Investigation of the electrochemical and electrocatalytic behavior of positively charged gold nanoparticle and L-cysteine film on an Au electrode.

Positively charged gold nanoparticle (positively charged nano-Au), which was prepared, characterized by xi-potential and transmission electron microscopy (TEM) was used in combination with L-cysteine to fabricate a modified electrode for electrocatalytic reaction of biomolecules. Compared with electrodes modified by negatively charged gold nanoparticle/L-cysteine, or L-cysteine alone, the electrode modified by the positively charged gold nanoparticle/L-cysteine exhibited excellent electrochemical behavior toward the oxidation of biomolecules such as ascorbic acid, dopamine and hydrogen peroxide. Moreover, the proposed mechanism for electrocatalytic response of positively charged gold nanoparticle was discussed. The immunosensor showed a specific to ascorbic acid in the range 5.1x10(-7)-6.7x10(-4) M and a low detection limit of 1.5x10(-7) M. The experimental results demonstrate that positively charged gold nanoparticle have more efficient electrocatalytic reaction than negatively charged gold nanoparticle, which opens up new approach for fabricating sensor.