Optical aliphatic hydrocarbon gas sensor based on Titanium Dioxide thin film

This work analyses the performances of an optoelectronic sensor based on a sensitive nanoscale film of Titanium Dioxide (TiO<inf>2</inf>), prepared via sol-gel method. The sensor was developed for fast and high resolution detection of aliphatic hydrocarbon gases. In particular, the change in reflectivity in presence of butane (C<inf>4</inf>H<inf>10</inf>) has been used as transduction property. Reflectance measurements have been performed by using a fiber optic refractometer, coated with either one or three TiO<inf>2</inf> films, which shows a high sensitivity and an excellent reversibility performance. The final sensor was characterized by a layered configuration, with a thin layer of Silicon Dioxide (SiO<inf>2</inf>) deposited directly onto the fiber optics tip to ensure the homogeneity of the overlying Titanium Dioxide film. Optical microscopy and Atomic Force Microscopy (AFM) have been used to study the morphology of the sensible layer. The chemical structure of the deposited oxides (TiO<inf>2</inf> and SiO<inf>2</inf>) has been analyzed using Fourier Transform Infrared (FTIR) Spectroscopy. Refractometer results have shown a better sensing behaviour for the sample obtained with a single dip-coating, in term of sensibility to butane, compared to the sample coated with three layer of TiO<inf>2</inf>.