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In the era of Photonics, design and development of novel rare earth ion-doped quantum dots (QDs) for optoelectronic applications has gained significant interest owing to their outstanding characteristics. Simultaneously, the creation of a new class of photocatalytic materials on the nanoscale is also imperative for environmental purification. Thus, we report on wet chemical synthesis, the structural, morphological, and optical characteristics, fluorescence, and hydrogen evolution of ZnS:Eu (0, 2, 4, and 6 at%) QDs for optoelectronic and photocatalytic applications. Comprehensive structural studies depicted that Eu3+ ions were efficiently substituted into the host matrix and altered the original structure of the ZnS compound. The emission spectra of the ZnS:Eu QDs exhibited distinctive red fluorescence owing to the transition of dopant ions in 5D0 - 7F1, 5D0 - 7F2, 5D0 - 7F3, and 5D0 - 7F4 energy levels of the 4f orbital of the Eu3+ ions. Moreover, the photocatalytic properties of ZnS:Eu (6 at%) QDs possess better catalytic efficiency toward hydrogen evolution through a water splitting mechanism under simulated sunlight irradiation. The observed photocatalytic phenomenon in the synthesized samples agreed well with the luminescence properties exhibited by the QDs.

In the present study, we fabricate the ZnS: V (0, 2, 4, and 6 at%) nanoparticles (NPs) using the chemical-refluxing technique. We analyzed these samples based on structural, optical, magnetic, degradation, and hydrogen evolution properties. Comprehensive analyses of the chemical, structural, and optical measurements show that the vanadium (V) ions occupied the Zn host site without altering their original structure and without forming new phases. We confirmed the paramagnetic nature of the doped samples via magnetic measurements. We examined the photocatalytic properties of the fabricated NPs by the degrading Rhodamine-B (RhB) dye in an aqueous solution under the ultraviolet (UV) light, and the ZnS: V of 2 at% displayed higher degradation efficiency than the other samples. Moreover, 2 at% ZnS: V (sample showed a higher H2 evolution rate (1140 μmolg−1h−1) than the other samples and was 17 times greater than that of pure ZnS lattice. The observed efficient photocatalytic organic pollutant degradation and better hydrogen fuel evolution in 2 at% ZnS: V sample could be due to the presence of a large surface area, creation of more defect sites, dislocation sites of the prepared compound, generation, and the presence of a huge number of charge carriers due to the substitution of V-dopant in the Zn host site and non-recombination rate of charges.

The design and production of co-doped diluted magnetic semiconductor nanostructures for the development of spin-related operating electronic devices have gained considerable attention owing to their formidable characteristics. In this study, we strived to fabricate ZnO, Zn0.98Ni0.02O, Zn0.97Ni0.02Er0.01O, and Zn0.96Ni0.02Er0.02O nanoparticles. The successful penetration of Ni and Er ions into the ZnO host material was confirmed through wide-ranging structural analyses. A slight change in the bandgap of ZnO was obtained by doping and co-doping. The photoluminescence spectra revealed that doping and co-doping induced various emissions as well as structural defects in the fabricated nanoparticles. Magnetic hysteresis loops revealed that the ZnO and Zn0.98Ni0.02O nanoparticles possessed a paramagnetic nature. However, the Zn0.97Ni0.02Er0.01O and Zn0.96Ni0.02Er0.02O nanoparticles exhibited robust ferromagnetism with clear hysteresis loops. Bound magnetic polaron behavior is well-anticipated to describe the ferromagnetism in the synthesized nanoparticles. Hence, (Ni + Er) co-doping is a promising approach for extending the ferromagnetic nature of the ZnO system for spin-based electronic devices.

