Ni Doping Concentration Research Articles

Low metal–insulator transition temperature of Ni-doped vanadium oxide films

Elemental doping is the main means to regulate the phase transition of vanadium oxide (VO2); however, the effects of low valence elemental (<4+) doping on the phase transition of VO2 are still controversial. In the present work, Ni-doped VO2 films were prepared on quartz glass by direct current reactive magnetron sputtering and subsequent annealing. With the increase of the Ni doping content, the phase transition temperature of heating (TH) of the VO2 films decreased from 73.4 °C to 52.4 °C. The temperature required for the occurrence of phase transition (Tb) was lower than TMIT. Different from the undoped VO2 film, the Ni-doped VO2 films had a Tb of around 30 °C. XRD and Raman results revealed that some rutile VO2 microcrystals appeared in the vanadium oxide films because of the lattice distortion by incorporated Ni. Hence, rutile VO2 micro-crystallinities significantly facilitated the phase transition of monoclinic VO2 to rutile one.

Enhanced opto-non-linear properties of low cost deposited pure and Ni@PbI2/glass nanostructured thin films for higher order non-linear applications

Herein, thin films of PbI2 with different Ni-doping concentrations (0.0, 1.0, 3.0, 5.0 and 7.5 wt%) have been fabricated using spin coating method. The fabricated films possess a hexagonal crystalline structure and growth along the (001) plane, as-confirmed by XRD analysis. EDS elemental-mapping confirmed the uniform doping of Ni throughout the PbI2 films. SEM images reveal the formation of nanoparticles/sheets with sizes of ⁓100 nm in the fabricated films. An optical absorption study reveal the change in absorption edge of PbI2 observed upon Ni doping. The fabricated films are highly transparent (i.e. 80–86%) in the visible to near-infra red region. The energy gap of PbI2 was determined to be 2.34 eV, which increased to 2.45 eV for the 5 wt% Ni@PbI2 film. The fabricated films show photoluminescence quenching when doped with Ni. The refractive index values were determine to be between 1.73 to 3.37 in the whole region studied. Furthermore, the dielectric-electrical-non-linear optical parameters were also determined. The χ(1), χ(3) and n(1) values were estimated to be in range of 0.16–0.83, 1.1 × 10−13 to 7.8 × 10−11 esu and 2.3 × 10−12 to 8.7 × 10−10 esu, respectively. It was noticed that these parameters were enhanced upon Ni doping up to 5.0 wt%. The enhanced opto-non-linear properties of PbI2 by Ni doping makes it a suitable candidate for optoelectronic applications.

Magnetic polaron-related optical properties in Ni(II)-doped CdS nanobelts: Implication for spin nanophotonic devices

Emissions by magnetic polarons and spin-coupled d–d transitions in diluted magnetic semiconductors (DMSs) have become a popular research field due to their unusual optical behaviors. In this work, high-quality NiI2(II)-doped CdS nanobelts are synthesized via chemical vapor deposition (CVD), and then characterized by scanning electron microscopy (SEM), x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and Raman scattering. At low temperatures, the photoluminescence (PL) spectra of the Ni-doped nanobelts demonstrate three peaks near the band edge: the free exciton (FX) peak, the exciton magnetic polaron (EMP) peak out of ferromagnetically coupled spins coupled with FXs, and a small higher-energy peak from the interaction of antiferromagnetic coupled Ni pairs and FXs, called antiferromagnetic magnetic polarons (AMPs). With a higher Ni doping concentration, in addition to the d–d transitions of single Ni ions at 620 nm and 760 nm, two other PL peaks appear at 530 nm and 685 nm, attributed to another EMP emission and the d–d transitions of the antiferromagnetic coupled Ni2+–Ni2+ pair, respectively. Furthermore, single-mode lasing at the first EMP is excited by a femtosecond laser pulse, proving a coherent bosonic lasing of the EMP condensate out of complicated states. These results show that the coupled spins play an important role in forming magnetic polaron and implementing related optical responses.

