Embedding Perovskite Nanocrystals into a Polymer Matrix for Tunable Luminescence Probes in Cell Imaging

Lead halide perovskite nanocrystals (NCs) with bright luminescence and broad spectral tunability are good candidates as smart probes for bioimaging, but suffer from hydrolysis even when exposed to atmosphere moisture. In this paper, a strategy is demonstrated by embedding CsPbX3 (X = Cl, Br, I) NCs into microhemispheres (MHSs) of polystyrene matrix to prepare "water-resistant" NCs@MHSs hybrids as multicolor multiplexed optical coding agents. First, a facile room-temperature solution self-assembly approach to highly luminescent colloidal CsPbX3 NCs is developed by injecting a stock solution of CsX center dot PbX2 in N,N-dimethylformamide into dichloromethane. Polyvinyl pyrrolidone (PVP) is chosen as the capping ligand, which is physically adsorbed and wrapped on the surface of perovskite NCs to form a protective layer. The PVP protective layer not only leads to composition-tunable CsPbX3 NCs with high quantum yields and narrow emission linewidths of 12-34 nm but also acts as an interfacial layer, making perovskite NCs compatible with polystyrene polymers and facilitating the next step to embed CsPbX3 NCs into polymer MHSs. CsPbX3 NCs@MHSs are demonstrated as multicolor luminescence probes in live cells with high stability and nontoxicity. Using ten intensity levels and seven-color NCs@MHSs that show non-overlapping spectra, it will be possible to individually tag about ten million cells.