CdS及其稀土掺杂纳米带的制备与发光性质的研究

采用热蒸发法制备CdS及其稀土掺杂的纳米带(CdS∶Ce3+、CdS∶Er3+)。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和荧光光谱仪(PL)对纳米带的形貌、晶体结构和发光性质进行了表征和分析。结果表明,所制备的纳米带的外形规则,表面光滑、平整,纳米带的厚度大约在20～60nm范围内;纳米带具有六方结构,晶格常数a=0.414nm、c=0.671nm;CdS纳米带的光致发光谱的谱峰位于405nm左右;CdS∶Ce3+纳米带的光致发光谱的谱峰位于523和535nm处;CdS∶Er3+纳米带的光致发光谱中观察到3个强的发光峰,分别位于525、556和582nm处。     

MoO3纳米纤维电极材料的水热合成和电化学表征

通过调控硝酸浓度,利用水热酸化钼酸盐溶液高产率地合成了的α-MoO3纳米纤维.并用X射线衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电镜(HRTEM)等技术对其形貌和结构作了表征.结果表明,当硝酸浓度＞6.73mol/L时,可制备出直径范围在50～400nm,沿[001]方向生长的正交相α-MoO3纳米纤维;硝酸浓度在2.6mol/L左右时,产物是针状的六方相MoO3;随着硝酸浓度的提高,产物由六方相MoO3向正交相MoO3过渡.对正交MoO3纳米纤维电极材料的电化学充放电测试表明,电流密度从0.195mA/cm2增至0.52mA/cm2时,首次锂插入容量降幅比通常的微米级粉体材料要小.     

Controlled synthesis of NiS nanoparticle/CdS nanowire heterostructures via solution route and their optical properties

In the present study, we have successfully synthesized the novel heterostructure of NiS nanoparticle (NP)/CdS nanowire (NW) through solution approach. The first step, CdS nanowires were synthesized by a convenient solvothermal route. Then, NiS nanoparticles were grown on the surface of CdS nanowires in a chemical solution of NiCl₂·6H₂O and anhydrous ethanol at 200 °C. The new catalyst-assisted growth mechanism of the NiS NP/CdS NW heterostructure has been tentatively discussed on the basis of experimental results. A detailed study of the effect of experimental parameters, such as reaction time, reaction temperature, and reaction solvent are also studied. The as-prepared products are characterized by field-emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their optical properties are measured by Raman spectra and PL spectra. Furthermore, using CdS nanowires and NiS NP/CdS NW heterostructure as examples, our study suggests that this general method can be employed for construction of other semiconductor heterostructures with novel properties.     

Controlled synthesis in large-scale of CdS mesospheres and photocatalytic activity

In the present work, we reported the controlled synthesis of CdS mesospheres composed of radially arranged nanorods by hydrothermal method without any surfactant. The as-prepared CdS mesospheres were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicated that these CdS mesospheres present a hexagonal structure and free of deleterious phases. SEM micrographs showed that CdS mesospheres are composed of several nanoparticles with growth mechanism via aggregation of particles. The photocatalytic activities were investigated by degradation of reactive brilliant dye X-3B (C.I. Reactive Red 2) under visible light irradiation. Results show that 93% X-3B was degraded after 100 min irradiation by the best one sample. The results indicate that the as-prepared CdS samples are promising candidate materials for visible light responsive photocatalysts.     

Controlled hydrothermal synthesis of VO2(B) nanobelts

Large-scale VO₂(B) nanobelts have been synthesized by hydrothermal strategy via one-step method using V₂O₅ as vanadium source and C₆H₅-(CH₂)_n-NH₂ with n = 2 and 4 (2-phenylethylamine and 4-phenylbutylamine) as structure-directing templates. The composition and morphology of the nanobelts were established by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The as-obtained VO₂(B) nanobelts have a length of 3-10 μm, a wideness of 100-375 nm and a thickness of 30-66 nm.     