First-principles study of the stability, electronic and mechanical properties of Cr2N and CrN with the variation of Ni doping concentration

First-principles approach was applied to investigate the stability, electronic and mechanical properties of Cr2-xNixN (x = 0, 0.083, 0.167,0.250, 0.333) and Cr1-xNixN (x = 0,0.125,0.25,0.375, 0.5). The calculated formation enthalpy and mechanical stability results show that Cr2-xNixN and Cr1-xNixN are all stable. The bulk, shear and Young's modulus results indicate that different variation trend is observed in Cr2-xNixN and Cr1-xNixN with the increase of x. Base on Pugh and Pettifor criteria, Cr2N belongs to the brittle area and the ductility of Cr2-xNixN increases with the increment of x, obtain the maximum results when x = 0.333. However, CrN, which belongs to the ductile area, alloying with Ni decreases its ductility and increases its brittleness, reach the maximum brittleness when x = 0.5. The charge density difference study reveals that the doped Ni atom affects the interaction between Cr and N in Cr2-xNixN and Cr1-xNixN differently. Furthermore, the stress-strain curve of Cr2N, Cr1.833Ni0.167N, and Cr1.667Ni0.333N under shear and tensile deformation shows that the ultimate stress of Cr2N is decreased and its ductility increased. Nevertheless, the stress-strain curve of CrN, Cr0.75Ni0.25N, and Cr0.5Ni0.5N under shear and tensile deformation indicates that the strength of CrN can be enhanced and its deformation process is significantly changed when x = 0.25.

Enhanced Photocatalytic Performance of Zinc Ferrite Nanocomposites for Degrading Methylene Blue: Effect of Nickel Doping Concentration

In the present work, undoped and nickel doped zinc ferrite (ZnFe2−xNixO4) nano-composites were synthesized using a facile auto-combustion method using glycine as fuel. Effects of Ni dopant concentration and annealing process on structural and morphological properties were investigated by X-ray Diffraction (XRD), Raman spectroscopy, Fourier Transform InfraRed (FTIR) spectroscopy, and Scanning Electron Microscopy/Energy-dispersive X-ray spectroscopy (SEM/EDS). The formation of cubic spinel ferrites is confirmed by XRD analysis while asserting particles with a size range of 55–58 nm. Analysis of Raman spectra showed a transition of normal to inverse spinel-type with the increase in Ni content. Photocatalytic studies of as-synthesized nanoparticles using methylene blue (MB) demonstrated a strong correlation between photocatalytic efficiency and Ni doping. Ni-doped zinc-ferrites exhibited 98% photocatalytic efficiency at an optimum Ni doping concentration of 30%. As-synthesized ferrites have the potential to be used as an efficient, reusable, and magnetically removable photocatalyst system for removing organic pollutants.

An ab initio investigation of the electronic and magnetic properties of graphite and nickel-doped graphite

In this paper, the KKR (Korringa, Kohn, and Rostoker) is presented with coherent potential approximation methods which is used to investigate the electronic and magnetic properties of allotropic graphite forms of carbon and nickel-doped graphite. The density of states (DOS), band structure, total energy, and the magnetic moments of atoms are computed. The crystallographic structure optimization is carried out by evaluating the total energy as a function of unit lattice parameters. The DOS analysis reveals a partially metallic behavior of the compound. The magnetism vs the Ni-doping content in C1−xNix is also investigated by computing moments induced on atoms; the sensitivity of the magnetism to Ni-doping is also analyzed.

Activate Fe3S4 Nanorods by Ni Doping for Efficient Dye-Sensitized Photocatalytic Hydrogen Production.

Developing suitable catalysts capable of receiving injected electrons and possessing active sites for hydrogen evolution reaction (HER) is the key to building an efficient dye-sensitized system for hydrogen production. Fe3S4 is generally regarded as an inferior HER catalyst among the metal sulfide family, mainly due to its weak surface adsorption toward H atoms. In this work, we demonstrate a facile metal-organic framework-derived method to synthesize uniform Fe3S4 nanorods and active them for HER by Ni doping. Our experimental results and theoretical calculations reveal that Ni doping can greatly modify the electronic structure of Fe3S4 nanorods, improving their electron conductivity and optimizing their surface adsorption energy toward H atoms. Sensitized by a commercial organic dye (eosin-Y), 1%Ni-doped Fe3S4 nanorods display a high H2 production rate of 3240 μmol gcat-1 h-1 with an apparent quantum yield of 12% under 500 nm wavelength, which is significantly higher than that of pristine Fe3S4 and even higher than that of 1% Pt-deposited Fe3S4. The working mechanism of this dye-sensitized system is explored, and the effect of Ni-doping concentration has been studied. This work presents a facile strategy to synthesize metal-doped sulfide nanocatalysts with greatly enhanced activity toward photocatalytic H2 production.