Diluted magnetic semiconductors related to II–VI-based compounds are of significant interest for the development of spin-based operating electronic devices such as magneto-optical instruments, spintronics, and nonvolatile memory devices. Thus, studies of electron paramagnetic resonance, magnetic characteristics, and the photocatalytic properties of transition metal-doped II–VI-based semiconductors are of great importance. We therefore comprehensively studied the structural, electron spin resonance, magnetic hysteresis, and photocatalytic characteristics of CdS:V4+ nanoparticles (NPs) fabricated by the rapid microwave route for the first time. The structural analyses revealed the authentic substitution of V4+ dopant ions into the CdS matrix. The widening of the optical band gap and relevant quantum confinement phenomenon are discussed in terms of the inclusion of V4+ ions into the CdS matrix. The electron paramagnetic resonance (EPR) spectroscopy results were corroborated by the increase in the number of magnetic spins with increasing V4+ dopant concentration. The assessed number of magnetic spins was nearly equal to 3.601597 × 106 and 7.254048 × 106 for the CdS:V (2 and 4 at%) NPs, respectively. Room-temperature magnetic hysteresis loops also revealed the existence of a large number of magnetic spins through the formation of clear paramagnetism in the CdS:V (2 and 4 at%) NPs. The CdS:V (4 at%) system displayed enriched visible light-driven photocatalytic degradation efficiency compared to bare CdS through the degradation of RhB dye in contaminated water.

Generation of hydrogen fuel via the photocatalytic water splitting mechanism using semiconductor nanoparticles under sunlight irradiation is highly important. Moreover, the development of nanophotocatalysts for polluted water treatment is significant. In this regard, we synthesized CdS, CdS:Er (2 at%), and CdS:Er (4 at%) nanoparticles by a simple reflux route. According to the comprehensive structural analysis, Er3+ ions were incorporated into the CdS host lattice at the substitutional and interstitial sites, without altering the original structure. Photocatalytic measurements revealed that the degradation efficiency of 2 at% Er-doped CdS nanoparticles reached 100% within 100 min of visible light irradiation. In addition, CdS:Er (2 at%) nanoparticles exhibited enhanced photocatalytic hydrogen generation ability under simulated sunlight irradiation. Hence, from the obtained results, we concluded that CdS:Er (2 at%) nanoparticles are promising semiconductor photocatalytic materials for wastewater treatment as well as hydrogen fuel generation.

Design and development of novel highly efficient diluted magnetic semiconductors for spintronic devices and photocatalytic application is of great importance. In this regard, we report on the synthesis and analysis of new class of highly efficient pure CeO2, Ce0.42Fe0.04Co0.04O50, Ce0.42Co0.04Ni0.04O50 and Ce0.38Fe0.04Co0.04Ni0.04O50 nanoparticles. The crystal structure, phase, optical characteristics, magnetic properties and photocatalytic characteristics of synthesized nanoparticles were measured using various analytical techniques. The comprehensive structural analyses revealed that incorporation of Fe, Co and Ni ions in host lattice without change their original structure. Presence of defect sites in synthesized nanoparticles was confirmed through photoluminescence studies. Room temperature magnetic measurements revealed that pure CeO2 and Ce0.42Fe0.04Co0.04O50 nanoparticles showed paramagnetic nature as well as Ce0.42Co0.04Ni0.04O50 and Ce0.38Fe0.04Co0.04Ni0.04O50 nanoparticles exhibited mixed behavior of paramagnetic and ferromagnetic characteristics. Further, Ce0.38Fe0.04Co0.04Ni0.04O50 nanoparticles showed better photocatalytic activity with pseudo first order rate constant 0.0157 (min−1) and it is 1.7 times larger than that of pristine CeO2 nanoparticles.

The design and development of one-dimensional nanostructures have been gaining considerable interest owing to the exceptional optoelectronic and catalytic properties of these structures. Thus, herein, wurtzite phase polycrystalline one-dimensional nanostructures of pristine and Co-substituted ZnO nanorods were fabricated using the hydrothermal method. Co ion substitution into the ZnO lattice was confirmed by structural analysis. Furthermore, an X-ray photoelectron spectroscopic survey suggested that Co ion inclusion in the host Zn2+ site occurred with a Co2+ oxidization state. The quenching of band gap with the Co inclusion into ZnO host sites was determined through optical studies. Room temperature hysteresis curves demonstrated the superparamagnetic nature of the synthesized ZnO and Co-doped ZnO nanorods. The photocatalytic activity of the synthesized nanorods was estimated by the exclusion of Rhodamine-B degradation under artificial solar light illumination. Distinctly, 66.5% photocatalytic degradation efficiency was achieved in Co-doped ZnO nanorods over 100 min; however, only 64.13% efficiency was observed for bare ZnO nanorods over 120 min. The enhanced photocatalytic activity in the Co-doped ZnO sample could be due to the creation of huge trapping sites, massive surface area, and generation and consequent separation of electron and hole pairs.

