Li_2025_Mikrochim.Acta_192_712

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 H(2)O(2) 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 x 10(-4) mg kg(-1) with a limit of detection (LOD) of 8.76 x 10(-4) mg kg(-1) (S/N = 3), while a ratiometric fluorescence (I(430)/I(568)) approach had a linear range of 6.68 x 10(-4)-384.3 x 10(-4) mg kg(-1) with an LOD of 6.63 x 10(-4) mg kg(-1) (S/N = 3). This work provides constructive insights to simplify biosensing platforms for food safety and environmental monitoring.