Triple-Mode Sensor Coupled by Photoelectrochemical, Electrochromic, and Spectral Signals for Sensitive Visualized...

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 LiMoO₃ 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 LiMoO₃ 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.