A new and clean method on synthesis of gold nanoparticles from bulk gold substrates

In this work, we report a new pathway to prepare clean gold nanoparticles in neutral solutions with aid of natural chitosan. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1N NaCl and 1 g L ^-1 chitosan from -0.28 to +1.22 V vs. Ag/AgCl at 500 mV s ^-1 for 200 scans. The durations at the cathodic and anodic vertices are 10 and 5 s, respectively. After this process, positively charged Au- and chitosan-containing complexes were produced in the solution. Then the solution was heated from room temperature to boiling at a heating rate of 6 °C min^-1 to prepare Au nanoparticles. The particle sizes of prepared Au (1 1 1) nanoparticles are ca. 10 nm. Moreover, the prepared Au nanoparticles in solutions are capable for anti-oxidation and stable in an ambient atmosphere for at least three months.