Ascorbic acid sensor using a PVA/laccase-Au-NPs/Pt electrode

Abstract

A surface-modified electrode, PVA/laccase-Au-NPs/Pt, was prepared to sense ascorbic acid (H₂A) in this study. An amount of the following composite, PVA/laccase-Au-NPs/Pt, the polyvinyl acetate (PVA) was employed as a surfactant to adhere the substrate, Pt; then the laccase peptides were spun inside the PVA fiber to wind around the immobilized Au-NPs and construct a hierarchical structure. The PVA shell layer was in charge of sensing H₂A and transmitting electrical signals, i.e. transducing redox reaction of H₂A. Inside the core region, laccase peptides were responsible for transducing electrons and the Au-NPs collected and relayed them to the substrate of the Pt electrode. It was found that the sensing mechanism for the transducing laccase molecules involved a long-chain electron transmission and peroxide bridging, and for the sensed object, H₂A, is related to a sequential discharge of two electrons. According to a test of the catalytic activity, the sensitivity increased with the increase of the doped Au-NPs up to a maximum amount and then decreased because excess Au-NPs tended to agglomerate and obstruct the relaying electrons. The response time and sensitivity were measured to be ca. 40 s and 1.8 μA cm⁻² ppm. The surface-modified electrode, PVA/laccase-Au-NPs/Pt, was found to show good selectivity among several disturbing reagents and good stability for 76 days.