Scalable Synthesis of Colloidal InSb Quantum Dots Using a Mild Reducing Agent

Indium antimonide (InSb) quantum dots (QDs) are a promising material for emerging optoelectronic and infrared sensing applications. However, their colloidal synthesis remains less developed due to the difficulty of synchronizing the reduction of In 3+ and Sb 3+ precursors and the widespread reliance on hazardous reagents, such as Superhydride. Here, we report a safer and scalable approach for the synthesis of nanocrystalline InSb QDs using sodium borohydride (NaBH 4 ) as a mild reducing agent of commercially available metal halide precursors. Thermodynamic analysis confirms that NaBH 4 is capable of coreducing In 3+ and Sb 3+, yet the inherent mismatch in their reduction kinetics results in mixed-purity products. To address this, zinc bromide is used as a halide-based reaction modulator to slow the reduction kinetics of Sb 3+ and enable phase-pure InSb quantum dots. The resulting QDs exhibit tunable sizes from ∼3.2 to ∼8.3 nm, with corresponding bandgap shifts from 1.18 eV to 0.73 eV due to quantum confinement. The controlled reaction dynamics are found to enable a 25-fold scale-up of the synthesis without compromising the phase purity or optical properties of the colloids. This work presents a practical and safe pathway for producing high-quality InSb QDs and offers a promising platform for infrared optoelectronic applications.