Engineering Biocompatible Glutathione-Capped Cu₂ZnSnS₄ Quantum Dots Toward Integrated Photothermal and Photodynamic...

Ultrasmall near-infrared (NIR)-responsive quantum dots (QDs) are highly promising for deep-tissue phototherapy but often face challenges with biocompatibility and clearance. In this study, Cu₂ZnSnS₄ quantum dots (CZTS QDs) were synthesized via a non-injection method and surface-functionalized with glutathione (GSH) to create water-dispersible and biocompatible CZTS@GSH QDs. Comprehensive characterization using XRD, TEM, DLS, XPS, and UV-Vis spectroscopy confirmed a sphalerite-type ZnS crystal structure, an average hydrodynamic diameter of ~6.2 nm, and a band gap of 1.47 eV (843.5 nm). The CZTS@GSH QDs demonstrated effective photothermal conversion under 808 nm laser irradiation, achieving a temperature increase sufficient for photothermal therapy (PTT). Furthermore, using a DPBF assay, the QDs were shown to generate singlet oxygen, confirming their photodynamic therapy (PDT) capability. Owing to their ultrasmall size, strong NIR absorption, and demonstrated dual PTT/PDT functions, the CZTS@GSH QDs are established as a nanoplatform with potential for combined cancer treatment.