Colloidal synthesis of MoS2 quantum dots: size-dependent tunable photoluminescence and bioimaging

Abstract

Although the synthesis of two-dimensional (2D) layered MoS₂ nanomaterials has been developing rapidly, there are many technical issues in preparing MoS₂ quantum dots (QDs) with photoluminescence properties. Herein, we design a facile colloidal chemical route to prepare photoluminescent MoS₂ QDs using ammonium tetrathiomolybdate ((NH₄)₂MoS₄) as a precursor and oleyl amine as a reducing agent. The optical properties and structure of as-prepared MoS₂ QDs are investigated systematically. The resultant MoS₂ QDs exhibit fluorescence (λ_max = 575 nm; quantum yield, 4.4%), spherical morphology with a uniform thickness of ∼3 nm and an excitation-dependent PL phenomenon. Moreover, the resultant MoS₂ QDs show size-dependent tunable photoluminescence in the wide visible region. With the help of amphiphilic compounds, the resultant MoS₂ QDs could be transferred from an organic to an aqueous phase. MoS₂ QDs in aqueous solution have many advantages, such as good dispersion, low toxicity and photoluminescent properties, which make them promising materials for application in optoelectronic and biological fields. In this study, the 293T cells are used as a model to evaluate the fluorescence imaging of MoS₂ QDs. The results confirm that the fluorescent signal appears in the cytoplasm which demonstrates that as-prepared MoS₂ QDs could be used as a probe for real-time optical cellular imaging.