Plasmon Resonance at Extreme Temperatures in Sputtered Au Nanoparticle Incorporated TiO2 Films

Sensor technologies that can operate under extreme conditions including high temperatures, high pressures, highly reducing and oxidizing environments, and corrosive gases are needed for process monitoring and control in advanced fossil energy applications. Au nanoparticle incorporated metal oxide thin films have recently been demonstrated to show a useful optical response to changing ambient gases at high temperatures as a result of modifications to the localized surface plasmon resonance (LSPR) of the Au nanoparticles. Au nanoparticle incorporated TiO2 films were prepared through sputter deposition techniques followed by high temperature oxidation treatments. Upon exposure to a 4% H-2/N-2 gas atmosphere at elevated temperatures, a shift of the absorption resonance associated with Au nanoparticles to shorter wavelengths is observed, as demonstrated in the literature previously. In this work, we also demonstrate that there is a shift of similar magnitude in the scattering resonance associated with Au. The LSPR absorption peak was monitored as a function of temperature up to 850 degrees C demonstrating a broadening and a decrease in the maximum peak absorptance. Calculations performed in the quasi-static approximation are also presented to explain observed changes in LSPR as a function of temperature and to illustrate the effects on sensitivity of Au - based LSPR sensor materials for extreme temperature applications.