Optical gas sensing properties of gold-nanoparticle incorporated LSTO films at high temperature

In-situ sensing in high temperature and chemically reactive environments - i.e., within solid oxide fuel cells or power plant boiler systems - is inherently challenging due to the rapid degradation of most traditional sensor materials within this regime. Although optical fiber based sensors provide clear advantages in this context, progress in this area of application has hinged on the development of (a) optical fiber materials and (b) thin film materials with strong optical response to gas environment, both of which must resist degradation under such conditions. Conducting metal oxide thin films have been examined in the literature as a candidate to solve the latter problem, due to a free-carrier governed optical response in the NIR (1- 2 mu m), that can be strongly dependent upon gas environment. In this work, we present the impact of incorporating gold nanoparticles in one such metal oxide, lanthanum- doped strontium titanite (LSTO), on the gas sensing response, both in the NIR and UV-VIS range. Via optical transmission measurements performed at high temperature (up to 800 C), the intertwined free-carrier response of the film and the localized surface plasmon response of the nanoparticles are examined in the presence of hydrogen of varying concentration. Measurements are presented for films coated both on planar substrates and on optical fibers.