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Pure and rare earth elements of samarium (Sm), lanthanum (La) and neodymium (Nd) doped cadmium oxide (CdO) thin films were deposited on glass substrates by radiofrequency magnetron sputtering at room temperature. The influence of rare earth dopants on the microstructural, morphological and optoelectronic properties of the CdO thin films were studied elaborately. The X-ray diffraction studies revealed the polycrystalline with face centered cubic structure of CdO thin films. The structural defects were increased with increase of dopant’s ionic radii. The presence of the dopants in host CdO thin films was confirmed by X-ray photoelectron spectroscopic analysis. The roughness of the films was decreased for the doped samples and Nd doped CdO thin film has the minimum roughness value of 1.29 nm. All the films exhibited high transmittance in visible range and well pronounced Moss-Burstein shift was observed in the band gap value. Emission bands of photoluminescence spectra depicted the presence of oxygen vacancies. Hall Effect measurement showed an increase in carrier concentration and electrical conductivity of the films with the addition of dopants. The suitable combination of high conductivity (2872 Ω−1·cm−1) with optical transparency (88%) and lower surface roughness of Nd doped CdO thin film, makes it a potential candidate for the transparent conducting oxide in optoelectronic devices.

The peculiar morphology of nanorods mixed with microspheres of manganese carbonate (MnCO3) doping with different percentages (0, 2, 4, 6%) of silver (Ag) was synthesized by simple co-precipitation method. The effect of Ag doping on structural, morphological and compositional properties of MnCO3 were investigated. XRD results revealed that the synthesized samples have hexagonal-rhombohedral structure and the peaks are shifted towards higher angles with increasing Ag content. The pure MnCO3 exhibited microsphere like morphology with the size in the rage of 0.8–2.5 μm. XPS analysis confirmed the presence of Mn, C, O and Ag elements. The specific capacitance values are calculated and 4% Ag-doped MnCO3 electrode exhibited a high specific capacitance of 554.6 Fg-1 at a current density of 0.5 Ag-1, good rate capability of 54.74% and excellent cycle stability of 87.22% capacitance retention after 1000 cycles. From these results, Ag-doped MnCO3 could be preferred as the potential competitor for future electrochemical supercapacitor devices.

The different attractive morphologies of micro-nano assembled sphere, pseudo sphere, rock candy and cube-like Mn2O3/NiO composites were synthesised by the facile solvothermal method through varying the solvents and their volume ratio. The structural, morphological and compositional properties of synthesised samples were investigated by using powder X-ray diffraction (XRD), FE-SEM, EDS and XPS. The TG/DTA results confirmed the transformation of MnCO3/NiCO3 to Mn2O3/NiO structures. XRD results revealed that the synthesised samples exhibited the body-centred cubic of Mn2O3 and face-centred cubic of NiO. FESEM images depicted the formation of different micro-nano assembled morphologies. XPS study confirmed the presence of manganese, nickel and oxygen elements and their oxidation states. Pseudocapacitance properties of Mn2O3/NiO electrodes were evaluated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy using 1M KOH electrolyte solution. The specific capacitance values of all the synthesised samples were calculated and the morphology of rock candy like Mn2O3/NiO composite exhibited superior properties of high specific capacitance of 566.21 Fg−1 at a current density of 0.5 Ag−1, better rate capability of 63.25% and good cycling stability of 87.42% capacitance retention even after 1000 cycles. From these results, the well morphological ordered Mn2O3/NiO composites may be preferred as the future electrode materials for electrochemical supercapacitor energy storage devices.

