An all chemical route to design a hybrid battery-type supercapacitor based on ZnCo2O4/CdS composite nanostructures

Recently, spinel-type binary metal oxides have attracted enormous interest in energy storage devices. In supercapacitors improving energy density is still challenging task and the composite nanostructures are found to address this issue in some extent. Herein, a composite nanostructure based on ZnCo₂O₄/CdS was synthesized on nickel foam using hydrothermal and successive ionic layer adsorption and reaction (SILAR) methods. A hydrothermally synthesized ZnCo₂O₄ nanoflowers were coated by CdS nanoparticles by varying SILAR cycles and studied its electrochemical performance. The ZnCo₂O₄/CdS nanostructured electrode with optimized four SILAR cycles of CdS coating exhibited a high areal capacity, energy density and power density of 2658 mCcm⁻², 517 μWhcm⁻² and 17.5 mWcm⁻² at 25 mA, which is higher than pristine ZnCo₂O₄. This work show ZnCo₂O₄/CdS nanostructure is a favorable electrode for supercapacitors.     

CdS纳米带和纳米锯的热蒸发法的合成和光学性质研究

利用氢气辅助的一步热蒸发法,在镀有金膜的硅片上制备出大量的CdS纳米结构. CdS纳米结构由纤锌矿结构的CdS纳米带和纳米锯组成. 研究表明沉积温度对CdS纳米结构的形貌和尺寸具有重要影响. 用气-液-固和气-固复合生长机理解释了CdS纳米结构的形成过程.光致发光测试表明CdS纳米带和纳米锯均发射出波长为512 nm的很强的绿色发光峰,对应于CdS的带-带跃迁. 同时对CdS纳米结构的光波导性质也进行了观察和讨论.     

Cadmium (II) pyrrolidine dithiocarbamate complex as single source precursor for the preparation of CdS nanocrystals by microwave irradiation and conventional heating process

The complex of cadmium with pyrrolidine dithiocarbamate Cd(pdtc)₂ has been used as single source precursor for the synthesis of CdS nanoparticles. The formation of CdS nanostructures was achieved by thermal decomposition of the complex under microwave irradiation and conventional heating in presence of hexadecylamine. The CdS nanoparticles with disordered close-packed structure were obtained under microwave irradiation, whereas wurtzite hexagonal phase CdS nanorods were obtained by conventional heating method (up to 150 °C). Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and high resolution transmission electron microscopy (HRTEM) studies also were carried out to study the structure and morphology of nanoparticles. The optical property of the CdS nanoparticles was studied by UV-visible and fluorescence emission spectral studies. Fluorescence measurements on the CdS nanoparticles show a strong emission spectrum with two sub bands that are attributed to band-edge and surface-defect emissions. The reduction of a suitable cadmium metal complex is considered to be one of the single pot methods to generate CdS semiconductor nanoparticles with different shapes and high yield.     

Electrochemical template-assisted fabrication of CdS micro/nanostructures

One-dimensional (1D) cadmium sulphide (CdS) nanostructures, including micro/nanorods, and nanostructures resembling flowers and cactus have been synthesized by electrochemical template deposition technique, using polycarbonate membranes, by controlling various reaction parameters. These 1D CdS nanostructures were characterized structurally through the X-ray diffraction (XRD) studies and morphologically through scanning electron microscopy (SEM). It was found that apart from the dimensions of the pores of the templates, the geometrical morphologies of the CdS 1D nanostructures were significantly influenced by the synthesizing parameters also. The optical characterization has been done by UV–visible absorption and room-temperature photoluminescence (PL) studies.     

Electrochemical template-assisted fabrication of CdS micro/nanostructures

One-dimensional (1D) cadmium sulphide (CdS) nanostructures, including micro/nanorods, and nanostructures resembling flowers and cactus have been synthesized by electrochemical template deposition technique, using polycarbonate membranes, by controlling various reaction parameters. These 1D CdS nanostructures were characterized structurally through the X-ray diffraction (XRD) studies and morphologically through scanning electron microscopy (SEM). It was found that apart from the dimensions of the pores of the templates, the geometrical morphologies of the CdS 1D nanostructures were significantly influenced by the synthesizing parameters also. The optical characterization has been done by UV–visible absorption and room-temperature photoluminescence (PL) studies.     

