Kazuhiro Nemoto, C Zhang, Daiki Kido, Daniel Limouchi, Masaki Takeguchi, Hong‐Tao Sun, Naoto Shirahata
High Resolution Image Download MS PowerPoint Slide Controlling precursor reactivity through ligand design remains a central challenge in the colloidal synthesis of III–V quantum dots (QDs). In particular, InSb QDs have been difficult to access due to hazardous metal-hydride reductants and limited precursor availability. Here, we report a metal-reductant-free route employing tris(dimethylamino)phosphine [P(NMe 2 ) 3 ], whose function as a reductant or a P(−III) source is determined by the coordination environment of SbCl 3 . When Sb–oleylamine (OlNH 2 ) complexes are used, P(NMe 2 ) 3 reduces both Sb and In precursors, producing phase-pure InSb QDs. In contrast, Sb–trioctylphosphine (TOP) complexes undergo partial Sb(+III) reduction via electrons released from TOP oxidation, while P(NMe 2 ) 3 simultaneously reduces In and generates P(−III) species, enabling controlled formation of alloyed InP 1– x Sb x QDs (0.6 ≤ x < 1). 31 P NMR and EXAFS analyses reveal that the Sb–TOP complex exists in a dynamic chloride–phosphine equilibrium, which governs P(−III) availability and reaction selectivity. This mechanistic insight demonstrates that ligand coordination can be leveraged to modulate precursor reactivity, selectively direct reduction pathways, and achieve controlled alloying in colloidal III–V QDs. The resulting QDs exhibit sharp excitonic absorption and band-edge emission in the short-wavelength infrared (SWIR) region, bridging the previously inaccessible spectral gap between InP and InSb. Beyond InSb and InP 1– x Sb x, these findings establish a general design principle: dynamic ligand environments can be exploited to tune reactivity, composition, and alloy formation in colloidal semiconductors. This work thus provides a safe, high-yielding, mechanistically rational strategy for Sb-based III–V QDs and lays the foundation for extending optoelectronic functionality through precise precursor engineering.