Evaluating effectiveness of electron shuttles in environments with a WO3 nanoprobe

Abstract

Electron shuttles (ESs) are a set of substances with reversible redox activity to mediate electron transfer from electron donors to acceptors. The effectiveness of various ESs depends on their intrinsic properties, which determine the efficiency of the mediated electron transfer. So far, however, studies about the ES effectiveness based on the kinetic investigation of the electron shuttling process are still lacking, and the quantitative criteria for electron shuttling rates (ESRs) are also required. In this work, the dose-dependence of the transferred electron number is elucidated via a kinetic study of the quasi-steady-state electron shuttling using a colourimetric WO₃ nanoprobe. An enzyme-like model is developed to describe the electron transfer rate as a function of ES concentration. With this model, the ESRs of ESs are quantified using the values of the fitted Michaelis–Menten constant, K_shuttle. In addition, an alginate-based test paper is fabricated and applied for the practical detection of ESs. This work demonstrates that WO₃ can quantitatively probe the ES-mediated electron transfer and provides a new tool for studying ESs in complex natural and engineered environments.