High-performance nano-Schottky diodes and nano-MESFETs made on single CdS nanobelts

Nano-Schottky diodes and nanometal-semiconductor field-effect transistors (MESFETs) on single CdS nanobelts (NBs) have been fabricated and studied. The Au/CdS NB Schottky diodes have very low reverse current density ( approximately 3.0 x 10-5 A.cm-2 at -10 V reverse bias) and the highest on/off current ratio (approximately 108) reported so far for nano-Schottky diodes. The single CdS NB MESFETs exhibit n-channel normally on (depletion) mode, low threshold voltage (approximately -1.56 V), high transconductance ( approximately 3.5 microS), low subthreshold swing ( approximately 45 mV/dec), and the highest on/off current ratio (approximately 2 x 108) reported so far for nanofield-effect transistors. We also show that the absolute value of threshold voltage for a metal-insulator-semiconductor field-effect transistor made on a single CdS NB can be reduced from approximately 12.5 to approximately 0.4 V and its transconductance can be increased from approximately 0.2 to approximately 3.2 microS by adding an extra Au Schottky contact on the CdS NB, the mechanism of which is discussed.     

Effect of thermal annealing on the cathodoluminescence of evaporated CdS films

Cathodoluminescence (CL) of evaporated undoped CdS films was investigated before and after thermal annealing in air and in vacuum at 300 °C for several hours. Pure CdS single crystals were studied for comparison. CL spectra were obtained at room temperature using the electron microprobe technique. The two well-known (green and red) CL bands of pure CdS were observed for all samples. Annealing of the films in air decreased the green luminescence while vacuum annealing led to its increase. The red luminescence increased under both annealing conditions. The results were explained in terms of radiative transitions attributed mainly to native defects and their complexes. The role of oxygen and residual impurities on the CL of thin films was discussed. A modulation of the CL spectra was obtained in thin films owing to optical interference.     

Phase and shape controlled synthesis of CdS nanocrystals and their characterization

We demonstrated simple solution based methods for preparing CdS nanostructure materials with distinct and well-defined morphologies, including spherical, rod and tripod/tetrapod by varying the solvents. It is also found that solvent plays an important role on tuning the crystal structure of nanocrystals, which is an important observation in this study. The mechanism related to crystal phase control is proposed and discussed. Our results reveal that the luminescence properties of CdS nanostructures depend on the size not on the shape of nanocrystals.     

Chemical synthesis of CdS nanoparticles and their optical and dielectric studies

Cadmium sulphide nanoparticles were synthesized by chemical displacement reaction method using cadmium nitrate as cadmium source and ammonium sulphide as sulphur source. The CdS samples are characterized using X-ray diffraction, UV–Vis spectroscopy, FTIR spectroscopy, scanning electron microscopy and impedance spectroscopy. CdS nanoparticles are found to possess cubic structure with the crystallite size ~10 nm. The absorption spectra of synthesized CdS nanoparticles revealed the blue shift in excitonic transitions with respect to CdS bulk material, clearly confirming the formation of nanoparticles. The dielectric properties of CdS nanoparticles are studied in the frequency range 10³–10⁷ Hz at room temperature. The dielectric properties of CdS nanoparticles are found to be significantly enhanced specially in the low frequency range due to confinement.     

Ultrasonic-assisted synthesis of Au nanobelts and nanowires

Au one-dimensional (1D) nanostructures, including nanobelts and nanowires, have been synthesized in an ethylene glycol (EG)/polyvinylpyrrolidone (PVP) system by a simple and convenient seed-mediated growth method. The nanobelts and nanowires have aspect ratios up to 600, a length distribution ranging from several to tens of microns, and an average width of 100 nm. In this method, we used an ultrasonic process to promote the formation of Au seeds, which largely determines the morphology of final product. Additionally, we have found that the ultrasonic process significantly increases the fabrication yield of 1D nanostructures. Further experimental results show strong polarization dependence of Surface-Enhanced Raman Scattering (SERS) on a single Au 1D nanostructure. This convenient, versatile and low-cost synthesis method can be applied to 1D nanostructures composed from a range of materials, making it widely applicable to many areas of modern science and technology.     

