Ni-doped vertically aligned zinc oxide nanorods prepared by hybrid wet chemical route

Ni-doped zinc oxide (Ni:ZnO) nanorods were synthesized by incorporating nickel in vertically aligned ZnO nanorods. Ni was evaporated onto ZnO nanorods and the composite structure was subjected to rapid thermal annealing for dispersing Ni in ZnO nanorods. The optical band gap decreased with increasing amount of Ni incorporation. The origin of the photoluminescence peak at ∼ 400 nm was related to the defect levels introduced due to substitution of Ni²⁺ in the Zn²⁺ site with annealing. The Raman spectra indicated the presence of the characteristic peak at ∼ 436 cm^− 1 which was identified as high frequency branch of E₂ mode of ZnO. The Fourier Transformed Infrared spectra indicated the existence of the distinct characteristic absorption peak at 481 cm^− 1 for ZnO stretching modes. Current-voltage characteristics indicated that the current changed linearly with voltage for both the doped and undoped samples.     

Low-temperature synthesis of CuS nanorods by simple wet chemical method

CuS nanorods of length 60–100 nm and 15 nm in diameter have been synthesized by simple wet chemical method at 105 °C using CuCl₂·2H₂O as Cu-precursor, CS₂ as S-source and ethylenediamine as the attacking reagent. The plausible reaction mechanism has been proposed and the effect of reaction temperature on morphology has been discussed. X-ray diffraction (XRD) pattern suggests the formation of hexagonal phase CuS. The morphology of the products has been studied by transmission electron microscope (TEM) analysis. A detailed optical study has also been done.     

Preparation of ZnO nanorods through wet chemical method

The different morphologies of nanorods have been obtained via a simple wet chemical method in the present of polyethylene glycol (PEG, M_w = 4000) by using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and ammonium hydroxide (NH₃·H₂O) as the starting materials. Samples were characterized by XRD, EDS, TEM, SEM, ED and PL. XRD results prove the formation of ZnO with wurtzite structure. The ED and HRTEM reveal that single ZnO nanorod is single crystal and preferentially grows up along the [001] direction. The PL spectra showed that the ZnO nanorods have blue emission at 466 nm and green-yellow emission at 542 nm. The influence of reaction temperature, pH in system and evaporation of ammonia on the morphology has been investigated. A possible growth mechanism of ZnO with various morphologies is discussed.     

Morphological investigation on cobalt oxide powder prepared by wet chemical method

In this paper cobalt oxide has been prepared by wet chemical method using Co(NO₃)₂ sol (Co: 80 g/L) and NaHCO₃ sol (100 g/L) as starting materials. When organic reagent: ethanol, acetone, and Polyethylene glycol-400 (PEG-400) (all are 2 mL) or three sodium salts: sodium chloride, sodium sulfate and sodium acetate (all are 1 g) had been introduced into reaction as inert additives once every time, and the measurement of PH value, zeta potential and viscosity in all solutions retains on the same level of magnitude, but the SEM shows that specific shapes of cobalt oxide particle is obtained after firing of CoCO₃ at 300 °C for 2 h in air. The DLVO theory discloses effect of dielectric constant of organic reagent and steric hindrance effect is the main factor for big molecular PEG-400. By replacing partly Co(NO₃)₂ with CoCl₂, the behavior of Cl⁻ is studied in the process of nucleus growth, the results show that Cl⁻ existed in the structure of nucleus with the content from 1300 to 2400 ppm, the structure, which can stand several time washing in an ultrasonic bath after reaction, but collapse as soon as it is fired at 300 °C for 2 h in air. It is reasonable to conclude that there may be directed anion chemical adsorption existed in cobaltous carbonate structure, which results in corresponding cobalt oxide particle morphology via anisotropic growth of nucleus.     

Polyurethane–silver fibers prepared by infiltration and reduction of silver nitrate

Silver-incorporating polyurethane fibers were prepared by infiltration of silver nitrate on electrospun polyurethane fibers and reduction with sodium borohydride. They were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray system. The Ag nanoparticles prepared by reduction of silver nitrate showed nano-sized crystals of 4–10 nm in diameter. However, larger aggregated Ag particles of 50–200 nm were also found to be dispersed in the polyurethane matrix when Ag particles were formed in electrospun fibers by the infiltration–reduction process of silver nitrate. As a result, infiltration method of silver nitrate into the electrospun fibers was significantly effective to produce silver-incorporating fibers due to a high specific surface area of fibers.     

Annealing effect on the photoluminescence properties of ZnO nanorod array prepared by a PLD-assistant wet chemical method

Well-aligned ZnO nanorod arrays were synthesized by a wet chemical method on the glass substrate with ZnO thin film as seed layer prepared by pulsed laser deposition. The effect of annealing temperature on the luminescence characteristics was investigated. As the annealing temperature increased, the photoluminescence properties show a general enhancing tendency. The nanorod array with high ultraviolet emission and negligible visible light emission (designated by the photoluminescence intensity ratio of ultraviolet to visible emission of 66.4) is obtained by annealing the sample at 700 °C for 1 h. Based on the results of X-ray photoelectron spectroscopy and photoluminescence spectra, the mechanisms of visible emission were discussed.     

