Electrodeposition of gold nanoparticles on ZnO nanorods for improved performance of enzymatic glucose sensors

Abstract

Well-arranged ZnO nanorods were hydrothermally grown on reduced graphene oxide coated indium tin oxide electrode, and subsequently gold nanoparticles (AuNPs) were electrodeposited on these nanorods. Glucose sensors were constructed with glucose oxidase (GOx) loaded on the AuNPs decorated ZnO nanorods via electrostatic interaction, and during the electrochemical measurements were stimulated with UV irradiation. The results indicate that the AuNPs simultaneously increase the yield and transfer rate of electrons. On the one hand, the AuNPs accelerate the electrons to transfer from the redox centers of GOx to the ZnO nanorods and hence, the transfer rate of the electrons is obviously increased. On the other hand, together with UV irradiation, the AuNPs effectively facilitate the separation of the photoinduced charges within the ZnO nanorods, and further enable more quantity of holes to participate in the oxidation of GOx(FADH2) to GOx(FAD) during the redox reaction. Therefore, the yield of the electrons is also raised. In comparison to the glucose sensor without the AuNPs, the sensitivity of the glucose sensor with the AuNPs is increased 4.8 times and the low detection limit (signal-to-noise of 3) is decreased 5 times. Besides, the other performance of the glucose sensor with the AuNPs, such as the detection range, selectivity, stability, and the detection accuracy to serum glucose concentration, is also improved accordingly. Therefore, it is an effective method to functionalize ZnO nanorods with AuNPs to enhance the electrochemical and photoelectrochemical performance of enzymatic glucose sensors.