Selective Determination of p-Nitrophenol Based on Its Unique Voltammetric Behavior on Nanoporous Gold

In this paper, an unsupported nanoporous gold (us-NPG) was applied as a novel electrochemical sensor material for the selective detection of p-nitrophenol (p-NP) among its isomers in acid solution based on the distinct cyclic voltammetric behavior. To ascertain the ascription of each peak in cyclic voltammograms (CVs) of three nitrophenol isomers (NPs) on the us-NPG, contrast voltammetric studies of NPs were conducted at an ultrathin NPG film supported on glassy carbon substrate (NPG/GC) and a well-defined Au(111) electrode, respectively. Effects of potential scan rate and rotation speed of the electrode on the redox reaction of NPs were investigated to further confirm the reaction mechanisms. Interestingly, unlike those obtained on NPG/GC and Au(111) electrodes, the CVs of both o-nitrophenol (o-NP) and m-nitrophenol (m-NP) on us-NPG presented a new pair of redox waves separated very well from the redox waves of p-NP, indicating an obviously different mechanism involved in the redox process. Based on the voltammetric behavior, trace level determination of p-NP can be achieved on us-NPG electrode in the presence of o-NP and m-NP. Thus, the fast electron transfer, high selectivity and good sensitivity make us-NPG act as an ideal electrochemical sensor material in the selective determination of p-NP in aqueous solutions.