Optical and room-temperature ferromagnetic properties of Ni-doped CuO nanocrystals prepared via auto-combustion method

The pure and Ni-doped CuO nanocrystals were prepared via auto-combustion method and characterized by X-ray diffraction, scanning electron microscope, UV spectroscopy, and vibrating sample magnetometer method. The X-ray diffraction patterns of all samples revealed the monoclinic CuO nanocrystals with the nanocrystalline phase. XRD data revealed that the lattice constants of CuO nanocrystals were decreased with increasing Ni concentration which indicate that Ni2+ ions incorporated in CuO lattice. The average crystallite size of nanocrystals is intended by Scherer’s formula and found in the range of 21–24 nm. The variation of microstrain was investigated for pure and Ni-doped CuO samples. The SEM images exhibited that the prepared particles have spherical-like structure. The optical absorption spectra of the nanoparticles obtained using UV–Vis spectrophotometer show the blue-shift with increasing Ni doping. The optical band-gap energy increased with increasing Ni doping concentration due to the sp-d exchange interaction between d localized electrons of Ni. Magnetic measurement showed a ferromagnetic behavior at room temperature. Structural and magnetic properties are also discussed in detail.

Reducing p-type Schottky contact barrier in metal/ZnO heterostructure through Ni-doping

Large contact resistance at metal-substrate/ZnO heterostructure interfaces prevents achieving highly efficient device performance. Herein, we present a systematic study on the effect of Ni-doping in the reduction of the Schottky contact barrier at metal-substrate/ZnO heterostructure. To this end, Ni-doped zinc oxide (Ni:ZnO) thin films were deposited on glass substrate by a spray technique with different Ni-doping concentrations. X-ray Diffraction and Atomic Force Microscopy (AFM) measurements showed that Ni-doping enhances the surface uniformity as compared to the undoped-ZnO films and significantly decreases the roughness (RMS) from 35 to 17 nm. Conductive Atomic Force Microscopy (C-AFM) with a Bruker's platinum coated probe (Pt-Ir) tip results in the stabilization of a p-type Schottky contact with a small height barrier of ~0.4 eV, which is among the smallest values reported in literature for ZnO thin films. Our first principle calculations, which are based on the relative alignment of the band edges of the components, also confirm the reduction in the Schottky barrier height by Ni-doping in line with the experimental tendency. Both experimental and theoretical results provide a robust evidence of the potential of stabilization of a small p-type Schottky contact at metallic-substrate/ZnO interface through a Ni-doping.

Characteristics of Ni-doped TiO2 nanorod array films

In this work, un-doped and Ni-doped titanium dioxide nanorod (TiO2 NR) arrays were synthesized by using a hydrothermal method in a Teflon-lined autoclave, on a fluorine tin oxide (FTO) substrate, at different Ni content (XNi = 0, 0.025, 0.05, 0.075, and 0.1). The grown nanorod array samples were studied by XRD, FESEM, DC conductivity, Hall effect measurements, ultraviolet-visible (UV-Vis) spectroscopy, and vibrating-sample magnetometer (VSM) measurements. Pure rutile phase with preferred orientation along (002) was noticed, indicating that the vertical growth of nanorods for the un-doped sample converts to the (101) direction with increasing doping content. The sharp (002) peaks compared with the broad behavior for other peaks indicate the longitudinal growth along this direction. The lattice constant (a), for tetragonal structure, increased with increasing Ni content, while small increment showed along the (c) direction. Uniformly distributed nanorod arrays with 2000-nm length and 200-nm diameter for the un-doped sample. The nanorod length decreases and their diameters increase with increasing Ni doping content. All the prepared samples showed that they behave like n-type semiconductors with a high carrier concentration and this can be attributed to the present of oxygen vacancies. DC conductivity increases due to increasing carrier concentration, while the charge carriers’ mobility decreases with increasing doping content from 0 to 0.1. Increasing Ni content enhances the TiO2 NR magnetic properties, where the residual magnetization increased from 0.0001 to 0.0058 emu/g, while the saturation magnetization increased from 0.0304 to 0.2652 emu/g with increasing Ni content from 0 to 0.1.

