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This work adopted a green synthesis route using cashew tree gum as a mediating agent to obtain Ni-doped ZnO nanoparticles through the sol–gel method. Structural analysis confirmed the formation of the hexagonal wurtzite phase and distortions in the crystal lattice due to the inclusion of Ni cations, which increased the average crystallite size from 61.9 nm to 81.6 nm. These distortions resulted in the growth of point defects in the structure, which influenced the samples' optical properties, causing slight reductions in the band gaps and significant increases in the Urbach energy. The fitting of the photoluminescence spectra confirmed an increase in the concentration of zinc vacancy defects (VZn) and monovacancies (Vo) as Zn cations were replaced by Ni cations in the ZnO structure. The percentage of VZn defects for the pure compound was 11%, increasing to 40% and 47% for the samples doped with 1% and 3% of Ni cations, respectively. In contrast, the highest percentage of VO defects is recorded for the material with the lowest Ni ions concentration, comprising about 60%. The influence of dopant concentration was also reflected in the photocatalytic performance. Among the samples tested, the Zn0.99Ni0.01O compound presented the best result in MB degradation, reaching an efficiency of 98.4%. Thus, the recovered material underwent reuse tests, revealing an efficiency of 98.2% in dye degradation, confirming the stability of the photocatalyst. Furthermore, the use of different inhibitors indicated that •OH radicals are the main ones involved in removing the pollutant. This work is valuable because it presents an ecological synthesis using cashew gum, a natural polysaccharide that has been little explored in the literature. [ABSTRACT FROM AUTHOR]

The synthesis of a Ni-doped ZnO nanocomposite incorporating chitosan (CS/Ni-doped ZnO) was achieved via a precipitation method, followed by annealing at 250 °C. This study comprehensively examined the nanocomposite's structural, functional, morphological, and porosity properties using various analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) analysis. The presence of chitosan (CS) and nickel (Ni) within the nanocomposite, along with their influence on reducing the band gap of ZnO particles and enhancing the generation of electron-hole pairs, was confirmed using UV-visible near-infrared spectroscopy (UV-vis-NIR). The electrochemical properties of the CS/Ni-doped ZnO nanocomposite were investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) by utilizing a phosphate buffer solution with a pH of 6, which closely resembled the typical pH of bacterial cell walls. Finally, the prepared CS/Ni-doped ZnO nanocomposite was evaluated for its antibacterial and anticancer activities. The results demonstrated the highest inhibition of bacterial growth in P. vulgaris, whereas the lowest inhibition was found in S. aureus across various concentrations, thus highlighting its potential in antimicrobial applications. The cytotoxicity of CS/Ni-doped ZnO nanocomposites demonstrated remarkable effects with a half-maximum inhibitory concentration of approximately 80 ± 0.23 µg mL−1 against MCF-7 breast cancer cell lines, following a dose-dependent manner. [ABSTRACT FROM AUTHOR]

Nickel-doped zinc-oxide nanoparticles are synthesized by the solvothermal method at different doping concentrations (x = 0.02, 0.04, 0.06, and 0.08). The structural properties of undoped and nickel-doped zinc oxide nanoparticles are carried out. X-ray diffraction analysis confirms the hexagonal wurtzite structure (belonging to the space group p63mc) and optical properties are analyzed through UV–visible, Fourier-transformed infrared, and hotoluminescence. Energy bandgap values are found using the Tauc plot method. The Lande splitting factor is calculated using EPR analysis. Magnetic properties of the sample are measured using a vibrating sample magnetometer at room temperature. It is observed that their behavior changes from paramagnetic to superparamagnetic structure with an increase in their doping values. In the large saturation magnetization, it is very suitable for magnetic storage device applications. [ABSTRACT FROM AUTHOR]

Pure and Ni-doped (1%, 2%, and 3%) nanostructures were synthesized using a novel laser-assisted chemical bath synthesis (LACBS) technique. For the first time, LACBS was used to create a doping solution utilizing a 7 W blue laser with a 444.4 nm wavelength and a continuous beam. The Ni-doping concentration was varied by changing the amount of Ni precursor added. All samples were analyzed using XRD, SEM, EDX, FTIR, UV–Vis, and photocatalysis tests for photodegradation under blue laser illumination. XRD was used to confirm that the tested ZnO had a hexagonal wurtzite structure. The crystallite size decreased as the Ni-doping concentration rose. EDX experiments were conducted to analyze the elemental characteristics of the pure and Ni-doped (1%, 2%, and 3%) nanostructures. The existence of nanoscale hexagonal structures was confirmed through SEM studies. The band gap values of the pure and Ni-doped ZnO nanostructures decreased as the doping concentration increased. FTIR studies were conducted to examine the functional groups of the pure and doped samples. The produced materials exhibited excellent photocatalytic performance toward the degradation of MB organic dye, an example of a pollutant found in wastewater. [ABSTRACT FROM AUTHOR]

In this article, evidence for the existence of illumination and bias-dependent negative differential conductance (NDC) in Ni-doped Al/ZnO/p-Si Schottky diodes, and the possible mechanism for its origin, are presented. The atomic percentages of Ni doping were 0%, 3%, 5%, and 10%. NDC is observed between -1.5 V to -0.5 V in reverse bias under illumination, but only at certain doping levels and specific forward bias. Furthermore, the devices show excellent optoelectronic characteristics in the photoconductive and photovoltaic modes, with device open circuit voltages ranging from 0.03 V to 0.6 V under illumination.

