Sensitized nonlinear emission of gold nanoparticles.

We have studied Stokes and anti-Stokes emission of Au nanoparticles suspended in pure methanol and methanol solution of rhodamine 6G dye. In the presence of dye, excitation of anti-Stokes emission of gold involves two-photon absorption in rhodamine 6G molecules followed by the energy transfer to Au nanoparticles with simultaneous absorption of one pumping photon by Au. The sensitization by dye molecules caused six-fold enhancement of the anti-Stokes emission of gold nanoparticles.