title: Synthesis and characterization of high-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) luminescent nanocrystals.
abstract: High-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) nanocrystals (NCs) were synthesized via a high-boiling solvent process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The monodisperse ZnS NCs (size = 8 nm), which self-assembled into several micrometer-sized domains, were achieved by adopting poly(ethylene glycol) (PEG) in the reaction process (without using a size-selection process). The obtained ZnS:Mn2+ and ZnS:Mn2+/ZnS core/shell NCs are highly crystalline and quasimonodisperse with an average particle size of 6.1 and 8.4 nm, respectively. All of the as-formed NCs can be well dispersed in hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for ZnS and red-orange for ZnS:Mn2+ and ZnS:Mn2+/ZnS) under UV excitation. The growth of a ZnS shell on ZnS:Mn2+ NCs, that is, the formation of ZnS:Mn2+/ZnS core/shell NCs, resulted in a 30% enhancement in the PL intensity with respect to that of bare ZnS:Mn2+ NCs due to the elimination of the surface defects.
authors.affiliation: Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
authors.forename: Zewei
authors.initials: Z
authors.lastname: Quan
authors.forename: Zhenling
authors.initials: Z
authors.lastname: Wang
authors.forename: Piaoping
authors.initials: P
authors.lastname: Yang
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
authors.forename: Jiye
authors.initials: J
authors.lastname: Fang