In first, the Ni-doped ZnO nanorods used as an appeal sonocatalyst was synthesized through co-precipitation method. Afterwards, the crystalline structure, functional groups, surface morphology, and elemental composition were characterized by a set of analysis. Removal of diazinon ((DZ) as a renowned pesticide) was investigated using sonocatalytic performance of US/Ni-doped ZnO system. In this empirical study, response surface methodology (RSM) based central composite design (CCD) was applied for optimization of operational factors. Under the optimum conditions such as initial pH = 5, initial DZ concentration = 15 mg L−1, sonocatalyst dosage = 1 g L−1, and in the presence of organic compounds (oxalic acid, humic acid, and folic acid) = 3 mg L−1, the sonocatalytic degradation of DZ after 15 min was 82.29%. The F-value (6.64) and P-value (< 0.0001) for DZ degradation in the quadratic model imply the proposed model was significant. A-factor (pH) considers as a prominent factor owing to having the highest F-value. In addition, the sonocatalytic data in this study exhibited valid fitting for the first order kinetic model (R2 > 0.98). After six consecutive cycles, the Ni-doped ZnO nanorods could be recyclable for sonocatalytic degradation of DZ. The five main compounds produced during the US/Ni-doped ZnO embracing 2-isopropyl-6-methyl-4-pyrimidinol (IMP), diethyl phosphonate, diazoxon, hydroxyldiazinon, and diazinon methyl ketone are formed in the path of DZ degradation. OFAT style also revealed 99.99% of DZ degradation with 73.26% of mineralization rate in optimum status. The Ni-doped ZnO presented agreeable sonocatalytic facility in the refinement of real water and wastewater matrix. Finally, the results of toxicity evaluation (Daphnia magna) in the sonocatalytic degradation of DZ (by US/Ni-doped ZnO system) showed that the toxicity of the DZ solution lessened under US waves (LC50 and TU 48 h equal to 36.472 and 2.741 volume percent, respectively). [ABSTRACT FROM AUTHOR]

This work adopted a green synthesis route using cashew tree gum as a mediating agent to obtain Ni-doped ZnO nanoparticles through the sol–gel method. Structural analysis confirmed the formation of the hexagonal wurtzite phase and distortions in the crystal lattice due to the inclusion of Ni cations, which increased the average crystallite size from 61.9 nm to 81.6 nm. These distortions resulted in the growth of point defects in the structure, which influenced the samples’ optical properties, causing slight reductions in the band gaps and significant increases in the Urbach energy. The fitting of the photoluminescence spectra confirmed an increase in the concentration of zinc vacancy defects (VZn) and monovacancies (Vo) as Zn cations were replaced by Ni cations in the ZnO structure. The percentage of VZn defects for the pure compound was 11%, increasing to 40% and 47% for the samples doped with 1% and 3% of Ni cations, respectively. In contrast, the highest percentage of VO defects is recorded for the material with the lowest Ni ions concentration, comprising about 60%. The influence of dopant concentration was also reflected in the photocatalytic performance. Among the samples tested, the Zn0.99Ni0.01O compound presented the best result in MB degradation, reaching an efficiency of 98.4%. Thus, the recovered material underwent reuse tests, revealing an efficiency of 98.2% in dye degradation, confirming the stability of the photocatalyst. Furthermore, the use of different inhibitors indicated that •OH radicals are the main ones involved in removing the pollutant. This work is valuable because it presents an ecological synthesis using cashew gum, a natural polysaccharide that has been little explored in the literature.

The synthesis of a Ni-doped ZnO nanocomposite incorporating chitosan (CS/Ni-doped ZnO) was achieved via a precipitation method, followed by annealing at 250 °C. This study comprehensively examined the nanocomposite’s structural, functional, morphological, and porosity properties using various analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) analysis. The presence of chitosan (CS) and nickel (Ni) within the nanocomposite, along with their influence on reducing the band gap of ZnO particles and enhancing the generation of electron-hole pairs, was confirmed using UV-visible near-infrared spectroscopy (UV-vis-NIR). The electrochemical properties of the CS/Ni-doped ZnO nanocomposite were investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) by utilizing a phosphate buffer solution with a pH of 6, which closely resembled the typical pH of bacterial cell walls. Finally, the prepared CS/Ni-doped ZnO nanocomposite was evaluated for its antibacterial and anticancer activities. The results demonstrated the highest inhibition of bacterial growth in P. vulgaris, whereas the lowest inhibition was found in S. aureus across various concentrations, thus highlighting its potential in antimicrobial applications. The cytotoxicity of CS/Ni-doped ZnO nanocomposites demonstrated remarkable effects with a half-maximum inhibitory concentration of approximately 80 ± 0.23 µg mL−1 against MCF-7 breast cancer cell lines, following a dose-dependent manner.

