posted on 2007-02-19, 00:00authored byZewei Quan, Zhenling Wang, Piaoping Yang, Jun Lin, Jiye Fang
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.