In situ photochemical generation of silver and gold nanoparticles on chitosan

Silver and gold nanoparticles (NPs) were generated via a mild wet-chemistry process in aqueous chitosan solutions. Gold and silver NPs were created in situ in presence of chitosan through the addition of the corresponding salt solution under a subsequent UV irradiation. Gold and silver NPs were also created by using a sequence of gold and then silver and vice versa. The amine function existing in the chain monomer operates as the anchoring centre of the metal NP, enabling thus a selective generation of the metal NPs through their nucleation followed by their growth. Ensuing hybrid systems were characterized by UV/vis spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Grazing Incident X-ray Diffraction (GIXRD). The NPs average sizes ranges from 10 to 40 nm for gold and 20 to 100 nm for silver. XPS studies on NPs generation through a sequence of gold followed by silver solutions suggest that gold cores enveloped by silver shells with some discontinuities exist.