Assembly of a self-powered electrochemical sensor with a biomass-derived bioanode and an abiotic cathode based on an...

Herein, a self-powered biosensor (SPB) was constructed using a biomass-derived bioanode and a Zn/Fe zeolitic imidazole framework (Zn/Fe-ZIF) derived-abiotic cathode. Specifically, a natural plant biomass (Juncus effuses) was carbonized to prepare a three-dimensional hierarchical carbon scaffold named as CJE, on which carbon nanotubes (CNTs) were grown under the catalysis of Co, Ni, and Co/Ni catalysts, respectively. The length, diameter and coverage of CNTs on CJE were regulated via adjusting the type and mass proportion of the metal catalysts. The optimum signal output (3.61 μW cm^-2) is achieved by the SPB with the CJE anode substrate catalyzed by the maximum Co loading (Juncus effuses immersed in10 mM Co²⁺), which enables the uniform growth of high-density, small-diameter CNTs on the CJE. The highly conductive CNTs effectively promote electron transfer from glucose oxidase (GOx) to the electrode and increase the specific surface area of the CJE. The GOx-modified bioanode exhibits excellent catalytic activity toward glucose oxidation under mild neutral conditions. Meanwhile, Zn/Fe-ZIF was calcined to obtain a composite cathode catalyst composed of iron oxides, iron carbide, and N-doped carbon, which electrochemically catalyses O₂ reduction at a relatively positive potential (E₁/₂ ≈ 0.862 V vs RHE). Based on an enzyme activity inhibition strategy, this SPB can sensitively monitor a vitally important cellular metabolite H₂O₂, which is closely associated with the occurrence and development of cancer cells. The application of abiotic non-precise metal cathode with high O₂ reduction activity greatly reduces the preparation cost and improves the stability of the SPBs. More importantly, this work also provides an effective strategy for constructing portable and sensitive sensors.