From Food Waste to Water Safety: Mango Endocarp-Derived Biogenic Carbon Dots as a Fluorescent Probe for Real-time Chlorine Monitoring in Pool Water

Abstract

Disinfection of water by chlorine is of paramount importance to public health, while higher than regulated concentrations are toxicologically dangerous and must be controlled with great accuracy in real-time. In the present study, we introduce an ultra-green fluorimetric sensor based on carbon dots (C-dots), synthesized for the first time from waste mango endocarp, for the quantification of free chlorine. The biogenic C-dots synthesized show strong blue fluorescence that is selectively quenched by hypochlorite by an oxidation-mediated process. The structural and surface characteristics of the synthesized C-dots were extensively characterized using UV-Vis spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and dynamic light scattering analysis (DLS) to measure size and zeta potential. To render monitoring field-deployable, the system is applied using a low-cost, Arduino-powered portable device with UV source and RGB sensor for real-time, reagent-free chlorine detection in pool water. The method has a wide range of linearity (0.01–100 ppm), good detection limit (3.0 ppb), and selectivity. The method’s sustainability was confirmed through Complex MoGAPI, BAGI, and RGB 12 tools. The present work synergistically combines food waste valorization, nanotechnology, and embedded systems into a smart, sustainable platform for water quality management.