Microwave-sonochemical synergistically assisted synthesis of hybrid Ni-Fe3O4/ZnO nanocomposite for enhanced antibacterial performance

The synergistic effect of microwave irradiation and ultra sonication on the bactericidal performance of Fe3O4/ZnO and the hybrid Ni doped Fe3O4/ZnO nanocomposites was demonstrated. The synthesized nanocomposite materials were characterized by ultra-violet visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. The diffraction patterns revealed clearly the integration of Ni ions into the Fe3O4/ZnO crystal lattice without changing the crystal structure. The crystallite size of Fe3O4/ZnO decreased with Ni dopant concentration, which supports antibacterial activity. The infrared spectra revealed significant transferences in the peaks with Ni addition, representing the successful incorporation of Ni ions into Fe3O4/ZnO. The energy band gap of Fe3O4/ZnO decreased from 2.4 to 2.2 eV, which established the existence of Fe3O4/ZnO stimulus interaction with different dopant level of Ni catalyst. Fe3O4/ZnO exhibited strong blue emission at 470 nm, which shifted to the green at 560 nm, when Ni2+ ions binded together with Fe3O4/ZnO nanoparticles, which is favorable for better antibacterial activity. Subsequently, with the addition of Fe3+ and Ni2+ ions, the spherical shaped morphology of Fe3O4/ZnO transformed to nano foil like structure. A novel approach for modifying the reactive oxygen species mechanism of the hybrid nanocomposite was made using ultra sonication. The potential toxicity of nanosized Fe3O4/ZnO and the hybrid Ni doped Fe3O4/ZnO nanocomposites were investigated with both Gram-positive and Gram-negative bacteria as test organisms. Compared to 3% Ni, 5% Ni doped Fe3O4/ZnO nanocomposite was found to show better antibacterial performance for both Gram-positive and Gram-negative bacteria due to large H2O adsorption, condensed particle size and improved particle surface reaction after sonication. Also S. aureus bacteria was found to show larger bactericidal efficiency with high zone of inhibition of 13−14 mm when tested with Ni-Fe3O4/ZnO nanocomposite than K. pneumoniae bacteria which was attributed to the thicker layers of peptidoglycan structure.

INFLUENCE OF NICKEL DOPING CONCENTRATION ON THE CHARACTERISTICS OF NANOSTRUCTURE CuS PREPARED BY HYDROTHERMAL METHOD FOR ANTIBACTERIAL ACTIVITY

Pure and nickel doped copper sulfide (CuS) nanostructure were prepared by hydrothermal method for 5 h at [Formula: see text]C. Structural, morphological and optical properties of the CuS nanostructure were studied for different Ni-doping concentration of 1%, 2%, 3%, 4%, and 5 %. X-ray diffraction studies showed the polycrystalline nature with hexagonal phase structure of CuS and Ni: CuS nanostructure. FE-SEM image showed that nickel doping concentration affected the nanostructure morphology. The absorbance spectra were then recorded at wavelengths ranging from 350 nm to 1000 nm, where the CuS nanostructures have strong absorbance in the NIR. The optical band gap energy of the samples increased as nickel concentration increasing. In particular, their optical band gap energies were 3.25, 3.48, 3.49, 3.49, 3.45 and 3.44 eV for undoped and Ni-doped CuS nanostructure with concentrations (1%, 2%, 3%, 4% and 5%), respectively. The antibacterial activity of Copper sulfide nanostructure against P. aeruginosa, E. coli, and S. aureus was evaluated by zone of inhibition. The test revealed that copper sulfide nanostructure have a strong antibacterial activity against gram-positive than for gram-negative with low concentration of CuS.

