3, the absorption spectroscopy of Bi2Se3 showed a large spectral overlap with the emission fluorescent of Rhodanmine 6G, which is the key to fluorescence resonance energy transfer. Reference | Related Articles | Metrics Review Synthesis Progress of Layered TMOC-based Intercalation Structures Liu Qin, Liu DaoBin, He Qun, Xiang Ting, Adnan Khalil, Song Li Acta Chim. Sinica 2015, 73 (9): 936-943. DOI: 10.6023/A15050331 Published: 17 July 2015 Abstract (834) PDF (2376KB)(1736) Knowledge map Different types of intercalated agents can be in-situ intercalated into two-dimensional (2D) layered transition metal oxides and chalcogens (TMOCs), which can engineer its electronic structure at the atomic scale and tune its intrinsic physical and chemical properties (i.e. carrier concentration and mobility, magnetic, optical, and other properties). Such intercalations provide a facile way to create new types of multifunctional materials, thus largely extend 2D material's applications for opto-electronic devices, energy storage and conversion, photoelectrocatalysis, etc. Recently, many efforts have been focused on seeking suitable synthesis routes to achieve different types of intercalated nanomaterials. Here, we concisely reviewed the recent development on TMOC-based intercalations produced by various intercalated agents in-situ intercalating. The synthetic strategy of alkali metal and non-alkali metal intercalation, polymer intercalation, small organic molecules intercalation and reduced graphene oxide intercalation were mainly reviewed. Through affecting the interlayer interactions and the crystal anisotropy can realize the strategy of in-situ intercalated layered materials. Reference | Related Articles | Metrics Accounts Controllable Growth of MoS2 on Au Foils and Its Application in Hydrogen Evolution Shi Jianping, Ma Donglin, Zhang Yanfeng, Liu Zhongfan Acta Chim. Sinica 2015, 73 (9): 877-885. DOI: 10.6023/A15030157 Published: 09 July 2015 Abstract (948) PDF (3181KB)(2026) Knowledge map Controllable synthesis of monolayer MoS2 on metal substrates is the basic premise for exploring the intrinsic electronic structure, some novel physical properties, and engineering its application in hydrogen evolution reaction (HER). In recent years, we have been working on low-pressure chemical vapor deposition (LPCVD) growth of monolayer MoS2 on Au foils, with the domain size can be tuned from several hundred nanometers to dozens of microns. By introducing H2 as carrier gas, we have synthesized large domain monolayer MoS2 triangular flakes on Au foils, with the edge length approaching to ca. 81 μm. By using low-energy electron microscopy/diffraction (LEEM/LEED) method, the crystal orientations and domain boundaries of monolayer MoS2 flakes directly on Au foils are further on-site identified. Of particular interest, the nanosized MoS2 flakes on Au foils are proven to be excellent electrocatalysts for HER, featured by a rather low Tafel slope (ca. 61 mV/dec) and a relative high exchange current density (ca. 38.1 μA/cm2). In this review, we summarized controllable growth and on-site domain boundary imaging of monolayer MoS2 on Au foils and its application in HER together with a brief discussion on the future directions, challenges and opportunities in this research area. Reference | Related Articles | Metrics Review Two Dimensional Transitional Metal Dichalcogenides for Biomedical Applications Liu Teng, Cheng Liang, Liu Zhuang Acta Chim. Sinica 2015, 73 (9): 902-912. DOI: 10.6023/A15040283 Published: 07 July 2015 Abstract (924) PDF (5224KB)(1407) Knowledge map Transitional metal dichalcogenides (TMDs) nanosheets are a new kind of two-dimensional nanomaterials emerging after graphene. Due to their intriguing physical and chemical properties, TMD nanosheets have attracted wide interests in many different fields in the past several years. Recently, many groups have also started to explore their biomedical applications. This review article summarizes the synthesis, surface modification, biomedical applications, as well as biosafety evaluation of TMDs nanosheets, and discusses future perspectives of applying this new type of two-dimensional nanomaterials in the area of biomedicine. Reference | Related Articles | Metrics Cited: CSCD(1) Review Synthesis of Two-dimensional Transition Metal Dichalcogenides with Chemical Vapor Deposition Xu Guanchen, Lu Zhixing, Zhang Qi, Qiu Hailong, Jiao Liying Acta Chim. Sinica 2015, 73 (9): 895-901. DOI: 10.6023/A15030203 Published: 02 June 2015 Abstract (956) PDF (6077KB)(1677) Knowledge map Two-dimensional atomic crystals have recently drawn intense attentions due to their unique 2D planar structure, novel properties and attractive applications. In this review, we summarized the recent advances on the synthesis of 2D transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD) with the emphasis on 2D MoS2 and WS2. We discussed the effects of various growth parameters on the synthesis of 2D MoS2 and WS2. We also covered the synthesis strategies for the growth of binary alloys and heterostructures