Mesoporous silica thin films for alcohol sensors

Silica mesoporous films using cetyltrimethylammonium bromide surfactant as a template have been prepared. The films have been deposited on silicon and alumina substrates by dip-coating and calcined at 250 and 450°C. The films were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy and Rutherford backscattering spectrometry. The films have been shown to maintain the mesophase after calcination, at 250°C the presence of residual surfactant has been observed. A density of 1.46 and 1.65 g cm^-3 has been measured by Rutherford backscattering spectrometry in the 250 and 450°C calcined samples, respectively. These densities are much lower than the value (2.07 g cm^-3) measured in a reference silica film obtained via sol-gel and with the same thermal history. The electrical response of the silica mesoporous films has been investigated with different concentrations of alcohols. The sensitivity of the material to changes in the atmospheres of ethanol, methanol, 2-propanol, butanol-1 and exane has been tested. The results have shown a large sensitivity to the alcohols at room temperature and the possibility to discriminate between the different alcoholic species.