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 degreesC. Th e films were characterized by Xray diffraction analysis, Fourier transform infrared spectroscopy and Rutherford backscattering spectrometry. The films have been shown to maintain the mesophase after calcination, at 250 degree sC 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 spectrome try in the 250 and 450 degreesC calcined samples, respectively. These densi ties 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 ele ctrical response of the silica mesoporous films has been investigated with different concentrations of alcohols. The sensitivity of the material to ch anges in the atmospheres of ethanol, methanol, 2-propanol, butanol-1 and ex ane has been tested. The results have shown a large sensitivity to the alco hols at room temperature and the possibility to discriminate between the di fferent alcoholic species. (C) 2001 Elsevier Science Ltd. All rights reserv ed.