Halide salt-tuning at interface: Highly water-stable and anion-exchange-active CsPbX3@SiO2 Trimurti nanoparticles for multicolor metabolite assay.

[Display omitted] • Crystal phase transition rate from Cs 4 PbX 6 to CsPbX 3 can be tuned by halide salt. • Monodisperse CsPbX 3 nanoparticles with double-side SiO 2 -coated is synthesized. • Trimurti nanoparticles exhibit high water stability and fast anion exchange activity. • Anion exchange-based multicolor sensing platform for metabolites is proposed. • The uric acid dual-readout result is the same as that of colorimetric assay kit. High water stability and fast anion exchange (FAE) activity are indispensable requirements of CsPbX 3 (X = Cl, Br, I) nanoparticles (NPs) for achieving multicolor fluorescence sensing in aqueous samples. In this study, we prove that the crystal phase transition rate from Cs 4 PbX 6 to CsPbX 3 can be finely tuned by halide salt, thereby facilitating the exposure of in-situ SiO 2 nucleation sites to CsPbX 3. Through the sol–gel method triggered by KX-containing water, monodisperse CsPbX 3 @SiO 2 Trimurti nanoparticles (TNPs), i.e., double-side SiO 2 -coated CsPbX 3 NPs, are successfully synthesized for the first time. As an example, the CsPbBr 3 @SiO 2 TNPs exhibit significantly enhanced photoluminescence quantum yield (80%), fluorescence lifetime (22.09 ns) and water stability (only 11.4% drop in FL intensity after 60 min reaction with water), meanwhile maintain consistent high FAE activity, compared to bare CsPbBr 3 NPs (57%, 6.56 ns, 97.9% drop) and single-side SiO 2 -coated NPs (69%, 9.76 ns, 39.1% drop). Furthermore, we propose an H 2 O 2 recognition strategy at the organic/aqueous phase interface based on the FAE effect between oleylammonium iodide (OLAI) and CsPbX 3 @SiO 2 TNPs. Thus, the TNPs-based multicolor sensing platform for small molecule metabolites is constructed and utilized for uric acid detection in serum, which obtains consistent results with the commercial method (relative error ≤ 5.67%). This work not only provides a guidance for the tunable surface modification of high-performance CsPbX 3 NPs, but also designs a universal strategy for selectively detecting small molecule metabolites in biological fluids based on the intrinsic FAE effect. [ABSTRACT FROM AUTHOR]