Adaptive Paramagnetism and Photoluminescence in Nitrogen Co-doped Mn: CdS Composite Quantum Dots

Abstract

Manganese-doped cadmium sulfide quantum dots (QDs), co-doped with nitrogen, were synthesized using the chemical co-precipitation method (CPM). Surfactant 2-mercaptoethanol (ME) was used to efficiently regulate the size of these QDs. X-ray diffraction (XRD) analyses verified that the particles fell within the nano-dimension, measuring between 1-2 nm. A Rietveld analysis with X’pert high score software (XPHS) proved that these synthesized QDs contained many phases. The energy dispersive X-ray spectroscopy (EDX) technique confirmed the successful incorporation of both manganese and nitrogen dopants into the CdS. Ultraviolet-visible analysis (UV-Vis) demonstrated a noticeable shift towards the blue end in the energy gap, indicating the presence of a quantum-confinement effect. The photoluminescence (PL) investigations revealed a significant emission peak at λ = 634 nm, linked to the transition from 4T1 to 6A1, attributed to the incorporation of Mn2+ within the CdS core. Electron paramagnetic spectroscopy (EPR) demonstrated paramagnetic characteristics. EPR assessments of the g factor (1.995) and hyperfine splitting constant (A) values (7 mT) verified the existence of nitrogen and manganese ions in the tetrahedral positions of the CdS core. The notable alterations noticed in the magnetic and optical characteristics of the fabricated quantum dots imply promising uses in optoelectronic and magneto-luminescent applications.