Mukha I. Interaction peculiarities of gold and silver nanoparticles with tryptophan and rhodamine 6G on the silica surface

The effect of gold and silver nanoparticles (NPs) on the fluorescence properties of rhodamine 6G (R6G) and tryptophan (Trp) in aqueous solution and on the silica surface was considered. For both cases the emission was quenched because of the direct contact between the molecule and Au NPs due to energy transfer from the excited molecule to the metal surface. Coadsorbed water on the surface of R6G/Au(Ag)/SiO2 promoted the fluorescence enhancement of R6G by 30-50% due to FRET. The increasing of absorption spectra intensity of R6G on the Au/SiO2 surface more than 2-fold with amounts of gold from 0.004 to 0.06 % wt. was found. The formation of charge-transfer complex between the amino acid Trp and Au NPs was shown. The SERS effect in the Trp/Au system was due to the chemical bonding between Au NPs and carboxy- and amino- groups of tryptophan. Silver NPs stable over time in solution and on the silica surface were obtained in the presence of complex stabilizer polyvinylpyrrolidone / sodium dodecylsulfate. Colloidal solutions of Ag NPs and Ag/SiO2 composites showed a high antimicrobial activity against a number of pathogenic microorganisms - S. aureus, E. coli, P. aeruginosa, C. albicans, and maintained their antimicrobial action for two years. Cyto- and genotoxicity of mono- and bimetallic NPs of Ag and Au on the primary cultures of lymphocytes, hepatocytes and Guerin's carcinoma cells in vitro were evaluated, and the antitumor activity in vivo were studied. Biocompatible stabilizer Trp reduced the toxicity while maintaining antitumor activity of NPs.