Highly stable gold nanoparticles (GNPs) have been prepared by heating chitosan (CHIT) and HAuCl₄ aqueous solution without the additional step of introducing other reducing agents and protecting agents. The samples were characterized by UV-Vis, FI-IR, TGA-DTA and TEM. Results indicated that the properties of resultant GNPs could be controlled by altering the CHIT concentration and the aging could be used as a control parameter in GNPs growth. Kinetic results suggested that the GNPs growth during aging should be a CHIT-mediated autocatalytic process. Fourier transform infrared spectroscopy (FTIR) showed that the hydroxyl in molecular CHIT or its hydrolytic product was oxidized to carbonyl groups, resulting in the formation of GNPs. Moreover, the abounding existence of raw materials made it amenable to a green industrial production and our study may help to clarify some of the obscure mechanisms of nanoparticle formation in solution at present.

Key words: chitosan, reducing agent, environmental-friendly, gold nanoparticles, aging