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) was developed using in situ growth of methylamine lead bromine (MAPbBr) perovskite on an aluminum hydroxide (Al(OH)) thin layer. The Al(OH) 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) thin layer reveals effective adsorption and excellent enrichment ability to Pb and is additionally used as the substrate for the in situ growth of lead halogen perovskite. The fluorescence sensing of Pb could be realized by the fluorescence intensity of lead halogen perovskite on the Al(OH) layer. The linear relationship between the fluorescence intensity and the concentration of Pb was found in the range from 80 to 1500 mg/kg. The detection limit of Pb 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) 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.