Reductant-Activated Indium Phosphide Magic-Sized Clusters for Dual-Path Synthesis of Bright Blue Emitters and Narrow-Band Quantum Dots

Blue-emitting indium phosphide (InP) nanocrystals remain challenging to synthesize due to poorly controlled nucleation and the difficulties associated with highly curved, ultrasmall structures, which hinder the realization of high efficiency and narrow emission. Herein, we report a reductant-activated strategy for the precise regulation of cluster intermediates during nanocrystal growth. Preactivation of safe aminophosphine precursors with a mild reductant generates highly reactive magic-sized clusters (MSC-R), which can be directed along two distinct synthetic pathways. Surface passivation with NH4PF6 yields deep-blue clusters with a record photoluminescence quantum yield of 32.6% and excellent stability, whereas treatment with 1-dodecanethiol induces rapid dissolution–renucleation into InP quantum dots exhibiting narrow emission (full width at half-maximum ≈ 38 nm). This work establishes active intermediate engineering as a powerful approach to control nucleation pathways and advance high-performance, cadmium-free blue emitters.