A Portable Smartphone Platform for Onsite Diphenyl Phosphate Detection Enabled by Dual-Signal Molecularly Imprinted...

Concerns regarding the environmental and health risks associated with diphenyl phosphate (DPhP) have prompted the development of sensitive, selective, and cost-effective analytical methods for its detection. In this study, we introduce a novel molecular imprinting polymer (MIP) with dual-mode detection capability for DPhP, leveraging both visual colorimetry and fluorescence. Iron-nitrogen codoped carbon dots (Fe/N-CDs) are embedded within the MIP structure, serving as the responsive signal and exhibiting peroxidase (POD)-like activity. Molecular docking simulations are used to optimize the binding ability between DPhP and the monomer. Briefly, the POD-like activity facilitates the conversion of H₂O₂ into ·OH, which oxidizes 3,3',5,5'-tetramethyl-benzidine (TMB) into blue oxTMB, thereby quenching the blue fluorescence of Fe/N-CDs@MIP via the inner filter effect (IFE). This results in a decrease in the fluorescence signal, accompanied by an increase in the colorimetric signals. However, the specific binding of DPhP to the MIP's imprinted sites hinders the access of TMB and H₂O₂ to the Fe/N-CDs@MIP's catalytic center, curbing the oxidation of TMB and yielding a DPhP concentration-dependent dual-mode response in fluorescence signal enhancement and a decrease in the colorimetric signal. Utilizing a smartphone to capture dual-mode signals for analysis enables the convenient detection of environmental pollution. This dual-readout assay provides a sensitive and selective platform for DPhP detection, with detection limits of 0.016 μg/L in colorimetric mode and 0.018 μg/L in fluorescence mode, offering a straightforward visual approach to onsite monitoring of DPhP for bolstering environmental and public health safety. This innovative work provides a cost-effective, portable, and accurate platform for intelligent marine DPhP monitoring.