Enhanced photoelectrochemical aptasensing for sensitive detection of diazinon pesticide used N-hydroxyphthalimide as an effective hole mediator.

Signal amplification strategies are of great interest in photoelectrochemical (PEC) sensing research. Herein, we explored a novel approach whereby hole transfer was accelerated from the photosensitive material Blue-TiO 2 (B-TiO 2) to the hole mediator N-hydroxyphthalimide (NHPI). Simultaneously, the introduction of the organic molecule NHPI can promote the efficiency of visible light absorption and expand the absorption range of B-TiO 2. Under visible light irradiation, the photocurrent value of NHPI/B-TiO 2 is 2.7-fold larger than that of B-TiO 2 , which can be ascribed to the acceleration of hole transfer by NHPI. More specifically, NHPI acts as a hole mediator, which effectively transfers photo-generated holes from the valence band (VB) of B-TiO 2 to NHPI. NHPI can be oxidized to phthalimide-N-oxyl radical (PINO*), thereby causing inhibition of photo-generated carrier recombination and enhancement of the photocurrent. Furthermore, a PEC aptasensor for the sensitive detection of diazinon (DIA) was constructed by combining specific aptamers on an NHPI/B-TiO 2 nanocomposite surface. The oxidation product of NHPI, PINO*, oxidizes the DIA captured by the aptamer. Under optimized experimental conditions, the linear range for DIA detection was 0.1–1000 nM, and the detection limit of the NHPI/B-TiO 2 nanocomposite aptamer sensing was 0.03 nM (S/N = 3). Therefore, this proposed method involving the hole mediator can be used as a new strategy to improve the performance of PEC. [Display omitted] • A new strategy for enhancing photoelectrochemical (PEC) signals was developed. • Hole mediator can accelerate photo-generated holes transfer. • Hole mediator can be oxidized by photo-generated holes and promote redox reaction. • Organic molecule have the advantage of high visible light absorption efficiency. • The PEC aptasensor exhibited excellent selectivity and sensitivity for Diazinon. [ABSTRACT FROM AUTHOR]