Pure and cobalt (Co)-doped tin oxide (SnO2) nanoparticles were prepared by using a simple co-precipitation method, and the effect of doping on structural, morphological and optical properties was studied. X-ray diffraction revealed a cassiterite tetragonal SnO2 structure with the space group of P42/mnm and without crystalline phases for the samples-doped with higher concentrations. The average crystalline size was found to be between 26.4 nm and 23.1 nm. Fourier-transform infrared spectra depicted the presence of O–H, C–H and Sn–OH absorption bands. It was observed from ultraviolet–visible spectra that the optical band gap values were decreased from 3.69 eV for pure SnO2 to 3.47 eV for 7% Co-doped SnO2. The photolumenescene emission spectra showed that the defect- and emissions-related peaks and the intensity of the peaks decreased with increasing Co concentrations. The presence of tin, oxygen and Co species were found from energy dispersive x-ray spectra. The photocatalytic activities of pure and Co-doped SnO2 nanoparticles were investigated by studying the photodecomposition of brilliant green dye, an organic pollutant. The 7% Co-doped SnO2 had higher photocatalytic activity compared to the pure SnO2, and a maximum degradation efficiency of 91% has been obtained under visible light irradiation.

Pure and alkaline earth metal (Ba2+, Ca2+ and Mg2+)-doped tin oxide nanoparticles were synthesized by simple co-precipitation, and their structural, optical, functional, morphological and compositional properties were analyzed in detail using powder X-ray diffraction, UV–visible spectroscopy, photoluminescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and energy-dispersive analysis of X-ray (EDAX). XRD revealed the formation of rutile tetragonal structure, and the crystallite size has decreased from 28 to 24 nm by the addition of alkaline metal dopants. FTIR spectra confirmed the presence of fundamental vibration modes of SnO2. The optical band gap energy was decreased to 3.05, 3.19 and 2.98 eV by introducing Ba2+, Ca2+ and Mg2+ ions, respectively. Photoluminescence spectra showed defect-related emission peaks, and their intensities were found to increase in doped SnO2 samples. EDAX spectra confirmed the presence of Sn, O, Ba, Ca and Mg elements. The photocatalytic activity of pure and alkaline metal-doped SnO2 catalyst has been investigated under visible light irradiation by using methylene blue dye. The results showed that the Mg-doped SnO2 catalyst has a higher photodegradation efficiency (~ 95.7%) compared with other investigated samples.

Highly transparent and conducting samarium doped cadmium oxide (CdO: Sm) thin films were deposited on glass substrates at room temperature by radio frequency (RF) magnetron sputtering technique using CdO(90 wt%): Sm2O3(10 wt%) mixed alloy target in pure argon atmosphere. The influences of RF power and Sm incorporation on structural, morphological, optical and electrical properties of the films were investigated. X-ray diffraction analysis revealed that the deposited films are polycrystalline nature and RF power has a large impact on the preferred orientation of the films. The X-ray photoelectron spectroscopy studies confirmed the presence of divalent cadmium (Cd2+) and trivalent samarium (Sm3+) in the deposited film. It is found from the atomic force microscopic analysis that the films were highly smooth with low roughness value of about1.3 nm. High transmittance value greater than 80% was retained by the films in visible and near infrared regions and the band gap value decreased with the increase of RF power by quantum confinement. At the moderate RF power of 200 W, the film has low resistivity of the order of 1.283 × 10−4 Ω cm, high mobility 157.8 cm2/V and a high figure of merit 769.04 (Ω cm2)−1 which could be used as an alternative TCO layer for future optoelectronic devices.

Transparent and conducting cadmium oxide (CdO) thin films were deposited on glass substrates at room temperature using radio frequency (RF) magnetron sputtering method. The carrier concentration and electron mobility are the key factors for the conducting properties of CdO thin films. The grain size, crystallinity, thickness, surface roughness and band gap of CdO thin films play an important role in optical and electrical properties. In this study, dual behaviour of CdO thin films is studied as a function of RF sputtering power. Crystalline quality, micro structure, surface morphology and optical and electrical properties of sputtered CdO thin films were investigated. The structural analysis revealed that the deposited CdO films were polycrystalline in nature with cubic structure ( Fm 3 ¯ m space group). The grain sizes were found to be increased with increase of RF power from 100 to 150 W and then decreased at high power (200 W). The optical studies revealed that all the films exhibited higher transmittance in visible and near infrared region and the optical energy band gap value decreased from 2.62 to 2.46 eV with increase of RF power. Luminescence spectra exhibited two strong emission peaks at 484 and 519 nm. The resistivity of CdO thin films gradually decreased with an increase of sputtering power and reached a minimum value of 3.041 × 10−4 Ω cm at 200 W. A maximum mobility of 67.01 cm2/Vs was found for the sample prepared at the sputtering power of 150 W.

