Recent progress in transparent oxide semiconductors: Materials and device application

This paper reviews our recent research progress on new transparent conductive oxide (TCO) materials and electronic and optoelectronic devices based on these materials. First, described are the materials including p-type materials, deep-UV transparent TCO(β-Ga₂O₃), epitaxially grown ITO with atomically flat surface, transparent electrochromic oxide (NbO₂F), amorphous TCOs, and nanoporous semiconductor 12CaO · 7Al₂O₃. Second, presented are TCO-based electronic/optoelectronic devices realized to date, UV/blue LED and UV-sensors based on transparent pn junction and high performance transparent TFT using n-type TCO as an n-channel. Finally, unique optoelectronic properties (p-type degenerate conduction, transfer doping of carriers, RT-stable exciton, and large optical nonlinearity) originating from 2D-electronic nature in p-type layered oxychalcogenides are summarized along with the fabrication method of epitaxial thin films of these materials.     

Recent progress in p-type doping and optical properties of SnO2 nanostructures for optoelectronic device applications

SnO(2) semiconductor is a host material for ultraviolet optoelectronic devices applications because of its wide band gap (3.6 eV), large exciton binding energy (130 meV) and exotic electrical properties and has attracted great interests. The renewed interest is fueled by the availability of exciton emission in nanostructures, high quality epitaxial films, p-type conductivity, and heterojunction light emitting devices. This review begins with a survey of the patents and reports on the recent developments on SnO2 films. We focus on the epitaxial growth, p-type doping and photoluminescence properties of SnO(2) films and nanostructures, including the achievements in our group. Finally, the applications of SnO(2) nanostructures to optoelectronic devices including heterojunction light emitting devices, photodetectors and photovoltaic cells will be discussed.     

Selenium nanomaterials: An overview of recent developments in synthesis,properties and potential applications

Advances in science and nanotechnology have facilitated the development of new methods for the preparation of pure selenium as selenium nanomaterials. They offer remarkable potential for technological applications in the fields of medicine, diagnostics, therapeutics, toxicology, electronics, catalysis and so on. Moreover, selenium nanomaterials also find applications in photographic exposure metres, rectifiers, signal emitting devices and transmitting devices, because of their unique structural, optical and electronic properties. This study describes a detailed advanced report on the synthesis, assembly, characterization and various applications of selenium nanomaterials. In addition, relevant synthesis methods, properties, challenges and opportunities associated with selenium nanomaterials are also presented.     

Recent progress in synthesis,properties and potential applications of SiC nanomaterials

As nanotechnology rapidly advanced over the past decades, a variety of nanomaterials have been developed and studied. Among them, SiC nanomaterials have recently attracted increasing attention for their demonstrated unique chemical and physical properties as well as wide potential applications. This article provides a comprehensive review of the recent progress on the synthesis, novel properties, and applications of SiC nanomaterials. It begins with the introduction of various techniques used for the rational design and synthesis of SiC nanomaterials, with an emphasis on vapor-based and solution-based methods. Discussion is then made on the mechanical, luminescent, electrical, thermal, and wetting properties of SiC nanomaterials as well as the characterizations that reveal them. Thereafter, various intriguing applications particularly in composites, field emitters, field effect transistors, sensors, nanoelectromechanical devices, catalyst, supercapacitors, bioimaging probes and microwave absorbers are highlighted. Finally, this review is concluded with an outlook of future research on SiC nanomaterials, major challenges to be met and possible solutions.     

Vertically aligned single crystal TiO2 nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis details and applications

Single-crystal one-dimensional (1D) semiconductor architectures are important in materials-based applications requiring a large surface area, morphological control, and superior charge transport. Titania has widespread utility in applications including photocatalysis, photochromism, photovoltaics, and gas sensors. While considerable efforts have focused on the preparation of 1D TiO2, no methods have been available to grow crystalline nanowire arrays directly onto transparent conducting oxide (TCO) substrates, greatly limiting the performance of TiO2 photoelectrochemical devices. Herein, we present a straightforward low temperature method to prepare single crystal rutile TiO2 nanowire arrays up to 5 microm long on TCO glass via a non-polar solvent/hydrophilic substrate interfacial reaction under mild hydrothermal conditions. The as-prepared densely packed nanowires grow vertically oriented from the TCO glass substrate along the (110) crystal plane with a preferred (001) orientation. In a dye sensitized solar cell, N719 dye, using TiO2 nanowire arrays 2-3 microm long we achieve an AM 1.5 photoconversion efficiency of 5.02%.     

