Nickel Oxide Nanorods Research Articles

Recovery of nickel oxide nanorods from a laterite-originated intermediate product by ammonia leach-deammoniation method

Extraction of nickel from laterites, especially low-grade limonitic ores has been facing challenges related to the lack of an effective beneficiation method. A chemo-physical laterite ore processing comprising oxalic acid leaching followed by size separation of the leach residue was recently introduced by the authors as a novel method to collect small amounts of nickel values dispersed in the ore matrix into distinct oxalate particles to form an intermediate product. In the present work, the ammonia leaching of such intermediate product containing about 12 wt% NiC2O4·2H2O was accomplished. Factors such as initial ammonia concentration (NH3: 2.5–25 wt%), temperature (T: 20–50 °C), pulp density (S/L: 50–200 g/L), and sonication were examined in a series of agitated leaching tests. It was found that under the conditions of 25% NH3, T = 50 °C, S/L = 200 g/L, and 15 min of sonication, about 93% of nickel is dissolved resulting in a pregnant leach solution (PLS) with a nickel content of 7.4 g/L. Besides, the activation energy for dissolution of nickel oxalate in ammonia solution was found to be about 71 kJ mol–1 from a kinetic analysis of leaching data. The PLS was subsequently deammoniated by either boiling or vacuum-assisted gentle heating to reclaim the nickel as an oxalate salt. Electron microscopic analysis of nickel oxalate precipitates formed from ammonia solutions exhibited rod-like morphology with high aspect ratio. Deammoniation under boiling led to well-shaped and distinct particles (∼150 nm width), while the precipitates obtained under partial vacuum were splintered and finer (∼40 nm width). The pyrolysis at 400 °C in an air atmosphere of the nickel oxalate particles from the boiling and the vacuum-assisted deammoniation methods generated mesoporous NiO nanorods with average widths of about 100 and 30 nm, and specific surface areas of about 45 and 70 m2 g−1, respectively.

Photocatalytic efficiency of graphene/nickel oxide nanocomposites towards the degradation of anionic and cationic dye molecules under visible light

Simplified synthesis of nickel oxide nanorods (NiO NRs) and graphene/NiO nanocomposites (Grn/NiO NCs) was achieved using a chemical reduction approach of Grn and nickel chloride precursors. The crystalline nature of the prepared NiO NRs and Grn/NiO NCs was investigated using X-ray diffraction analysis, and the surface morphology was examined using transmission electron microscope. We examined the phtocatalytic efficiency of Grn/NiO NCs against anionic and cationic dye molecules. The Grn/NiO NCs showed 100% photocatalytic activity for methylene blue (MB) and methyl orange (MO) dye molecules within 90 and 120 min, respectively. The presence of Grn sheets has enhance the photocatalytic activity of NCs under visible light irradiation by reducing the recombination of excited electrons in the conduction band (CB) with holes in the valence band (VB) when Grn/NiO NCs reacted with dyes. We have developed efficient visible light functionalized Grn/NiO NCs photocatalysts for practical environmental applications using simple and cost-effective approach for large-scale manufacturing.

Fabrication of 2D-MoSe2 incorporated NiO Nanorods modified electrode for selective detection of glucose in serum samples