Photoelectrochemical Studies on Metal-Doped Graphitic Carbon Nitride Nanostructures under Visible-Light Illumination

Recently, the engineering of optical bandgaps and morphological properties of graphitic carbon nitride (g-C3N4) has attracted significant research attention for photoelectrodes and environmental remediation owing to its low-cost synthesis, availability of raw materials, and thermal physical–chemical stability. However, the photoelectrochemical activity of g-C3N4-based photoelectrodes is considerably poor due to their high electron–hole recombination rate, poor conductivity, low quantum efficiency, and active catalytic sites. Synthesized Ni metal-doped g-C3N4 nanostructures can improve the light absorption property and considerably increase the electron–hole separation and charge transfer kinetics, thereby initiating exceptionally enhanced photoelectrochemical activity under visible-light irradiation. In the present study, Ni dopant material was found to evince a significant effect on the structural, morphological, and optical properties of g-C3N4 nanostructures. The optical bandgap of the synthesized photoelectrodes was varied from 2.53 to 2.18 eV with increasing Ni dopant concentration. The optimized 0.4 mol% Ni-doped g-C3N4 photoelectrode showed a noticeably improved six-fold photocurrent density compared to pure g-C3N4. The significant improvement in photoanode performance is attributable to the synergistic effects of enriched light absorption, enhanced charge transfer kinetics, photoelectrode/aqueous electrolyte interface, and additional active catalytic sites for photoelectrochemical activity.

Atomic-scaled surface engineering Ni-Pt nanoalloys towards enhanced catalytic efficiency for methanol oxidation reaction

Surface engineering is known as an effective strategy to enhance the catalytic properties of Pt-based nanomaterials. Herein, we report on surface engineering Ni-Pt nanoalloys with a facile method by varying the Ni doping concentration and oleylamine/oleicacid surfactant-mix. The alloy-composition, exposed facet condition, and surface lattice strain are, thereby manipulated to optimize the catalytic efficiency of such nanoalloys for methanol oxidation reaction (MOR). Exemplary nanoalloys including Ni0.69Pt0.31 truncated octahedrons, Ni0.45Pt0.55 nanomultipods and Ni0.20Pt0.80 nanoflowers are thoroughly characterized, with a commercial Pt/C catalyst as a common benchmark. Their variations in MOR catalytic efficiency are significant: 2.2 A/mgPt for Ni0.20Pt0.80 nanoflowers, 1.2 A/mgPt for Ni0.45Pt0.55 nanomultipods, 0.7 A/mgPt for Ni0.69Pt0.31 truncated octahedrons, and 0.6 A/mgPt for the commercial Pt/C catalysts. Assisted by density functional theory calculations, we correlate these observed catalysis-variations particularly to the intriguing presence of surface interplanar-strains, such as {111} facets with an interplanar-tensile-strain of 2.6% and {200} facets with an interplanar-tensile-strain of 3.5%, on the Ni0.20Pt0.80 nanoflowers.

Hydrophilic nickel doped porous SnO2 thin films prepared by spray pyrolysis

This work deals with the preparation and characterization of pure and Nickel-doped porous Tin oxide (SnO2) thin films, using Spray pyrolysis technique for an eventual application in optoelectronics. The structural, morphological, optical, and electrical properties of these prepared samples were investigated using various techniques. X-ray diffraction analysis confirmed the tetragonal structure of pure SnO2 and Ni-doped films. The preferred orientation of the crystallites changed from (110) to (200) with the film doped at 15.3 at.% Ni, with crystallite size of about 10 and 18 nm for 15.3 at.% Ni-doped and 5.6 at.% Ni-doped SnO2, respectively. Scanning Electron Microscopy shows that the 15.3 at.% Ni-doped SnO2 film surface is relatively homogeneous, while the 5.6 at.% Ni-doped film is highly porous. The measured contact angles are less than 90° for all the prepared samples confirming the hydrophilic character of all the films. Transmittance as high as 85% in the visible region was observed for 5.6 at.% Ni-doped films, while lower transmittance is observed for 15.3 at.% Ni-doped films. A decrease of the optical band gap and the resistivity with increasing Ni dopant concentration were also observed.

