Sol-Gel Derived Thin Films for Hydrogen Sulphide Gas Sensing

Utilizing the sol-gel fabrication route, we have successfully modified and tailored the optical absorption in the visible spectrum of thionine dye trapped in an MTMS gel-matrix to coincide with the emission of a red diode laser operating at 660 nm. These thionine-doped MTMS thin films coated onto transparent substrates have shown a remarkable change in optical absorption in the presence of gaseous hydrogen sulphide (H₂S) diluted in air and in the absence of any buffer gas. The rapid response, sensitivity, reversibility and durability shown by this material can be exploited in developing absorption-based optical H₂S sensors in either an integrated optics or all-optical fiber approach using a red diode laser source.