A novel molecularly imprinted photoelectrochemical sensor utilizing Ag/SnO2 for the highly sensitive and selective detection of 2,4-dichlorophenoxyacetic acid

Abstract

The pervasive use of herbicides in agriculture has necessitated the development of sensitive and selective detection methods for environmental monitoring. In this work, a novel photoelectrochemical sensor based on molecular imprinting technology was engineered to specifically detect 2,4-dichlorophenoxyacetic acid (2,4-D) using an Ag/SnO2 composite. The SnO2 was chosen as the photoelectric material due to its abundant surface defects, excellent thermal stability, and high electron carrier density, which are essential for enhanced photoelectrochemical reactions. The introduction of Ag to the SnO2 matrix exploited the surface plasmon resonance effect to bridge its wide band gap, thereby improving the photoelectric conversion efficiency. This Ag/SnO2 composite was then deposited onto an indium tin oxide (ITO) substrate to utilize its high conductivity and optical transparency, followed by the strategic layering of molecularly imprinted polymers (MIPs) that offer selective recognition sites for 2,4-D. To ensure the robustness of the sensor, a Nafion solution was meticulously applied dropwise, which served to immobilize the MIPs/Ag/SnO2 complex on the ITO surface and enhance the sensor's durability. Under optimized conditions, the sensor exhibited a broad linear detection range from 3 × 10-12 to 3 × 10-5 mol/L and a low detection limit of 1.13 × 10-12 mol/L (S/N = 3). The sensor also demonstrated exceptional performance in the analysis of 2,4-D in complex matrices, such as milk, tap water, and beef, highlighting its potential for practical applications in the accurate monitoring of herbicide contamination. These findings affirm the sensor's superior photoelectrochemical properties and introduce an innovative method for the sensitive detection of 2,4-D in environmental and food samples.