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Pristine and Co-doped ZnS quantum dots (QDs) were fabricated via a hydrothermal technique. Morphology studies showed that the fabricated QDs were nearly spheroidal with narrow size distribution. X-ray diffraction and Raman spectroscopy analyses demonstrated that the Co ions effectively penetrated the host matrix without changing its cubic phase. A minimal blue shift was found in the pristine ZnS QDs after doping with Co. The pristine and Co-doped samples exhibited similar blue emission, while increased (two times) photoluminescence intensity was observed for the Co-doped sample. X-ray photoelectron spectroscopy analysis showed trivalent Co ions in the ZnS lattice. The diamagnetic ZnS QDs were turned into ferromagnetic through Co-doping. The Co-doped ZnS QDs portrayed higher photocatalytic degradation (PCD) of Rhodamine B dye under artificial solar simulator irradiation than pristine ZnS. Hence, the Co-doped ZnS QDs may find applications in luminescent, spintronic and photocatalytic devices.

CdS and CdS:Eu quantum dots (QDs) with relatively uniform size and a narrow size distribution were fabricated by a solvothermal method. X-ray diffraction and Raman spectroscopy analyses revealed that the synthesized samples were polycrystalline with a cubic structure. An almost spheroidal morphology with slight polydispersity was observed in both low and high-resolution transmission electron microscopy images. The optical band gap of the CdS and CdS:Eu QDs was found to be 3.1–3.3 eV. An X-ray photoelectron spectroscopy analysis disclosed the existence of Eu with a trivalent state and the obtained composition values are nearer to stoichiometry. The CdS:Eu QDs displayed room-temperature ferromagnetism. The CdS:Eu QDs showed enhanced photocatalytic activity compared to CdS during malachite green oxalate dye degradation under artificial solar illumination. Hence, Eu doping is a promising path for facilitating better photocatalytic activity and ferromagnetism of CdS.

The tunable room-temperature ferromagnetism (RTFM) of ZnO nanoparticles through Dy doping were fabricated through a simple co-precipitation method for spintronic device applications. The synthesized samples were analyzed by studying their structural, morphological, optical, chemical, and magnetic properties. X-ray diffraction, selected area electron diffraction, and X-ray photoelectron spectroscopy results display that the Dy3+ have successfully entered for a few of the Zn2+ as a substitute in the ZnO crystal lattice without altering their hexagonal structure. Morphology studies of the suspensions consist of monodisperse and slightly hexagonal shaped nanoparticles. The tunable optical band gap was observed in the ZnO samples via Dy doping, confirmed by diffuse reflectance spectroscopy studies. Declaration of RTFM of the ZnO:Dy has been established with the noticed hysteresis in M–H loops and these studies indicate that the saturation magnetization of the ZnO sample as a function of Dy content. Amalgamating with the above results, it is suggested that, the observed RTFM in the ZnO:Dy nanoparticles may be interpreted by the contribution of the magnetic moments from the unpaired 4f electrons of Dy3+ ions.

The present study describes the elemental and structural as well as the room temperature magnetic properties of pure ZnS, Zn0.96Eu0.04S, and Zn0.95Eu0.04Tb0.01S NPs. The energy dispersive X-ray spectroscopy (EDAX) perceived the existence of zinc, terbium, europium, and sulfur in the prepared samples in expected stoichiometry ratio. X-ray diffraction (XRD) studies revealed that all the prepared NPs had a cubic structure. Transmission electron microscopy (TEM) studies showed the creation of wispy particles with an average size in the range of 5–8 nm. Magnetization (M) versus applied magnetic field (H) studies indicated that the pure ZnS NPs exhibited diamagnetic behavior, whereas both Zn0.96Eu0.04S and Zn0.95Eu0.04Tb0.01S NPs evinced the ferromagnetic nature at room temperature. However, suppression in ferromagnetism was observed in Zn0.95Eu0.04Tb0.01S compared to Zn0.96Eu0.04S nanoparticles due to the interactions between the Eu–Eu ions, Tb–Tb ions, and Eu–Tb ions. The above experimental results suggesting that both doped and co-doped ZnS nanoparticles are useful for spintronic device applications.

Cr (0, 3 and 5 at.%) doped ZnS nanoparticles were successfully synthesized by hydrothermal method using PVP as capping agent. The influence of Chromium doping on the structural, luminescence and magnetic properties of ZnS nanoparticles is investigated. EDS spectra confirmed the presence of zinc, chromium and sulfur in the doped samples in near stoichiometric ratio. XRD and Raman analysis demonstrated successful incorporation of Cr3+ ions into ZnS lattice with the absence of metallic clusters or precipitates. TEM micrograph indicated that the particles were a few nm (