NiO Nanostructures Research Articles

NiO nanostructure by RF sputtering for gas sensing applications

ABSTRACTA nanostructured thin film of NiO with thickness (1250 ± 30) nm was synthesized using the RF-reactive planer magnetron sputtering technique over a cleaned glass substrate. Structural analysis of the nanostructured NiO films was conducted utilising the XRD method, and the films were found to have a polycrystalline nature with a preferred (200) plane reflection at the angle 2θ equal to 43.35ᵒ. The optical measurement for NiO thin films manifested the transmittance, the energy band gap and the absorption coefficient in the ultraviolet and visible regions. A scanning electron microscope (SEM) was used to analyses the surface morphology of the NiO thin film sample. The ability of nanostructured NiO thin films to sense different NO2 gas concentrations in terms of the time working was studied and reported. The nanostructured NiO film had better sensitivity at the gas ratio of 350 ppm and the operating temperature 150ᵒC.

Tailoring of pyramid cobalt doped nickel oxide nanostructures by composite-hydroxide-mediated approach

Nickel oxide nanostructures have been synthesized successfully by composite hydroxide mediated (CHM) approach at 200 °C for various cobalt concentrations (0%, 5%, 10% and 15%). Incorporation of cobalt was explored by employing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM, and ultraviolet visible spectroscopy. An influence of increase in cobalt doping on average crystallite size was found from 31 to 56 nm. The increase in crystallite size is due to the introduction of point defects and oxygen vacancies caused by the incorporation of Co ions in NiO lattice. The influence of defects is also seen from variation in lattice parameters and X-ray density. The effect of incorporation of increasing cobalt contents was seen from SEM micrographs. The spherical characteristics of pure NiO nanostructures changed to sharp edge pyramids with smooth surfaces. The growth of pyramids is evident with increase in side length 421–691 nm for various cobalt concentrations (5%, 10% and 15%). FT-IR confirms the purity of product while the band gap was estimated by UV–Vis spectroscopy which was found from 5.59 to 1.50 eV.

Nanoporous nickel oxide catalyst with uniform Ni dispersion for enhanced hydrogen production from organic waste

In this report, we propose magnetically separable porous nickel oxide nanostructure with uniform Ni distribution having the large surface area and atomically dispersed Si sites for enhanced hydrogen production from organic waste. The catalyst showed ten times higher production rate from volatiles during carbonization of organic waste and coal than that in the absence of the catalyst. The reduced Ni/NiO catalyst yielded two times higher hydrogen production compared to the traditional Ni/Al2O3 catalyst. The highest yield of hydrogen over reduced Ni/NiO was 32 g/kgfeed at 600 °C in fixed bed reactor via pyrolysis-reforming of bagasse. The Ni/NiO showed far more efficient recyclability compared to traditional Ni/Al2O3. The economic aspect of the Ni/NiO catalyst was compared with the Ni/Al2O3 catalyst based on H2 yield. TGA and TPO analysis confirmed the presence of amorphous coke.

HMT-Controlled Synthesis of Mesoporous NiO Hierarchical Nanostructures and Their Catalytic Role towards the Thermal Decomposition of Ammonium Perchlorate

In this work, mesoporous nickel oxide (NiO) hierarchical nanostructures were synthesized by a facile approach by hydrothermal reaction and subsequent calcination. The phase structure, microstructure, element composition, surface area, and pore size distribution of the as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and the Brunauer–Emmett–Teller (BET) technique. The precursor of Ni3(NO3)2(OH)4 nanosheet, Ni3(NO3)2(OH)4 microsphere, and Ni(HCO3)2 sub-microsphere was obtained by hydrothermal reaction at 160 °C for 4 h when the ratio of Ni2+/HMT (hexamethylenetetramine) was 2:1, 1:2, and 1:3, respectively. After calcination at 400 °C for 2 h, the precursors were completely transformed to mesoporous NiO hierarchical nanosheet, microsphere, and sub-microsphere. When evaluated as additives of the thermal decomposition of ammonium perchlorate (AP), these NiO nanostructures significantly reduce the decomposition temperature of AP, showing obvious catalytic activity. In particular, NiO sub-microsphere have the best catalytic role, which can reduce the high temperature decomposition (HTD) and low temperature decomposition (LTD) temperature by 75.2 and 19.1 °C, respectively. The synthetic approach can easily control the morphology and pore structure of the NiO nanostructures by adjusting the ratio of Ni2+/HMT in the reactants and subsequent calcination, which avoids using expensive templates or surfactant and could be intended to prepare other transition metal oxide.

