Here, the experimental value of 𝜅̅ of a dense polycrystalline TiO2 nanoparticle film is used for that of P25 film. The temperature of a single Au particle (Tnano) is shown in Figure . The temperature increase was 130 K for 532 nm and 6 K for 638 nm laser irradiation with 15 mW power and 0.7 μm beam size (~ 9.1 x 10 5 W/cm 2 or 19 mW/μm 2 ). The temperature increase from the resonance (532 nm) irradiation is about 20 times that from the non-resonance (638 nm) irradiation. However, this rise in temperature from a single Au nanoparticle could not account for the observed Au surface evaporation and melting of the TiO2 NPs, even under resonance irradiation. In another study using similar CW laser irradiance, Setoura et al. observed the surface evaporation of Au NPs into satellite NPs when well-dispersed ( >10 μm apart) single Au NPs with a 100 nm diameter were irradiated on glass. The estimated single particle temperature is about an order of magnitude higher than the single particle temperature estimated in our study. This is because the thermal conductivity of glass is much less than that of TiO2. The effective 𝜅̅ (0.2 𝑊 𝑚𝐾 ⁄ for the air/glass is about five times smaller than the air/TiO2 interface. Additionally, the larger particle (100 nm in diameter) has an order of magnitude larger cross-section than the 30 nm Au particles. The When the collective heating is considered, the temperature increase (ΔTglobal) at the center of the illuminated area with an ensemble of Au NPs on TiO2 can be estimated from the second term in Equation 2 , which sums up the contribution of all the heat generated by the NPs in the irradiation area. A Gaussian CW laser illumination of an infinite particle array yields,