Lead halide perovskite quantum dots (QDs) are controversial due to their high lead content. Tin, a low-toxic element with an outer electronic structure similar to that of Pb, becomes a strong candidate for preparing lead-free perovskite QDs. However, tin-based perovskite QDs, especially CsSnCl 3 QDs, exhibit poor environmental stability. Herein, we proposed an strategy for highly stable CsSnCl 3 QDs using an ionic liquid as a solvent and antioxidant and gelatin as a multidentate ligand and coating material through an in situ method ([AMIM]Cl/gelatin-QDs). The results showed that the abundant active groups of gelatin served as the nucleation growth center for QDs and further passivated QDs. At the same time, the long molecular chain of gelatin can coat the QDs to isolate the environment and fully protect QDs, and the size of QDs grown in gelatin was 5−10 nm. In addition, the oxidation resistance of ionic liquids and the halogen-rich environment formed also played an important role. Even if [AMIM]Cl/gelatin-QDs were treated with water and ultraviolet light simultaneously, its remaining fluorescence intensity was still above 60% within 72 h. Meaningfully, QDs endowed the composite system mildew resistance, which can resist the erosion of gelatin by molds, thereby realizing the system's long-term protection toward CsSnCl 3 QDs.

Lead-based perovskite nanocrystals (NCs) are controversial because of their high lead content. Tin is a promising candidate for constructing lead-free perovskite NCs owing to its similar outermost electronic structure with lead. However, the environmental stability of tin-based perovskite NCs is poor, which hinders their commercial applications. Herein, CsSnCl 3 NCs were synthesized via an in situ method with the addition of a hydrolysate of waste leather scraps. The as-synthesized NCs have excellent water resistance, ultraviolet resistance, oxidation resistance, and mildew resistance. The remaining fluorescence intensity of CsSnCl 3 is still above 70% within 72 h when treated with water and ultraviolet rays, which means that the rich active groups in the hydrolysate of waste leather scraps can be used as multidentate ligands to passivate the CsSnCl 3 NCs, and the long molecular chain of the hydrolysate of waste leather scraps can wrap the CsSnCl 3 NCs, isolate the environment, and further improve its stability.

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