In this work, zinc oxide (ZnO), nickel (Ni) and aluminum (Al)‐doped ZnO nanoparticles are synthesized via an ultrasound‐assisted sol–gel technique. X‐ray diffraction analysis reveals a correlation between structural parameters (lattice parameters, crystallite size, dislocation density and micro‐strain) and the dopant ions incorporation. Scanning electron microscopy studies show changes in morphology in doped samples derived from the effect of restriction on the growth dynamics. A growth mechanism is proposed in order to explain the properties of ZnO‐based sensors. Gas sensing tests are carried out, delivering the best results as follows: an 89% sensing response at 500 ppm of carbon dioxide (CO2), 0.54 MΩ s−1 of sensitivity, and 52/48 s for average response and recovery times respectively, in the Ni‐doped ZnO sample. Additionally, selectivity evaluations for all samples are also performed. By comparing the obtained structural and morphological characteristics with the gas sensing properties of the samples, Ni‐doped ZnO samples have optimal characteristics for CO2 detection due to the high surface area and abundant oxygen vacancies resulting from the Ni incorporation. The gas sensing mechanism of each sample is also reported and discussed in detail. [ABSTRACT FROM AUTHOR]

Dye sensitized solar cells (DSSC) is one of the promising candidates which are efficient, low-cost, and clean hybrid molecular solar cell devices. Zinc oxide (ZnO) has been widely used as the phoanode in DSSC due to its excellent charge conduction mechanism, yet still suffers from poor cell efficiency. In this study, aluminium doped ZnO (ZnO:Al) and Ni doped ZnO (ZnO:Ni) were studied as photoanode material in DSSC using solar cell capacitance simulator (SCAPS) simulation, and the electrolyte liquid considered a single solid p-type layer as hole transporting materials. Both studied photoanodes have demonstrated better cell performance than pure ZnO photoanode due to the small amount of aluminium (Al) and nikel (Ni) impurities added have enhanced the physiochemical properties of ZnO films. A power conversion efficiency (PCE) of 3.96% was obtained at 3 mol% ZnO:Al photoanode with optimized key parameters. These simulation results proved an opportunity to improve the performance of the DSSCs via doping engineering into the ZnO photonaode. [ABSTRACT FROM AUTHOR]

Pure and Ni-doped (1%, 2%, and 3%) nanostructures were synthesized using a novel laser-assisted chemical bath synthesis (LACBS) technique. For the first time, LACBS was used to create a doping solution utilizing a 7 W blue laser with a 444.4 nm wavelength and a continuous beam. The Ni-doping concentration was varied by changing the amount of Ni precursor added. All samples were analyzed using XRD, SEM, EDX, FTIR, UV–Vis, and photocatalysis tests for photodegradation under blue laser illumination. XRD was used to confirm that the tested ZnO had a hexagonal wurtzite structure. The crystallite size decreased as the Ni-doping concentration rose. EDX experiments were conducted to analyze the elemental characteristics of the pure and Ni-doped (1%, 2%, and 3%) nanostructures. The existence of nanoscale hexagonal structures was confirmed through SEM studies. The band gap values of the pure and Ni-doped ZnO nanostructures decreased as the doping concentration increased. FTIR studies were conducted to examine the functional groups of the pure and doped samples. The produced materials exhibited excellent photocatalytic performance toward the degradation of MB organic dye, an example of a pollutant found in wastewater.

