Smartphone-assisted dual-mode visual sensing platform for rapid ratiometric colorimetric and upconversion luminescence detection of hypochlorite

Excessive intake of hypochlorite (ClO - ) poses significant health risks, demanding rapid and reliable detection methods for food safety. Herein, we developed an intelligent dual-mode visual sensing system that strategically integrates upconversion nanoparticles (UCNPs) with a rationally designed meso-phosphino-substituted BODIPY probe (TMBP) for rapid ratiometric colorimetric and upconversion luminescence (UCL) detection of ClO - . The reaction of ClO - with the diphenylphosphine group of TMBP yields an electron-withdrawing phosphine oxide, a transformation confirmed by mass spectrometry and density functional theory (DFT) calculations. This transformation induces an obvious increase in the A 600 /A 545 ratio and a remarkable color transformation from pink to blue. Under 980 nm excitation, the upconversion luminescence concurrently exhibits an increase in the I 548 /I 664 intensity ratio and a distinct color transition from red to green, which is primarily attributed to an inner filter effect between UCNPs and ClO - -reactive probes. This dual-ratiometric signal readout provides built-in self-validation through mutual cross-checking, substantially enhancing detection reliability and reducing the risk of false positives. The system responds within 5 s and is suitable for diverse detection scenarios. Furthermore, a portable 3D-printed device integrated with a smartphone and a freely available color-analysis application was developed, enabling practical on-site quantification with results comparable to laboratory spectrophotometry. The system has been successfully applied to detect ClO - in food samples, demonstrating high accuracy via spike-recovery tests. This work not only presents a sensitive and rapid ClO - sensor but also bridges advanced nanotechnology with practical, user-friendly applications, offering a robust tool for food safety monitoring.