Electrochemical deposition of high density gold nanoparticles on indium/tin oxide electrode for fabrication of biosensors.

High density gold nanoparticles (GNPs) on indium tin oxide (ITO) film coated glass have been prepared by one-step electrochemical deposition from KAu(CN)2 in phosphate buffer (pH 8.0) solution. The resulting electrode surface was characterized by scanning electron microscopy (SEM), UV-vis spectroscopy, X-ray diffraction (XRD) and electrochemical method. Experimental results revealed that the number density of the nanoparticles was increased by the negative shift of the applied potential, while the coverage of the deposited GNPs on ITO substrate surface was also increased by means of the increasing deposition cycles. The presence of GNPs with high coverage improved the electrochemical response of Fe(CN)6 (3-/4-). This high coverage GNP/ITO substrate was applied to immobilization superoxide dismutase (SOD) for fabrication of electrochemical biosensors. The direct electron transfer between enzyme and electrode was realized, and the electrochemical performance of the SOD electrode was improved with the high coverage of GNPs. The biosensor exhibited a rapid and high response to superoxide anion.