Predictive Synthesis of InSb Quantum Dots: Zerovalent Intermediates, Surface Chemistry, and Optical Tunability

<jats:p>Indium antimonide (InSb) colloidal quantum dots (QDs) are transformative for short-wave infrared (SWIR) to mid-infrared (MIR) optoelectronics due to their narrow bandgap (0.17 eV for bulk) and exceptional electronic properties and carrier mobilities. Here, we quantitatively refine the mechanistic framework of InSb QDs formation by demonstrating the the zise of zerovalent In0 and Sb0 intermediate nanoparticles strictly governs intermetallic diffusion and subsequent growth kinetics By systematically tuning precursor halide choice (Cl-, Br-, I-), reducing agent ratios, In/Sb ratios (2:1 – 5:1), and reaction time (15-180 min), we achived monodisperse InSb QDs with tunable absorption from 1160 to 2200 nm, and exceptional optical and colloidal stability. Temperature-dependent studies reveal that Sb0 nanoparticles (NPs, 3-4 nm) template InSb QD nucleation at 140-160 ºC, while larger In0 NPs (50 nm) facilitate In diffusion. Validation experiments using pre-synthetised In0 and Sb0 NPs confirm that size-matched intermediates (14-17 nm) enable complete conversion to phase-pure zinc-blende InSb QDs. Spectroscopic analysis identifies a dominant non-radiative decay channel (τ1 ≈ 0.12 ns, for 9.6 nm InSb QDs) at room temperature, attributed to surface trapping, alongside a preserved radiative lifetime, consistent with the presence of In and Sb surface oxides. This diffusion-mediated kinetic framework transforms transient metallic intermediates into predictive descriptors for nanocrystal synthesis, enabling scalable, reproducible, and size-tunable InSb QDs with distinct excitonic features, achieving 80–100 mg of purified product per batch for next-generation SWIR technologies.</jats:p>