A review on recent progress of p-type nickel oxide based gas sensors: Future perspectives

Recently, technological and industrial advances uninterruptedly cause the release of hazardous and toxic gases that are harmful to human life; as a result gas sensing devices that are highly sensitive and selective to such gases are in a high demand. Presently, gas sensors based on p-type NiO are pleasing more consideration, because of its excellent reproducibility, high specific surface areas, great sensitivity, low cost and environmental friendly. Herein, we reviewed the different synthesis methods on p-type NiO nanostructures and their application as gas sensors. The fundamental gas sensing mechanism related to the p-type NiO is briefly explained. The effects of noble metals, transition metals, and transition metal dichalcogenide and phosphors materials on the NiO gas sensing performance are also discussed in detail. Influence of 0D, 1D, 2D and 3D heterostructures on NiO gas sensing characteristics are also given. The arrangement of various semiconductor metal oxides to form heterostructures which further improve the selectivity and sensitivity of the sensing parameters is also discussed and we show that number of publications on heterostructures related to NiO increased drastically since the year 2010.

Fabrication, characterization of polyaniline intercalated NiO nanocomposites and application in the development of non-enzymatic glucose biosensor

Determination of glucose plays very important part in diagnostics and management of diabetes. Nowadays, determination of glucose is necessary in human health. In order to develop the glucose biosensor, polymer modified catalytic composites were fabricated and used to detect glucose molecules. In this work, NiO nanostructure metal oxide (NMO) was fabricated via thermal decomposition method and polyaniline (wt% = 2, 4 and 6) assisted nanocomposites (NiO/PANI) were also prepared. The morphology and structure of synthesized nanocomposites were characterized by UV–visible diffusion reflectance spectroscopy (UV–vis-DRS), Fourier transform- infra red spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption-desorption isotherm measurement. The modified NiO/6%PANI/GCE had higher catalytic activity toward the oxidation of glucose than NiO/GCE, PANI/GCE, NiO/2%PANI/GCE and NiO/4%PANI/GCE. This is due to the larger surface area of NiO/6%PANI nanocomposites provide a ploform for faster electron transfer to the detection of glucose. The constructed glucose biosensor have been exhibited a high sensitivity of 606.13 µA mM−1 cm−2, lowest detection limit of 0.19 µM, high selectivity, stability, simplicity and low cost for the quick detection of glucose in real sample as well.

Synthesis of Quantum Confined Nickel Oxide and Differentially Doped Nickel Oxide Nanostructure and Their Antifungal Activities

Synthesis of Quantum Confined Nickel Oxide and Differentially Doped Nickel Oxide Nanostructure and Their Antifungal Activities

Controllable synthesis of crescent-shaped porous NiO nanoplates for conductometric ethanol gas sensors

NiO has been widely used as building blocks for gas sensing because of its excellent physicochemical properties. However, the high working temperature of most NiO-based sensors (<200 °C) hinders their further applications. In this work, a novel nanostructure, crescent-shaped porous NiO nanoplates, has been synthesized via hydrothermal approach combining with calcination treatment, which shows low working temperature for ethanol gas sensing. The volume ratio of ethanol to distilled water, the adding amount of PVP, and annealing temperature have been investigated in detail for precisely controlling the morphology of NiO nanostructure. Subsequently, the crescent-shaped porous NiO nanoplates are employed to fabricate conductometric ethanol gas sensors. Under optimal experimental conditions, the NiO nanoplates based gas sensor demonstrates fast response and recovery speed (5 and 20 s, respectively) to 100 ppm ethanol at a low working temperature of 130 °C with excellent long-term stability and selectivity. Furthermore, the limit of detection is experimentally calculated to be as low as 200 ppb. The results show that the crescent-shaped porous NiO nanoplates has great potential in ethanol sensing applications and the feasibility of morphology control for high performance gas sensing.

