Silver nanoparticles in nonlinear microscopy

Nanotechnology has led to the manufacture of nanometer-sized objects which can be explored in multiphoton microscopy. In particular, metal nanoparticles (NPs) do not generate the multiphoton signal by itself, but rather it can enhance the nonlinear (NL) emission of fluorochromes, owing to the influence of local field effects. Energy transfer process is also observed in systems consisting of metal nanoparticles and organic dye molecules, leading to fluorescence quenching caused by an increased nonradiative rate and decrease in the dye´s radiative rate. Here we have measured and analyzed the fluorescence of Tryptophan solution with and without silver nanoparticles, excited by one, two and three photon absorption. Due to the molecule interaction with the metallic NPs, fluorescence enhancement and quenching process were observed. We show that silver nanoparticles can be explored as a new tool in fluorescence microscopy.