Effect of Different Acids and Solvents on Optical Properties of SiO2 Nanoparticles Prepared by the Sol-Gel Process

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.