White light emission from surface-oxidized manganese-doped ZnS nanorods

Mn-doped ZnS nanorods synthesized on zinc foils by a solvothermal approach exhibited white light emission upon excitation in the UV range (300-330 nm). X-ray diffraction studies coupled with energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy indicated the presence of a thin oxide layer on the Mn-doped ZnS nanorods. The diameters and lengths of the nanorods varied within the ranges 5-12 and 50-100 nm, respectively. The emitted white light was found to be the result of blue, green, and orange emission bands. The blue bands at ∼400 and 459 nm were attributed to sulfur vacancies and surface states, respectively. The green band at ∼511 nm was associated with the singly ionized oxygen vacancy of the ZnO shell layer. The orange emission originated from the ⁴T₁-⁶A₁ transition of the Mn²⁺ ions. Thus, the emissions from the Mn-doped ZnS core and the outer ZnO shell combine together to produce the white light.