Structural, photoluminescence, and photo-catalytic analysis of Mn and Cr dual doped ZnS nanostructures via co-precipitation route

Undoped ZnS, Mn = 4 % doped ZnS (Zn_0.96Mn_0.04S), and Mn = 4 % and Cr = 2 % dual-doped ZnS (Zn_0.94Mn_0.04Cr_0.02S) nanostructures have been prepared using the chemical co-precipitation route. Cubic structure of ZnS with predominant peaks along the (111) plane was confirmed via X-ray diffraction studies, and also the basic cubic structure was not distorted by either single (Mn) or double (Mn, Cr) doping into Zn–S lattice. The modification in crystallite size (∼16–19 Å) lattice parameters, and peak position shift (∼28.5° - 28.8°) by doping suggested that Mn/Cr ions are appropriately substituted into the Zn–S lattice without altering the basic cubic structure. The modification in optical properties and fine-tuning of the energy gap (3.79–3.93 eV) by Mn/Cr-doping are useful for optoelectronic applications. The red shift/blue shift of the energy gap induced by Mn/Cr–ZnS is due to the exchange interaction between the electrons and explained by the energy level diagram. The existence of Cr and Mn in the Zn–Cr–Mn–S lattice was validated by Fourier transform Infra-red studies with appropriate functional groups. Yellowish-orange emission band centered at 571 nm in Mn/Cr doped ZnS is very useful to develop optical device applications such as organic LEDs and solar cells. The elevated photo-induced degradation efficiency (∼85.9 %) at Zn_0.94Mn_0.04Cr_0.02S is demonstrated by the collective effect of the generation of electron-hole pairs and their recombination, elevated optical properties, modification in energy gap, and Mn/Cr-induced new defect-linked states, and a consistent degradation rate was noticed even after four re-cycles.