Amperometric sensing based on glutathione protected Au₂₅ nanoparticles and their pH dependent electrocatalytic activity

We report here the electrochemical behavior of quantum sized glutathione protected Au₂₅ nanoclusters and their use in electrochemical sensing. The Au₂₅ modified electrode was found to show excellent electrocatalytic activity towards the oxidation of ascorbic acid and dopamine over a wide linear range from 0.71 to 44.4μM. The modified electrode exhibited pH dependent electrocatalytic activity, which was attributed to the consequence of electrostatic attraction/repulsion between the charged Au₂₅ clusters and the charged analytes at different pH. This result demonstrates the feasibility of enhancing the sensing selectivity among the charged analytes by controlling the charges on the clusters.