Field Emission Properties and Fabrication of CdS Nanotube Arrays

A large area arrays (ca. 40 cm²) of CdS nanotube on silicon wafer are successfully fabricated by the method of layer-by-layer deposition cycle. The wall thicknesses of CdS nanotubes are tuned by controlling the times of layer-by-layer deposition cycle. The field emission (FE) properties of CdS nanotube arrays are investigated for the first time. The arrays of CdS nanotube with thin wall exhibit better FE properties, a lower turn-on field, and a higher field enhancement factor than that of the arrays of CdS nanotube with thick wall, for which the ratio of length to the wall thickness of the CdS nanotubes have played an important role. With increasing the wall thickness of CdS nanotube, the enhancement factor β decreases and the values of turn-on field and threshold field increase.     

Photolithographic Approaches for Fabricating Highly Ordered Nanopatterned Arrays

In this work, we report that large area metal nanowire and polymer nanotube arrays were successfully patterned by photolithographic approach using anodic aluminum oxide (AAO) templates. Nanowires were produced by electrochemical deposition, and nanotubes by solution-wetting. The highly ordered patterns of nanowire and nanotube arrays were observed using scanning electron microscopy (SEM) and found to stand free on the substrate. The method is expected to play an important role in the application of microdevices in the future.     

硫化镉纳米材料的合成方法

硫化镉是一种非常重要的光电半导体材料,它的性能极大地依赖于其合成方法。采用不同的合成方法,所得CdS纳米材料的粒径、粒度均匀性、纯度及相结构也各不相同,进而对其属性产生较大影响。对CdS纳米材料的合成方法进行了综述,主要包括固相法、液相法和气相法。     

Synthesis,Magnetic Anisotropy and Optical Properties of Preferred Oriented Zinc Ferrite Nanowire Arrays

Preferred oriented ZnFe₂O₄ nanowire arrays with an average diameter of 16 nm were fabricated by post-annealing of ZnFe₂ nanowires within anodic aluminum oxide templates in atmosphere. Selected area electron diffraction and X-ray diffraction exhibit that the nanowires are in cubic spinel-type structure with a [110] preferred crystallite orientation. Magnetic measurement indicates that the as-prepared ZnFe₂O₄ nanowire arrays reveal uniaxial magnetic anisotropy, and the easy magnetization direction is parallel to the axis of nanowire. The optical properties show the ZnFe₂O₄ nanowire arrays give out 370–520 nm blue-violet light, and their UV absorption edge is around 700 nm. The estimated values of direct and indirect band gaps for the nanowires are 2.23 and 1.73 eV, respectively.     

纳米阵列膜磁性质的蒙特卡罗模拟

计算机的模型数字模拟是进行新一代超高密度磁记录材料的研究和开发的重要手段。本文介绍了利用蒙特卡罗方法研究纳米阵列膜的磁性质的基本思想、目前取得的主要结果、面临的问题和可能的解决办法。     

Fe_(0.97)Pt_(0.03)纳米线的制备与磁性研究

以FeSO4与H2PtCl6的混合溶液作为沉积液,采用电化学沉积法成功地制备了Fe0.97Pt0.03合金纳米线.磁性测量表明,样品的矫顽力为1925Oe,剩磁比为0.95,磁各向异性显著提高。δM曲线,起始磁化曲线及回复曲线的分析表明,纳米线之间以及纳米线内部的主要相互作用可归结为静磁相互作用;同时发现,回复曲线的面积随磁场增大而增大。     

固相法合成纳米硫化镉研究进展

纳米硫化镉以其独特的光电性能，在光致发光、电致发光、传感器、红外窗口材料、光催化等许多领域有着广泛的应用，其合成方法受到人们的广泛关注。综述了我国近年来用固相法合成CdS纳米材料的研究现状，指出各种制备方法的优缺点，并展望其未来发展。     

Fabrication of Highly Ordered Polymeric Nanodot and Nanowire Arrays Templated by Supramolecular Assembly Block Copolymer Nanoporous Thin Films

Realizing the vast technological potential of patternable block copolymers requires both the precise controlling of the orientation and long-range ordering, which is still a challenging topic so far. Recently, we have demonstrated that ordered nanoporous thin film can be fabricated from a simple supramolecular assembly approach. Here we will extend this approach and provide a general route to fabricate large areas of highly ordered polymeric nanodot and nanowire arrays. We revealed that under a mixture solvent annealing atmosphere, a near-defect-free nanoporous thin film over large areas can be achieved. Under the direction of interpolymer hydrogen bonding and capillary action of nanopores, this ordered porous nanotemplate can be properly filled with phenolic resin precursor, followed by curation and pyrolysis at middle temperature to remove the nanotemplate, a perfect ordered polymer nanodot arrays replication was obtained. The orientation of the supramolecular assembly thin films can be readily re-aligned parallel to the substrate upon exposure to chloroform vapor, so this facile nanotemplate replica method can be further extend to generate large areas of polymeric nanowire arrays. Thus, we achieved a successful sub-30 nm patterns nanotemplates transfer methodology for fabricating polymeric nanopattern arrays with highly ordered structure and tunable morphologies.     