Ni-dopant concentration effect of ZrO2 photocatalyst on photoelectrochemical water splitting and efficient removal of toxic organic pollutants

Recent years, metal oxide semiconductor photoelectrochemical (PEC) and photocatalytic technology is a compassionate of eco-friendly methods that has displayed significant consideration in the environmental and energy fields. Ni-doped ZrO2 has studied several studies but its PEC water splitting and organic pollutant dye degradation have not been exploited yet. Hence, in the present study, we prepared the Ni-doped ZrO2 (0.1, 0.3 and 0.5 mol %) photocatalyst using a simple hydrothermal technique and studied their PEC water splitting and methyl (MB) blue organic pollutant dye degradation under visible light irradiation. Compared with pure ZrO2 photocatalyst, the Ni-doped photocatalysts displayed extra-prolonged light response and greater separation rate of photo-generated charge carrier’s. The optimized doped (0.3 mol %) photocatalyst showed higher photocurrent (~89 times) density and lesser charge resistance over pure photocatalyst. Moreover, the optimized doped photocatalyst showed 90.2% degradation of methyl blue dye under 100 min of visible light irradiation.

In-situ exsolution of nanoparticles from Ni substituted Sr2Fe1.5Mo0.5O6 perovskite oxides with different Ni doping contents

Perovskite oxide molybdenum doped strontium ferrite, Sr2Fe1.5Mo0.5O6-δ (SFM), is a promising alternative hydrogen electrode material for solid oxide cells (SOCs) because of its robust stability, but usually suffers from insufficient electrochemical performance. In this work, the easily reducible and catalytically active nickel ion (Ni2+) has been substituted on the B-sites of perovskite oxide SFM in the oxidizing atmosphere to form Sr2Fe1.5-xNixMo0.5O6-δ (SFMNix, x = 0.1, 0.2, and 0.3), and then partially in-situ exsolved out of the parent matrix lattices as active nano-catalysts in the reducing atmosphere to fabricate Fe–Ni alloy nanoparticles decorated SFMNix (Fe–Ni@SFMNix) materials. It is demonstrated that the electrode electrochemical performance could be effectively enhanced by tuning the Ni doping content in the parent oxide. Sr2Fe1.3Ni0.2Mo0.5O6-δ (SFMNi0.2) electrode with the Ni doping content of 0.2 exhibits the excellent electrochemical performance with a relatively low electrode polarization resistance of 0.82 Ωcm2 in a symmetrical cell at 800 °C in 97%H2–3%H2O atmosphere, which is ascribed to the maximum exsolved Fe–Ni alloy nanocatalysts from the parent oxide SFMNi0.2. In addition, the electrode reaction process with a high resolution based on the electrochemical impedance spectra has been systematically analyzed by using the distribution of relaxation times (DRT) technique. It is demonstrated by the DRT analysis results that the low-frequency electrode reaction process associated with the hydrogen adsorption, dissociation and ionization process in the frequency range of 1–10 Hz is identified as the rate-limiting step during the operation, meanwhile, this sub-step could be effectively accelerated by varying the Ni doping content with an optimal Ni doping content of 0.2. These results demonstrate that the variation of doping content in the parent perovskite oxide is an effective strategy to manipulate the electrode electrochemical performance, and exsolved Fe–Ni alloy nanoparticles decorated perovskite oxide SFMNi0.2 is a promising hydrogen electrode candidate for SOCs application. Our findings will guide the development of other ceramic oxides electrodes with effectively enhanced electrochemical performance for energy conversion and storage applications.

Effect of Ni Doping Content on Phase Transition and Electrochemical Performance of TiO2 Nanofibers Prepared by Electrospinning Applied for Lithium-Ion Battery Anodes.

