Enhanced Quantum Yield and Long-Term Stability of Eco-Friendly Water-Dispersed InP/ZnSe/ZnS Quantum Dots via Photochemical Surface Passivation

Quantum dots (QDs) are essential in fields such as bioimaging and electronics due to their unique optical properties. However, traditional cadmium (Cd)-based QDs pose significant environmental and health risks. This study aimed to develop efficient, Cd-free QDs suitable for water dispersion and long-term stability. We synthesized InP/ZnSe/ZnS multi-shell QDs and employed a photochemical surface passivation method using a halogen lamp to enhance their photoluminescence. For water dispersion, we used ligand exchange with hydrophilic agents, such as 3-mercaptopropionic acid (3-MPA) and 11-mercaptoundecanoic acid (11-MUA). This process facilitated the dispersion of QDs in water while maintaining their quantum yield (QY). The results revealed that the water-dispersed QDs retained 92.5% of their initial QY after 2 months, a notable improvement compared to the 47.3% retention of QDs dispersed in chloroform solvents. This demonstrates that our photochemical passivation method and ligand exchange effectively stabilize QDs in aqueous environments. These Cd-free, water-dispersed QDs offer significant advantages for sustainable electronics, water treatment, and biomedical applications. The study highlights the potential for broader commercialization and further research into optimizing QD performance through advanced ligand and synthesis techniques.