Schematic diagram of the synthesis of ZnO: Ni sample and fabrication photodetector. [Display omitted] • Hydrothermal technique was used to prepare Ni-doped ZnO nanorods with 0 to 5% concentration. • Surface morphology performed using FESEM confirmed the formation of nanorods, and synthesized samples were evenly dispersed. • Responsivity (R), Detectivity (D*), and External Quantum Efficiency (EQE) values are 1.87 × 10-2(AW−1), 4.11 × 109 (Jones), and 43.23 %, respectively. • a strong correlation between Ni-doped ZnO nanoparticles' structural, optical, morphology, magnetic, and photoconductive behaviour. In the present work, Ni-doped ZnO nanorods with concentrations ranging from 0 to 5 % are synthesized using a cost-effective hydrothermal method for the application of photodetectors. The prepared nanoparticles are analyzed by several techniques to examine their structure, optical, magnetic, and photosensing properties. The X-ray diffraction (XRD) study shows that the synthesized samples exhibits the hexagonal structure without any impurity with the P63mc space group. Surface morphology was performed using Scanning electron microscope (SEM) confirmes the formation of nanorods, and homogeneous nature of synthesized samples. Energy Dispersive X Ray Spectroscopy (EDX) spectrum confirms the presence of Zn, Ni, and O elements in the prepared samples. Optical studies revealed that the estimated bandgap values are around 3.20 eV, 3.16 eV, 3.15 eV 3%, and 3.18 eV for pure ZnO, ZnO:Ni(1%), ZnO:Ni(3%) and ZnO:Ni(5%) samples, respectively. The vibrating-sample magnetometry (VSM) study indicates the that all the samples exhibit ferromagnetic behavior at room temperature and also significant changes in the M−H loop as the dopant concentration changes. The photosensing properties of 3 % Ni doped ZnO nanorods photodetector, showed enhanced Responsivity (R), Detectivity (D*), and External Quantum Efficiency (EQE) values of 1.87 × 10-2(AW−1), 4.11 × 109 (Jones), and 43.23 %, respectively. Hence the 3 % Ni doped ZnO sample might be better for commercial photodetector applications. [ABSTRACT FROM AUTHOR]

The current research aims to investigate the effect of nickel doping on the structural and opto-electrical characteristics of zinc oxide thin films. Sol-gel spin coating technique has been utilized to deposit Zn _1-x Ni _x O (x = 0, 0.005, 0.010, and 0.015) films on glass substrates. X-ray diffraction (XRD) analysis confirms the formation of crystalline zinc oxide thin films with hexagonal wurtzite structure. Williamson-Hall analysis has been performed to study the individual contribution of lattice strain and crystallite size to the peak broadening in the XRD pattern. Scanning electron microscopy (SEM), Photoluminescence spectroscopy, and UV–visible spectroscopic techniques have been used to examine the surface morphology and optical properties of the deposited films. Transient photocurrent measurements have been performed on all the films under the exposure of ultraviolet (UV) light of wavelengths 365 and 254 nm with on/off cycle of 100 s, and various device key parameters such as sensitivity, responsivity, and quantum efficiency, etc have been determined. Sensitivities of the fabricated photodetectors (PDs) are found to be 5463%, 3809%, 3100%, and 831% for pristine ZnO, Zn _0.995 Ni _0.005 O, Zn _0.99 Ni _0.01 O, and Zn _0.985 Ni _0.015 O, respectively. The UV photodetection mechanism, which is based on the interaction between chemisorbed oxygen on the surface of ZnO and photo-generated holes, has been thoroughly discussed.

The study of ZnO nanostructures is interested because the various types of nanostructures can be easily fabricated. However, the magnetic ground state of Ni-doped ZnO nanostructures can either be ferromagnetic or antiferromagnetic. Therefore, this work used DFT calculation to investigate the ZnO in low dimensional structures in both polar (0001) surfaces and non-polar () surfaces. The two Ni atoms were substituted on the Zn sites. The results show that the polar (0001) surfaces is more stable than the non-polar () surfaces. The energy differences between ferromagnetic states and antiferromagnetic state indicate that the ground states are ferromagnetic except only when the Ni atoms substitute on the slab surface in ZnO polar (0001) surfaces. The total magnetic moments of about 4 µB are found to be contributed by the Ni-3d states in both polar and non-polar surfaces, and the half-metallic behavior is also predicted in the ZnO non-polar () surfaces. [ABSTRACT FROM AUTHOR]

Abstract Over the past few decades, doped ZnO structures have attracted significant attention because of their distinctive properties and a wide range of applications in catalysis and energy-storage devices. However, effective simple synthesis of doped ZnO structures for photoelectrocatalytic and supercapacitor applications still remains challenging. In this study, Ni-doped ZnO structures were synthesized at different Ni concentrations. Analysis of the obtained samples confirmed the formation of Ni-doped ZnO; 1.5 mol% Ni-doped ZnO showed enhanced water splitting activity and supercapacitor properties. The highest photocurrent density of 4.6 mA/cm2 was obtained in a 0.1 M KOH solution at an applied bias photon-to-current efficiency of 4.2%, which is almost twice that obtained with pristine ZnO (2.8%), indicating an enhanced electron-hole separation. Doped ZnO exhibits a photocurrent 1.78 times higher than pristine ZnO under light illumination. Ni-doping induces effective charge separation and transfer, efficiently diminishing the recombination rate and reducing intrinsic defects. Further, the highest specific capacity of ~96 F g−1 was observed for 1.5% Ni-doped ZnO at an applied scan rate of 10 mV s−1. The optimized sample, 1.5% Ni-doped ZnO, exhibited a high specific capacitance retention and coulombic efficiency of ~98% and ~99.2%, respectively. These results are expected to be very helpful in developing cheap and simple fabrication methods and efficient electrode materials for photoelectrochemical water splitting and supercapacitor applications. Graphical abstract Unlabelled Image Highlights • Photoelectrochemical and supercapacitor properties of Ni-doped ZnO has been systematically investigated. • The 1.5 mol% Ni-doped ZnO showed the highest photocurrent density of 4.6 mA/cm2. • The highest specific capacitance of 1.5 mol% Ni-doped ZnO was obtained of ~ 96 F g−1 at 10mVs-1. • The optimal 1.5 % Ni-doped ZnO shows the highest specific capacitance retention and Coulombic efficiency of ~98 % and ~99.2 %, respectively. [ABSTRACT FROM AUTHOR]

