EPR and photoluminescence properties of Mn2+ doped CdS nanoparticles synthesized via co-precipitation method

The structural properties of Mn doped CdS (Mn:CdS) nanoparticles (NPs) are studied using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet–visible (UV–vis), Photoluminescence (PL), Raman and Electron paramagnetic resonance (EPR) spectroscopy. XRD analysis shows the nanostructure with 2–4 nm of average crystallite size. The planes (1 1 0), (1 0 3) and (1 1 2) in XRD pattern distinguish the wurtzite structure of the Mn:CdS NPs. The intensity of the plane (1 0 2) increases as the doping concentration of Mn2+ increases. UV–vis absorption spectra show blue shift as compared to bulk CdS. The optical band gap energy of Mn2+ (0, 0.35, 0.70 and 1.35 at.%) doped CdS NPs corresponding to absorption edge are found to be 5.29, 5.28, 5.25 and 5.21 eV, respectively. The intensity of luminescence is changing with the concentration of Mn2+ doped in CdS NPs. Raman spectra show blue shift in fundamental optical phonon mode (1LO) as well as second optical phonon mode (2LO) as compared to bulk CdS. The intensity ratio of the 2LO to 1LO modes slightly decreases as Mn2+ concentration increases. EPR shows the existence of Mn2+ with different local structures in CdS nanoparticles. The values of spectroscopic splitting factor (g) and hyperfine interaction constant (A) decrease as Mn2+ concentration increases in CdS NPs.

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► XRD of Mn:CdS shows nanostructure crystallite size with 2–4 nm average diameters.
► Intensity of the plane (1 0 2) increases as the doping concentration of Mn increases.
► Intensity of luminescence changes with the concentration of Mn in CdS NPs.
► Intensity ratio of the 2LO to 1LO modes decreases as Mn concentration increases.
► EPR shows the existence of Mn2+ with different local structures in CdS NPs.