Insights into the Utilization and Quantification of Thermoplasmonic Properties in Gold Nanorod Arrays

Doing chemistry with plasmons is rewarding but is often challenged by the competition between the intriguing relaxation processes in plasmonic materials. One of the currently debated and prominent examples of this is the interference of the thermalization process in bringing out different physicochemical transformations. We present here insights into the utilization and quantification of thermoplasmonic properties in configurable arrays of gold nanorods (AuNRs), which will help in accomplishing the desired outcome from the thermalization process. The plasmonic heat generated in AuNR arrays is used to perform versatile and useful photothermal processes, such as polymerization, solar-vapor generation, Diels–Alder reaction, and crystal-to-crystal transformation. The unprecedented use of thermochromism in quantifying the thermalization process shows that the surface of AuNR arrays can heat up to ∼250 °C within ∼15 min of irradiation, which is independently validated with standard infrared-based thermometric imaging studies. The plasmonic heat reported by the thermochromic studies is the lower limit corresponding to the phase change temperature of the thermochromic molecule, and the actual surface temperature of bundled AuNR arrays could be higher. The choice of reaction conditions is crucial for the effective utilization as well as dissipation of thermoplasmonic heat. The maximum impact of surface temperature was observed when substrates were adsorbed onto the AuNR arrays, whereas the influence of thermoplasmonic heat was minimum when the experiments were performed in a solution state. The insights provided here will have far-reaching implications in the emerging area of plasmonically powered processes, especially in plasmonic photocatalysis.