High sensitivity ammonia (NH 3 ) gas sensor based on nickel-doped ZnO (NZO) hexagonal microdisc like-nanostructures is reported in this work. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) revealed that the undoped ZnO revealed interconnected hexagonal microdiscs transformed into hollow square shaped interconnected hexagonal microdiscs. NZO (6 wt%) showed higher response compared with other wt% and exhibited highest response of 15.1 when exposed to 100 ppm concentration of ammonia (NH 3 ) gas at 150 °C. NZO (6 wt%) possessed good response time of 5.5 s at 100 ppm. [ABSTRACT FROM AUTHOR]

Zn1-xNixO aerogel nanopowders with nickel concentration in the range of 0.05 ⩽ x ⩽ 0.25, were synthesized by the sol-gel processing technique and post-annealed in air at 500 °C. Structural, vibrational, thermal and magnetic properties of the as-prepared and annealed Zn1-xNixO powdered samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman scattering, thermal gravimetric analysis (TGA) and electron paramagnetic resonance (EPR) spectroscopy. In addition to the ZnNiO phase, XRD analysis revealed the formation of a secondary NiO phase when the Ni content was greater than or equal to 10 %. The TEM images confirm that the particle size is in the range of 20 nm to 40 nm, in accordance with XRD results, and the particles are well dispersed. Raman scattering measurements confirm the wurtzite structure of the synthesized Zn1-xNixO nanopowders and show that intrinsic host-lattice defects are activated when Ni2+ ions are substituted to the Zn sites. Room temperature ferromagnetic order was observed in all of the samples and was strongly dependent on the Ni content and thermal annealing. These results indicate that the observed room temperature ferromagnetism in ZnNiO may be attributed to the substitutional incorporation of Ni at Zn sites. [ABSTRACT FROM AUTHOR]

A simple chemical synthesis method of pristine ZnO and Ni-doped ZnO (NixZn1-xO; x = 0.01-0.05) nanoparticles is reported. Structural and morphological properties of the synthesized nanoparticles have been studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and high-resolution transmission electron microscopy (HRTEM). Average crystallite size calculated from XRD peak widths using Debye Scherrer’s formula comes out to be 12 nm, 8 nm and 10 nm in pristine ZnO, Ni0.01Zn0.99O, and Ni0.05Zn0.95O samples, respectively. HRTEM images clearly show high crystalline order in the derived nanoparticles with particle size of 15-18 nm, which are in good agreement with the XRD results. Magnetic measurements reveal that the incorporation of Ni2+ cations into the ZnO lattice results in induced room-temperature ferromagnetism in the otherwise non-magnetic ZnO.

In this article, evidence for the existence of illumination and bias-dependent negative differential conductance (NDC) in Ni-doped Al/ZnO/p-Si Schottky diodes, and the possible mechanism for its origin, are presented. The atomic percentages of Ni doping were 0%, 3%, 5%, and 10%. NDC is observed between -1.5 V to -0.5 V in reverse bias under illumination, but only at certain doping levels and specific forward bias. Furthermore, the devices show excellent optoelectronic characteristics in the photoconductive and photovoltaic modes, with device open circuit voltages ranging from 0.03 V to 0.6 V under illumination., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)

Monodispersed nanoplatelets of Ni-doped ZnO with tailored room-temperature ferromagnetism (RTFM) were synthesized through a facile and highly reproducible process involving a Zn 2+ –Ni 2+ -polymer composite precursor. Single phase ZnO of P63mc hexagonal wurtzite crystal structure lies in the derived samples (Zn 1-x Ni x O, x = 0–0.1) after firing the corresponding precursors at 400–600 °C for 2 h in ambient air. Structural and optical analyses confirmed the incorporation of Ni 2+ ions into the ZnO lattice by replacing the Zn 2+ ions. Microstructural analysis revealed the uniformity in the shape and size of the finely dispersed particles in the form of hexagonal nanoplatelets. Typical samples derived at 500 °C have an average diameter, D ∼22 nm with <5 nm thickness ( δ ). The observed RTFM ordering in the derived samples can be precisely tuned by controlling the Ni concentration and the processing temperature. The synthesis technique provides excellent control over the doping concentration and microstructure in these diluted magnetic semiconductor (DMS) materials for pertinent applications in wide areas starting from spintronics and magneto-optics to biosensors. [ABSTRACT FROM AUTHOR]