Titanium dioxide (TiO2), as a potential anode material applied for lithium-ion batteries (LIBs), is constrained due to its poor theoretical specific capacity (335 mAh·g−1) and low conductivity (10−7-10−9 S·cm−1). When compared to TiO2, NiO with a higher theoretical specific capacity (718 mAh·g−1) is regarded as an alternative dopant for improving the specific capacity of TiO2. The present investigations usually assemble TiO2 and NiO with a simple bilayer structure and without NiO that is immersed into the inner of TiO2, which cannot fully take advantage of NiO. Therefore, a new strategy was put forward to utilize the synergistic effect of TiO2 and NiO, namely doping NiO into the inner of TiO2. NiO-TiO2 was fabricated into the nanofibers with a higher specific surface area to further improve their electrochemical performance due to the transportation path being greatly shortened. NiO-TiO2 nanofibers are expected to replace of the commercialized anode material (graphite). In this work, a facile one-step electrospinning method, followed by annealing, was applied to synthesize the Ni-doped TiO2 nanofibers. The Ni doping content was proven to be a crucial factor affecting phase constituents, which further determined the electrochemical performance. When the Ni doping content was less than 3 wt.%, the contents of anatase and NiO were both increased, while the rutile content was decreased in the nanofibers. When the Ni doping content exceeded 3 wt.%, the opposite changes were observed. Hence, the optimum Ni doping content was determined as 3 wt.%, at which the highest weight fractions of anatase and NiO were obtained. Correspondingly, the obtained electronic conductivity of 4.92 × 10−5 S⋅cm−1 was also the highest, which was approximately 1.7 times that of pristine TiO2. The optimal electrochemical performance was also obtained. The initial discharge and charge specific capacity was 576 and 264 mAh·g−1 at a current density of 100 mA·g−1. The capacity retention reached 48% after 100 cycles, and the coulombic efficiency was about 100%. The average discharge specific capacity was 48 mAh·g−1 at a current density of 1000 mA·g−1. Approximately 65.8% of the initial discharge specific capacity was retained when the current density was recovered to 40 mA·g−1. These excellent electrochemical results revealed that Ni-doped TiO2 nanofibers could be considered to be promising anode materials for LIBs.

Fabrication of ON/OFF switching response based on n-Ni-doped MoO3/p-Si junction diodes using Ni-MoO3 thin films as n-type layer prepared by JNS pyrolysis technique

The influence of nickel (Ni) doping concentrations on structural, optical, electrical and diode properties of molybdenum trioxide (MoO3) thin films has been studied systematically. Ni-doped MoO3 films and diodes were prepared for various doping concentrations of Ni such as 0, 3, 6 and 9 wt.% by jet nebulizer spray (JNS) pyrolysis technique. The structural properties of Ni-doped MoO3 films were analyzed by X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM). The prepared films were exhibited in the orthorhombic crystal structure and sub-microsized plate-like surface morphology. The energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of Ni, Mo and O elements in the prepared films. Ultraviolet–visible (UV–vis) analysis results showed that the absorbance decreases with the increasing of Ni doping concentration and the minimum band gap energy (Eg = 2.25) was obtained for 9 wt.% Ni-doped MoO3 film. From current–voltage (I–V) characterization, the conductivity is increased by increasing the Ni doping concentration in MoO3 thin films. The diode measurements were performed in darkness and under light illumination of a halogen lamp. The methods of I–V, Cheung’s and Norde were used to calculate the diode parameters of ideality factor (n), barrier height (Φb) and sheet resistance (Rs). Also, the light ON/OFF switching response of the fabricated n-NiMoO3/p-Si diodes was analyzed.

Transition Metal (Ni) Doped SnO2 Nanoparticles Synthesized by Co-Precipitation Method

In this work, we have been reported the transition metal (Ni) doped SnO2 nanoparticles were successfully prepared by chemical co-precipitation method with various Ni doping concentrations such as 0%, 2% and 4%. The prepared Ni doped SnO2 nanoparticles characterized by X-ray diffraction pattern (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy and Photoluminescence Spectroscopy (PL). The XRD Pattern confirms the presence of polycrystalline nature with the tetragonal structure of SnO2 and the peaks are identified with the JCPDS card No. 88-0287. The SEM image indicates that the particles were irregular shape for all prepared samples. The SEM image showed that the agglomeration process is occurring slowly down with the inclusion of Ni doping content. An EDX study confirms the presence of Sn, O and Ni elements. In FTIR studies the functional groups were identified based on host and doping materials. The minimum band gap value obtained for 0% Ni concentration. When the doping concentration increases, band gap also increases. From PL studies strong band orientation was observed.