Layered molybdenum diselenide (MoSe2) nanosheets were formed by the weak Van der Waals forces of attraction between Se and Mo atoms. MoSe2 has a larger space between the adjacent layers and smaller band gaps in the range of 0.85 to ~ 1.6 eV. In this study, MoSe2 nanosheets decorated nickel oxide (NiO) nanorods have been synthesized by hydrothermal method using sodium molybdate and selenium metal powder. NiO/MoSe2 composite formation was confirmed by powder X-ray diffraction analysis. In addition, the presence of MoSe2 nanosheets on NiO nanorods were confirmed by field emission scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The Nyquist plots of NiO/MoSe2 coated glassy carbon electrode (GCE) was indicated that it had lower charge transfer resistance compared to NiO/GCE and MoSe2/GCE. Furthermore, as-prepared NiO/MoSe2/GCE was used to detect glucose in alkaline solution by cyclic voltammetry and amperometry techniques. The NiO/MoSe2/GCE was exhibited a linear response for the oxidation of glucose from 50 µM to 15.5 mM (R2 = 0.9842) at 0.5 V by amperometry. The sensor response time and the limit of detection were found to be 2 s and 0.6 µM for glucose. Moreover, selectivity of the NiO/MoSe2 sensor was tested in the presence of common interferent molecules such as hydrogen peroxide, fructose, lactose, ascorbic acid, uric acid, and dopamine. It was found that NiO/MoSe2/GCE did not respond to these interfering biomolecules. In addition, NiO/MoSe2/GCE had shown high stability, reproducibility and repeatability. Finally, the practical application of the sensor was demonstrated by detecting glucose in human blood serum with the acceptable recovery.

Green mediated NiO nano-rods using Phoenix dactylifera (Dates) extract for biomedical and environmental applications

The study reports the biosynthesis of Nickel oxide nanorods (NiO NRs), using Phoenix dactylifera (Dates) extract, a safe, environment friendly and cost effective method. X-ray diffraction analysis confirmed the high crystallinity with face centered cubic phase and HR- TEM (high resolution transmission microscopy) studies confirmed the existence of nanorod like morphology with average particle size of 32 nm. Optical study using UV–Vis spectroscopy revealed a sharp band edge with an energy band gap of 3.62eV. Photoluminescense spectroscopy showed strong defect derived emission from UV and visible region while magnetic measurements indicated a superparamagnetic behavior. The as-synthesized NiO NRs were examined for cytotoxic activity against A549 cell lines, antibacterial activity and photocatalytic degradation of 4-chlorophenol (4-CP). NiO NRs exhibited strong toxicity over A549 cell culture by imparting severe damage to cell functions, a superior antibacterial activity against gram positive than gram negative bacterial strains, as well as competent photocatalyst by mineralizing 4-CP under UV light. Thus NiO NRs prepared by green protocol using Phoenix dactylifera extract, can be considered very promising for biomedical and environmental applications.

Synthesis of nickel oxide nanorods by Aloe vera leaf extract

Nickel oxide nanorods were synthesized simply using Aloe vera extract solution and characterized by Fourier transform infrared spectroscopy and powder X-ray diffraction and the morphology of synthesized NiO nanorods were investigated by using of scanning electron microscopy technique. The electrochemical feature and specific capacitance of NiO nanorods were investigated by cyclic voltammetry method, and the results showed the high specific capacitance of NiO nanorods (about 1965 Fg−1). Also, the catalytic activity of NiO nanorods on the thermal decomposition of ammonium perchlorate (AP) was studied by differential scanning calorimetry and thermogravimetry analysis. The results indicated that addition of NiO nanorods increased the heat of decomposition of AP from 450 Jg−1 to 1450 Jg−1 and decreased the temperature of high-temperature decomposition step from 420 °C to about 351 °C. Also, the rate constant (k) enhanced from 5.7(± 0.2) × 10−3 to 1.4(± 0.2) × 10−2 s−1 in the presence of NiO nanorods via catalytic path.

Fabrication and H2S Sensing Property of Nickel Oxide and Nickel Oxide-Carbon Nanotube Composite

Nickel oxide(NiO) thin films, nanorods, and carbon nanotube(CNT)/NiO core-shell nanorod structures are fabricated by sputtering Nickel at different deposition time on alumina substrates or single wall carbon nanotube templates followed by oxidation treatments at different temperatures, 400 and 700 °C. Structural analyses are carried out by scanning electron microscopy and x-ray diffraction. NiO thinfilm, nanorod and CNT/NiO core-shell nanorod structurals of the gas sensor structures are tested for detection of H2S gas. The NiO structures exhibit the highest response at 200 °C and high selectivity to H2S among other gases of NO, NH3, H2, CO, etc. The nanorod structures have a higher sensing performance than the thin films and carbon nanotube/NiO core-shell structures. The gold catalyst deposited on NiO nanorods further improve the sensing performance, particularly the recovery kinetics.