Nickel-doped zinc oxide thin films (ZnO : Ni) at different percentages were deposited on glass substrates using a chemical spray technique. The effect of Ni concentration on the structural, morphological, optical and photoluminescence (PL) properties of the ZnO : Ni thin films were investigated. X-ray diffraction analysis revealed that all films consist of single phase ZnO and was well crystallized in würtzite phase with the crystallites preferentially oriented towards the (002) direction parallel to the c-axis. The optical transmittance measurement was found to be higher than 90%, the optical band gap values of ZnO thin films decreased after doping from 3.29 to 3.21 eV. A noticeable change in optical constants was observed between undoped and Ni-doped ZnO. Room-temperature PL is observed for ZnO, and Ni-doped ZnO thin films. [ABSTRACT FROM AUTHOR]

Branched ZnO nanowires (NWs) doped with Ni were grown by a three-step vapor phase method for the sensitive and selective detection of p -xylene. ZnO NWs were directly grown on sensor substrates with Au electrodes, which were transformed into NiO NWs by the thermal evaporation of NiCl 2 powder at 700 °C. ZnO branches doped with Ni were grown from NiO NWs by the thermal evaporation of Zn metal powder at 500 °C. The stem NiO NWs played the role of catalyst for the growth of ZnO branches through vapor–liquid–solid mechanism. The Ni-doped branched ZnO NWs showed enhanced gas response ( S = resistance ratio) to methyl benzenes, especially to 5 ppm p -xylene ( S = 42.44) at 400 °C. This value is 1.7 and 2.5 times higher than the responses to 5 ppm toluene ( S = 25.73) and C 2 H 5 OH ( S = 16.72), respectively, and significantly higher than the cross-responses to other interfering gases such as benzene, HCHO, trimethylamine, H 2 , and CO. The selective detection of xylene was attributed to the catalytic role of the Ni component. This novel method to form catalyst-doped hierarchical ZnO NWs provides a promising approach to accomplish superior gas sensing characteristics by the synergetic combination of enhanced chemiresistive variation due to the increased number of branch-to-branch Schottky barrier contacts and the catalytic function of the Ni dopant. [ABSTRACT FROM AUTHOR]

In this paper, we present experimental results on doping under 1% of Ni into ZnO sprayed thin films to create a ZnO intrinsic layer and evaluate the resulting beneficial effects. X-ray diffraction (XRD) analysis showed that undoped and Ni-doped ZnO films crystallized into a hexagonal structure, where the crystallites preferentially oriented along the (002) direction that was perpendicular to the substrate. The optical transmittance was found to exceed 80%. An investigation of the variation in the band gap with the x =[Ni]/[Zn] ratio showed that the energy gap decreased from 3.29 eV to 3.22 eV as x increased from 0% to 0.25% and then increased to 3.28 eV at x =1%. The Urbach energy E u , the refractive index and the extinction coefficient were found to depend on the Ni content. The refractive index could be described as a single oscillator using the Wemple–DiDomenico model, which was used to determine the dispersion parameters and the high-frequency dielectric constant. [ABSTRACT FROM AUTHOR]

In this research, Ni-doped ZnO (ZnNiO: x = 0.02, 0.04, 0.06, and 0.08) nanoparticles have been synthesized using a simple wet chemical precipitation method. X-ray diffraction analysis reveals the Ni-doped ZnO crystallized in a hexagonal wurtzite structure and confirming phase purity. The lattice parameters of Ni-doped ZnO decreased slightly with increasing doping concentration. The vibrating sample magnetometry measurement results of samples at room temperatures and annealed at 400 °C show a weak magnetic hysteresis loop that confirms the ferromagnetic properties of the samples. The origin of magnetic behavior in Ni-doped ZnO could be the presence of O vacancies and exchange interaction between Ni ions. Also, the magnetic saturation of the samples increased with increasing Ni concentration in the range of 1.2 × 10 to 5.0 × 10 (emu/g). The effects of annealing on the morphology of Ni-doped ZnO nanoparticles were investigated using scanning electron microscopy. The crystallite size of the nanoparticles increased and the magnetic saturation decreased slightly at the annealing temperature 400 °C. [ABSTRACT FROM AUTHOR]

