Well-defined high-entropy alloyed nanoplates triggering cocktail effect for dual-mode detection of organophosphorus pesticide

Well-defined high-entropy alloy PtPbBiFeMn nanoplates (HEAPs) were synthesized by a wet-chemical co-reduction approach. The PtPbBiFeMn HEAPs exhibited excellent peroxidase (POD)-like activity. Leveraging this POD-mimicking property, a dual-mode sensor was developed for quantitative determination of a typical organophosphorus (OP) omethoate. Specifically, the nanozyme oxidizes colorless 3,3′,5,5′-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) with H₂O₂ to its colored form. This reaction is regulated by alkaline phosphatase (ALP)-mediated hydrolysis of ascorbic acid 2-phosphate (AAP) to ascorbic acid (AA), which reduces oxidized TMB and modulates the detection signals. Additionally, ascorbic acid (AA) is converted to dehydroascorbic acid (DHAA). Consequently, an ALP-dependent fluorescence response is obtained through the condensation reaction between OPD and DHAA, yielding the fluorescent compound 3-(1,2dihydroxy ethyl) furo[3,4-b] quinoxalin-1(3 H) with a maximum emission wavelength in the range 568 to 430 nm. When ALP existed, the colorimetric method for omethoate displayed a linear range of 10.02–167.10 × 10⁻⁴ mg kg⁻¹ with a limit of detection (LOD) of 8.76 × 10⁻⁴ mg kg⁻¹ (S/N = 3), while a ratiometric fluorescence (I₄₃₀/I₅₆₈) approach had a linear range of 6.68 × 10⁻⁴–384.3 × 10⁻⁴ mg kg⁻¹ with an LOD of 6.63 × 10⁻⁴ mg kg⁻¹ (S/N = 3). This work provides constructive insights to simplify biosensing platforms for food safety and environmental monitoring.

Graphical Abstract