Magnetically polarized semiconductors are of significant interest in view of their application in spintronic devices. In this study, the microstructure and room temperature ferromagnetic characteristics of ZnO, Zn0.48Tb0.02O50, and Zn0.47Tb0.02Cu0.01O50 nanoparticles (NPs) have been reported. The crystal structure and grain size of the samples were elucidated from comprehensive structural analyses; the results revealed a wurtzite crystal structure with dopant and co-dopant ions located at substitutional or interstitial sites in the ZnO host lattice. The nanoparticles sizes estimated from X-ray diffraction were confirmed by transmission electron microscopy. Diffuse reflectance spectra and the corresponding Kubelka-Munk plots suggested band gap quenching due to the inclusion of dopant ions. Magnetic measurements revealed diamagnetic character for the bare host material, while Zn0.48Tb0.02O50 and Zn0.47Tb0.02Cu0.01O50 showed bending of hysteresis loops in the low magnetic field region and linear behavior within a certain range at higher fields, indicating ferromagnetic and paramagnetic behavior in the two regimes.

Zinc Sulfide (ZnS) quantum dots (QDs) with enhanced fluorescence efficiency and photocatalytic activity have been attained through Ga doping for the first time. Ga-doped ZnS QDs were synthesized via a solvothermal method using Polyethylene glycol (PEG) as a stabilizer. Transmission electron microscopy studies disclosed that the obtained QDs were slightly polydispersed with an average size of 5.5–3.8 nm. The results of X-ray diffraction and Raman and X-ray photoelectron spectroscopy stipulated that the Ga ions were successfully incorporated into the ZnS crystal lattice without amending their internal structure. A blue shift was noticed in the ZnS QDs when doped with Ga. The photoluminescence spectra of all the QDs displayed the same blue emission and enhanced fluorescence efficiency with increase in Ga doping content. The photocatalytic degradation of the phenol red dye under UV-light illumination was enhanced with increasing Ga doping concentration. Thus, the Ga-doped ZnS QDs are potential and favorable candidates for both photoluminescent and photocatalytic device applications.

In recent years, CuSbS2 has attracted significant research interest because of its direct optical band gap of 1.5 eV, high optical absorption coefficient, p-type electrical conductivity, and composition involving earth-abundant and non-toxic precursor elements. We prepared CuSbS2 thin films by annealing chemically grown Sb2S3 and sputter deposited Cu (Sb2S3/Cu) stacks in a graphite box, and studied the effect of the Cu/Sb ratio on the growth and properties of these films by varying the thickness of Cu while keeping the thickness of Sb2S3 constant. The Cu/Sb ratio significantly impacted the phase purity, grain growth, and morphology of the CuSbS2 films. The CuSbS2 films prepared with a Cu/Sb ratio of 0.78 showed some unreacted Sb2S3 and nonuniform grain growth. Upon increasing the Cu/Sb ratio from 0.85 to 0.97, the Sb2S3 phase was consumed completely, and phase-pure CuSbS2 with homogeneous grain formation was obtained. These films exhibited an orthorhombic crystal structure with the (410) preferred orientation. Further increase in the Cu/Sb ratio from 1.28 to 1.52 resulted in a change in the growth direction along the (200) plane and the formation of several micron-sized grains with a compact morphology and Cu3SbS4 secondary phase. The direct optical band gap of the films decreased from 1.52 to 1.48 eV when Cu/Sb ratio was increased from 0.91 to 1.28. The films exhibited p-type electrical conductivity and their electrical resistivity decreased with increasing Cu/Sb ratio. From this investigation it was clear that deviation in the Cu/Sb ratio from the stoichiometric proportion leads to inhomogeneous grain growth of CuSbS2 films, which affect the performance of devices using these films.

