Effect of acid, water and alcohol ratios on sol-gel preparation of antireflective amorphous SiO2 coatings

Varying amounts of nitric acid catalyst, water and ethyl alcohol were used in the preparation of SiO2 sols by hydrolysis and condensation reactions of tetraethyl orthosilicate in a one step acid catalysis process. Hydrolysis of TEOS was followed by FT-IR analyses. Size of SiO2 particles was seen to vary in 8-41 nm range with respect to changing HNO3 and water amounts in the sols. Gelation occurred in some systems. Surfaces of films were examined by FESEM and AFM, after coating on glass substrates by dip coating. Thicknesses of the films were measured to be in the range of 80-120 nm. 5.6 +/- 0.2% point increase in light transmittance was obtained when HNO3/TEOS (mol/mol) ratio of 4.74 x 10(-4) and H2O/TEOS (mol/mol) ratio of 9.08 were utilized. Sols were found to be stable for months and coatings prepared after 45 days still provided 5.2 +/- 0.2% point increase in light transmittance. (C) 2011 Elsevier B.V. All rights reserved.