Synthesis and characterization of chitosan-stabilized gold nanoparticles through a facile and green approach

In the present study, gold nanoparticles (Au NPs) were synthesized through a facile and green approach encompassing chitosan in citric acid as a reducing and stabilizing agent, water as solvent, low reaction time, and temperature. The size and dispersity of the Au NPs were optimized by varying the method of addition of reagents. Addition of the reducing agent to a preheated metal precursor solution results in polydispersed nanoparticles whereas reversing the addition yields small and monodispersed nanoparticles. Au NPs of uniform shape and size with an average size range of 14.5 to 16 nm were obtained by controlling the nucleation and growth steps during the synthesis. The role of chitosan is found to be multifold as a mild reducing, chelating, and stabilizing agent. The as-prepared Au NPs are stable in the aqueous phase without any agglomeration, thus offering ample scope for catalytic and sensor applications.