A self-powered photoelectrochemical glucose biosensor based on supercapacitor Co3O4-CNT hybrid on TiO2.

In this study, a photoelectrochemical (PEC) biosensor was constructed by depositing supercapacitor carbon nanotubes (CNT) and Co3O4 onto the anatase TiO2 coated ITO electrodes. Herein, supercapacitor Co3O4 was employed as a semiconductor with a band gap of ~2.07 eV, and the supercapacitor behavior of the PEC system was improved by introducing CNT into the electrode material. Furthermore, a self-empowering glucose biosensor operating at 0 V was constructed for the first time. Also, upon the formation of p-n junction, Co3O4 was rendered electron accepting material, unlike its usual use in photocatalytic systems. Co3O4-CNT-anatase TiO2 semiconductor hybrid was used to reduce recombination of exited electrons, and increasing the visible light absorption. Prior to enzyme immobilization, CNT containing electrode material was modified with 1-pyrene boronic acid via π-π interactions. The enzyme immobilization was carried out through covalent esterification between the boronic acid moiety and the carbohydrate part of GOx. Enzyme immobilization way enabled the close contact between FAD and electrode material, and the electron donor FADH2 forming after the enzymatic reaction can give electrons to the photogenerated holes of Co3O4 through CNT along with H2O2 by enhancing the photocurrent. The obtained PEC biosensor demonstrated acceptable reproducibility and decent stability with a linear measurement range of 0-4 mM, a sensitivity of 0.3 µA mM-1 cm-2, and lower detection limit of 0.16 µM. Thus, a self-powered biosensor was constructed by combining the PEC, and supercapacitor behavior of Co3O4 for the first time, and the utilization of the present PEC material can be extended to the other analytes detection through photoelectrochemistry. The supercapacitor materials led to the high current at direct electron transfer potential range, and this phenomenon implies that the PEC electrode can also be used in biofuel cells to obtain high power.