High-performance multicolor metal-semiconductor-metal Si photodetector enhanced by nanostructured NiO thin film

The performance of multicolor metal-semiconductor-metal (MSM) Si photodetector was improved by integrating nanostructured NiO film on Si (100) substrate using a sol-gel spin coating technique. To investigate the photoelectric performance of Si and NiO/Si heterostructure photodetectors, Au metal interdigitated electrodes were deposited on both bare Si and NiO film/Si heterostructure by a thermal evaporator. The NiO/Si photodetector exhibited excellent reproducibility and fast photoresponse under illumination with UV (365 nm), red (625 nm) and near-infrared (850 nm) lights. In addition, the NiO/Si photodetector showed higher responsivity and sensitivity towards 365, 625, and 850 nm lights as compared to bare Si photodetector. A remarkable increase in the responsivity and sensitivity of NiO/Si photodetector were measured under 365 nm illumination. The values of responsivity and sensitivity were calculated to be higher than that of bare Si photodetector by a factor of 15 and 948, respectively. Based on the photoelectric results, nanostructured NiO film/Si heterostructure is a valuable candidate to be used in UV–Vis–NIR photodetection applications.

Hydrothermal synthesis of novel lotus-root slice NiO architectures with enhanced gas response properties

The porous NiO nanostructures have received considerable attention owing to high surface-to-volume ratio, low density and sufficient interior space for potential applications, such as gas sensing. The novel lotus-root slice NiO architectures were prepared via a facile hydrothermal method. The cetyltrimethylammonium bromide and urea played an important role for the formation of the lotus-root slice NiO. A possible formation mechanism has been proposed. The lotus-root slice NiO showed excellent gas-sensing performance to ethanol. Such unique architectures may open up an avenue to further enhance the gas-sensing performances of NiO nanostructures for future sensor applications.

A facile one-step flash combustion synthesis and characterization on C doped NiO nanostructures

Synthesis of NiO nanostructures in presence of different concentrations of citric acid (CA) was achieved through flash combustion technique. The NiO nanostructures formation was confirmed through X-ray diffraction analysis. At low concentrations of CA no extra peak was observed in XRD patterns, however when the CA concentration was raised to 5 and 10 g, two new extra peaks appeared at 44.6° and 51.9° which may be attributed to the presence of C. The crystallite size was noticed to reduce from 29 to 18 nm with increase in the CA concentration. All observed Raman bands were noticed to be shifted owing to the quantum size effect. EDX and SEM mapping confirm the existence of C. SEM images confirm the cubic nanocrystalline morphology for 0.5 g CA:NiO, however with increasing CA concentration a drastic change in morphology, i.e. from nanocrystals to extended nanosheets, was observed. The energy gap values were determined using Kubelka-Munk theory and found in range of 3.5–4.0 eV. An additional energy gap ∼2 eV was also noticed at higher CA concentration. The values of relative permittivity, εr′, were found in the range of 18–110 for CA concentration upto 5g, however, at 10.0 g CA its value was found to be order of 104 at 2 × 105 Hz.

Exploring the Role of pH on the Physical and Optoelectronic Attributes of Nanostructured NiO Thin Films

Exploring the Role of pH on the Physical and Optoelectronic Attributes of Nanostructured NiO Thin Films

Fabrication of graphene-based electrochemical capacitors through reactive inverse matrix assisted pulsed laser evaporation

Electrodes constituted by nitrogen-doped reduced graphene oxide (NrGO) in combination with NiO nanostructures were fabricated by means of reactive inverse matrix assisted pulsed laser evaporation technique. The structure-composition of the electrode composites was tailored by laser-inducing chemical reactions of graphene oxide (GO) flakes with different precursor molecules (citric acid, ascorbic acid and imidazole) during GO deposition. Structural characterizations reveal the formation of wrinkles and nanoholes in the NrGO sheets, besides their coating with NiO nanostructures. Compositional studies disclose that imidazole precursor promotes the synthesis of NrGO with the largest degree of reduction and nitrogen doping (mainly with graphitic and pyridinic N). Electrochemical analyses of the obtained electrodes reveal that NiO nanostructures increase surface charge storage processes (double layer – pseudocapacitive) over diffusive ones, being the imidazole-based electrodes the ones exhibiting the best performance (up to 114 F cm−3 at 10 mV s−1). Symmetric and asymmetric electrochemical capacitors were also fabricated showing excellent robustness over 10,000 charge-discharge cycles at high specific currents.

