Effect of the surface plasmon on second harmonic generation from tyrosine

The first hyperpolarizability of the aromatic amino acid Tyrosine has been obtained by Hyper Rayleigh Scattering (HRS) in aqueous environment and under non resonant conditions. The rather large value determined is in agreement with previous HRS studies and confirms that Tyrosine can be targeted as an endogenous molecular probe for the second harmonic studies of biological molecules. The same experiment was also performed in an aqueous environment containing 20 nm diameter gold metallic nanoparticles. The resulting first hyperpolarizability measured with the fundamental wavelengths of 815 nm and 1050 nm in these conditions for Tyrosine is reduced as compared to that obtained in absence of metallic nanoparticles.