Microemulsion-based synthesis of BaCO3 nanobelts and nanorods

The BaCO₃ nanorods and nanobelts were successfully synthesized in CTAB/cyclohexane/H₂O and NP₁₀/cyclohexane/H₂O microemulsion. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and infrared spectroscopy (IR). The possible mechanisms for the formation of BaCO₃ samples in series of microemulsion systems were discussed. Various comparison experiments show that several experimental parameters, such as the concentration of surfactant and reactant, and solvent hydrothermal treatment play important roles in the morphological control of BaCO₃ nanostructures.     

The facile synthesis of nickel silicide nanobelts and nanosheets and their application in electrochemical energy storage

Ni silicides in the form of nanobelts and nanosheets were synthesized for the first time based on the chemical reaction of Ni substrate with SiHCl(3) under H(2) atmosphere at 900?°C. Their morphological, structural and compositional features were characterized in detail using scanning electron microscopy, transmission electron microscopy, electron diffraction, energy-dispersive x-ray spectroscopy and x-ray diffraction. It was found that the nanobelts, 120-180?nm in thickness and 1-5?μm in width, comprise a single Ni(3)Si phase and the nanosheets 20-80?nm in thickness consist of Ni(3)Si and Ni(31)Si(12), which is influenced by the concentration ratio of SiHCl(3) to H(2). Moreover, the potential application of these Ni silicides in electrochemical energy storage was also investigated. The results indicate that the nanosheets have excellent electrochemical performance when used as anode material for high energy density lithium ion batteries: a reversible capacity of more than 540?mA?h?g(-1) can be maintained even for the 20th cycle in a standard Li(+) half-cell.     

Large-scale hydrothermal synthesis of SnS2 nanobelts

SnS2 nanobelts were successfully synthesized through a controllable solution-phase hydrothermal method on a large scale. The nanobelts have a very high yield, which is more than 95%, with widths ranging from 100 to 200 nanometers, lengths up to several micrometers and thicknesses ca. 10 nanometers. X-ray diffraction patterns, electronic diffraction, X-ray photoelectron spectra, field emission scanning electron microscopy images, transmission electron microscopy images and high-resolution transmission electron microscopy investigated the phase structures, compositions, and morphologies of SnS2 nanobelts. Dodecanethiol played important roles in the process of SnS2 nanobelts formation and growth. The formation mechanism of SnS2 nanobelts was investigated and discussed on the basis of the experimental results.     

Heavily doped ZnO nanobelts and their violet emission

In-doped ZnO nanobelts have been synthesized by a thermal evaporation method with absence of catalysts. The morphology and microstructure of the doped ZnO nanobelts have been extensively investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The results show that the belts grow along the (1010) direction with the typical lengths in the range of several tens to several hundreds of micrometers, and the typical widths of the belts are several hundreds of nanometers. According to the XRD pattern of the sample, the most of belts are ZnO with heavy doping content and ternary Zinc Indium Oxide (such as Zn5In2O8, Zn4In2O7). The X-ray energy dispersive spectrometer (EDS) analysis demonstrates that the In content in the as-examined belt is as high as 27 at%. Notably, the photoluminescence spectrum reveals a novel violet emission peak (425 nm) in the as-synthesized product.     

Controlled Growth and Cathodoluminescence Property of ZnS nanobelts with Large Aspect Ratio

Nano-Micro Letters - ZnS nanobelts with large aspect ratio are successfully synthesized on a large scale through thermally evaporating of ZnS powder with a trace of SnO2 powder using gold coated Si...     

A facile synthesis of ordered ultralong silver nanobelts

Large-scale ordered ultralong silver nanobelts, which built a beautiful chrysanthemum-like structure, are prepared on the interface between dibutyl sebacate (DBS) and silver nitrate solution by a chemical electro-deposition technique. The influences of chemical circumvent of interface, concentration of silver nitrate solution and applied voltage on the formation of silver nanobelts are investigated. It is shown that the silver nanobelts possess a perfect single crystal structure and well-defined nanobelt-like morphology with a length of 5 mm, width 80-150 nm, and thickness 20 nm, respectively. The growth mechanism of the nanobelts is discussed. Furthermore, UV-vis spectra of the silver nanobelts show similar surface plasmon resonance properties to silver nanowires.     