Recent developments and applications in electroabsorption semiconductor modulators

State of the art developments in electroabsorption modulators that utilize quantum well-semiconductors are reviewed. Special emphasis is given to recent progress made in materials for modulators. On technological grounds, optimized Multiple Quantum Well modulators in the GaAs/AlGaAs system have been driven by applications in photonic switching and optical interconnects. Surprisingly, these same structures exhibit a wealth of new behavior that ranges from Bloch oscillations to excitons in Coupled Well, Wannier–Stark and Shallow Well superlattices. Several types of excitonic phases have been identified, optically and found to transform as the system dimensionality changes from 2D to 3D. In addition, new material systems have shown that quantum well excitonic absorption quality can be transferred to technologically important wavelengths at 1.06 or 1.55 μm.     

Optical and electrical properties of p-type transparent conducting CuAlO2 thin film

P-type transparent conducting CuAlO₂ thin films were prepared by e-beam evaporation and wet-oxidation technique. CuAlO₂ film was preferentially (006) oriented after wet-oxidation. The transmittance varied from 20 to 85% and the resistivity varied from 5 × 10^− 3 to 4 Ω cm with wet-oxidation conditions. The nature of p-type films was confirmed by the positive hall coefficient. Optical band gap was estimated to be in the range of 3.96-4.20 eV. These behaviors were due to the decrease of oxygen deficient state in the film as oxidation progresses. Microstructural observations of films showed smooth morphology with 23.2-29.7 Å rms roughness.     

炭与TiO2光催化剂的复合及协同作用研究进展

通过论述炭与TiO2光催化剂的复合方式，系统总结了复合光催化剂的各种制备方法，指出炭与TiO2的复合呈现多样化的特征，炭不仅作为载体，还可以用作涂层、造孔剂以及助剂。同时，炭在复合体中也展现出多方面的作用，不仅可以富集目标污染物，捕获中间产物，还可以抑制水蒸气和其他组分对光催化降解的影响，并且可以抑制热处理时TiO2相变和晶粒长大。可见，炭与TiO2光催化剂的复合将为推动光催化技术的实用化产生积极影响。     

Semiconducting transparent thin films: their properties and applications

The present state of the art of transparent, electrically conducting films, with special reference to In₂O₃, SnO₂ and Cd₂SnO₄, has been reviewed. Various production techniques currently in use, and typical parameters used in the processes have been discussed in detail. Electrical and optical properties of these films have been reported as a function of various parameters, e.g. substrate temperature, doping, oxygen pressure, etc. Finally, the applications of these films in research and industry have been discussed in detail.     

非金属元素掺杂TiO2的可见光催化活性研究进展

TiO2(锐钛矿)的禁带宽度限制了其光诱导特性的广泛应用,非金属元素掺杂为TiO2在可见光辐射环境下的应用提供了新的机会.详细介绍了非金属元素(N、C、S、F)掺杂TiO2的制备方法和可见光催化活性研究的最新进展,讨论了制备工艺与掺杂TiO2可见光催化活性的关系,深入分析了非金属元素对TiO2可见光催化活性的诱导机理.制备工艺显著影响了掺杂元素的化学态和含量,从而决定了掺杂TiO2带隙中局域态的特征.带隙中局域态特征正是影响掺杂TiO2可见光催化活性的关键因素.文章也对未来的研究方向进行了展望.     

