The surface chemistry of colloidal semiconductor nanocrystals (QDs) profoundly influences their physical and chemical attributes. The insulating organic shell ensuring colloidal stability impedes charge transfer, thus limiting optoelectronic applications. Exchanging these ligands with shorter inorganic ones enhances charge mobility and stability, which is pivotal for using these materials as active layers for LEDs, photodetectors, and transistors. Among those, InP QDs also serve as a model for surface chemistry investigations. This study focuses on group III metal salts as inorganic ligands for InP QDs. We explored the ligand exchange mechanism when metal halide, nitrate, and perchlorate salts of group III (Al, In Ga), common Lewis acids, are used as ligands for the conductive inks. Moreover, we compared the exchange mechanism for two starting model systems: InP QDs capped with myristate and oleylamine as X- and L-type native organic ligands, respectively. We found that all metal halide, nitrate, and perchlorate salts dissolved in polar solvents (such as n-methylformamide, dimethylformamide, dimethyl sulfoxide, H₂O) with various polarity formed metal–solvent complex cations [M(Solvent)₆]³⁺ (e.g., [Al(MFA)₆]³⁺, [Ga(MFA)₆]³⁺, [In(MFA)₆]³⁺), which passivated the surface of InP QDs after the removal of the initial organic ligand. All metal halide capped InP/[M(Solvent)₆]³⁺ QDs show excellent colloidal stability in polar solvents with high dielectric constant even after 6 months in concentrations up to 74 mg/mL. Our findings demonstrate the dominance of dissociation–complexation mechanisms in polar solvents, ensuring colloidal stability. This comprehensive understanding of InP QD surface chemistry paves the way for exploring more complex QD systems such as InAs and InSb QDs.

中文翻译：

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InP 胶体量子点表面金属-溶剂络合物的形成

胶体半导体纳米晶体（QD）的表面化学深刻影响其物理和化学属性。确保胶体稳定性的绝缘有机壳会阻碍电荷转移，从而限制光电应用。用较短的无机配体交换这些配体可以增强电荷迁移率和稳定性，这对于使用这些材料作为 LED、光电探测器和晶体管的活性层至关重要。其中，InP 量子点还可以作为表面化学研究的模型。本研究重点关注 III 族金属盐作为 InP QD 的无机配体。我们探索了当金属卤化物、硝酸盐和高氯酸盐（Al、In Ga）、常见路易斯酸用作导电油墨的配体时的配体交换机制。此外，我们还比较了两种起始模型系统的交换机制：分别用肉豆蔻酸酯和油胺作为 X 型和 L 型天然有机配体封端的 InP QD。我们发现所有金属卤化物、硝酸盐和高氯酸盐溶解在极性溶剂（如正甲基甲酰胺、二甲基甲酰胺、二甲基亚砜、H ₂ O）中，形成不同极性的金属-溶剂络合物阳离子[M(Solvent) ₆ ] ³⁺（例如，[Al(MFA) ₆ ] ³⁺、[Ga(MFA) ₆ ] ³⁺、[In(MFA) ₆ ] ³⁺ )，在去除初始有机配体后钝化了InP QD的表面。所有金属卤化物封端的 InP/[M(溶剂) ₆ ] ³⁺ QD 在高介电常数的极性溶剂中表现出优异的胶体稳定性，即使在浓度高达 74 mg/mL 的情况下 6 个月后也是如此。我们的研究结果证明了极性溶剂中解离-络合机制的主导地位，确保了胶体稳定性。对 InP QD 表面化学的全面了解为探索 InAs 和 InSb QD 等更复杂的 QD 系统铺平了道路。