Impact of organic coatings on the toxicity profile of zinc selenide quantum dots in aquatic ecosystems

Zinc selenide quantum dots (ZnSe QDs) are semiconductor nanomaterials that exhibit size-dependent optical properties, making them attractive for use in optoelectronics, bioimaging, and environmental remediation. However, their potential toxicity in aquatic environments remains a critical concern. This study aimed to synthesize and evaluate water-dispersible ZnSe QDs capped with different organic ligands and assess their optical behavior and biological impact. ZnSe QDs were prepared using three surface-modifying agents: N-acetyl-L-cysteine (NAC), 3-mercaptopropionic acid (MPA), and thioglycolic acid (TGA). The nanocrystals were characterized using photoluminescence, Fourier-transform infrared, and high-resolution transmission electron microscopy. All samples exhibited strong blue photoluminescence, with 2–7 nm particle sizes and spherical morphology. The infrared spectra confirmed the successful surface functionalization of the QDs by each capping ligand. Toxicological evaluations were conducted using Artemia salina as a marine model organism. Nanoparticles were tested at concentrations ranging from 0 to 1000 parts per million (ppm), with 24 and 48 h exposure times. Results showed that toxicity increased with concentration and exposure time, and varied depending on the capping ligand used. Notably, ZnSe QDs capped with N-acetyl-L-cysteine showed lower toxicity than those capped with MPA and TGA. These findings suggest that surface chemistry plays a crucial role in modulating the biological interactions and safety profile of ZnSe quantum dots. Understanding these effects is essential for the safe design and deployment of QDs in environmental and biomedical applications.