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Modifiers are commonly used in natural, biological, and synthetic crystallization to tailor the growth of diverse materials. Here, we identify tautomers as a new class of modifiers where the dynamic interconversion between solute and its corresponding tautomer(s) produces native crystal growth inhibitors. The macroscopic and microscopic effects imposed by inhibitor-crystal interactions reveal dual mechanisms of inhibition where tautomer occlusion within crystals that leads to natural bending, tunes elastic modulus, and selectively alters the rate of crystal dissolution. Our study focuses on ammonium urate crystallization and shows that the keto-enol form of urate, which exists as a minor tautomer, is a potent inhibitor that nearly suppresses crystal growth at select solution alkalinity and supersaturation. The generalizability of this phenomenon is demonstrated for two additional tautomers with relevance to biological systems and pharmaceuticals. These findings offer potential routes in crystal engineering to strategically control the mechanical or physicochemical properties of tautomeric materials.

The integration of highly luminescent CsPbBr₃quantum dots on nanowire waveguides has enormous potential applications in nanophotonics, optical sensing, and quantum communications. On the other hand, CsPb₂Br₅nanowires have also attracted a lot of attention due to their unique water stability and controversial luminescent property. Here, the growth of CsPbBr₃nanocrystals on CsPb₂Br₅nanowires is reported first by simply immersing CsPbBr₃powder into pure water, CsPbBr_3−γ X_γ(X = Cl, I) nanocrystals on CsPb₂Br_5−γ X_γnanowires are then synthesized for tunable light sources. Systematic structure and morphology studies, including in situ monitoring, reveal that CsPbBr₃powder is first converted to CsPb₂Br₅microplatelets in water, followed by morphological transformation from CsPb₂Br₅microplatelets to nanowires, which is a kinetic dissolution–recrystallization process controlled by electrolytic dissociation and supersaturation of CsPb₂Br₅. CsPbBr₃nanocrystals are spontaneously formed on CsPb₂Br₅nanowires when nanowires are collected from the aqueous solution. Raman spectroscopy, combined photoluminescence, and SEM imaging confirm that the bright emission originates from CsPbBr_3−γ X_γnanocrystals while CsPb₂Br_5−γ X_γnanowires are transparent waveguides. The intimate integration of nanoscale light sources with a nanowire waveguide is demonstrated through the observation of the wave guiding of light from nanocrystals and Fabry–Perot interference modes of the nanowire cavity.