Terbium (0, 2, and 4 at%)-doped ZnS quantum dots (QDs) were synthesized via a solvothermal method. The crystal structures of the synthesized QDs were determined to be zinc blend by X-ray powder diffraction (XRD) and Raman analyses. Transmission electron microscopy (TEM) studies revealed that particles with a mean size of 2–4 nm were formed. An X-ray photo electron spectroscopy (XPS) examination disclosed the existence of terbium with a trivalent state in the ZnS host lattice. The absorption bands of all QDs were located around 325 nm (3.81 eV) and were higher than that of the bulk ZnS band gap (3.67 eV), consistent with the quantum confinement effect. The photoluminescence spectra of the terbium-doped samples displayed five emission peaks at 467 nm (5D4→7F3), 491 nm (5D4 → 7F6), 460 nm (5D4 – 7F5), 484 nm (5D4 – 7F4), and 530 nm (5D4 – 7F3), respectively. The terbium-doped QDs exhibited a higher photocatalytic activity during the degradation of crystal violet dye under UV-light illumination compared to the undoped ZnS QDs. These interesting properties of terbium-doped ZnS QDs are potentially useful for both luminescent and photocatalysis applications.

Cu 3 SbS 4 is a promising material for thin film heterojunction solar cells owing to its suitable optical and electrical properties. In this paper, we report the preparation of Cu 3 SbS 4 thin films by annealing the Sb 2 S 3 /CuS stacks, produced by chemical bath deposition, in a graphite box held at different temperatures. The influence of annealing temperature on the growth and properties of these films is investigated. These films are systematically analyzed by evaluating their structural, microstructural, optical and electrical properties using suitable characterization techniques. X-ray diffraction analysis showed that these films exhibit tetragonal crystal structure with the lattice parameters a=0.537 nm and b=1.087 nm. Their crystallite size increases with increasing annealing temperature of the stacks. Raman spectroscopy analysis of these films exhibited modes at 132, 247, 273, 317, 344, 358 and 635 cm −1 due to Cu 3 SbS 4 phase. X-ray photoelectron spectroscopy analysis revealed that the films prepared by annealing the stack at 350 °C exhibit a Cu-poor and Sb-rich composition with +1, +5 and −2 oxidation states of Cu, Sb and S, respectively. Morphological studies showed an improvement in the grain size of the films on increasing the annealing temperature. The direct optical band gap of these films was in the range of 0.82–0.85 eV. Hall measurements showed that the films are p-type in nature and their electrical resistivity, hole mobility and hole concentration are in the ranges of 0.14–1.20 Ω-cm, 0.05–2.11 cm 2 V −1 s −1 and 9.4×10 20 –1.4×10 19 cm −3 , respectively. These structural, morphological, optical and electrical properties suggest that Cu 3 SbS 4 could be used as an absorber layer for bottom cell in multi-junction solar cells.

Zn1−xDyxS (x=0, 0.02 and 0.04) nanoparticles (NPs) were synthesized by chemical refluxing technique at 100 °C. The prepared samples were analyzed by studying their compositional, morphological, structural, optical and magnetic properties. EDS analysis confirmed the presence of zinc, dysprosium and sulfur in the samples in near stoichiometric ratio. The X-ray diffraction patterns do not show any Dy related peaks for the as-synthesized ZnS nanoparticles. The average diameter of the particles confirmed by TEM studies, was in the range 2–4 nm. Raman studies revealed that all the samples are single phase and exhibit cubic structure. From DRS studies, the band-gap was found to be in the range of 3.85–3.70 eV. All the doped ZnS nanoparticles exhibit ferromagnetic behavior with the Curie temperature higher than room temperature and the magnetic properties of doped ZnS nanoparticles depend on the concentration of Dy ions.

Diluted magnetic semiconducting (DMS) ZnS:Ni (Ni=0, 1, 3 and 5 at%) nanoparticles were synthesized by the refluxing technique at 80 °C. X-ray diffraction studies showed that undoped ZnS and Ni doped ZnS nanoparticles exhibited the expected zinc blende structure. X-ray photoelectron spectroscopy results revealed that the Ni ions existed in a +2 state in these nanoparticles. Reflectance measurements showed a decrease in band gap with increasing Ni concentration. Room temperature photoluminescence (PL) studies indicated that all the samples exhibited broad and asymmetric PL peaks covering a wide visible range. Gaussian fitting of PL data resulted in three deconvoluted peaks corresponding to blue and green emissions. Dramatic enhancement in fluorescence efficiency was observed in the doped ZnS nanoparticles indicating their possible applications in photoluminescent devices. Magnetic studies revealed that all the doped samples exhibited carrier mediated ferromagnetism at room temperature. Saturation magnetization ( M s ) increased with increasing Ni content reaching a maximum for 3 at% Ni and decreased for samples of 5 at% Ni.