碳量子点的合成、性质及其应用

碳量子点(CQDs,C-dots or CDs)是一种新型的碳纳米材料,尺寸在10nm以下,具有良好的水溶性、化学惰性、低毒性、易于功能化和抗光漂白性、光稳定性等优异性能,是碳纳米家族中的一颗闪亮的明星。自从2006年[1]报道了碳量子点(CQDs)明亮多彩的发光现象后,世界各地的研究小组开始对CQDs进行了深入的研究。最近几年的研究报道了各种方法制备的CQDs在生物医学、光催化、光电子、传感等领域中都有重要的应用价值。这篇综述主要总结了关于CQDs的最近的发展,介绍了CQDs的合成方法、表面修饰、掺杂、发光机理、光电性质以及在生物医学、光催化、光电子、传感等领域的应用。     

TiO2/聚苯胺复合材料的合成、结构表征及光催化性能

在室温下,以苯胺为单体、钛酸四丁酯为反应物,通过化学氧化原位聚合和溶胶-凝胶的方法制备了TiO2/聚苯胺复合材料。利用X-射线衍射仪、傅立叶变换红外光谱仪、紫外-可见吸收光谱仪、热失重分析仪等对复合材料表面的微观结构及热稳定性进行了表征。通过光催化降解甲基橙实验评价了TiO2/聚苯胺复合光催化剂在紫外光条件下的光催化活性,实验表明,TiO2/聚苯胺复合材料的催化效率大大提高,特别是TiO2/聚苯胺(质量比例为1/2)复合材料对甲基橙的降解效率最高达到85.7%。     

稀土Eu掺杂纳米TiO2的荧光特性研究及其应用

以Eu2O3试剂为荧光前驱体,与钛酸正丁酯在酸-水溶液中发生溶胶-凝胶反应,制备了一种可作为荧光标记分子的Eu3+/TiO2荧光性纳米微粒,并对样品的形貌、组成及结构进行了表征.结果表明,纳米粒子的平均粒径5nm.用468nm激发光源激发样品,荧光强度随着Eu3+的掺杂含量0、0.5%、1%、2%、3%、4%先升高后降低,当掺杂含量为2%时,荧光强度最强.采用倒置荧光显微镜观察了Eu3+/TiO2纳米荧光探针在洋葱表皮细胞膜上聚集受激发射荧光行为.     

Graphene-based materials: synthesis, characterization, properties, and applications

Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.     

Hydrothermal synthesis of different TiO2 nanostructures: structure, growth and gas sensor properties

A type of titanium precursor, H-exchanged titanate nanobelts, was used to prepare nanosized anatase titanium dioxide (TiO₂) with various morphologies by hydrothermal method. Nanorods, nanobelts, nano-polyhedrons and nanoparticles were successfully synthesized. We found that CTAB and EDTA-4Na⁺ play critical roles in synthesizing the nanorods and nano-polyhedrons. All the samples exhibit rapid response and recovery time to ethanol, but Nanorods, nanobelts and nano-polyhedrons show lager response than nanoparticles.     

Recent advances in germanium nanocrystals: Synthesis,optical properties and applications

Germanium nanocrystals (Ge NCs) have recently attracted renewed scientific interest as environmentally friendlier alternatives to classical II–VI and IV–VI QDs containing toxic elements such as Hg, Cd and Pb. Importantly, Ge NCs are nontoxic, biocompatible, and electrochemically stable. An essential requirement is the ability to prepare Ge NCs with narrow size distributions and well characterized surface chemistry, as these define many of their photophysical properties. However, a thorough discussion on these criteria has not been achieved to date. Here, size, surface control, and mechanisms for light emission in Ge NCs are discussed and their exciting recent applications are highlighted. The beneficial properties of Ge NCs suggest that this material can improve the performance of numerous devices like solar cells, photodetectors, and lithium ion batteries.     