based on MoX2 and WX2 (X=S, Se). Finally, we discussed the challenges and opportunities for the CVD growth of 2D TMDCs. Reference | Related Articles | Metrics Cited: Baidu(2) CSCD(5) Article Photoluminescence Enhancement in Monolayer Molybdenum Disulfide by Annealing in Air Shen Cheng, Zhang Jing, Shi Dongxia, Zhang Guangyu Acta Chim. Sinica 2015, 73 (9): 954-958. DOI: 10.6023/A15030220 Published: 02 June 2015 Abstract (947) PDF (1493KB)(1599) Knowledge map Monolayer molybdenum disulfide is a novel two-dimensional material beyond graphene. It is a direct band gap semiconductor with excellent electrical and optical properties, promising wide application in nanoelectronics and optoelectronics, thus has drawn much attention recently. In this paper, we investigate the enhancement of photoluminescence of monolayer molybdenum disulfide by annealing in air. Monolayer molybdenum disulfide samples were prepared by mechanical exfoliation and chemical vapor deposition with molybdenum oxide and sulfur as sources, and argon as carrier gas. We found that air annealing for several minutes can distinctly enhance the photoluminescence intensity of A exciton by an order of magnitude, which is much better than annealing in argon. The blue shift of A exciton peak is observed after air annealing for all the monolayer molybdenum disulfide samples prepared by different methods above. We also found that this phenomenon widely exists in samples with different substrates like silicon dioxide and sapphire. Electrical transport measurements were carried out and indicate that the carrier mobility of monolayer molybdenum disulfide is largely reduced after annealing in air, which might mean the formation of considerable defects. This phenomenon is believed to be due to the doping effect caused by adsorption of oxygen, which is bonded to the defects after annealing. As acceptors, these oxygen dopants change the distribution of trions and neutral excitons, resulting in less tritons but more neutral excitons. Neutral excitons yield much higher quantum efficiency. As a comparison, we carried out control experiments in which annealing was in NH3 atmosphere. We found that photoluminescence is red shifted and can be quenched. This research results give a simple and effective method to enhance the photoluminescence of monolayer molybdenum disulfide. Reference | Related Articles | Metrics Cited: CSCD(3) Communication Two-Dimensional WS2 Sheets as Interfacial Layer for High-Performance Organic Solar Cells Ma Chunyan, Fu Weifei, Huang Guowei, Chen Hongzheng, Xu Mingsheng Acta Chim. Sinica 2015, 73 (9): 949-953. DOI: 10.6023/A15040246 Published: 02 June 2015 Abstract (723) PDF (2209KB)(1412) Knowledge map Two-dimensional layered WS2 sheets is used as the hole extraction layer (HEL) in organic solar cells (OSCs). We find that UV-ozone treatment of the chemically exfoliated WS2 sheets can significantly improve the device performance of the OSCs with the power conversion efficiency (PCE) of about 8.37%, which is comparable to the OSCs with the standard PEDOT:PSS as the HEL. We attribute the improvement to the incorporation of oxygen into the lattice of the WS2 sheets. The oxygen incorporation reduces the lattice vacancies of WS2 sheets and makes the WS2 partially oxidized and consequently improves the electrical properties of the WS2 sheets. Reference | Supporting Info. | Related Articles | Metrics Accounts Advances in Fabrication of Two-dimensionally Ordered Porous Membranes by Nanosphere Lithography at the Gas-liquid Interface Li Yang, Qi Limin Acta Chim. Sinica 2015, 73 (9): 869-876. DOI: 10.6023/A15020144 Published: 25 May 2015 Abstract (651) PDF (4112KB)(1186) Knowledge map Two-dimensionally (2D) ordered porous membranes are attractive structures with potential applications in a broad variety of fields such as separation and purification, controlled drug delivery, scaffolds for tissue engineering, biosensors, wetting and adhesion, photonic crystals and optical devices, electric and optoelectric devices, antireflective coatings, low dielectric constant materials, and templates or microreactors for nanofabrication. Nanosphere lithography (NSL) based on monolayer colloidal crystals (MCCs) is a general nanofabrication approach toward 2D patterned nanostructures with high controllability and reproducibility. Recently, nanosphere lithography at the gas-liquid interface, which employs MCCs floating at the solution surface as templates, has been demonstrated to be a facile, inexpensive, efficient, and versatile method for the controllable fabrication of self-standing, large-area, 2D ordered porous membranes with tunable structural parameters. This account summarizes our recent efforts devoted to the fabrication and applications of a variety of inorganic 2D ordered porous membranes including nanonets, nanobowl arrays and nanonet-nanobowl composite arrays by NSL at the gas-liquid interface via controlled chemical deposition. First, free-standing, hexagonally ordered Ag2S nanonets were prepared through interfacial deposition induced by gas