Tuning Dimensions of CsPbBr₃ Nanocrystals through Pb(II) Counter Anions: A Dance of Dimensions and Product Selectivity in Visible-Light Photocatalysis

The size tuning of perovskite nanocrystals has been extensively studied and is commonly influenced by factors such as reaction temperature, duration, ligand type, ligand chain length, and choice of halogen source. This study presents a cost-efficient strategy for precise control over the dimensions, shape, size, and phase, of nanocrystals by modulating Pb(II) counteranions during hot-injection synthesis. By employing diethyl 2-bromomalonate as the bromide precursor, distinct nanocrystal morphologies were achieved using different lead sources: lead acetate, lead bromide, lead oxide, and lead nitrate yielded 1D nanorods, 2D nanoplatelets, 3D nanocubes, and quantum dots (QDs), respectively. The resulting CsPbBr3 nanocrystals exhibited high photoluminescence quantum yields (PLQY > 90%) and prolonged excited-state lifetimes (τ ≈ 6.1–15.1 ns). Furthermore, these nanocrystals displayed variable photocatalytic efficiencies in radical cascade cyclization reactions involving N-alkyl/aryl-maleimide and N-phenyl glycine under visible light (blue LED) in dichloroethane. Notably, the reaction yields were strongly influenced by the distinct sizes and morphologies of the nanocrystals.