Enhanced optical properties of pure and Sr doped NiO nanostructures: A comprehensive study

We have discussed the detailed optical properties of Ni1-xSrxO (x = 0.0, 0.02, 0.04) nanoparticles calcined at 700 °C which have been synthesized using liquid-solid phase route such as sol-gel method. To discuss the optical behavior, we focus on the reflectance/transmittance spectra of pure and Sr doped NiO samples. Here, we found low reflectance about 15% and high transmittance 41.48% in the visible region which more confirm the high transparency in the visible region. The refractive index n (λ) and extinction coefficient k (λ) spectra of our samples show normal and anomalous dispersion in the range 200–800 nm. In addition, optical dielectric constants, optical conductivity (σ), high frequency dielectric constant using dispersion through both of free carriers and bound carriers, static refractive index (no), Wemple Di-Domenico (WDD) static refractive index (noWDD), ratio of free carrier concentration, effective mass ( Nm*) and plasma frequency (ωp) have been determined. The refractive index dispersive behavior is also examined through WDD single oscillator model and optical dispersion parameters Eo and Ed were calculated using WDD model. Simultaneoulsy, through deconvoluted PL spectra using Gaussian function for all the samples, we found extra green and yellow bands are originate in PL emission spectrum for pure NiO sample and further these bands supressed in Sr doped NiO samples which confirm the reduced defects in the NiO on the Sr doping.

Template-free synthesis of hierarchical NiO microtubes as high performance anode materials for Li-ion batteries

Hierarchical nanostructured NiO (h-NiO) microtubes were prepared by a simple wet-chemical synthesis without the use of template or surfactant, followed by the calcination of α-Ni(OH)2 precursor. The structural characterization of the h-NiO microtubes were performed by scanning microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), the results of which indicated that the obtained h-NiO microtubes are covered by the nanosheet grown perpendicularly on the tube surface. The unique hierarchical nanostructure of h-NiO microtubes with high surface area and many voids facilitates the electrochemical reaction as well as the short ion and electron transport pathway. Therefore, as anode electrode of Li-ion batteries, the h-NiO microtubes deliver largely enhanced cycle capacity of 770 mAh·g−1 at a current density of 0.5 C after 200 cycles with high columbic efficiency, compared to the NiO rods. These results suggest that the h-NiO microtubes can be a promising anode material for Li-ion batteries.

Characteristics of point defects on the room temperature ferromagnetic and highly NO2 selectivity gas sensing of p-type Mn3O4 nanorods

This study investigates the room temperature (RT) gas-sensing and ferromagnetic behavior of p-type materials based on a comparison of NiO, Mn3O4, and CuO nanostructures prepared using a hydrothermal method. The Mn3O4 nanorods based sensor exhibited high sensitivity and responses to 40 ppm NO2 and a selectivity to NO2 over the interference of CO, NH3, CH4, C6H6, C7H8 and C3H6O gases at 23 °C. The observed response and selectivity to 40 ppm NO2 are ascribed to the vastly gas accessibility induced by ample porosity, high surface area and point defects of Mn3O4. This is justified by a clear correlation of point defects with the ferromagnetic and gas-sensing properties. The linear behavior observed for the response versus gas concentration (adj R2 = 0.98519), signified that the Mn3O4-based sensor is suitable for NO2 detection at 23 °C. A model of the gas-sensing mechanism and the influence of point defects were presented to further illustrate the sensing performance.

