Synthesis of silver/SiO2/Eu:Lu2O3 core-shell nanoparticles and their polymer nanocomposites

We report a core-shell approach that combines silver nanoparticles as the metal core component with Eu:Lu₂O₃ as the phosphor shell component. The core-shell design contains an optically transparent SiO₂ intermediate layer that separates the metallic nanoparticle core and the phosphor shell. The thickness of the SiO₂ layer is in the nanometer range and can be tuned, so as to provide for different interactions between the core and shell. To demonstrate the versatility of the design, spherical silver nanoparticles or wavelength-tunable plasmonic silver nanoplates are used as the core component. In addition, a nanocomposite phosphor was fabricated by embedding the core-shell nanoparticles into a transparent polymeric matrix. The core-shell metal-phosphor design presented here serves as framework for the fabrication of inexpensive nanocomposite scintillator.     

Free vibration of functionally graded arbitrary straight-sided quadrilateral plates in thermal environment

As a first endeavor, the free vibration of functionally graded (FG) arbitrary straight-sided quadrilateral plates under thermal environment and based on the first order shear deformation theory (FSDT) is presented. The material properties are assumed to be temperature-dependent and graded in the thickness direction. The initial thermal stresses are evaluated by solving the thermo-elastic equilibrium equations. The solution procedure is based on transformation of the governing equations from physical domain to computational domain and then the discretization of the spatial derivatives by employing the differential quadrature method (DQM) as an efficient and accurate numerical tool. The accuracy of the present method is demonstrated by studying the free vibration of isotropic and FG plates with various shapes and comparing the solutions obtained against existing results in literature. Then, the effects of thickness-to-length ratio, volume fraction index, temperature rise, geometrical shape and the boundary conditions on the frequency parameters of the plate are studied.     

Preparation of triangular and hexagonal silver nanoplates on the surface of quartz substrate

In this paper, triangular and hexagonal silver nanoplates were prepared on the surface of quartz substrate using photoreduction of silver ions in the presence of silver seeds. The obtained silver nanoplates were characterized by atomic force microscopy and UV–vis spectroscopy. It was found that the silver seeds played an important role in the formation of triangular and hexagonal silver nanoplates. By varying the irradiation time, nanoplates with different sizes and shapes could be obtained. The growth mechanism for triangular and hexagonal nanoplates prepared on quartz substrate was discussed.     

ZnSb/Ti3C2Tx MXene van der Waals heterojunction for flexible near-infrared photodetector arrays

Two-dimension (2D) van der Waals heterojunction holds essential promise in achieving high-performance flexible near-infrared (NIR) photodetector. Here, we report the successful fabrication of ZnSb/Ti₃C₂T_x MXene based flexible NIR photodetector array via a facile photolithography technology. The single ZnSb/Ti₃C₂T_x photodetector exhibited a high light-to-dark current ratio of 4.98, fast response/recovery time (2.5/1.3 s) and excellent stability due to the tight connection between 2D ZnSb nanoplates and 2D Ti₃C₂T_x MXene nanoflakes, and the formed 2D van der Waals heterojunction. Thin polyethylene terephthalate (PET) substrate enables the ZnSb/Ti₃C₂T_x photodetector withstand bending such that stable photoelectrical properties with non-obvious change were maintained over 5000 bending cycles. Moreover, the ZnSb/Ti₃C₂T_x photodetectors were integrated into a 26 × 5 device array, realizing a NIR image sensing application.     

Polyaniline–vanadium oxide hybrid hierarchical architectures assembled from nanoscale building blocks by homogeneous polymerization

BACKGROUND: Polyaniline–vanadium oxide hybrid materials have been much researched due to their potential applications in lithium batteries. Although many methods have been reported for the fabrication of conventional polyaniline–vanadium oxide hybrid materials by in situ oxidative polymerization/intercalation of aniline in V₂O₅ and by layer‐by‐layer approaches, studies on polyaniline–vanadium oxide hybrid nanostructures have been rare. RESULTS: Polyaniline–vanadium oxide hybrid hierarchical architectures assembled from nanoscale building blocks, such as nanoplates and nanobelts, have been synthesized by a one‐step hydrothermal homogeneous reaction between aniline and peroxovanadic acid without the aid of any surfactant or template. The influences of synthesis parameters, i.e. reaction time, temperature and medium, on the morphologies of the polyaniline–vanadium oxide hybrid nanostructures have been investigated. With increasing reaction time/temperature, the alignment of nanoplates in the hierarchical architectures becomes gradually dense. CONCLUSION: The formation mechanism of the polyaniline–vanadium oxide hybrid hierarchical architectures involves a one‐step precipitation–polymerization–assembly process. The method may be applicable for the synthesis of other conducting polymer–vanadium oxide hybrid nanostructures. Copyright © 2009 Society of Chemical Industry     