Nickel-doped zinc oxide hollow nanospheres have been synthesized using a simple solvothermal approach through a morphological transformation driven by a localized Ostwald ripening process. The saturation magnetization of the system shows that the materials have only a short-range magnetic ordering in them. Based on the visible-light photocatalytic experiment, we could confirm that, with a high doping content (10 mol%), the doping accompanied with increased recombination which reduced the energy of photoinduced electron leading to suppressed photocatalytic activity. Changing reaction parameters, i.e. the mixed reactant concentration, doping content, and different solvents, Zn 1− x Ni x O powders exhibited the elongated prismatic form with sharp tips, quasi-spherical structure, and hexagonal-based polyhedron, respectively. The photocatalytic results demonstrate that different crystal growth orientations, specific surface areas, particle size distributions, and doping levels have strong influences on the photocatalytic activity performances. Among the samples, hexagonal-based polyhedrons have the best photodegradation efficiency standing on higher fraction of exposed polar facets, larger specific surface area, as well as an optimal doping level. The 1 mol% nickel content showed the best photocatalytic activities among the nickel-doped zinc oxide samples. [ABSTRACT FROM AUTHOR]

Zn 0.98 Ni 0.02 O nanoparticles have been synthesized successfully by the sol–gel method. Effects of thermal annealing temperature (400, 500 and 600 °C) and atmosphere (argon and air) on the structural, magnetic and optical properties of the samples were investigated. Results indicated that Ni ions were successfully incorporated into the ZnO matrix and replaced Zn ions. By varying temperature and atmosphere of the thermal annealing treatment, we found that Zn 0.98 Ni 0.02 O nanoparticles exhibited ferromagnetism at room temperature and this behavior was believed to be from oxygen vacancies. [ABSTRACT FROM AUTHOR]

Abstract: Pure and Ni-doped ZnO nanofibers were synthesized using the electrospinning method. The morphology, crystal structure and optical properties of the nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy, respectively. It is found that Ni doping does not change the morphology and crystal structures of the nanofibers, and the ultraviolet emissions of ZnO nanofibers present red shift with increasing Ni doping concentration. C2H2 sensing properties of the sensors based on the nanofibers were investigated. The results show that the C2H2 sensing properties of ZnO nanofibers are effectively improved by Ni doping, and 5at% Ni-doped ZnO nanofibers exhibit a maximum sensitivity to C2H2 gas. [Copyright &y& Elsevier]

Abstract: The transparent thin films of undoped, Mn-doped, and Ni-doped zinc oxide (ZnO) have been deposited on glass substrates via sol–gel technique using zinc acetate dehydrate, nickel chloride, and manganese chloride as precursors. The structural properties and morphologies of the deposited undoped and doped ZnO thin films have been investigated. X-ray diffraction (XRD) spectra, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used to examine the morphology and microstructure of the thin films. Optical properties of the thin films were determined by photoluminescence (PL) and UV/vis spectroscopy. The analyzed results indicate that the obtained films are of good crystal quality and have smooth surfaces, which have a pure hexagonal wurtzite ZnO structure without any Mn or Ni related phases. The band gap energy was estimated by Tauc''s method and found to be 3.28, 3.26, and 3.34eV for ZnO, Ni-doped ZnO, and Mn-doped ZnO thin films at room temperature, respectively. Room temperature photoluminescence is observed for the ZnO, Ni-doped ZnO, and Mn-doped ZnO thin films. [Copyright &y& Elsevier]

Abstract: In this work, the spin coating sol–gel technique has been successfully used to deposit highly uniform and good adhesion of nano structure thin films of ZnO doped with different Ni concentrations. The morphological properties of ZnO:Ni films were studied by atomic force microscopy (AFM) technique. The surface morphology of the nanostructure films is found to depend on the concentration of Ni. The effects of Ni contents on the structural and photoluminescence (PL) properties of ZnO films were investigated. Optical constants (refractive index, n, and absorption index, k) of the undoped and Ni-doped ZnO of 0.2%, 0.4%, 0.6%, 0.8%, 1%, 3%, 5% and 7% concentrations have been obtained in the wavelength range 200–1000nm by using spectrophotometric measurements. The dispersion parameters were determined and discussed based on the single oscillator model. [Copyright &y& Elsevier]

Ni-doped ZnO nanopowder (ZnNiO) was synthesized by improved coprecipitation method. The average particle size of the powder was estimated to be 50 nm. The powder was then processed by thermal treatment. Samples were annealed at 1 073, 1 273, and 1 473 K, respectively. The solubility of NiO in ZnO and the lattice parameters of ZnO both increased with the temperature. The magnetic property of the doped samples was examined, and hysteresis loops were got. The results showed all the samples were ferromagnetic, while powder processed at 1 273 K for 4 h got a highest saturation magnetization ( M) of 0.0457 emu/g. Also, magnetic properties were related to the grain size of the powder. [ABSTRACT FROM AUTHOR]