Tailored Nickel Oxide Nanorods Via Hydrothermal Growth for Gas Sensors and Electrocatalysts

Nickel oxide, a p-type wide-bandgap semiconductor, is a very attractive material for various applications including catalysts, electrode materials for lithium ion batteries and fuel cells, electrochemical capacitors, electrochromic thin films, biosensors, and gas sensors. In nanoscience research the morphology-controlled synthesis is a crucial issue to change and improve properties of materials at nanoscale. Among many methods, the solution-based chemical process has developed into a promising technique because it allows to easily tune morphologies with changing experimental parameters. To achieve different aspect ratios of NiO nanostructures, a NiCl2-Na2C2O4-H2O hydrothermal system with polyethylene glycol, ethylene glycol, and glycine as surfactant was suggested. However, their work was limited to form a nanowire bundle during the chemical reaction. Therefore, a solution system to obtain a wider range of morphological features of NiO needs to be developed. In addition to synthesis of NiO nanostructure, its coating to desired substrates is important. As a possible pathway, electrophoretic deposition (EPD) can be considered because of its high versatility and low cost equipment. EPD process can also be applied to various types of substrates such as fibers, cloths and complex shaped materials. Such a flexible, soft and nonfragile substrate has been explored for flexible and wearable functional devices. In this study, nanostructured nickel oxide is synthesized using a hydrothermal method and tailored by triethanolamine. The structural properties of the nickel oxide particles were analyzed by using SEM and XRD. Strong dependence of the triethanolamine on NiO nanorods was found and their mechanism was investigated. For the fabrication of the devices, EPD of tailored nickel oxide was then used to construct nickel oxide electrodes on polyimide films for gas sensing measurements and carbon papers for electrochemical measurements. The morphology-controlled gas sensing properties of NiO were investigated with VOC gases. The performance of NiO for gas sensors were evaluated in terms of sensitivity and selectivity. The mechanism of p-type NiO for gas sensors is discussed in details. For nickel oxide catalysts, the urea electrooxidation in alkali medium were investigated and evaluated by cyclic voltammetry and chronoamperometry. In order to improve electrocatalytic activities, nickel oxide decorated by nickel and cobalt composite structures were also investigated. The work was partially supported by the KIET Evaluation and Planning (20158520000210) grant funded by the Korea Government Ministry of Trade, Industry and Energy and Agency for Defense Development (ADD) as global cooperative research for high performance and light weight bio-urine based fuel cell (UD160050BD).

Synergetically Selective Toluene Sensing in Hematite‐Decorated Nickel Oxide Nanocorals

The decoration of p‐type nickel oxide (NiO) with n‐type hematite (α‐Fe2O3) to achieve vertically ordered 1D nanostructures is an attractive strategy to enhance gas sensing properties. Herein, the authors report a facile method for α‐Fe2O3 decoration of the whole surface of vertical NiO nanorods. An NiO/Fe heterostructure is deposited in multiple steps using a glancing angle deposition method, which is followed by the oxidation of Fe into α‐Fe2O3. Thermally agglomerated α‐Fe2O3 nanoparticles are uniformly distributed on the whole surface of the NiO nanorods. Due to the α‐Fe2O3 decoration, the NiO nanorods exhibit a coral‐like rough surface and, more interestingly, their preferential crystallographic orientation changed from (111) to (200). Compared to bare NiO nanorods, the α‐Fe2O3‐decorated NiO nanocorals exhibit a 45.4 times higher response to 50 ppm toluene (C7H8) at 350 °C. Their theoretical detection limit for C7H8 is calculated to be ≈22 ppb. The observed unprecedented synergetic effects of α‐Fe2O3‐decorated NiO nanocorals for the extremely selective C7H8 sensing, as well as their facile synthetic route, establish a new perspective on heterostructured metal oxide 1D nanostructures for selective gas sensing.