Vertically aligned Mn-doped zinc oxide nanorods by hybrid wet chemical route

Mn-doped zinc oxide (Mn:ZnO) nanorods were synthesized by incorporating manganese in aligned ZnO nanorods. For this, Mn was evaporated onto ZnO nanorods and the composite structure was subjected to rapid thermal annealing. The nanorods were preferentially oriented in (0 0 2) direction as indicated by the XRD measurement. Optical band gap was seen to decrease with increasing amount of Mn incorporation. XPS studies indicated that incorporated Mn was in Mn²⁺ and Mn⁴⁺ states. Mn²⁺ atomic concentration was found to be larger than Mn⁴⁺ concentration in all the samples. The Raman spectra of the Mn:ZnO nanorods indicated the presence of the characteristic peak at ∼438 cm⁻¹ for high frequency branch of E₂ mode of ZnO. The PL peak at ∼376 nm (∼3.29 eV) was ascribed to the band edge luminescence while the peak at ∼394 nm (∼3.15 eV) was assigned to the donor bound exciton (D^oX) and free exciton transition related to Mn²⁺ states.     

Silicon nanorods prepared by glancing angle catalytic chemical vapor deposition

Vertically oriented amorphous and microcrystalline Si nanorods grown on different substrates were successfully obtained by Cat CVD with the glancing angle incident silane flux at low temperatures. The influences of the substrate type, substrate temperature, post treatment and hydrogen dilution on the microstructure of Si nanorods were investigated. The density and diameter of nanorods are varying with the substrates. The hydrogen dilution of silane dominates the crystallization of Si nanorods rather than high substrate temperature at 550 °C and annealing at 900 °C in nitrogen for 6 h. The crystallized Si nanorods with crystalline volume fraction, Xc, of 0.55 were achieved under a low substrate temperature of 140 °C.     

Single particle plasmon spectroscopy of silver nanowires and gold nanorods

The excitation of surface plasmons in individual silver nanowires and gold nanorods is investigated by means of high-resolution electron energy loss spectroscopy in a transmission electron microscope. The transverse and longitudinal modes of these nanostructures are resolved, and the size variation of the plasmon peaks is studied. The effect of electromagnetic coupling between closely spaced nanoparticles is also observed. Finally, the relation between energy-loss measurements and optical spectroscopy of nanoparticle plasmon modes is discussed.     

Gas sensing properties of ZnO nanorods prepared by hydrothermal method

ZnO nanorods are prepared by a hydrothermal process with cetyltrimethylammonium bromide (CTAB) and zinc powder at 182°C. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The gas sensing properties of the materials have been investigated. The results indicate that the as-prepared ZnO nanorods are uniform with diameters of 40–80 nm and lengths about 1 μm, the relatively high sensitivity and stability of these sensors made from ZnO nanorods demonstrate the potential for developing a new class of stable and very sensitive sensors.     

Size-controlled synthesis of hydroxyapatite nanorods by chemical precipitation in the presence of organic modifiers

Size-controlled synthesis of hydroxyapatite nanorods was carried out by chemical precipitation method using citric acid, sodium dodecyl sulphate, and sodium dodecylbenzene sulphonate as organic modifiers and starting from calcium nitrate, phosphoric acid, and ammonia solution. The crystallinity of the resultant hydroxyapatite increased with increasing the autoclaving temperature. The particle sizes of the resultant HAP nanorods varied with the presence of the different structured organic modifiers and the synthetic temperature. The interaction between the anions of the modifiers and the hydroxyapatite crystallites controlled the crystal growth.     

Nanoneedles of maghemite iron oxide prepared from a wet chemical route

Nanometer-sized maghemite iron oxide (γ-Fe₂O₃) particles were produced first by synthesis of a precursor, γ-FeO(OH), in a surfactant-less microemulsion and subsequent heat treatment of the γ-FeO(OH). The precursors and γ-Fe₂O₃ powder were characterized using thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Susceptometer from Quantum Design (SQUID) measurements. TGA and XRD analysis indicated the formation of single cubic phase when the samples were heat-treated at 240 °C. TEM reveals that the γ-Fe₂O₃ particles are needle-shaped with an aspect ratio of ∼20; typically 5-10 nm wide and over 150 nm long. It was found that these microemulsion-derived γ-Fe₂O₃ nanoneedles possess an intrinsic coercivity of 28 Oe at 300 K and 950 Oe at 2 K.     