硅纳米线阵列电极作为细胞色素c传感器的研究

利用化学刻蚀法由p型硅片制备了硅纳米线阵列,经过表面去氧化层处理后,制备了检测蛋白质细胞色素c的电化学传感器.实验表明,硅纳米线阵列电极对细胞色素c有良好的电化学响应,并且在低浓度条件下具备线性响应的特点.根据与未经表面处理的硅纳米线阵列电极的实验结果相对比,提出了细胞色素c所具备的羧基末端与硅纳米线阵列电极表面的Si-H相互作用从而改善传感性能的检测机理.     

钕氟复合掺杂二氧化钛纳米线阵列的光催化性能

利用溶胶-电泳沉积技术,以多孔有序阳极氧化铝膜为模板制备Nd~(3+)/F~-共掺杂的二氧化钛纳米线阵列.用扫描电子显微镜、X射线衍射仪对其进行表征,并以甲基橙为降解物,对Nd~(3+)单掺杂TiO_2、F~-单掺杂TiO_2和Nd~(3+)/F~-共掺杂TiO_2进行了光催化降解性能研究.结果表明:Nd~(3+)/F~-共掺杂TiO_2纳米线阵列具有比单元素掺杂更高的光催化活性,光照1 h对甲基橙的降解率均达到90%以上.同时,杂质离子的引入使得TiO_2薄膜的吸收波长发生红移,实现了在不降低TiO_2光催化性能的同时又具有可见光活性.     

基于钯纳米线阵列修饰电极的抗坏血酸电化学研究

以氧化铝模板为基础,采用电化学沉积方法制备了钯纳米线阵列修饰金电极。电化学方法研究了该修饰电极对抗坏血酸电化学行为,实验结果表明,抗坏血酸在高度有序的钯纳米线饰电极表面出现显著的氧化峰。氧化峰的峰电流与抗坏血酸的浓度在4.0×10-4~3.15×10-3 mol/L范围内有良好的线性关系,检测限可达1×10-4 mol/L。该电极制备方便,有良好的灵敏度和稳定性。     

多孔阳极氧化铝模板法合成纳米线阵列的研究及应用进展

综述了以多孔氧化铝为模板，采用电化学沉积技术合成金属、半导体、导电聚合物等纳米线材料的最新研究进展，阐述了多孔氧化铝模板在合成与组装纳米线材料方面的良好应用前景，以进一步拓展该领域的研究。     

Synthesis and photoelectrochemical response of CdS quantum dot-sensitized TiO2 nanorod array photoelectrodes

A continuous and compact CdS quantum dot-sensitive layer was synthesized on TiO₂ nanorods by successive ionic layer adsorption and reaction (SILAR) and subsequent thermal annealing. The thickness of the CdS quantum dot layer was tuned by SILAR cycles, which was found to be closely related to light absorption and carrier transformation. The CdS quantum dot-sensitized TiO₂ nanorod array photoelectrodes were characterized by scanning electron microscopy, X-ray diffraction, ultraviolet–visible absorption spectroscopy, and photoelectrochemical property measurement. The optimum sample was fabricated by SILAR in 70 cycles and then annealed at 400°C for 1 h in air atmosphere. A TiO₂/CdS core-shell structure was formed with a diameter of 35 nm, which presented an improvement in light harvesting. Finally, a saturated photocurrent of 3.6 mA/cm² was produced under the irradiation of AM1.5G simulated sunlight at 100 mW/cm². In particular, the saturated current density maintained a fixed value of approximately 3 mA/cm² without decadence as time passed under the light conditions, indicating the steady photoelectronic property of the photoanode.     

一维铂纳米线阵列的模板电沉积及其表征

将一种复合无机介孔膜作为新型的模板应用于一维纳米线阵列的模板合成研究中,通过采用模板恒电位沉积的方法制备出一维铂纳米线阵列,并利用扫描电镜,透射电镜,X射线衍射,能量分布谱,选区电子衍射对该铂纳米线阵列进行了表征。结果表明:通过模板恒电位沉积的方法可以将金属铂组装在复合无机介孔膜内的二氧化硅介孔管中,除去模板后,进而得到长度为10μm的一维多晶铂纳米线(半径为3～4nm)阵列。     

Synthesis and Photoluminescence Properties of Porous Silicon Nanowire Arrays

Herein, we prepare vertical and single crystalline porous silicon nanowires (SiNWs) via a two-step metal-assisted electroless etching method. The porosity of the nanowires is restricted by etchant concentration, etching time and doping lever of the silicon wafer. The diffusion of silver ions could lead to the nucleation of silver nanoparticles on the nanowires and open new etching ways. Like porous silicon (PS), these porous nanowires also show excellent photoluminescence (PL) properties. The PL intensity increases with porosity, with an enhancement of about 100 times observed in our condition experiments. A “red-shift” of the PL peak is also found. Further studies prove that the PL spectrum should be decomposed into two elementary PL bands. The peak at 850 nm is the emission of the localized excitation in the nanoporous structure, while the 750-nm peak should be attributed to the surface-oxidized nanostructure. It could be confirmed from the Fourier transform infrared spectroscopy analyses. These porous SiNW arrays may be useful as the nanoscale optoelectronic devices.     

