Growth of a secondary material-shell on a core of another material and so, formation of a core-shell
system has been a successful route in the surface modification of nanostructured samples. In this
research, ZnSe:Cu and ZnSe:Cu@ZnS core-shell nanocrystals (NCs) with different contents of Cu-dopant
under microwave irradiation times (MWIRTs) ¼ 0 & 6 min were synthesized by a new and rapid
photochemical microwave-assisted method at home temperature. Crystal structure, crystallite size (by
XRD analysis), morphology and elemental analysis (by TEM, FESEM, EDX and Map), strain, dislocation
density, absorption edge, energy band gap (by exact method of DASF), the exact nature of charge carrier
optical transition (m), Urbach energy (Etail), Refractive index (n), dielectric constant (ε) at the absorption
edge and third order non-linear optical susceptibility (c(3)) were determined. The influences of various
experimental variables, including formation of ZnS shell on ZnSe:Cu core, Cu content and MWIRT on
their opto-structural features were systematically investigated. The obtained NCs present high degree of
crystallinity and have a cubic zinc blende structure which their diameters varies from 1.81 to 2.26 nm.
The formation of core-shell structures was confirmed TEM. For ZnSe:Cu@ZnS core-shell NCs, XRD
diffraction peaks shifted slightly to higher angles. Band gap of ZnSe NCs was obtained about 3.45 eV,
which was tunable by formation of ZnS shell on ZnSe:Cu NCs core and also by altering the synthesis
conditions. However, the band gap values of ZnSe:Cu@ZnS systems were generally smaller than that of
ZnSe:Cu NCs; also, in each cases of bare ZnSe:Cu NCs and ZnSe:Cu@ZnScore/shell NCs, increase in MWIRT
results to the red shift in band gap. For all samples, optical charge carrier transition index of m were
found to be nearly around 3/2 (correspond to the direct non-allowed transition gap type), except for
ZnSe:Cu(1.5%)@ZnS with MWIRT ¼ 6 min with m-index nearly around 1/2 (correspond