Synthesis and characterization of dye-doped TiO2-SiO2 core-shell composite microspheres

RhodamineB (RB) dye-doped TiO2-SiO2 core-shell composite microspheres were synthesized by a chemical method from the hydrolysis of the titanium tetrachloride (TiCl4). The morphology and chemical bonding information of composite material was investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). TEM and SEM images illustrate that core-shell composite microspheres are spherical in shape and have a nano-range thin coating of TiO2 on the surface of SiO2. The core-shell composite microspheres calcined at 400 degrees C exhibit sharp XRD peaks of anatase and rutile crystalline phases of TiO2. The unit cell parameters were calculated from different peaks. The FTIR spectrum confirms the existence of stretching modes (Si-O-Si and Ti-O-Ti) in the core-shell composite microspheres. The photocatalytic properties were evaluated by the photo degradation of K2Cr2O7 under ultraviolet-visible irradiation for as-synthesized and at an 850 degrees C calcination temperature of the core-shell composite. (c) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JNP.6.063511

Synthesis and characterization of dodecanethiol-stabilized gold nanoparticles

Dodecanethiol-stabilized gold nanoparticles of different sizes were synthesized using Bi-phasic reduction method by varying the concentration of stabilizer. These particles were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). TEM images show the average particle size of different samples ranging from similar to 1.7 nm to 5.7 nm. FTIR study confirms the linkage of thiol group and their partial crystalline self assembly onto the surface of nano gold particles. From the UV-Vis spectra, it is noticed that absorption peak position is sensitive to the size of the particles. Theoretical fit for absorbance spectra was obtained using Mie theory and the deviation from experimental results demonstrates the large size and shape distribution. A linear relationship between logarithms of extinction coefficient and particle diameter is obtained, which explains the extinction coefficient dependence on the size of the particle

Fabrication and optical study of dye doped TiO2-SiO2 multilayer colloidal structures

Multilayer colloidal structures of TiO2 coated silica microspheres have been synthesized by using self-assembly vertical deposition technique and optical properties of these structures were also investigated using UV-visible spectroscopy. Morphology, elemental distribution and chemical bonding information is analysed using scanning electron microscopy (SEM), Energy dispersive X-ray Spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) respectively. It is noticed that position of transmission dip is dependent upon the annealing temperature of the samples. The experimental measured normalized stop band width results are in good agreement with theoretical results at packing fraction value of 0.74. (C) 2012 Elsevier B.V. All rights reserved

Structural and optical tunability of metallodielectric composites with gradual shell growth

Metallodielectric (gold@silica) composites were prepared by seed and grow method. The dielectric microspheres (core material) of an average size of 400 rim were synthesized by sol gel method and gold nanoparticles (AuNPs) were prepared by reducing the chloroauric solution. Shell growth around silica (SiO2) microspheres was carried out in a multistep layer-by-layer process. The synthesized composites were characterized using techniques such as field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and UV-Visible (UV-Vis) spectroscopy. FE-SEM and FTIR analyses have confirmed the functionalization of SiO2 surfaces with the amine terminal group along with the gold shell growth. XRD analysis has given an average crystallite size of 12.3 nm for metallodielectric composites. Absorption spectra have demonstrated the dependence of surface plasmon resonance (SPR) peak on the successive shell growth by exhibiting a red shift

INFILTRATED SILICA PHOTONIC CRYSTAL WITH LIQUID CRYSTAL AND VARIOUS ORGANIC LIQUIDS

Tunable photonic crystal has been developed by infiltration of nematic liquid crystal (NLC) and different organic liquids in the void of silica microspheres. Optical properties were investigated by ultraviolet-visible (UV-Vis) spectroscopy. It has been observed that the position of photonic band gap (PBG) shifts from 336nm to 326nm with the increase of applied field from 0V to 9V and 316nm to 324nm after the infiltration of the organic liquids. The refractive index of in infiltrated liquid crystal (LC) is calculated at different applied electric field. The present results could be suited for implementation of low cost and compact design tunable devices with low power consumption for high density integrated optics

Development and annealing of colloidal multilayer structures of silica microspheres

Colloidal multilayer structures of silica microspheres have been developed on the quartz substrates using vertical deposition technique and effect of annealing on optical properties of samples was investigated using UV-Visible spectroscopy. It is noticed that forbidden photonic band gap is a function of annealing temperatures and annealing times. Morphology of particles was characterized using scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). SEM and TEM micrographs illustrate the uniform size distribution of silica microspheres with an average size of 280 nm. (C) 2011 Elsevier B.V. All rights reserved

Planar Alignment of Liquid Crystal in Silica-Based Photonic Structure

The planar orientation of Nematic Liquid crystal (NLC) molecules on the surface of (111) plane of silica photonic structure has been investigated. Nano voids of silica photonic crystal has been obtained by vertical deposition technique on indium tin oxide-coated substrate. NLC was infiltrated into the channels of voids in the photonic structures. Optical texture studies under with and without electric field were applied to investigate the NLC orientation. It is observed that NLC molecules in the nano voids of silica photonic structure exhibit an excellent planar alignment. This obtained hybrid composite structure on infiltration of NLC will be a promising candidate for electro optic applications