The laser itself can generate an intense amount of heat on the sample. Here, the role and the effect of laser heating alone were studied by measuring the power-dependence Raman spectra of the P25 thin film without Au NPs. No deformation or cracks were observed on the surface (Figure and Figure ) when a 532 nm laser at 30 mW irradiated a thin film of P25 sample. Raman spectra (Figure ) obtained at different laser powers from 10 mW to 40 mW show that the phase of the P25 remains mainly unchanged. Only a tiny peak at 445 cm -1 showed the contribution of the rutile phase. The anatase of the B1g mode position shifted from 395 cm -1 to 392 cm -1 due to a temperature increase caused by laser irradiation, which is far lower than the ART required temperature of 600 -700 o C for P25. Our results showed that plasmonic NPs, Au in this case, and an on-resonance wavelength irradiation attributed to the observed phase transition and melting of the P25 NPs.