Triple-Mode Sensor Coupled by Photoelectrochemical, Electrochromic, and Spectral Signals for Sensitive Visualized Detection of Nonylphenol

Abstract

Conventional photoelectrochemical (PEC) biosensors suffer from the difficulty of visualizing rapid detection and limited accuracy due to a single-signal output. Here, we develop a PEC, electrochromic (EC), and spectral (ST) triple-mode platform for the sensitive visualized detection of nonylphenol (NP). First, the reasonably stepped Fermi energy level arrangement between the defective TiO₂ anode and MoO₃ cathode enables a remarkable photocurrent response (Mode 1). Then, MoO₃ itself is a widely used EC candidate, which can react with free Li-ions to form a Li_<i>x</i>MoO₃ intermediate, and its color will change from white to blue accordingly (Mode 2). More importantly, MoO₃ is also a Li-ion host and the potential of Li_<i>x</i>MoO₃ depends on the inserted Li-ion quantity deduced by spectral analysis on residual Li-ions in the electrolyte (Mode 3). The EC signal endows fast visual detection, and triple-mode cross-validation improves reliability and accuracy. As a result, this PEC-EC-ST triple-mode molecularly imprinted sensor has a wide linear range (1-5000 μg L^-1), a low detection limit (0.18 μg L^-1), selectivity, stability, reproducibility, and actual sample detection capability. This innovative multimode platform not only improves detection reliability but also broadens applications of electrochromic/energy storage materials in biosensors.