Growth of ZnO nanodisk, nanospindles and nanoflowers for gas sensor: pH dependency

Suitable morphology for fast electron transportation is a crucial requirement for the fabrication of gas sensor application. Highly oriented and well defined zinc oxide (ZnO) nano/micro-scale structures are grown on the glass substrates using aqueous chemical route. The grown nanostructures have been characterized by X-ray diffraction pattern (XRD), scanning electron microscope (SEM) and optical absorption techniques. The SEM micrographs revealed the formation of disk, rod, spindle and flower-like morphologies at different pH values ranging from 5 to 10. The grown nanostructures were employed for acetone gas-sensing measurement. It is observed that the sensors based on nanoflowers showed higher response (95%) for acetone gas at 325 °C. The high acetone gas sensitivity of ZnO nanoflowers can be attributed to the surface morphology. Moreover, nanoflower-like structure exhibits the fast response and recovery.     

Fragmentation of gold flowers into nanopetals by high energy electron irradiation

Gold nanoflowers were obtained by reducing chloroauric acid with tri-sodium citrate at a temperature of 95 °C. The UV-vis spectroscopy and scanning electron microscopy techniques were employed to monitor the growth of gold nanoflowers. The size and shape of the nanocrystallites of gold in the flowers were determined by X-ray diffraction and transmission electron microscopy methods. The 3-dimensional gold nanoflowers got fragmented into 2-dimensional petal-like nanostructures upon irradiation with 6-MeV electrons. The average size of crystallites of gold after electron beam irradiation was found to be ∼10 nm.     

ZnS:Ag/CdS: a new family of color-tunable quantum dots

ZnS:Ag/CdS quantum dots (QDs) have been synthesized by a reverse micelle process under ambient environment. Excited by 350?nm, the emission peak of ZnS:Ag/CdS QDs changes from 425 to 625?nm with increasing the thickness of CdS shells. Although the quantum yields of QDs decrease with CdS shells thickening, the luminescent brightness remains stable throughout. Compared with the traditional color-tunable CdSe QDs, the synthesis of ZnS:Ag/CdS QDs is less toxic and more economic. Therefore, this synthesis process can be regarded as an efficient way to fabricate a series of luminescent nanostructures for a variety of applications.     

Simplistic surface active agents mediated morphological tweaking of CdS thin films for photoelectrochemical solar cell performance

This study reports on the formation of cadmium sulfide (CdS) nanostructures with controlled morphology synthesized via a simple chemical route in surface active agent environment. The effect of organic surface active agents (surfactants) as sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB) on structural, morphological, optical and photoelectrochemical properties of CdS thin films have been studied. Our results reveal that the organic surfactants play key roles in tweaking the surface morphology. A compact spongy ball like morphology was observed for the CdS samples grown without organic surfactants. The cauliflower's with nanopetals from the CTAB, whereas crowded star fish like morphology is observed in PEG-mediated growth. Water hyacinth like morphology is tweaked using SDS. Considering the importance of these nanostructures, the growth mechanism has been discussed in details. Additionally, the samples are photoelectrochemically (PEC) active and having a compact surface with a nanoporous structure twig helps in improved photoelectrochemical performance compared to that of CdS deposits from surfactant free solution. This is a simplistic way to tune the morphology using surfactants, which can be applied to other energy conversion applications.     

Surface enhanced Raman scattering by CdS quantum dots

Surface enhanced Raman scattering is studied in nanostructures with CdS quantum dots formed using the Langmuir-Blodgett technology. Features due to quantum dot longitudinal optical phonons are observed in the Raman spectra of both free CdS quantum dots and such dots distributed in an organic matrix. The surface enhanced Raman scattering by nanostructures with CdS quantum dots covered by an Ag cluster film is observed experimentally. Applying Ag clusters onto the nanostructure surfaces results in a sharp (40-fold) increase in the intensity of Raman scattering by optical phonons in the quantum dots. It is shown that the dependence of surface enhanced Raman scattering on the excitation energy is resonant with a maximum at the energy corresponding to the maximum absorption coefficient of Ag clusters.     

Synthesis and magnetic properties of CdS/α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> hierarchical nanostructures

