Eco-friendly N,P-CQDs from Phyllanthus emblica: A fluorescent Nanoprobe for ultra-sensitive detection of plasticizers in packaged dairy products.

In this study, nitrogen- and phosphorus-co-doped carbon quantum dots (N,P-CQDs) were synthesized via a green hydrothermal method using Phyllanthus emblica for the sensitive detection of dibutyl phthalate (DBP) in plastic-packaged milk products. This research aimed to develop a sustainable, cost-effective sensing platform for monitoring food safety. The synthesized N,P-CQDs exhibited distinctive fluorescence properties with a quantum yield (QY) of 36.65 % and were characterized using high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and UV-visible spectroscopy (UV-Vis). These N,P-CQDs showed stable fluorescence, good resistance to changes in pH, and the ability to adapt to changes in ionic strength. This made them ideal for detecting DBP in food materials. A fluorescence quenching assay revealed a broad linear response in the 1-25 μM range and achieved a low limit of detection (LOD) of 0.632 μM. Fluorescence lifetime analysis and FTIR studies confirmed a dynamic quenching mechanism driven by the inner filter effect (IFE) between DBP and N,P-CQDs. This fluorescence-based approach offers a more cost-effective, rapid, and environmentally friendly alternative than conventional DBP detection methods such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). Recovery experiments conducted in spiked food matrices (milk, cheese, and yogurt) demonstrated recovery rates ranging from 97.60 % to 101.67 %, further validating the method's reliability in complex food samples. This method provides a reliable, sustainable, and cost-effective strategy for DBP detection, ensuring food safety and environmental monitoring while addressing the limitations of conventional analytical techniques.