Low-voltage electro-optical memory device based on NiO nanorods dispersed in a ferroelectric liquid crystal

A low-power nonvolatile memory device is fabricated by dispersing nickel oxide nanorods (nNiO) into a ferroelectric liquid crystal (FLC) host. The dipolar nNiO adsorbed ions in the FLC and thereby reduced the screening effect, which resulted in the enhanced memory behavior.

Development of Wide Bandgap Multifunctional NiO Nanostructures and Thin Films for Sensing Applications

Realizations of transparent pn homo-junction have become more important for the development of transparent electronics for the next-generation optoelectronic devices. The tunability of the electrical conductivity of NiO thin films with both P-type and N-type conduction by varying growth kinetics using RF sputtering technique with good optical and properties in the visible region have been demonstrated. The pn homo-junction of NiO thin films has been fabricated. The room-temperature conductivities for n-type and p-type NiO thin films have been studied using Hall measurement. Glancing angle deposition (GLAD) configuration of rf sputtering technique is utilized to fabricate the array of vertically align nanorods of NiO and are exploited for the development of homojunction devices. The fabricated homo-junction exhibits good rectifying behaviour with efficient ultra-violet (UV) photodiode characteristics, and providing suitable solution for the development of low-cost UV photo-detectors with enhanced response characteristics. The obtained results on the developed UV photo-detector will be elaborated. Further, Nickel oxide (NiO) nanoparticles (NiO-NPs) have been synthesized by a simple chemical route and exploited successfully for the fabrication of urea biosensors. A thin layer of NiO nanoparticles deposited on indium tin oxide (ITO) coated glass serves as efficient platform for the immobilisation of Urease (Ur) biomolecules for the detection of Urea. The array of NiO nanorods prepared by GLAD was also used as a matrix for making bio-electrode for the efficient detection of Urea using electrochemical techniques. The prepared amperometric bio-electrodes based on NiO nanostructures (Ur/NiO/ITO/glass) exhibits a high sensitivity of about 21.0 mA/(mM-cm2) and good linearity over a wide range (up to 16.65 Mm) of urea concentration.

Rapid synthesis of nickel oxide nanorods and its applications in catalysis

This work reports a rapid, efficient and economical synthesis of nickel oxide nanorods via microwave assisted method. The synthesis of nickel oxide nanorods has been achieved by using nickel (II) acetate as a precursor in 1,4-butanediol as a solvent under microwave irradiation within few minutes eliminating the need of conventionally used fuels and capping agents. It was observed that 1,4-butanediol plays multiple roles in the synthesis such as solvent, reactant, promoter and capping agent. The prepared nickel oxide nanorods were characterized using different techniques like XRD, FEG-SEM, EDS, TEM and FT-IR. Furthermore the application of synthesized NiO nanorods as a catalyst for the synthesis of substituted benzimidazole, benzoxazole and benzothiazole has been studied. Excellent yields of respective products under mild reaction conditions suggest a big potential for the synthesized NiO nanorods.

An efficient methodology for measurement of the average electrical properties of single one-dimensional NiO nanorods

We utilized a metal tantalum (Ta) ball-probe to measure the electrical properties of vertical-aligned one-dimensional (1D) nickel-oxide (NiO) nanorods. The 1D NiO nanorods (on average, ~105 nm wide and ~700 nm long) are synthesized using the hot-filament metal-oxide vapor deposition (HFMOVD) technique, and they are cubic phased and have a wide bandgap of 3.68 eV. When the 1D NiO nanorods are arranged in a large-area array in ohmic-contact with the Ta ball-probe, they acted as many parallel resistors. By means of a rigorous calculation, we can easily acquire the average resistance RNR and resistivity ρNR of a single NiO nanorod, which were approximately 3.1 × 1013 Ω and 4.9 × 107 Ω.cm, respectively.