MoSx@NiO Composite Nanostructures: An Advanced Nonprecious Catalyst for Hydrogen Evolution Reaction in Alkaline Media

AbstractThe design of the earth‐abundant, nonprecious, efficient, and stable electrocatalysts for efficient hydrogen evolution reaction (HER) in alkaline media is a hot research topic in the field of renewable energies. A heterostructured system composed of MoSx deposited on NiO nanostructures (MoSx@NiO) as a robust catalyst for water splitting is proposed here. NiO nanosponges are applied as cocatalyst for MoS2 in alkaline media. Both NiO and MoS2@NiO composites are prepared by a hydrothermal method. The NiO nanostructures exhibit sponge‐like morphology and are completely covered by the sheet‐like MoS2. The NiO and MoS2 exhibit cubic and hexagonal phases, respectively. In the MoSx@NiO composite, the HER experiment in 1 m KOH electrolyte results in a low overpotential (406 mV) to produce 10 mA cm−2 current density. The Tafel slope for that case is 43 mV per decade, which is the lowest ever achieved for MoS2‐based electrocatalyst in alkaline media. The catalyst is highly stable for at least 13 h, with no decrease in the current density. This simple, cost‐effective, and environmentally friendly methodology can pave the way for exploitation of MoSx@NiO composite catalysts not only for water splitting, but also for other applications such as lithium ion batteries, and fuel cells.

Cost effective green synthesis of NiO nanostructures as highly efficient photocatalysts for degradation of organic dyes

Here, the cost effective green synthesis of nickel oxide (NiO) nanostructures has been reported. The organic capping and/or reducing agents were obtained by extraction from wastes of three different vegetables (cauliflower, potatoes and peas). The extracts of cauliflower and peas peels gave nanowhiskers while the extract of potato peels gave nanorods of NiO, as confirmed by scanning electron microscopy. X-ray diffraction analyses demonstrated the nanocrystalline cubic phase of NiO in all the samples. However, crystallite size varied with the extract of vegetable waste used. Fourier transform infrared analysis helps in identifying different vibrations, particularly Ni–O stretching vibrations, and diffuse reflectance spectra analyses led to the establishment of bandgap energies. The resulting NiO nanostructures were tested for their efficiencies as photocatalysts for Methylene blue degradation. All the three samples have shown significant photocatalytic activities. The exploration in this study clearly demonstrates the very high photocatalytic activities of the synthesised NiO nanostructures, which can be used as competent agents for treatment of wastewater to remove toxic dyes.

Enhancement of the supercapacitive properties of laser deposited graphene-based electrodes through carbon nanotube loading and nitrogen doping.

Several technological routes are being investigated for improving the energy storage capability and power delivery of electrochemical capacitors. In this work, ternary hybrid electrodes composed of conducting graphene/reduced graphene oxide (rGO), which store charge mainly through electric double-layer mechanisms, covered by NiO nanostructures, for adding pseudocapacitance, were fabricated through a matrix assisted pulsed laser evaporation technique. The incorporation of multiwall carbon nanotubes (MWCNTs) provokes an increase of the porosity and thus, a substantial enhancement of the electrodes' capacitance (from 4 to 20 F cm-3 at 10 mV s-1). Volumetric capacitances of 34 F cm-3 were also obtained with electrodes containing just carbon nanotubes coated with NiO nanostructures. Moreover, the use of nitrogen containing precursors (ammonia, urea) for laser-induced N-doping of the nanocarbons also provokes a notable increase of the capacitance. Remarkably, N-containing groups in rGO-MWCNTs mainly add electric double layer charge storage, pointing to an increase of electrode porosity, whereas redox reactions contribute with a minor diffusion fraction. It was also observed that the loading of carbon nanotubes leads to an increase of diffusion-controlled charge storage mechanisms versus capacitive ones in rGO-based electrodes, the opposite effect being observed in graphene electrodes.

Water radiolysis by gamma –irradiation for high quality synthesis of Nickel Oxide nano sheet

A simple, time effective and cost effective, methos was reported for synthesis of nickel oxide nanostructure. The NiO nanostructure was synthesized by gamma-irradiation method from NiSO4 precursor. The solution was irradiated by 60Co gamma-ray source at the dose rate of 40 Gy/min for determined time. The synthesized powders are characterized by means of X-ray powder diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), Scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. The XRD and FTIR results confirmed the formation of high pure phase of NiO nanostructure. Results of scanning electron microscope (SEM) images showed that product has flowe-like nano nanostructure morphology with average particle size of 60 nm. The mechanism of product formation through water radiolysis was discussed. Three main stages can be considered for the radiolytic reactions of water in different time scales. (a) The physical stage (1 fs after the initial radiation interaction), (b) Physico-chemical stage (10−15–10−12 s), (c) The chemical stage (10−12–10−6 s).