The low-temperature synthesis and optical properties of near-white light-emission nanophosphors based on manganese-doped zinc sulfide

Manganese-doped zinc sulfide as a nano scale phosphor has been prepared via a solid-state reaction employing zinc acetate, manganese acetate and thioacetamide (TAA). At a synthesis temperature of 100-300°C, the structure of 2 mol % Mn²⁺-doped ZnS nanoparticles was cubic, as identified from X-ray diffraction (XRD) patterns. Four temperatures were adopted to synthesize 2 mol % Mn²⁺-doped ZnS with particle sizes ranging from 3.9 to 7.0 nm. According to the quantum size effect, the increases in ZnS band-gap energy (calculated from photoluminescence excitation spectra and the Brus formula) were examined, and similar tendencies were obtained in the results of the two methods. From the photoluminescence (PL) spectra, two emission bands (blue-light emission and orange-light emission) were observed. The blue-light emission band resulted from the energy level of the ZnS matrix, and the orange-light emission band was assigned to the ⁴T₁→ ⁶A ₁ transition of a Mn²⁺ ion in a ZnS matrix. By controlling the synthesis temperature, the ratio of the two light-emission intensities was tuned by increasing the excitation surface of ZnS matrix material. According to Commission Internationale de L'clairage (CIE) coordinates, a near-white-light emission was observed by this simple and rapid method.