Monitoring the levels of polluting gases such as CO and NO<sub>x</sub> from high temperature (500°C and higher) combustion environments requires materials with high thermal stability and resilience that can withstand harsh oxidizing and reducing environments. Au nanorods (AuNRs) have shown potential in plasmonic gas sensing due to their catalytic activity, high oxidation stability, and absorbance sensitivity to changes in the surrounding environment. By using electron beam lithography, AuNR geometries can be patterned with tight control of the rod dimensions and spacings, allowing tunability of their optical properties. Methods such as NR encapsulation within an yttria-stabilized zirconia overcoat layer with subsequent annealing procedures will be shown to improve temperature stability within a simulated harsh environment. Since light sources and spectrometers are typically required to obtain optical measurements, integration is a major barrier for harsh environment sensing. Plasmonic sensing results will be presented where thermal energy is harvested by the AuNRs, which replaces the need for an external incident light source. Results from gas sensing experiments that utilize thermal energy harvesting are in good agreement with experiments which use an external incident light source. Principal component analysis results demonstrate that by selecting the most “active” wavelengths in a plasmonic band, the wavelength space can be reduced from hundreds of monitored wavelengths to just four, without loss of information about selectivity of the AuNRs. By combining thermal stability, the thermal energy harvesting capability, and the selectivity in gas detection (achieved through multivariate analysis), integration of plasmonic sensors into combustion environments can be greatly simplified.
Monitoring polluting gases such as CO and NO<sub>x</sub> emitted from gas turbines in power plants and aircraft is important, in order to both reduce the effects of such gases on the environment as well as to optimize the performance of the respective power system. Fuel cost savings as well as a reduced environmental impact can be realized if air traffic utilized next generation jet turbines with an emission/performance control sensing system. These monitoring systems must be sensitive and selective to gases as well as be reliable and stable under harsh environmental conditions where the operation temperatures are in excess of 500 °C within a highly reactive environment. In this work, plasmonics based chemical sensors with nanocomposites of a combination of gold nano particles and Yttria Stabilized Zirconia (YSZ) has enabled the sensitive (PPM) and stable detection (100s of hrs.) of H<sub>2</sub>, NO<sub>2</sub> and CO at temperatures of 500 °C. Selectivity remains a challenging parameter to optimize and a layer by layer sputter deposition approach has been recently demonstrated to modify the resulting sensing properties through a change in the morphology of the deposited films. It is expected that further enhancements would be realized through control of the shape and geometry of the catalytically active Au nanoparticles. This level of control has been realized through the use of electron beam lithography to fabricate nanocomposite arrays. Sensing results towards the detection of H2 will be highlighted with specific concerns related to optimization of these nanorod arrays detailed.