Structural evolution and hydrogen sulfide sensing properties of NiTiO\u2083-TiO\u2082 sol-gel thin films containing Au nanoparticles

摘要

Thin films composed of a matrix of titanium and nickel oxides, doped with gold nanoparticles have been prepared with the sol\u2013gel method and annealed at different time/temperature combinations. Structural characterizations demonstrate the crystallization of nickel titanate and of TiO\u2082-rutile due to nickel capability to promote rutile crystallization over anatase. Optical characterizations show a tunable refractive index of the samples according to the Ti/Ni ratio, and a high amount of residual porosity even after high temperature annealing. Sensor functionality measurements were performed with H2, CO and H\u2082S: high sensitivity for hydrogen sulfide detection has been proved, and the cross sensitivity to the other two gases can be tuned by controlling the nickel amount. For high Ni concentrations, the matrix is composed of NiTiO\u2083 and TiO\u2082-rutile, and no cross sensitivity is experienced. For lower Ni amounts, TiO\u2082-anatase starts to crystallize and the films become sensitive to H\u2082 and CO.