Cysteamine-mediated upconversion sensor for lead ion detection in food

Lead ion (Pb2+) accumulation in food consumed by humans and animals possess health threats and effects. The development of a senor for its monitoring at its minutest accumulation in edible materials becomes an antidote to safeguarding human lives. A fabricated fluorescence-based sensor made of carboxyl modified upconversion nanoparticles (UCNPs), gold nanorods (GNRs), and cysteamine (Cys) were used as energy donor, receptor and a bridge respectively for the rapid sensing of Pb2+ in Matcha. The UCNPs-Cys-GNRs sensor showed weak fluorescence signals due to the FRET, and was inhibited in the presence of Pb2+ to form a complex with Cys, and the consequent recovery of fluorescence signals. Under optimized conditions, a good linear relationship was established between the relative fluorescence intensity and Pb2+ concentrations from 1 to 100 μM with a low detection limit (LOD) of 0.5 μM. The developed sensor was applied to detect Pb2+ in Matcha samples with recoveries within 93.99—102.16% and relative standard deviations (RSD) < 8%. Satisfactory results (p > 0.05) were obtained upon validation using a standard inductively coupled plasma mass spectrometry (ICP-MS).