Impact of H2O–Si(OC2H5)4 and H2O–C2H5OH Molar Ratios in the H2O–Si(OC2H5)4–NH3–C2H5OH Mixtures on Structural and Spectral Features of Synthetic Photonic Crystals Based on SiO2

Photonic crystals based on amorphous SiO2 nanospheres have been obtained in four-component H2O–Si(OC2H5)4–NH3–EtOH systems at a constant initial volume (100 mL), a constant molar ratio of NH3:Si(OC2H5)4 = 10 : 1, and varied molar ratio of H2O–Si(OC2H5)4 (x1) and H2O–EtOH (x2) within the range of 30–110 and 0.4–2.8, respectively. The increase in water concentration and simultaneous decrease in the alcohol concentration in the initial mixture have resulted in the reduction of mean diameter of the SiO2 spheres from 440 to 270 nm. The curves of the correlation curves between effective diameter of the nanospheres– and the H2O–Si(OC2H5)4 and H2O–EtOH molar ratio have shown two regions with different slopes: for the samples obtained at low H2O–Si(OC2H5)4 and H2O–EtOH molar ratios for these obtained at [H2O] : [Si(OC2H5)4] > 50, [H2O] : [EtOH] > 1. Correlations between the size of the nanospheres of oligomerized SiO2, the initial rate of the process, and the dielectric constant of the initial mixture have been found. The spectral parameters of the photonic crystals obtained on the basis of the amorphous SiO2 spheres have been affected by the H2O–Si(OC2H5)4 and H2O–EtOH molar ratios in the initial mixtures.