CdS/α-Fe₂O₃ hierarchical nanostructures, where the CdS nanorods grow irregularly on the side surface of α-Fe₂O₃ nanorods, were synthesized via a three-step process. The diameters and lengths of CdS nanorods can be tuned by changing the ethylenediamine (EDA) and Cd ion concentrations. The magnetic investigations by superconducting quantum interference device indicate that the hierarchical nanostructures have an Morin transition at lower temperature (230 K) than that of the single bulk α-Fe₂O₃ materials (263 K). Importantly, the hierarchical nanostructures exhibit weakly ferromagnetic characteristics at 300 K. A sharp peak assigned to the surface trap induced emission are observed in room temperature PL spectra. Combining with the optoelectronic properties of CdS, the CdS/α-Fe₂O₃ hierarchical nanostructures may be used as multi-functional materials for optoelectronic and magnetic devices. Supported by the National Natural Science Foundation of China (Grant Nos. 50772025 and 50872159), the Ministry of Science and Technology of China (Grant No. 2008DFR20420), the China Postdoctoral Science Foundation (Grant Nos. 20060400042 and 200801044), the Natural Science Foundation of Heilongjiang Province, China (Grant No. F200828), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070217002), and the Innovation Foundation of Harbin City (Grant No. RC2006QN017016)     

Controlling morphology and structure of nanocrystalline cadmium sulfide (CdS) by tailoring solvothermal processing parameters

Cadmium sulfide (CdS) with different morphologies was successfully prepared by solvothermal process by controlling the processing parameters, including nature of precursor and solvent, reaction temperature and process time. X-ray diffraction patterns revealed that, in all cases highly pure and crystallized CdS with hexagonal structure were obtained. In addition, it was found that the processing parameters influence on preferable growth direction of CdS nanostructures. Field emission scanning electron microscope analysis showed that CdS nanowires with different aspect ratios were obtained (depending upon the reaction temperature and process time) in presence of sulfur powder and ethylenediamine, whereas CdS nanoparticles were produced by sulfur powder and ethanolamine. Moreover, CdS nanorods were prepared using thiourea and ethylenediamine. Transmission electron microscope image confirmed that CdS nanowire with one of the highest aspect ratio reported in the literature (i.e., 255) was achieved using sulfur powder and ethylenediamine at 200 °C reaction temperature for 72 h process time. UV–Vis absorption spectra of CdS nanostructures prepared under different conditions displayed a blue shift relative to that of bulk CdS due to the quantum size effect.     

Synthesis and optical characterization of monodispersed Mn doped CdS nanoparticles

Monodispersed Mn²⁺ doped CdS nanoparticles with average size as small as 1.8 nm have been synthesized through chemical method. The nanostructures of the prepared nanoparticles have been confirmed through X-ray diffraction (XRD), ultraviolet-visible (UV-vis) absorption and transmission electron microscope (TEM) measurements. The photoluminescence emission covering 450-650 nm of the visible region is observed under ultraviolet light excitation, from Mn²⁺ doped CdS nanoparticles dispersed in dimethyl sulfoxide (DMSO).     

CdS纳米粒子的微波法制备及其光谱特性研究

用微波法以硫代乙酰胺为硫源,成功合成了CdS纳米粒子。透射电子显微镜(TEM）对合成的CdS纳米粒子的表征结果为粒径约12 nm, 粒径分布较为均匀,分散性较好。研究了微波功率、pH值、反应时间等因素对其吸收光谱,荧光光谱和粒径的影响。结果表明,在微波功率为30％、初始反应pH 9.0、微波反应时间为25 min时,可合成质量较高的CdS纳米粒子。比较了以硫代乙酰胺、硫脲和硫化钠为硫源合成的CdS纳米粒子,结果表明,以硫代乙酰胺为硫源合成的CdS纳米粒子荧光带边发射强,缺陷发射弱,荧光性质较好;而以硫脲为硫源合成的CdS纳米粒子荧光边带发射弱;以硫化钠为硫源合成的CdS纳米粒子荧光以缺陷发射为主。铜离子在6.4～512 μg·L-1范围内对该纳米粒子荧光的猝灭呈现良好线性, 可用于痕量铜离子的测定。     

Mixed-solvothermal synthesis of CdS micro/nanostructures and their optical properties

Several novel cadmium sulfide (CdS) micro/nanostructures, including cauliflower-like microspheres, football-like microspheres, tower-like microrods, and dendrites were controllably prepared via an oxalic acid-assisted solvothermal route using ethylene glycol (EG) and H₂O as pure and mixed solvents with different S sources. The as-prepared products were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM) and UV-vis spectrophotometer (UV). It was found that CdS micro/nanostructures can be selectively obtained by varying the composition of solvent, concentration of oxalic acid, and sulfur sources. UV-vis absorption spectra reveal that their absorption properties are shape-dependent. The possible formation process of the CdS micro/nanostructures was briefly discussed. This route provides a facile way to tune the morphologies of CdS over a wide range.     

