Green synthesis of gold nanoparticles by amino acids: Bioconjugation and uv-fluorescence

A green synthesis process has been accomplished for the construction of self-assembled UVfluorescent gold nanoparticles (GNPs) in colloidal aqueous solution. The amino acids such as glycine (G), tryptophan (T), phenylalanine (P) and their mixtures as GT, TP and GTP with equivalent molar ratio were used. The GNPs obtained by different amino acids and their mixtures were characterized by UV-Vis spectral analysis, transmission electron microscopy, fluorescence spectral analysis and Fourier transform infrared spectroscopy. The UV-Vis spectrum demonstrated that amino acids are playing an important role in the synthesis of GNPs and having a major impact on the shape, size and surface chemistry of GNPs. The TP- and GTP-GNPs were strongly enhanced the intrinsic UV-fluorescence up to 250 and 350%, respectively, as compared to T-GNPs indicating that the role of mixed surface ligands of GNPs in enhancing the UV-fluorescence at the GNPs surface. This work is expected to motivate the design of UV-fluorescent GNPs and development of advanced biomedical, optoelectronic, and fluorescence sensing applications.