Highly Luminescent Indium Phosphide Magic-Sized Clusters via Kinetically Controlled Surface Fluorination

InP Quantum Dots (QDs) are promising materials with significant potential as environmentally benign alternatives to toxic Cd-based QDs. However, the high oxophilicity, strong covalent-bonding nature, and steep size-band gap relationship of InP hinder their complete replacement of Cd-based QDs. To address these challenges, post-treatment methods such as HF treatment are commonly employed. Despite these approaches, the complexity of QD surfaces makes it difficult to correlate observed optoelectronic changes to actual surface phenomena. To overcome this issue, a precise atomic-level understanding of surface chemistry is necessary.<br/>Fortunately, InP QDs are known for their nonclassical nucleation, often forming unique intermediates called Magic-Sized Clusters (MSCs) during synthesis. MSCs are atomically precise intermediates with sizes typically between 1-2 nm, exhibiting higher thermodynamic and kinetic stability compared to nanocrystals of the same size. Understanding these intermediates is essential for comprehending the overall behavior of QDs, and the near-monodispersity of MSCs can provide a platform to address the complexity of QDs.<br/>We developed a novel recipe using zinc chloride and benzoyl fluoride to generate HF via a Friedel–Crafts acylation reaction. This approach avoids the harsh conditions of previous methods by kinetically controlling the HF generation rate to prevent MSC degradation. With this novel recipe, we achieved unprecedented luminescence in InP MSCs and confirmed the mechanism through various analyses. Additionally, we demonstrated that the optoelectronic properties of InP MSCs change while their crystal structure remains stable.<br/>We conducted an in-depth analysis of the surface modifications induced by our novel treatment, revealing the mechanisms behind the observed improvements. Our findings highlight the potential for controlling surface defects at the atomic level, suggesting that this approach can achieve superior optoelectronic performance in InP QDs.