Preparation and characterization of mesoporous Nb2O5 films for sensing applications

The possibility of combining sol-gel synthesis with molecular self-assembly and phase separation is explored to produce Nb2O5 films with tailored pore structures at the nanometer scale. Thin Nb2O5 film are fabricated by spin coating of a Nb sol prepared by sonocatalytic method using NbCl5 and ethanol mixed with structure directing agent Pluronic PE 6800 in different concentrations which acts as a supra molecular pore template. Post deposition treatment is applied for film consolidation and pore formation. Surface morphology and structure of the films are studied by Transmission Electron Microscopy and Selected Area Electron Diffraction. The optical properties (refractive index and extinction coefficient) along with the thickness of the films are determined from reflectance spectra of films deposited on silicon substrates. The overall porosity of the films and the amount of adsorbed acetone vapors are quantified by means of Bruggeman effective medium approximation using already determined optical constants. The sensing properties of the samples are studied by measuring reflectance spectra prior to and after exposure to acetone vapors with controlled concentrations. Furthermore, the potential of using the studied mesoporous Nb2O5 films for chemical sensing with optical read-out is demonstrated and discussed.