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

Abstract Although Ag2S quantum dots (QDs) have attracted extensive attention in the fields of diagnosis and therapy, it is still a challenge to prepare Ag2S QDs with well-controlled size distribution. Herein, size-tunable Ag2S 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 Ag2S QDs with 2.0–5.8 nm in diameter are coordinated with GSH through thiol group. The as-prepared Ag2S 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 Ag2S QDs has a significant influence on the fluorescence intensity and photothermal effect. The cell viability evaluation in vitro demonstrates that Ag2S 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 Ag2S QDs, which are capable to act as ideal theranostics probes for photothermal therapy and simultaneously monitoring the therapeutic effect for effective cancer treatment.