In this work, we report a new pathway to prepare pure gold nanoparticles with high concentrations in acid solutions via the aid of chitosan without the addition of other stabilizers and reductants based on electrochemical methods. Interestingly, this fabrication of gold nanoparticles with high concentrations in solutions is pH-insensitive. The characteristics of prepared gold nanoparticles were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (HRXPS) measurements. Experimental results indicate the concentration and the particle size of Au nanoparticles prepared in 0.1 N HCl are ca. 50 ppm and 12 nm in diameter, respectively. Similar experiment performed in 0.1 N NaCl with the aid of chitosan shows that the corresponding concentration of prepared Au nanoparticles is ca. 100 ppm. Further similar experiments performed in 0.1N HCl and 0.1N NaCl without the aid of chitosan show that the corresponding concentrations of prepared Au nanoparticles are ca. 1 and 60 ppm, respectively. (C) 2009 Elsevier Ltd. All rights reserved.