Single phase cadmium stannate thin films were deposited on glass substrates through rf magnetron sputtering by varying rf power and keeping substrates at room temperature. The effect of rf power on physical properties of the films and the correlations were systematically investigated. It has been found from XRD that structural phase transition occurred from amorphous to spinel structure with increase of rf power. AFM images revealed that the deposited films show smooth surface with nano grains. High transmittance was retained by the films in visible region and the band gap was decreased from 3.05 to 2.49 eV for increasing rf power by quantum confinement effect. The Mott-Davis model and drude model were used to evaluate the optical constants and free carrier absorption. The electrical resistivity of the films varied in three orders of magnitude as a function of rf power which could be explained by oxygen vacancies formation. From these results, the films deposited at 150 W has the low resistivity of the order of 10 −3 Ω cm with high optical transparency as 80% which could be the preferred conditions to deposit high quality films for future TCO layers for cadmium based CdTe/CdS solar cell devices.

Cerium (Ce) doped SnO2/g-C3N4 composites were synthesized by a facile hydrothermal method. The obtained Ce doped SnO2/g-C3N4 composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–Vis), scanning electron microscope (SEM), energy dispersive spectra (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS). An electrode made of Ce doped SnO2/g-C3N4 exhibited a maximum specific capacitance of 274 F/g at 1 A/g current density. The supercapacitor device fabricated by using Ce-SnO2/g-C3N4//Activated Carbon as electrodes has showed an energy and power densities of 39.3 W h kg−1 and 7425 W kg−1. The asymmetric device gives the retention of 84.2% after completing 5000 cycles. When the same, Ce-SnO2/g-C3N4, composite is used as a photo-catalyst for reduction of methylene blue dye under visible light irradiation, exhibits a higher degradation efficiency of 98% which is higher efficiency compared to all other synthesized samples.

In this article, we synthesize the bifunctional materials of various transition metals (TM) (Co, Ni and Mn) doped SnO2@MoS2 composites for enhanced energy storage and improved photocatalytic activity for removing organic pollutants. Herein, we use a facile hydrothermal method for sample synthesis and the physico chemical properties of the synthesized samples were investigated in detail using various analytical tools. The energy dispersive X-ray spectra and elemental mapping confirmed the presence of species in the synthesized samples. X-ray photoelectron spectroscopy analysis revealed the corresponding energy state of various TM doped SnO2@MoS2 samples. The Mn doped SnO2@MoS2 composite exhibited a higher specific capacitance of 242 F/g at a current density 0.5 A/g. The capacitance retention of 83.95% was observed after 5000 continuous charge/discharge cycles. Further, the Mn doped SnO2@MoS2 composite had higher degradation efficiency (97%) compared to all other samples using methylene blue as an organic dye under visible light irradiation. Henceforth, this study demonstrates the optimum concentration of Mn doped SnO2@MoS2 composite is the outstanding bifunctional materials for supercapacitor and photocatalytic applications.