Fabrication of the stable adduct CdS/CTAB/Clay with sandwich-like nanostructures

The ordered multilayer adducts have been synthesized by electrostatic self-assembly between exfoliated sodium montmorillonite nanoplatelets and substituted CdS/CTAB cationic polyelectrolytes, in which sodium montmorillonite particles are exfoliated by means of extensive swelling and CdS/CTAB polyelectrolytes are obtained by sonicating CdS nanoparticles in CTAB water suspension. The build-up of the stable adducts with sandwich-like nanostructures has been demonstrated by X-ray diffraction (XRD) pattern. TEM cross-sectional images indicate that the nanocomposites are aligned parallel to form ordered structures. And UV–Vis and PL spectra show the presence of the inorganic functional components. It may be predicted that this self-assembly technique can be generalized to prepare other sandwich-like nanocomposites with desired optical, electro-optical, electronic, catalytic and magnetic properties.     

A novel humidity sensor based on NH2-MIL-125(Ti) metal organic framework with high responsiveness

Noble metal nanostructures with branched morphologies [i.e., 3-D Pt nanoflowers (NFs)] by tri-dimensionally integrating onto conductive carbon materials are proved to be an efficient and durable electrocatalysts for methanol oxidation. The well-supported 3-D Pt NFs are readily achieved by an efficient cobalt-induced/carbon-mediated galvanic reaction approach. Due to the favorable nanostructures (3-D Pt configuration allowing a facile mass transfer) and supporting effects (including framework stabilization, spatially separate feature, and improved charge transport effects), these 3-D Pt NFs manifest much higher electrocatalytic activity and stability toward methanol oxidation than that of the commercial Pt/C and Pt-based electrocatalysts.     

In situ controlled synthesis of various TiO<Subscript>2</Subscript> nanostructured materials via a facile hydrothermal route

Various TiO₂ nanomaterials, such as nanosheets, nanoflowers, and nanowires were directly self assembled on titanium substrate on a large scale under hydrothermal conditions. The morphology of the formed TiO₂ nanomaterials could be easily tuned by varying the experimental parameters of temperature, reaction time, and the NaOH concentration. A possible formation mechanism was suggested on the basis of the shape evolution of TiO₂ nanostructures by SEM images in combination with XRD patterns of as-grown samples. The optical properties of TiO₂ nanosheets, nanoflowers, and nanowires were characterized by reflectance spectroscopy. The studies revealed that the absorption capability of visible light is obviously different for TiO₂ with different morphologies. Moreover, TiO₂ nanosheets exhibited better light trapping than TiO₂ nanoflowers and TiO₂ nanowires due to their unique nanostructure.     

Microtubule‐Templated Cadmium Sulfide Nanotube Assemblies

This paper describes the use of microtubules (MTs) as nanoscale templates for the biologically directed growth and assembly of cadmium sulfide (CdS) nanotubes. CdS is a wide bandgap semiconductor with valuable optical, electronic, and chemical properties, and the organization of CdS nanostructures is critical to their widespread utility. The present work explores a bioinspired, biomediated approach to the formation and assembly of CdS nanotubes. In particular, a biomimetic synthetic strategy is used to control the uniform growth of cubic zinc blende CdS nanocrystals on MT templates, replicating the MTs' tubular morphology with dense CdS only a single nanocrystal thick. Furthermore, specific interactions between MTs and functional microtubule‐associated proteins (MAPs) are exploited to manipulate the secondary organization of these MT templates. The subsequent directed growth of CdS nanotubes on these structures produces specific biomediated architectures including linear arrays, 3D asters, and rings. Finally, cathodoluminescence from MT‐templated CdS structures verifies that the valuable semiconducting character of these materials is exhibited. These demonstrations of nanoscale materials synthesis and assembly illustrate a new level of complexity and control over materials synthesis that may be achieved using such biological tools and processes.     

Ag nanoparticle mediated growth of CdS nanobelts

Catalytic growth of CdS have been carried out on large scale by evaporation of bulk CdS on Ag deposited Si (1 1 1) at atmospheric pressure. The as prepared CdS had wurtzite structure as evidenced by X-ray diffraction. The nanostructures were beltlike with several tens of micrometers length, several micrometers width and few nanometers to tens of nanometers thick as seen by scanning electron microscope and confirmed by TEM studies. The nanobelts were single crystalline in nature and showed reflection corresponding to (1 1 2) and (0 0 2) planes in SAED. The PL studies revealed the green band due to band gap emission and red band due to emission from the surface states. The higher intensity of the defect emission indicated the presence of considerable concentration of surface defects in the as prepared sample. The deposition of CdS could be explained on the basis of catalyst assisted vapor-liquid-solid and vapor-solid mechanism.