AlN nanowires: synthesis, physical properties, and nanoelectronics applications

One-dimensional aluminum nitride (AlN) nanostructures, especially AlN nanowires, have been subjected to numerous investigations due to their unique physical properties and applications ranging from electronics to biomedical. This article reviews the synthesis of AlN nanowires and studies their physical properties and potential nanoelectronics applications. First, the different fabrication techniques used to synthesize AlN nanowires and their growth mechanisms are discussed. Next, the physical properties of AlN nanowires, such as the field emission, transport, photoluminescence, as well as the mechanical and piezoelectric properties are summarized. Finally, the potential applications of AlN nanowires in the field of nanoelectronics are described. Furthermore, this review summarizes the perspectives and outlooks on the future development of AlN nanowires.     

Recent progress in patterned silicon nanowire arrays: fabrication, properties and applications

Currently there is great interest in patterned silicon nanowire arrays and applications. The accurately controlled fabrication of patterned silicon nanowire arrays with the desirable axial crystallographic orientation using simpler and quicker ways is very desirable and of great importance to material synthesis and future nanoscale optoelectronic devices that employ silicon. The recent advances in manipulating patterned silicon nanowire arrays and patents are reviewed with a focus on the progress of nanowire fabrication and applications.     

Nanofibrous TiO2-core/conjugated polymer-sheath composites: synthesis, structural properties and photocatalytic activity

Nanofibrous TiO2-core/conjugated polymer-sheath composite nanocables were synthesized by in-situ chemical oxidative polymerization of aniline with oxidant in the presence of TiO, nanofibers prepared through an electrospinning process. During the polymerization process, aniline molecules were adsorbed on the surface of TiO2. Upon the addition of oxidant, the polymerization of aniline takes place on the surface of the TiO2 nanofibers and polyaniline (PANI) is gradually deposited on their surface. The resulting TiO2-PANI nanocomposites have a coaxial nanocable structure. The morphological and structural properties of the composite nanocables were analyzed by using high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and UV-visible spectroscopy (UV-vis), respectively. The HRTEM images proved that PANI (20 nm thickness) covered the surface of the TiO2 nanofibers. Also, the photocatalytic activity for the degradation of organic dyes on fibrous photocatalysts under UV-light was studied. The photocatalytic experiments showed that dye could be degraded more efficiently on the TiO2-PANI composite nanocables than on pure TiO2, due to the charge transfer from PANI to TiO2. The method for the synthesis of these unique structured composite nanocables is simple, rapid and reproducible. This facile method may be developed to produce multifunctional nanocomposites of various polymers with metal oxide fibers on a large scale for various technological applications such as sensors, solar cells, and catalysts.     

Recent progress in molten salt synthesis of low-dimensional perovskite oxide nanostructures,structural characterization,properties, and functional applications: A review

Molten salt synthesis (MSS) method has advantages of the simplicity in the process equipment, versatile and large-scale synthesis, and friendly environment, which provides an excellent approach to synthesize high pure oxide powders with controllable compositions and morphologies. Among these oxides, perovskite oxides with a composition of ABO3 exhibit a broad spectrum of physical properties and functions (e.g. ferroelectric, piezoelectric, magnetic, photovoltaic and photocatalytic properties). The downscaling of the spatial geometry of perovskite oxides into nanometers result in novel properties that are different from the bulk and film counterparts. Recent interest in nanoscience and nanotechnology has led to great efforts focusing on the synthesis of low-dimensional perovskite oxide nanostructures (PONs) to better understand their novel physical properties at nanoscale. Therefore, the low-dimensional PONs such as perovskite nanoparticles, nanowires, nanorods, nanotubes, nanofibers, nanobelts, and two dimensional oxide nanostructures, play an important role in developing the next generation of oxide electronics. In the past few years, much effort has been made on the synthesis of PONs by MSS method and their structural characterizations. The functional applications of PONs are also explored in the fields of storage memory, energy harvesting, and solar energy conversion. This review summarizes the recent progress in the synthesis of low-dimensional PONs by MSS method and its modified ways. Their structural characterization and physical properties are also scrutinized. The potential applications of low-dimensional PONs in different fields such as data memory and storage, energy harvesting, solar energy conversion, are highlighted. Perspectives concerning the future research trends and challenges of low-dimensional PONs are also outlined.