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Haque F.Z.,Optical Nanomaterials Laboratory | Nandanwar R.,Barkatullah University | Singh P.,Barkatullah University | Syed F.F.,University of Mumbai
Silicon | Year: 2016

SiO2 nanoparticles are prepared via a simple solgel method to provide a basic understanding of the effect of different acids, acetic acid [CH3COOH], hydrochloric acid (HCl), sulfuric acid (H2SO4) and oleic acid [C18H34O2] and solvents dimethylformamide and formamide on the morphological and optical properties. The resulting SiO2 nanoparticle were characterized by photoluminescence spectrophotometry (PL) for the study of optical properties, Transmission electron microscopy (TEM) to determine particle size and Fourier transform infrared spectroscopy (FTIR) for identification of materials and impurities. SiO2 formed with formamide and HCl shows high crystallinity and transperancy in the material. PL spectra reveal that SiO2 nanoparticles show absorbance in the UV region. For each solvent, the PL emission intensity of the SiO2 sample prepared with acid was reduced which shows the formation of well-defined lattice sites and decrease of deffects. The PL intensity of SiO2 prepared with dimethyl-formamide to acetic-acid (SD1) and SiO2 prepared with formamide to acetic-acid (SF1) samples increased. The particle size is confirmed by TEM which was indicative of the successful synthesis of SiO2 nanoparticles in spherical shape. The estimated particle size is in the range of 2-4 nm. The chemical changes were observed from the FTIR results. Strong and broad bands appeared at 3459 cm1-3458 cm−1 and 1640 cm−1-1638 cm−1 corresponding to the bending vibrations of -OH groups and carbon impurity atoms. The peaks that appeared at 989 cm−1-801 cm1 and at 966 cm-1-802 cm1 show the bending vibrations of Si-O-Si and Si-OH bonds in prepared samples. © 2016 Springer Science+Business Media Dordrecht

Parra M.R.,Optical Nanomaterials Laboratory | Haque F.Z.,Optical Nanomaterials Laboratory
Journal of Materials Research and Technology | Year: 2014

This article reports the controlled size of ZnO nanoparticles synthesized via simple aqueous chemical route without the involvement of any capping agent. The effect of different calcination temperatures on the size of the ZnO nanoparticles was investigated. X-ray diffraction (XRD) results indicated that all the samples have crystalline wurtzite phase, and peak broadening analysis was used to evaluate the average crystallite size and lattice strain using Scherrer's equation and Williamson-Hall (W-H) method. Morphology and elemental compositions were investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy. The average crystallite size of ZnO nanoparticles estimated from Scherrer's formula and W-H analysis was found to increase with the increase in calcination temperature. These results were in good agreement with AFM results. Optical properties were investigated using UV-vis spectroscopy in diffused reflectance (DR) mode, with a sharp increase in reflectivity at 375 nm and the material has a strong reflective characteristic after 420 nm at 500°C calcination temperature. Furthermore, photoluminescence spectroscopic results revealed intensive ultraviolet (UV) emission with reduced defect concentrations and a slight shifting in band gap energies with increased calcination temperature from 200°C to 500 °C. This study suggests that the as-prepared ZnO nanoparticles with bandgap tunability might be utilized as window layer in optoelectronic devices. © 2014 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda. All rights reserved.

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