Thermo-Optical Effects in Plasmonic Metal Nanostructures

The effects of the temperature on the surface plasmon resonance (SPR) in noble metal nanoparticles at various temperatures ranging from 77 to 1190 K are reviewed. A temperature increase results in an appreciable red shift and leads to a broadening of the SPR in the nanoparticles (NPs). This observed thermal expansion along with an increase in the electron-phonon scattering rate with rising temperature emerge as the dominant physical mechanisms producing the red shift and broadening of the SPR. Strong temperature dependence of surface plasmon enhanced photoluminescence from silver (Ag) and copper (Cu) NPs is observed. The quantum photoluminescence yield of Ag nanoparticles decreases as the temperature increases, due to a decrease in the plasmon enhancement resulting from an increase in the electron-phonon scattering rate. An anomalous temperature dependence of the photoluminescence from Cu nanoparticles was also observed; the quantum yield of photoluminescence increases with the temperature. The interplay between the SPR and the interband transitions plays a critical role in this effect. The surface-plasmon involved laser heating of a dense 2D layer of gold (Au) NPs and of Au NPs in water colloids is also examined. A strong increase in the Au NP temperature occurs, when the laser frequency approaches the SPR. This finding supports the resonant plasmonic character of the laser heating of metal NPs. The sharp blue shift of the surface plasmon resonance in colloidal Au NPs at temperatures exceeding the water boiling point indicates the vapor-bubble formation near the surface of the NPs.