Synthesis of nanocomposite glass-like films containing semiconductor nanocrystals and noble bimetallic colloids by sol-gel route and their characterisation

Zwei Arten von Gläsern liegen im Schwerpunkt des aktuellen Interesses und werden zur Zeit intensiv untersucht. Dies sind zum einen dotierte Gläser mit halbleitenden Nanopartikeln und solche mit Edelmetallkolloiden. Zusätzlich zu ihren Anwendungen in der nichtlinearen Optik kann man die mit Halbleiterkolloiden dotierten Gläser dabei als zukünftige optische Filter ansehen. Edelmetallkolloidhaltige Gläser können als farbige Beschichtungen verwendet werden. Gegenstand dieser Arbeit war daher die auf dem Sol-Gel-Prozeß basierende Herstellung von nanokomposithaltigen glasartigen Beschichtungen, welche halbleitende Nanopartikel sowie gemischte und legierte Kolloide zweier Edelmetalle enthalten.Two type of glasses are currently of interest and being studied extensively. One is a glass doped with semiconducting nancrystals while the other type is doped with noble metal colloids. In addition to their applications in non-linear optics, the first type glasses can also be seen as future optical filters and the second type of glasses can be used as coloured glasses. Therefore the present work was carried out with an objective of synthesizing nano-composite glass like thin films containing semiconductor nanocrystals and mixed- and alloy- noble bimetallic colloids using the sol-gel process

Synthesis of nanocomposite glass-like films containing semiconductor nanocrystals and noble bimetallic colloids by sol-gel route and their characterisation

Zwei Arten von Gläsern liegen im Schwerpunkt des aktuellen Interesses und werden zur Zeit intensiv untersucht. Dies sind zum einen dotierte Gläser mit halbleitenden Nanopartikeln und solche mit Edelmetallkolloiden. Zusätzlich zu ihren Anwendungen in der nichtlinearen Optik kann man die mit Halbleiterkolloiden dotierten Gläser dabei als zukünftige optische Filter ansehen. Edelmetallkolloidhaltige Gläser können als farbige Beschichtungen verwendet werden. Gegenstand dieser Arbeit war daher die auf dem Sol-Gel-Prozeß basierende Herstellung von nanokomposithaltigen glasartigen Beschichtungen, welche halbleitende Nanopartikel sowie gemischte und legierte Kolloide zweier Edelmetalle enthalten.Two type of glasses are currently of interest and being studied extensively. One is a glass doped with semiconducting nancrystals while the other type is doped with noble metal colloids. In addition to their applications in non-linear optics, the first type glasses can also be seen as future optical filters and the second type of glasses can be used as coloured glasses. Therefore the present work was carried out with an objective of synthesizing nano-composite glass like thin films containing semiconductor nanocrystals and mixed- and alloy- noble bimetallic colloids using the sol-gel process

Effect of glass substrates on the formation of gold-silver colloids in nanocomposite thin films

A sol-gel route to synthesize nanocomposite thin films containing phase separated metal colloids of gold (Au) and silver (Ag) was developed. Ag - Au colloids were prepared in silica films using dip coating technique. The annealing of the samples in air results in the formation of phase separated Ag and Au colloids in SiO2 thin films, showing the surface plasmon peaks at 410 nm and 528 nm. For the synthesis of phase separated Ag and Au colloids on float glass substrates, formation of the silver colloids was found strongly dependent on the surface of the float glass. On the tin rich surface formation of both gold and silver colloids took place, whereas, on the tin poor surface the formation of only gold colloids was observed. The surface dependence of the formation of silver colloids was attributed to the presence of tin as Sn2+ state on the glass surface, which oxidizes into Sn4+ during heat treatment, reducing Ag+ into silver colloids

Semiconducting CuClxBr1-x(x=0-1) nanocrystals in thin films : synthesis and characterization

Thin films containing semiconducting nanocrystals of CuClxBr1-x( x = 0 1) were synthesized by the sol gel process, by stepwise substitution of chloride ions by bromide ions. Cuprous oxide was used as the precursor for copper, HCl and HBr as halide sources, and the matrix sol was synthesized from 3-glycidoxypropyl-(trimethoxy)silane (GPTS) and tetraethoxysilane (TEOS). The films were characterized using ultraviolet visible (UV-VIS) spectroscopy, high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction analysis. Thin films (thickness 0.7-1.0 mum) containing cubic CuClxBr1-x (x = 1-0) nanoparticles were obtained. For the samples having no bromide, the absorption spectrum showed a sharp absorption edge at 371 nm. Addition of HBr shifted the peak towards a higher wavelength, giving a peak that is characteristic of CuClxBr1-x; the addition of 1.85 x 10(-2) mole of HBr leads to the complete substitution of chloride by bromide ions. The same observations were also made using X-ray diffraction

Sol-gel synthesis of cuprous halide nanoparticles in a glassy matrix and their characterization

A sol-gel route to synthesize semiconductor cuprous halide CuX (X = Cl, Br) nanoparticles in a glassy matrix has been developed. Cu2O and HCl or HBr were used as the precursors for CuX and the matrix was prepared from 3-glycidoxypropyl trimethoxysilane (GPTS)/tetraethoxysilane (TEOS). Samples were dip-coated and cured either by ultraviolet (UV) irradiation at a temperature of 150 degreesC or in an oven at temperatures of 150-250 degreesC. Thin films (thicknesses 0.7-1.0 mm) containing cubic CuCl and CuBr nanoparticles with diameters ranging from 4-16 nm and 2-28 nm, respectively, were obtained. The ultraviolet-visible (UV-Vis) absorption spectra recorded at room temperature exhibited peaks at 371 and 379 nm for CuCl and at 410 and 391 nm for CuBr, corresponding to the Z(1,2) and Z(3) excitons respectively. X-Ray diffraction patterns showed the characteristic (111), (220) and (311) peaks of cuprous halides. High resolution transmission electron microscopy (HR-TEM) characterization proved that the lattice plane spacings correspond to copper halide nanocrystals

Synthesis of nanocomposite thin films containing Ag-Au alloy colloids for wavelength tunability

A chemical solution deposition route to synthesize silver-gold alloy colloids in thin films with diameters between 8-35 nm has been developed. Ag-Au alloy colloids were synthesized by the addition of silver ions to a polymer protected aqueous gold sol in presence of a seeding agent \u27hydroxylamine hydrochloride\u27, followed by a heat-treatment under reducing atmosphere at temperatures ranging from 150-550°C. The resonance wavelength of Ag-Au alloy colloids exists between those of pure Ag (410 nm) and pure Au (525 nm) colloids, which can easily be controlled by selecting the molar ratio of Ag to Au. This allows the tunability of the absorption wavelength (hence the color) by using Ag-Au alloy colloids in thin films