Synthesis and characterization of Mn doped ZnS d-dots with controllable dual-color emissions.

High-quality Mn doped ZnS d-dots were successfully synthesized via an alternative route based on the solvothermal method using oleic acid as stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as photoluminescence (PL) spectra were employed to characterize the obtained samples. The as-obtained d-dots are highly crystalline and uniform sized, and they can be well dispersed in hexane to form stable and clear colloidal solution. The optical properties of the d-dots with different Mn doped concentration are investigated in detail. The Mn doped ZnS d-dots have two emission bands, including surface state emission (blue) and Mn emission (orange), which are both sensitivity to the Mn doped concentration. By varying the Mn doped concentration, the relative PL intensities of dual-color emissions can be well manipulated, showing their application in tunable color output. Furthermore, a subsequent ligand exchange has been introduced to give the d-dots hydrophilic surfaces, which are favorable for biological applications.