Ultrastable Carbon Quantum Dots-Doped MAPbBr₃ Perovskite with Silica Encapsulation

Having suffered from intrinsic structural lability, perovskite quantum dots (PQDs) are extremely unstable under high-temperature and moisture conditions, which have greatly limited their applications. In this work, we propose a novel method to synthesize ultrastable carbon quantum dots (CQDs)-doped methylamine (MA) lead bromide PQDs with SiO2 encapsulation (CQDs-MAPbBr3@SiO2). The kernel CQDs-MAPbBr3 is formed by the interaction of carboxyl-rich CQDs with MAPbBr3 via H-bond, which greatly improves the thermal stability of CQDs-MAPbBr3. Furthermore, highly compact SiO2 encapsulates the proposed CQDs-MAPbBr3 via a facile in situ growth strategy, which effectively enhances the water resistance and air stability of CQDs-MAPbBr3@SiO2. As a result, the proposed nanomaterial shows extremely high water stability in aqueous solution for over 9 months and ideal thermal stability with strong fluorescence (FL) emission after 150 °C annealing. Based on the superior stability and ultrahigh FL efficiency of this proposed nanomaterial, a primary sensing method for ion (Ag+ and Zn2+) FL detection has been developed and the mechanism of PQDs-based ion determination has also been discussed, thus exhibiting the potential applications of CQDs-MAPbBr3@SiO2 in the area of FL assay and environment monitoring.