Vanadium pentoxide nanobelts and nanorolls: from controllable synthesis to investigation of their electrochemical properties and photocatalytic activities

Uniform V(2)O(5)· xH(2)O nanobelts with high aspect ratios and ultra-long V(2)O(5)· xH(2)O nanorolls with novel scroll-like structures were synthesized on a large scale by a simple hydrothermal growth route using NH(4)VO(3) as the raw material in the presence of different acids at 180?°C for 24?h. Their morphologies were observed by scanning electron microscopy (SEM). X-ray powder diffraction measurement and thermal gravimetric analysis revealed the composition of nanobelts and nanorolls to be V(2)O(5)·0.9H(2)O and V(2)O(5)·0.6H(2)O, respectively. The possible mechanisms of formation of the nanobelts and nanorolls were schematically elucidated based on the layered structure of vanadium pentoxide. In addition, corresponding anhydrous V(2)O(5) nanostructures with better crystallinity were obtained by calcining the precursors of V(2)O(5)·0.9H(2)O nanobelts or V(2)O(5)·0.6H(2)O nanorolls. Furthermore, we have investigated the electrochemical intercalation properties with Li(+) and the photocatalytic activities of the synthesized V(2)O(5)·0.9H(2)O nanobelts, V(2)O(5)·0.6H(2)O nanorolls and their corresponding post-annealing products. It was observed that the morphologies and compositions of the synthesized products had an evident influence on the electrochemical intercalation properties with Li(+) and photocatalytic activities.     

Polymer-directed large-scale synthesis of single-crystal vanadium oxide nanobelts

Large-scale single crystalline vanadium oxide nanobelts were synthesized by hydrothermal treatment of NH₄VO₃ in the presence of polymer PEG-4000 at 180 °C for 24 h. Techniques of SEM, TEM, XRD, FT-IR, HRTEM, and SAED were used to characterize the morphology, composition and structure of the as-obtained nanobelts. The as-prepared vanadium oxide nanobelts are up to several hundreds micrometers in length, 100 nm–1 μm in width, 20–30 nm in thickness, and grow along the [1 0 0] direction. PEG plays a critical role for the formation of the vanadium oxide nanobelts in the present synthetic system. A preliminary formation mechanism was proposed to account for the formation of the as-obtained nanobelts.     

Vanadium dioxide nanobelts: Hydrothermal synthesis and magnetic properties

VO₂ (B) nanobelts were prepared by a hydrothermal method at 180 °C using V₂O₅·nH₂O sol and H₂C₂O₄·2H₂O as starting agents. The obtained nanobelts have diameters ranging from 50 to 100 nm in width, 20-30 nm in thickness with lengths up to 1.5 μm. Measurements of the static magnetic susceptibility provide evidence for two phase transitions at T₁ = 225 K and T₂ = 290 K, respectively. Below T₁, the data suggest the presence quasi-free as well as of strongly antiferromagnetic correlated spins associated to V⁴⁺-ions.     

Controlled synthesis of porous particles via aerosol processing and their applications

Aerosol processes such as spray drying and/or spray pyrolysis for the controlled synthesis of porous particles were introduced in this review. Typical experimental setup, general experimental procedure for the preparation of porous particles, as well as key factors affecting the properties of final porous particles, was described. We then discussed the various routes for the controlled synthesis of porous particles: (1) the preparation of self-assembled porous particles with ordered pores by using organic template particles; (2) the preparation of pore size- and porosity-controlled particles from aggregated nanoparticles; (3) the preparation of nanoparticle-laden encapsulated porous particles from graphene nano-sheets and nanoparticles. Finally, we introduced interesting applications of the porous particles such as photocatalysts, drug delivery carriers, and biosensors.