Abstract: Ni-doped ZnO powder was synthesized by thermal co-decomposition of a mixture of bis(acetylacetonato) zinc(II)hydrate and bis(dimethylglyoximato)nickel(II) complexes. The samples were characterised by X-ray diffraction (XRD), Energy dispersion X-ray fluorescence (EDXRF), and FT-IR spectroscopy. The atomic ratio Ni/Zn of the samples was determined by the EDXRF method to be 1%, 4.3%, 7.4% and 22.5wt%. The XRD studies show the formation of nanocrystalline (14–18nm) of Ni-doped ZnO along with nanoparticles of NiO. By magnetic measurements, it was observed that powder contains 1%Ni, 4.3%Ni, 7.4%Ni exhibits superparamagnetic behaviour while the sample of 22.5%Ni prepared in closed atmospheric environment shows clear ferromagnetic (FM) loop at room temperature due to the formation of solid solution Zn1− x Ni x O. [Copyright &y& Elsevier]

[Display omitted] • Zn 1-x Ni x O (x = 0.00, 0.05, 0.1, 0.15 and 0.2) nanorods were successfully synthesized by simple wet chemical precipitation method. • Fine-tuning the optical properties of ZnO by Ni2+ ion doping. • Improved bio-sensing behavior of ZnO/MCPE towards UA by Ni2+ ion doping. • Antibacterial activities of pure and Ni-doped ZnO nanoparticles were evaluated. The wet chemical precipitation method has been used to synthesize Zn 1-x Ni x O (x = 0.0, 0.05, 0.1, 0.15, 0.2) nanorods. The morphological and optical properties of Ni-doped ZnO samples annealed at 500 0C are characterized by X-ray diffraction (XRD), reveals that Ni-doped ZnO crystallites were in hexagonal wurtzite crystal structure with secondary phase (NiO) was detected with a sensitivity of XRD measurement with increasing in the dopant concentration (X = 0.1–0.2). The FTIR spectroscopy furnishes additional evidence on functional groups. The outcome scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated the presence of hexagonal rods like nanostructures. From the BET technique, calculated the pore size distribution and specific surface area of fabricated nanorods. Further, the optical energy bandgap obtained in the series of 3.33–3.11 eV was determined by Kubelka-Munk method. Room temperature photoluminescence (PL) spectra exhibited band edge emission, violet, blue, green, orange, and red emission regardless of the concentration of doping, but intensity increased with levels of Ni2+ ion doping. Cyclic voltammetric (CV) reveals that the Ni incorporation ZnO lattice notably enhanced electrochemical activity with regards to electrochemical sensing of 10 µM uric acid (UA) at a scan rate of 50 mVs−1. Antibacterial studies reveal that the Ni-doped ZnO nanorods possess improved antibacterial activity against both gram-positive (Escherichia coli) and the gram-negative (Enterococcus faecalisis) bacterial strains than the pure ZnO nanorods. [ABSTRACT FROM AUTHOR]

• Un- and Ni-doped ZnO thin films are synthesized and characterized. • Experimental and theoretical characterizations demonstrate stabilization of a small p-Schottky barrier upon Ni doping. • Reduction in p-Schottky barrier is mainly due to amelioration in the surface uniformity and modulization in the relative alignment of band edges at the interfaces. 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. [ABSTRACT FROM AUTHOR]

The origin of room temperature (RT) ferromagnetism (FM) in Zn 1-x Ni x O (0< x < 0.125) samples are systematically investigated through physical, optical, and magnetic properties of nanostructure, prepared by simple low-temperature wet chemical method. Reitveld refinement of X-ray diffraction pattern displays an increase in lattice parameters with strain relaxation and contraction in Zn/O occupancy ratio by means of Ni-doping. Similarly, scanning electron microscope demonstrates modification in the morphology from nanorods to nanoflakes with Ni doping, suggests incorporation of Ni ions in ZnO. More interestingly, XANES (X-ray absorption near edge spectroscopy) measurements confirm that Ni is being incorporated in ZnO as Ni 2+ . EXAFS (extended X-ray absorption fine structure) analysis reveals that structural disorders near the Zn sites in the ZnO samples upsurges with increasing Ni concentration. Raman spectroscopy exhibits additional defect driven vibrational mode (at 275 cm -1 ), appeared only in Ni-doped samples and the shift with broadening in 580 cm -1 peak, which manifests the presence of the oxygen vacancy (V O ) related defects. Moreover, in photoluminescence (PL) spectra, we have observed a peak at 524 nm, indicating the presence of singly ionized V O + , which may be activating bound magnetic polarons (BMPs) in dilute magnetic semiconductors (DMSs). Magnetization measurements indicate weak ferromagnetism at RT, which rises with increasing Ni concentration. It is therefore proposed that the effect of the Ni ions as well as the inherent exchange interactions arising from V O + assist to produce BMPs, which are accountable for the RT-FM in Zn 1-x Ni x O (0< x < 0.125) system.