Luminescence-Tunable ZnS-AgInS₂ Nanocrystals for Cancer Cell Imaging and Photodynamic Therapy

A highly luminescent I-III-VI group of semiconductor nanocrystals (NCs) has attracted considerable attention for applications in biomedical engineering and design of novel optoelectronic devices. In this work, high quality ZnS-AgInS₂ (ZAIS) solid solution NCs were synthesized by thermal decomposition of a organometallic diethyldithiocarbamate precursor complex of (AgIn)Zn_2(1- (S₂CN(C₂H₅)₂)₄ in the presence of specific stabilizing and structure directing agents. By changing the composition of the precursor complex (value of x), the structure and optical property could easily be adjustable, thus leading to the formation of nanowire, nanorod, and tetrapod-like NCs and highly luminescent green to yellow to red color tunable NCs. The ZAIS NCs were further transferred to aqueous medium by 3-mercaptopropionic acid (MPA) capping without losing any optical properties. The color-tunable, water-soluble, and biocompatible ZAIS NCs were utilized for the in vitro cellular imaging of human cervical cancer cells (HeLa cells) and showed intense localization in the cell cytoplasm after 6 h of incubation. In addition, the inherent photocatalytic property of ZAIS NCs under light illumination showed promising photodynamic therapy of cancer cells, and thus, ZAIS NCs could be a promising candidate for future biomedical applications.