diffusion; moreover, a variety of 2D ordered gold nanoarrays with unusual patterns were produced by using nanonet bilayers as unique deposition masks. Second, free-standing, honeycomb-patterned nanobowl arrays of Ag and CaCO3 were fabricated through gas diffusion-induced deposition whereas large-area ZnS nanobowl arrays with high regularity were produced through direct solution deposition. The potential applications of the obtained Ag and ZnS nanobowl arrays as plasmonic crystal-based and photonic crystal-based sensors were demonstrated, respectively. Third, unique Ag2S-Ag heterostructured nanobowl arrays were fabricated by two-step NSL at the gas-liquid interface, which involved the successive deposition of Ag2S nanonets and Ag nanobowl arrays. The produced Ag2S-Ag heterostructured nanobowl arrays exhibited effective resistance switching behaviors and enhanced photoresponses, showing potential applications in both electric devices and photocatalysis. Finally, the research trend in this field is briefly described and the remaining challenges are discussed. Reference | Related Articles | Metrics Cited: Baidu(5) CSCD(8) Review Preparation, Structure and Properties of Two-dimensional Semiconductor Alloys Wang Xinsheng, Xie Liming, Zhang Jin Acta Chim. Sinica 2015, 73 (9): 886-894. DOI: 10.6023/A15030187 Published: 22 May 2015 Abstract (1055) PDF (3043KB)(1943) Knowledge map Atomically thick two-dimensional (2D) semiconducting materials have attract broad interest because of their low-dimensional effect. Towards optoelectronic applications, 2D semiconducting materials with tunable band structures (such as tunable band gaps, conducting band and valence band positions) are favored. Alloying is a general approach to tune the band structures. Here, this review introduces the research progresses on 2D semiconductor alloys in recent years, including their thermodynamic stability, controlled preparation, structure characterization and property investigation. The transition- metal dichalcogenide monolayer alloys, mainly Mo, W metal elements and S, Se dichalcogenide elements is focused. Reference | Related Articles | Metrics Cited: Baidu(4) CSCD(4) Review Preparation and Applications of Two-Dimensional Crystals Based on Organic or Metal-Organic Materials Li Shaozhou, Huang Xiao, Zhang Hua Acta Chim. Sinica 2015, 73 (9): 913-923. DOI: 10.6023/A15030221 Published: 21 May 2015 Abstract (1078) PDF (3510KB)(2390) Knowledge map Besides graphene and transitional metal dichalcogenide nanosheets which have aroused tremendous research interest over the last decade, recently, two-dimensional (2D) organic or metal-organic nanosheets have also attracted increasing research interest. These ultrathin nanomaterials possess the long range structural order, the tunable surface properties, and/or controllable porosity, making them promising in a wide range of applications, such as electronics, optoelectronics, catalysis, molecular separation and so on. This review article aims to provide a brief overview on free-standing 2D nanosheets of organic or metal-organic materials that have been reported so far, especially focusing on their synthetic methods and possible applications. Reference | Related Articles | Metrics Cited: Baidu(1) Article Phonon-assisted Upconversion Photoluminescence in Monolayer MoSe2 and WSe2 Xu Weigao, Zhao Yanyuan, Shen Chao, Zhang Jun, Xiong Qihua Acta Chim. Sinica 2015, 73 (9): 959-964. DOI: 10.6023/A15030216 Published: 19 May 2015 Abstract (878) PDF (2316KB)(1606) Knowledge map Phonon-assisted upconversion photoluminescence is the basis of laser cooling effect in solids. Compared to conventional cooling methods, laser cooling has many advantages such as compactness, high efficiency, free of vibrational disturbance and refrigerant-free, etc. Exploring more semiconducting materials in which a net cooling effect can be observed is an important area among the laser cooling community. Monolayer two-dimensional transition metal dichalcogenides (TMDs) like MoSe2 and WSe2 are direct band gap semiconductors. The perfect crystal structure and high extraction efficiency (due to thickness at atomic level) guarantee them the possibility to be potential candidates for laser cooling. In this work, with a Ti-sapphire tunable laser (pumped by a 532 nm laser), we studied the upconversion photoluminescence and its wavelength-dependence. In detail, we implemented experiments on laser power-dependent photoluminescence intensity, the linearity fitting results (at low power) show that it is a phonon-assisted upconversion photoluminescence process; furthermore, this mechanism is also verified from the temperature-dependent upconversion photoluminescence intensity. Further experiments on the investigation of which kinds of phonons are involved in the upconversion process and its efficiency, as well as the design of a sample structure that is free of background absorbance, are still required to help to tell whether net laser cooling can be achieved, or how it can be achieved in monolayers TMDs. Reference | Related Articles | Metrics