Efficient electrochromic properties of high-density and large-area arrays of one-dimensional NiO nanorods

We report on the electrochromic properties of transparent one-dimensional nickel oxide (NiO) nanorods grown in a high-density and large-area array. The NiO nanorod array was synthesized on a conducting indium tin oxide thin film via hot-filament metal-oxide vapor deposition (HFMOVD). The array contained ∼100 nanorods per square micrometer, which were ∼500nm long and ∼100nm wide. XRD analysis revealed the 1D NiO nanorods to be in cubic crystalline form within space group Fm3¯m . The outstanding electrochromic properties, including the stable and reversible coloration–bleaching cycles, and large diffusion coefficient (∼6.33×10−8cm2/s), as well as good coloration efficiency (43.3cm2/C), great optical transmittance difference (60%), high optical density (1.06), and very fast coloration and bleaching times (1.55 and 1.22s) at a wavelength of 630nm, make the NiO nanorods excellent materials for use in smart windows.

The microemulsion preparation and high catalytic performance of mesoporous NiO nanorods and nanocubes for toluene combustion

Cubically crystallized mesoporous nickel oxide nanorods and nanocubes were fabricated by using a facile microemulsion strategy with cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) as surfactant. Physicochemical properties of the materials were characterized by means of a number of analytical techniques, and their catalytic activities were evaluated for the combustion of toluene. It was shown that the morphology of the samples strongly depended on the nature of surfactant: when CTAB was used, the product was mesoporous NiO nanorods; when SDS was adopted, mesoporous NiO nanocubes were obtained. The NiO-CTAB-2 sample derived with a Ni2+/CTAB molar ratio of 0.364 displayed the highest surface area (ca. 46m2/g) and the best low-temperature reducibility. A clear correlation of oxygen adspecies concentration or low-temperature reducibility with catalytic performance was observed. The high catalytic activity (T50%=256°C and T90%=278°C at SV=20,000mL/(gh)) for toluene combustion of NiO-CTAB-2 was related to its larger surface area, higher oxygen adspecies concentration, and better low-temperature reducibility.

A highly efficient microfluidic nano biochip based on nanostructured nickel oxide

We present results of the studies relating to fabrication of a microfluidic biosensor chip based on nickel oxide nanorods (NRs-NiO) that is capable of directly measuring the concentration of total cholesterol in human blood through electrochemical detection. Using this chip we demonstrate, with high reliability and in a time efficient manner, the detection of cholesterol present in buffer solutions at clinically relevant concentrations. The microfluidic channel has been fabricated onto a nickel oxide nanorod-based electrode co-immobilized with cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) that serves as the working electrode. Bare indium tin oxide served as the counter electrode. A Ag/AgCl wire introduced to the outlet of the microchannel acts as a reference electrode. The fabricated NiO nanorod-based electrode has been characterized using X-ray diffraction, Raman spectroscopy, HR-TEM, FT-IR, UV-visible spectroscopy and electrochemical techniques. The presented NRs-NiO based microfluidic sensor exhibits linearity in the range of 1.5-10.3 mM, a high sensitivity of 0.12 mA mM(-1) cm(-2) and a low value of 0.16 mM of the Michaelis-Menten constant (Km).

A facile approach to the synthesis of high-quality NiO nanorods: electrochemical and antibacterial properties

This report describes a new approach to successfully synthesize high-quality nickel oxide (NiO) nanorods with an average diameter of about 60 nm and a length of less than one micrometre viathermal decomposition of a precursor complex nickel benzoate dihydrazinate at 100 °C. The structural features, crystallinity, purity and morphology of the as-synthesized NiO nanorods were investigated by Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and transmission electron microscopy (TEM). The electrochemical property of the as-synthesized NiO nanorods was investigated to determine their suitability as anode materials for lithium-ion batteries. The nanorod electrode exhibited better reversibility and high capacity. In addition, the nanorods showed good antibacterial properties. The magnetic measurement demonstrated that the NiO nanorods are ferromagnetic and may be used in the fields of MR imaging and magnetic drug delivery.