Membrane elements insensitive to distortion using the quadrilateral area coordinate method

Two 4-node quadrilateral membrane elements, denoted as AGQ6-I and AGQ6-II, have been developed in this paper. Instead of the traditional isoparametric coordinate, the quadrilateral area coordinates were used to establish the formulations of the new elements. And several generalized conforming conditions were then introduced to determine all unknown parameters. Numerical examples showed that the presented elements exhibit excellent performances in both regular and distorted mesh divisions. They could even yield exact solutions for pure bending problems under distorted meshes and provide lock-free solutions for the MacNeal’s test problem of trapezoidal locking. Besides, the weak patch test was conducted to guarantee the convergence of both new elements. It has also been demonstrated that the area coordinate method is an efficient tool for developing simple, effective and reliable serendipity plane membrane elements.     

Two step novel chemical synthesis of polypyrrole nanoplates for supercapacitor application

Simple and inexpensive two step novel chemical method for the synthesis of polypyrrole (PPy) nanoplates has been reported. These PPy nanoplates are characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polypyrrole nanoplates exhibit amorphous nature as confirmed from XRD study. Based on SEM and TEM analysis, the formation of the spherical bunches of PPy nanoplates with average size of about 20 nm are inferred. The electrochemical performance of PPy electrode was evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurement. A high specific capacitance of 533 F g⁻¹ was obtained within the potential range of −0.4 to 0.6 V in 0.5 M H₂SO₄ solution. Moreover, PPy electrode exhibited high discharge/charge efficiency of 93% and the capacitance retention of 83% at a current density of 10 mA cm⁻² indicating good electrochemical reversibility and rate capability.     

气相传输法制备大尺寸单晶Bi2Se3纳米片、纳米带

低维Bi₂Se₃纳米材料是最新研究发现的一种新型三维拓扑绝缘体材料, 在微电子器件和传感器领域具有广阔的应用前景。本研究采用气相传输法在真空石英管中合成了大尺寸单晶Bi₂Se₃纳米片、纳米带。通过XRD、EDS、Raman、SEM等手段对Bi₂Se₃纳米片、纳米带的物相结构、组成、表面形貌等进行表征。测试结果表明: 气相传输法合成的单晶Bi₂Se₃纳米片、纳米带相纯度高, 结晶性能好, 均是{001}取向; Bi₂Se₃纳米片水平尺寸大, 约为15~180 μm; Bi₂Se₃纳米带长度达860 μm, 宽度约5 μm。根据不同温度下制备的Bi₂Se₃纳米片、纳米带SEM照片及其不同方向结合能的差异, 分析了其可能的生长机制: 在较高温度下沿<001>和方向生长速度快, 生成大尺寸单晶Bi₂Se₃纳米片; 在较低温度下, 沿方向生长速度快, 生成大尺寸单晶Bi₂Se₃纳米带。这些研究结果完善了大尺寸Bi₂Se₃纳米材料的制备工艺, 有望在微电子器件领域得到商业化应用。     

晶种生长法制备银纳米片:老化过程对产物的影响

晶种生长法是获得形貌尺寸可控纳米银材料的常用方法.本文采用晶种生长法制备银纳米片.通过紫外吸收光谱及透射电子显微镜研究了老化过程对产物形貌的影响;同时通过在晶种生长阶段使用不同稀释浓度的晶种溶液,验证了硼氢化钠浓度对产物的影响.结果表明,经充分老化后的晶种溶液,残留的硼氢化钠分解更充分,以此溶液作为晶种进行后续生长时,银离子在琥珀酸作用下缓慢还原并逐渐沉积到晶种上,由于晶种(111)面被柠檬酸根保护,银离子在非(111)面的优先沉积导致片状结构的生成,产物以银纳米片为主.而未经充分老化的晶种溶液中含有未完全反应的硼氢化钠,后续加入的银离子将被残留在晶种溶液中的硼氢化钠迅速还原成银颗粒,而不能缓慢沉积在晶种表面,最终产物以银纳米颗粒为主.