Controllable preparation of Ag2S quantum dots with size-dependent fluorescence and cancer photothermal therapy

Although Ag 2 S quantum dots (QDs) have attracted extensive attention in the fields of diagnosis and therapy, it is still a challenge to prepare Ag 2 S QDs with well-controlled size distribution. Herein, size-tunable Ag 2 S QDs with glutathione (GSH) as ligands were prepared via a facile aqueous precipitation method. The QDs are precisely prepared through carefully controlled growth of Ag2S QDs by varying the heating time. Morphology and structure characterization verify that Ag 2 S QDs with 2.0–5.8 nm in diameter are coordinated with GSH through thiol group. The as-prepared Ag 2 S QDs exhibit broad absorption spectra and narrow fluorescence emission spectra in the near-infrared region. Meanwhile, the QDs perform excellent and stable photothermal effect with a photothermal conversion efficiency up to 58.6%. More importantly, it is found that the size of Ag 2 S QDs has a significant influence on the fluorescence intensity and photothermal effect. The cell viability evaluation in vitro demonstrates that Ag 2 S QDs have low cytotoxicity to 293 T cells and Hela cells by methyl thiazolyl tetrazolium test. This paper proposes a convenient route to prepare unique Ag 2 S QDs, which are capable to act as ideal theranostics probes for photothermal therapy and simultaneously monitoring the therapeutic effect for effective cancer treatment.