Fabrication and Properties of Ag-nanoparticles Embedded Amorphous Carbon Nanowire/CNT Heterostructures

Carbon nanotubes were subjected to doping with an energetic Ag ion beam, and the carbon nanotubes on the top of the array were transformed into amorphous carbon nanowires with embedded Ag-nanoparticles. The field emission characteristics of these nanowires were investigated. The minimum turn-on and threshold fields were 0.68 and 1.09 V/μm, respectively, which were lower than those of the as-grown carbon nanotubes. This was probably because Ag-nanoparticles embedded in the carbon nanowires reduced the effective work function from 4.59 to 4.23 eV. Large doping amounts produced serious structural damage at the top of the nanowires and impaired the field emission characteristics.     

Structure and Properties of CdS/Regenerated Cellulose Nanocomposites

Summary: Novel inorganic‐organic hybrid materials composed of cadmium sulfide (CdS) semiconducting nanocrystals and regenerated cellulose (RC) were prepared by using in situ synthesizing method. Cellulose was dissolved in a 6 wt.‐% NaOH/4 wt.‐% urea/thiourea aqueous solution at low temperature followed by addition of cadmium chloride (CdCl₂), resulting that the CdS nanocrystals were successfully grown in situ in the cellulose solution. Nanocomposite films containing homogeneous CdS nanoparticles were obtained by casting the resulting solution. Their structure and optical properties were characterized by X‐ray photoelectron spectroscopy, wide‐angle X‐ray diffraction, thermogravimetry analysis, dynamic mechanical analysis, atomic force microscopy, transmittance electronic microscope, UV‐vis spectroscopy, and photoluminescence spectroscopy. The experimental results confirmed that the CdS nanocrystalline existed in the composite films, and cellulose matrix provided a confined medium for CdS particle growth in uniform size. The CdS/RC composites showed narrow emission in photoluminescence spectra, and their optical absorbance in the UV range was higher than that of the cellulose film without CdS. This work provided a simple method to prepare cellulose functional materials in NaOH/urea aqueous solution.

Photoluminescence of CdS/RC nanocomposites and TEM image of CdS nanocrystals dispersed in RC matrix.     

Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

Novel hierarchical Cd₄SiS₆/SiO₂ based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire is composed of a single crystalline Cd₄SiS₆ nanowire core sheathed with amorphous SiO₂ sheath. Furthermore, secondary nanostructures of SiO₂ nanowires are highly dense grown on the primary Cd₄SiS₆ core-SiO₂ sheath nanowires and formed hierarchical Cd₄SiS₆/SiO₂ based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.     

One-Pot Synthesis of Biocompatible CdSe/CdS Quantum Dots and Their Applications as Fluorescent Biological Labels

We developed a novel one-pot polyol approach for the synthesis of biocompatible CdSe quantum dots (QDs) using poly(acrylic acid) (PAA) as a capping ligand at 240°C. The morphological and structural characterization confirmed the formation of biocompatible and monodisperse CdSe QDs with several nanometers in size. The encapsulation of CdS thin layers on the surface of CdSe QDs (CdSe/CdS core–shell QDs) was used for passivating the defect emission (650 nm) and enhancing the fluorescent quantum yields up to 30% of band-to-band emission (530–600 nm). Moreover, the PL emission peak of CdSe/CdS core–shell QDs could be tuned from 530 to 600 nm by the size of CdSe core. The as-prepared CdSe/CdS core–shell QDs with small size, well water solubility, good monodispersity, and bright PL emission showed high performance as fluorescent cell labels in vitro. The viability of QDs-labeled 293T cells was evaluated using a 3-(4,5-dimethylthiazol)-2-diphenyltertrazolium bromide (MTT) assay. The results showed the satisfactory (>80%) biocompatibility of as-synthesized PAA-capped QDs at the Cd concentration of 15 μg/ml.     

CdS的制备及其光催化性能研究

以硫化钠、醋酸锌和醋酸镉为原料,采用沉淀法制备了CdS粉体。用傅立叶红外（FT-IR）、X射线衍射仪（XRD）以及紫外-可见漫反射（UV-Vis DRS）对制备的粉体进行了表征。并研究了焙烧温度对其晶型以及光催化降解甲基橙的影响。结果表明：随着焙烧温度的升高,六方相晶型CdS含量逐渐增加;且都对甲基橙有一定的催化降解作用,当热处理温度为80℃时,CdS光催化剂的光催化降解活性最高。