A simple method to synthesize fluorescent modified gold nanoparticles using tryptamine as the reducing and capping agent

A simple method to synthesize fluorescent modified gold nanoparticles using tryptamine as the reducing and capping agent is described. The presented method produces gold nanoparticles with 36.65 ± 5.30 nm average size. The modified gold nanoparticles were characterized by elemental and thermal analyses, dynamic light scattering, transmission electron microscopy, zeta potential, X-ray powder diffraction and spectroscopic techniques, such as electronic spectroscopy in ultraviolet–visible and fluorescence excitation–emission. In addition, modified gold nanoparticles were analyzed by solid state 15N nuclear magnetic resonance spectroscopy, which confirmed the coordination of tryptamine on the gold nanoparticles surface. A prominent characteristic observed is the fluorescence of tryptamine which was not quenched after the coordination to gold nanoparticles. The results presented in this paper confirm the modification of gold nanoparticles by tryptamine and suggest potential use of such nanoparticles as labeling dye in biological systems.