Spectroscopic Study of Mn²⁺ Doped PbS Nanocrystals

Mn²⁺ doped PbS (PbS:Mn²⁺) semiconductor nanocrystals have been synthesized by standard chemical method and characterized using various techniques for possible applications in quantum dots. This work describes new physical properties of these nanocrystals that have emerged from our investigations. The PbS:Mn²⁺ nanocrystals have cubic structure (space Group Fm3m) and the average crystallite size lies between 5 and 10 nm as characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis. The structural properties of PbS:Mn²⁺ nanoparticles are also studied by UV/Vis absorption spectrum and High-Resolution Transmission Electron Microscopy (HRTEM). The quantitative chemical analysis of pure and Mn²⁺ doped PbS nanocrystals has been done by Energy Dispersive Spectroscopy (EDS) spectra. The energy band gaps have been determined by UV/Vis absorption study using Tauc Plot as (in eV):1.79, 1.90, 2.23, and 2.39 for Mn²⁺ concentration equal to 0, 0.05, 0.26, and 0.52%, respectively. The luminescence behavior of the nanocrystals has been studied by photoluminescence (PL) spectra. The magnetic and electronic properties of PbS:Mn²⁺ nanocrystals were studied using Electron Paramagnetic Resonance (EPR) spectroscopy. Analysis of EPR spectra enabled determination of the electronic g-factor, the second-rank axial zero-field splitting parameter D and the hyperfine parameter A.