Linlin Gui

Preparation and characterization of CdS nanowire arrays by dc electrodeposit in porous anodic aluminum oxide templates

Abstract Aligned CdS nanowires have been prepared by dc electrodeposition in porous anodic aluminum oxide template from dimethylsulfoxide solution containing cadmium chloride and elemental sulfur. These nanowires have uniform diameters of about 20 and 100 nm, which correspond to the pore sizes of the templates used, and lengths are up to tens of micrometers. HREM investigations demonstrate that these nanowires have a uniform crystalline structure of hexagonal CdS single crystal. It was proposed that the steady diffusing process of ions probably plays an important role in the growth of the nanowire by dc electrodeposition.

Preparation of II-VI group semiconductor nanowire arrays by dc electrochemical deposition in porous aluminum oxide templates

II-VI group compound semiconductors such as CdS, CdSe, and CdTe nanowire arrays have been prepared by direct current electrodeposition in porous anodic aluminum oxide template from nonaqueous electrolyte. SEM and TEM results show that these nanowires have a highly anisotropic structure of aligned nanowires with diameters of 15-200 nm, which are consistent with the diameters of the templates used. Electron diffraction and HREM investigations demonstrate that the crystalline structures of these nanowires are uniform hexagonal single crystal. This approach can be used to fabricate single crystal nanowire arrays of a wide range of semiconductors and other materials.

Hydrolysis and silanization of the hydrosilicon surface of freshly prepared porous silicon by an amine catalytic reaction

A novel catalytic reaction using a trace of organic amine as the catalyst enables hydrolysis of the silicon–hydrogen groups on the fresh prepared porous silicon (PS), generating the hydroxyl-terminated surfaces without extensive oxidation of the Si–Si backbonds. The reactivity of the hydroxyl-terminated surfaces with various silanization reagents was investigated, which proceeds by abstraction of the surface –OH to form an organic monolayer of Si–O–Si–C bonds and importantly retains the intrinsic structural properties of the PS layers. Furthermore, an in situ silanization modification of the silicon–hydrogen surfaces has been established. Stability testing shows that the resulting organic monolayers are densely packed and are shown to be highly stable under a variety of conditions including hot water, hot organic solvent, acid, and base, but can be removed by a HF rinse.

Silver telluride nanowires prepared by dc electrodeposition in porous anodic alumina templates

Silver telluride nanowire arrays were synthesized by cathodic electrolysis into porous anodic alumina membranes from dimethyl sulfoxide (DMSO) solutions containing 0.1 M NaNO3, 5.0 mM AgNO3 and 6.0 mM TeCl4. XRD and SAED patterns of the nanowires were indexed to be a monoclinic structure of Ag2Te. TEM images show that the nanowires have smooth surfaces with uniform diameters. Near stoichiometric Ag2Te nanowires were obtained for potentials between −0.55 and −0.65 V vs. Ag/AgCl. Furthermore, the composition of the nanowires can be controlled continuously from Ag-rich to Te-rich mainly by changing the concentration of TeCl4 in the solutions.

Preparation of colloidal solutions of thin platinum nanowires

Colloidal solutions of thin platinum nanowires having lengths of 10 to 70 nm and diameters of 1.5–3 nm were prepared by reducing K2PtCl4 with hydrogen in a glycol solution containing K2C2O4 and preformed Pt seeds. TEM, HRTEM, XRD and UV-Vis absorption spectroscopy were used to study the structure of the obtained nanowires and the effect of preparation conditions, such as pH value, temperature, preformed Pt nanoseeds and stabilizing agents, on the morphology of the products. The mechanism for forming the thin Pt nanowires in the absence of a 1D structure template was discussed based on the experimental results. Stable colloidal solutions of mercaptan-modified Pt nanowires were prepared for the first time by transferring the prepared thin Pt nanowires into toluene containing octadecylmercaptan.

Preparation of Ag2Se and Ag2Se1-xTex nanowires by electrodeposition from DMSO baths

We have developed a novel electrochemical route to fabricate highly ordered stoichiometric Ag2Se nanowire arrays by electrodeposition from non-aqueous dimethyl sulfoxide (DMSO) solutions. Cyclic voltammetry technique was used to study this cathodic deposition process. X-ray energy dispersion analysis shows that stoichiometric; Ag2Se nanowires can be obtained in a wide range of deposition condition. X-ray diffraction and electron diffraction patterns demonstrate that the as-deposited nanowires are [002] oriented orthorhombic beta-Ag2Se. Furthermore, ternary Ag2Se1-xTex nanowires have been electrodeposited in mixed SeCl4-TeCl4 DMSO solutions

Silver Selenide Nanowires by Electrodeposition

Silver selenide nanowires were synthesized by potentiostatic electrodeposition into porous anodic alumina membranes from an aqueous acid electrolyte containing silver ion complexed with SCN and selenium dioxide at room temperature. Electron microscopy results showed that the lengths, diameters, and growth directions of the nanowires are quite uniform. X-ray energy dispersion analysis indicated that the nanowires are composed of Ag and Se with an atomic ratio of Ag/Se = 2.08, which is close to stoichiometric Ag 2 Se. X-ray diffraction patterns showed that the as-deposited nanowires are polycrystalline orthorhombic β-Ag 2 Se, and the annealed nanowires are highly [002] oriented. Furthermore, the selected area electron diffraction pattern and the high-resolution transmission electron microscopy image demonstrated that after annealing the nanowires have a uniform crystalline structure of orthorhombic β-Ag 2 Se, which are (002) oriented along the direction vertical to the wire axes.

Intense and stable blue-violet emission from porous silicon modified with alkyls

An intense blue-violet band, centered at 3.0 eV, has been observed besides the red-orange band of the photoluminescence (PL) from the chemically modified porous silicon (PS) samples. The PS samples were formed on 30–50 Ω cm p-type (100) Si wafers by anodic etching at large current densities and then treated with 5-cyano-1-pentynes in toluene solution at 110–120 °C. The intensities of the blue-violet lights increase with the increasing of the etching current densities, while the peak energies are hardly changed. The Fourier transform infrared spectra of the modified samples show that the alkyls have been bonded to the surfaces of the nanometer crystallite silicon particles. The decays of the blue-violet emission with a lifetime about 0.5 μs are different from the nanosecond lifetimes of the blue emissions in the oxidized PS samples reported before, and the 20 μs lifetimes of the concomitant orange PL bands. A carbon-compounds-related luminescence center has been proposed as the origin of this blue-violet P...

Influence of supercritical and natural drying methods on structure and properties of porous silicon

We have studied the surface morphology, photoluminescence (PL), Raman spectra and optical absorption of the porous silicon (PS) samples prepared under supercritical drying (SD) and natural drying (ND) process. The experimental results of scan electron microphotograph and Raman spectra show that there are obvious differences in microstructure between the SD and ND samples. No crack of the skeleton has been found in the SD sample, but the skeleton of the ND sample has heavily destroyed. Besides, the PL and absorption spectra of the SD sample are not the same as those of the ND sample.

Ordered porous films of organically-modified silica prepared by a two-step replicating process

Abstract An ordered porous film of vinyl-modified silica was prepared by a two-step replication of the honeycomb structure of anodic porous alumina. Preparation of the negative porous structure of anodic porous alumina followed by the formation of the positive structure with vinyl-modified silica resulted in a honeycomb structure of vinyl-modified silica. The silica film has nearly uniform, closely packed nanoholes with an average diameter of 198 nm and length of 11 μm. The porous silica film was characterized by using the X-ray photoelectron spectroscopy (XPS) and FT-IR techniques.