Synthesis of high energy density and long durability electrode materials are huge urgency for futuristic hybrid supercapacitors (HSCs). In the present work, self-assembled three-dimensional (3D)-mesoporous regimented pristine and neodymium (Nd) doped α-Mn2O3 microspheres (MSs) are prepared by simple hydrothermal method. Due to uniform morphology, presence of oxygen vacancies, mesoporous robust structure, and optimum doping (Nd5%-doped Mn2O3 3D-MSs) offers a high specific capacitance of 862.14 F g−1 (431.07 C g−1) at 0.5 A g−1 with superior cycling retention of 97.30% after 2000 cycles. Additionally, a pouch-type HSC device is fabricated using Nd5%-Mn2O3 3D-MSs as a battery-type positive electrode and activated carbon (AC) as a capacitive-type negative electrode. The fabricated device delivers a maximum energy density of 32.26 Wh kg−1 at a power density of 800 W kg−1 with superior cyclic retention and exhibit a little loss of 4.56% after 10,000 cycles. This superior performance is due to robust microstructures that can alleviate swelling and shrinking of active material at cycling test. Two pouch-type HSCs are connected in series to power light-emitting diodes (LEDs) for real-time applicability. Overall, this study demonstrates that rational doping, porous architecture, oxygen vacancies, and robust micro-nano structure greatly assist to achieve high energy density as well as long life HSCs devices.

Transparent and conducting thin films of pure and gadolinium(Gd) doped cadmium oxide (CdO) were deposited on glass substrates by RF magnetron sputtering at ambient temperature to develop indium free, alternate transparent conducting electrode for optoelectronic devices. The impacts of Gd doping and film thickness on physical properties of the deposited films were investigated. Mechanism of transmittance, conduction and the scattering process were also discussed. The films showed cubic structure with predominant orientation along (111) plane. All the deposited films were smooth and homogeneous with decreasing roughness from 2.23 nm to 1.69 nm for Gd doped CdO thin film. Pristine CdO film showed peculiar morphology of nano pyramidal shaped grains on the surface. The average transmittance of the films increased from 79% to 88% with the doping of Gd. The Gd doped CdO (GCO) film at a thickness of 900 nm exhibits a maximum transmittance of 93% in visible range. The Gd doped CdO film deposited at a thickness of 900 nm showed the best optoelectronic properties with high average transmittance (88%) and low resistivity (7.203 × 10−5 Ω cm). This result indicates that the Gd doped CdO thin films deposited with suitable thickness can be used as an alternative for high performance TCO in various optoelectronic devices.

In this paper, the structural and magnetic behavior of Ni/Mn co-doped ZnO nanoparticles (NPs) synthesized by co-precipitation method are presented. Powder X-ray diffraction data confirm the formation of a single phase wurtzite type of ZnO structure for all the synthesized Ni, Mn doped and co-doped ZnO nanoparticles. The average crystallite size of NPs is found to be 26–38 nm. FTIR and UV spectroscopic results confirm the incorporation of the dopant into the ZnO lattice structure. Photoluminescence intensity varies with doping due to the increase of oxygen vacancies. Furthermore, M-H curve demonstrates that the Ni/Mn co-doped ZnO NPs possess obvious ferromagnetic characteristics at room temperature. Our study enhances the understanding of the novel performances of transition metal co-doped ZnO NPs and also provides possibilities to fabricate spintronic devices.

In this paper, we present the structural, morphological, optical and magnetic properties of Zn1−x A x O (A = Ni, Co and x = 0.20 mol%) and Zn0.80Ni0.10Co0.10O nanoparticles synthesized by a chemical co-precipitation method. Powder X-ray diffraction data confirm the formation of a single-phase wurtzite-type ZnO structure for all the samples. FTIR and EDS measurements ensure that the divalent Ni and Co ions are incorporated in the wurtzite host matrix without any impurity phase. Photoluminescence and Raman spectra indicate the presence of donor defects and oxygen vacancies in the prepared samples. In VSM analysis, undoped ZnO nanoparticles exhibit diamagnetic behavior at room temperature. A systematic increase in ferromagnetic moment (~0.70 emu/g) is observed for Ni-, Co-doped and Co co-doped Ni/ZnO at 300 K. The exchange interaction between delocalized carriers and the localized ‘d’ spins of Ni and Co ions is predicted as the cause of the room temperature ferromagnetism.