Improved thermal stability of Au nanorods by use of photosensitive layered titanates for gas sensing applications

Au nanorods have shown high potential applications due to strong and aspect ratio dependent surface plasmon resonances. A major limitation in the use of such nanostructures is related to their tendency to transform into the most thermodynamically stable spherical shape under heat or radiation exposure. In this work, we propose a method to delay the rod to sphere transformation, stabilizing the cylindrical shape up to 400 °C. This has been accomplished by using photosensitive-layered titanates, which can be densified and stiffened by UV irradiation. Au nanorods dispersed in titanate films were deposited by spin coating and treated by both UV irradiation and thermal annealing at different temperatures. By properly combining UV curing and thermal annealing, this method allows to obtain Au nanorods covered by crystalline TiO2 rigid shells and to retain their shape and peculiar optical properties. Finally, the effect of interaction with specific gas analytes on the plasmon resonances of Au nanorods in TiO2 anatase films has been exploited for optical gas sensing applications.