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.