Photoluminescence Sensing of Soluble Lead in Children's Crayons Using Perovskite Nanocrystal In Situ Growth on an Aluminum Hydroxide Layer.

In this study, a fluorescence sensing approach for lead ion (Pb 2+ ) was developed using in situ growth of methylamine lead bromine (MAPbBr 3 ) perovskite on an aluminum hydroxide (Al(OH) 3 ) thin layer. The Al(OH) 3 thin layer could be obtained on a glass slide by liquid phase deposition and is of a large specific surface area and insoluble in water. After sulfhydryl functionalization, the Al(OH) 3 thin layer reveals effective adsorption and excellent enrichment ability to Pb 2+ and is additionally used as the substrate for the in situ growth of lead halogen perovskite. The fluorescence sensing of Pb 2+ could be realized by the fluorescence intensity of lead halogen perovskite on the Al(OH) 3 layer. The linear relationship between the fluorescence intensity and the concentration of Pb 2+ was found in the range from 80 to 1500 mg/kg. The detection limit of Pb 2+ is found to be 40 mg/kg, which is lower than the maximum permission of lead residue in student products (90 mg/kg) stipulated by the National Standard of the People's Republic of China (GB21027-2020). After being grinded and pre-treated, soluble lead in watercolor paint and crayon samples can be extracted by the sulfhydryl functionalization Al(OH) 3 layer, then lead halogen perovskite can be generated in situ on the layer to achieve the fluorescence sensing for the determination of soluble lead in the samples.