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 (110), (103) and (112) in XRD pattern distinguish the wurtzite structure of the Mn:CdS NPs. The intensity of the plane (102) increases as the doping concentration of Mn(2+) increases. UV-vis absorption spectra show blue shift as compared to bulk CdS. The optical band gap energy of Mn(2+) (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 Mn(2+) 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 Mn(2+) concentration increases. EPR shows the existence of Mn(2+) with different local structures in CdS nanoparticles. The values of spectroscopic splitting factor (g) and hyperfine interaction constant (A) decrease as Mn(2+) concentration increases in CdS NPs.