Preparation of mesoporous silica thin films on polystyrene substrate by electrochemically induced sol-gel technique

The mesoporous silica thin films with an oriented hexagonal mesostructure were prepared on polystyrene (PS) substrate by electrochemically induced sol-gel technique using tetraethoxyorthosilicate (TEOS) as silica source and cetyltrimethyl-ammonium bromide (CTAB) as structure-directing agent. Prior to coating deposition, the PS substrate was made hydrophilic by sulfonation with concentrated sulfuric acid for 72 h to provide better adhesion of silica films to the substrate. The effects of synthesis parameters required to obtain well-ordered crack-free layers, such as deposition voltage and deposition time, were evaluated in detail. The samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared-Attenuated total reflectance (FT-IR-ATR), small-angle X-ray diffraction (SAXRD) and transmission electron microscopy (TEM). According to the experimental results, the deposition voltage of 3.6 V and the deposition time of 10 s were determined as the optimum conditions. The silica films with the thickness of ca. 1.5 μm obtained under this condition was crack-free smooth and had a hexagonally ordered pore array pattern nanostructure. The pore diameter was about 3 nm and the distance between the neighboring pore centers was ca. 4.6 nm.