简单醇热法制备ZnO纳米棒及其抗菌性能研究

通过Zn(NO3)2.6H2O和NaOH的醇溶液制备ZnO,利用XRD和TEM对产物进行表征,产物为具有较高的结晶度和纯度的ZnO纳米棒,直径约为30nm,长度约为130～500nm。取市售ZnO和产物,采用抑菌圈法对3种常见致病菌作药物敏感试验,并测定了产物对金黄色葡萄球菌的最小杀菌浓度(MBC)。结果表明,产物与市售ZnO试剂均对大肠杆菌不敏感,对金黄色葡萄球菌和白色念珠菌有不同程度的敏感,且产物比市售试剂抑菌效果更为明显,产物对金黄色葡萄球菌的最小杀菌浓度(MBC)为1.5%。     

Fine-tuning longitudinal plasmon resonances of nanorods by thermal reshaping in aqueous media

Metallic nanoparticles that support surface plasmons are potential building units for future nanophotonic circuits, metamaterials, high-density optical data storage, etc. Many of these applications require the ability to 'dial-up' the desired plasmonic resonance modes and frequencies with high precision. Here, we demonstrate a thermal reshaping route that can be used to tailor longitudinal plasmon resonance energies of gold nanorods almost continuously from ~800 to ~560 nm. The longitudinal plasmon resonance wavelength exhibits an exponential decay function of the thermal annealing time at a given temperature. This correlates with the transmission electron microscopy characterization (TEM) which showed that the nanorod aspect ratio decreases exponentially with time, accompanying a gradual shape transformation from rod to sphere. The exponential decay half-time decreases with increasing annealing temperatures, with a value of 1.43 × 10(5) s at 50?°C down to 0.02 × 10(5) s at 100?°C. Our experimental results show that the shape transformation could be attributed to desorption of silver ions and side facet-binding Ag-Br-CTA ligands, which therefore promote the side growth leading to nanorod fattening. Compared to other synthetic methodologies to tune plasmonics, our thermal reshaping approach presents a straightforward paradigm for precisely tailoring plasmon resonance energy with a single parameter.     

Negative photoconductivity in silver nanocubes prepared by simple photochemical method

Silver nanocubes embedded in polyvinyl alcohol matrix have been synthesised by photoirradiation technique. The composite films are characterised by FESEM, XRD, UV-Visible absorption and photoluminescence. These show characteristics of silver nanoparticles with FESEM showing the cubic shape. The photoconductivity study of these films shows decrease in photocurrent with light irradiation. Such negative photoconductivity behaviour may be attributed to dominant scattering of electrons by excited surface plasmon polaritons in nanoscale.     

Controlled growth of well-aligned hierarchical ZnO arrays by a wet chemical method

A simple synthesis route to hierarchical ZnO arrays on zinc substrate in aqueous solution containing zinc nitrate and ammonia water was reported, without the assistance of any seeds, catalysts and surfactants. The as-prepared product consisted of very thin nanosheets attached onto the top of well-aligned nanorod arrays. A possible growth mechanism was proposed. The room-temperature photoluminescence spectrum showed UV emission around 398 nm and diverse visible emission peaks, indicating there might be a large concentration of oxygen defects in the sample. This method is both controllable and reproducible.     

湿化学法合成纳米AlN粉末

采用醇盐水解工艺结合碳热氮化还原法进行纳米Al N粉末的制备。以异丙醇铝、果糖、无水乙醇为原料,制备出透明的凝胶,干燥后得到分子水平混合的前驱体,在1 450℃经碳热氮化还原法制备出单相Al N纳米粉末。系统研究了前躯体形成机制,以及碳热氮化还原的温度和时间、C/Al摩尔比、凝胶温度等因素对合成粉体的影响。采用XRD、TG-DSC和SEM对合成产物的特性进行了分析和表征。通过优化工艺,制得类球形的Al N粉末颗粒,其颗粒大小为30~90 nm。     

A comparison of silver electrodes by the sintering method and the chemically prepared method

Abstract

Silver electrodes were made by the sintering method and by the chemically prepared method. Their charging and discharging performances were compared.

It was found that the capacity of the chemically prepared electrode is larger than that of the sintered electrode at low rate charging current and smaller at high rate charging current at 100 mA discharging rate.

The sintered electrode was more porous than the chemically prepared electrode from observations with scanning electron microscope (SEM).

The difference of performances was tentatively explained by the mass transfer of hydroxyl ions.     

Synthesis of organic ligand passivated zinc selenide nanorods via wet chemical route

Zinc selenide (ZnSe) nanorods have been synthesized by simple and inexpensive wet chemical method using N-Methylaniline as a capping agent. The morphologies and structure of ZnSe nanorods have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The SEM and TEM reveal the formation of nanorods. XRD shows the cubic structure with the lattice constant of 5.633 Å. Strong “blue shift” absorption is observed from UV-visible spectrophotometry. The enhanced luminescence property is measured from photoluminescence spectrophotometry. The presence of N-Methylaniline in the ZnSe nanorods is confirmed by the Fourier transformed infrared spectrum.     

Surface passivation of CdS/Zn2SiO4 nanocomposites prepared by a wet chemical route

Highly luminescent CdS/Zn2SiO4 nanocrystals were prepared by a wet chemical method. The effect of surface passivation was observed in photoluminescence measurements of CdS nanocrystals embedded in colloidal nanocrystallite or amorphous Zn2SiO4 matrix. The resultant luminescent emission of as-prepared CdS/Zn2SiO4 nanocomposite thin films displays two distinct components. One is attributed to the band-edge emission and the other is due to the surface defects. The effect of aging on CdS/Zn2SiO4 nanocomposite thin films has been investigated, showing the active role of Zn2SiO4 matrix in modifying the surface states.