Synthesis of high quality monodisperse Nickel Oxide Nanocrystals

Monodisperse nickel oxide (NiO) nanocrystals with a particle size of 2.7±0.7nm have been synthesised using low temperature reflux of hydrated nickel acetate and methanol. It has also been possible to create NiO nanocrystals without refluxing. The fabrication of NiO nanorods with size varying from 2 – 10 μm in length and about 0.25μm in width and crystalline pellets with approximate dimensions of 150nm by 300nm was also achieved.

Biosurfactant mediated synthesis of NiO nanorods

Nickel Oxide (NiO) nanorods were synthesized using a solution based water-in-oil microemulsion technique, which uses biosurfactant dispersed in n-heptane hydrocarbon phase. The synthesized nickel hydroxide particles were found to have a flaky morphology at lower pH and changed to a mixture of flaky and spherical particles as the pH of the solution was increased. Calcination treatment of the nickel hydroxide particles gave rise to nanorods of NiO. X-ray diffraction (XRD) was used for the phase identification. The morphology of the synthesized nickel hydroxide particles and NiO nanorods was evaluated using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis. The nanorods were found to be approximately 22 nm in diameter and 150–250 nm in length. This environment friendly approach for nanomaterial synthesis is simpler compared to other conventional methods.

One-Step Synthesis of Highly Ordered Mesoporous Silica Monoliths with Metal Oxide Nanocrystals in their Channels

A simple, one-step synthetic route to prepare ordered mesoporous silica monoliths with controllable quantities of metal oxide nanocrystals in their channels is presented. The method is based on the assisted assembly effect for mesostructure-directing of the metal complexes formed by the interaction of metal ions with the –O– groups of copolymers. Highly ordered hexagonal silica monoliths, loaded with various metal oxide nanocrystals, including those of Cr2O3, MnO, Fe2O3, Co3O4, NiO, CuO, ZnO, CdO, SnO2, and In2O3, can be obtained by this one-step pathway. In the NiO/SiO2 nanocomposite, nickel oxide nanorods with face-centered cubic lattices are formed at low doping ratios, and they can be transformed into nanowires by increasing the quantities of the precursors. In the Fe2O3/SiO2 nanocomposites, a one-dimensional assembly of iron oxide nanoparticles is observed. In the In2O3/SiO2 nanocomposites, single crystal nanowires with high aspect ratios are obtained. For the other metal oxide nanocomposites, including Cr2O3, MnO, Co3O4, CuO, ZnO, CdO, and SnO, only crystalline nanorods are obtained. N2 sorption results of the metal oxide/SiO2 mesostructured nanocomposites reveal that nanocrystals inside the pores do not severely decrease the pore volume or the Brunauer–Emmett–Teller (BET) surface area of the mesoporous silica host. The bandgaps of SnO2 and In2O3 nanocrystals, calculated from UV-vis spectra, are much larger than the corresponding bulk materials, implying the quantum confinement effect in the small particles. Co3O4/SiO2 mesostructured nanocomposites catalyze the complete combustion of CH4. These studies provide a new and simple method for templating synthesis of metal oxide nanostructures.

Preparation and characterization of NiO nanorods by thermal decomposition of NiC2O4 precursor

Synthesis of nickel oxide (NiO) nanorods was achieved by thermal decomposition of the precursor of NiC2O4 obtained via chemical reaction between Ni(CH3COO)2·2H2O and H2C2O4·2H2O in the presence of surfactant nonyl phenyl ether (9)/(5) (NP-9/5) and NaCl flux. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure features and chemical compositions of the as-made nanorods. The results showed that the as-prepared nanorods is composed of NiO with diameter of 10–80 nm, and lengths ranging from 1 to 3 micrometers. The mechanism of formation of NiO nanorods is also discussed.