Nanostructured NiO Thin Films Research Articles

Effect of Al doping on the structural, optical and photocatalytic properties of sol-gel spin-coated NiO thin films

Nanostructured NiO thin films are renowned for their catalytic activity and potential for degradation of industrial effluents. In this study, Al-doped NiO (Ni1-xAlxO with x = 0, 0.02, 0.04, 0.06, and 0.08) thin films were synthesized by sol–gel spin coating, and the influence of Al doping on their physical properties, surface morphology, optical band gap, and photo-catalytic performance was investigated. X-ray diffraction (XRD) analysis confirmed the high crystallinity of the thin films and revealed a pronounced doping effect on parameters such as crystallite size, microstrain, and dislocation density. Scanning electron microscopy (SEM) revealed the formation of spherical nanoparticles with particle sizes ranging from 26 nm to 11 nm. The elemental composition was verified through energy-dispersive x-ray (EDX) analysis. The optical bandgap of the prepared films was determined through UV-visible spectroscopy. The Ni0.98Al0.02O films exhibited the lowest PL intensity, indicating a reduced recombination rate. To assess the photo-degradation capability of the prepared thin film catalysts, industrial effluent Indigo Carmine was employed as a test compound. The Ni0.98Al0.02O sample demonstrated the highest degradation efficiency, achieving about 96% degradation within 2 h of UV–vis light irradiation. Furthermore, the degradation followed pseudo-first-order kinetics.

"Electrical and Magnetic Properties of Nanostructured NiO Thin Films Prepared by Spray Pyrolysis Method"

"Electrical and Magnetic Properties of Nanostructured NiO Thin Films Prepared by Spray Pyrolysis Method"

Effect of precursor concentration on stoichiometry and optical properties of spray pyrolyzed nanostructured NiO thin films

In this study, spray pyrolysis was used to produce nanostructured NiO thin films from high purity nickel acetate (Ni(CH3COO)2.3H2O) precursors on pre-heated ultrasonically cleaned soda-lime glass substrates. The metallic constituent concentrations in the films were varied, and the precursors were produced in distilled water at various molarities ranging from 0.1 to 0.4 M. In the study, the field-emission scanning electron microscope (FESEM) results strongly confirmed adherence of the films to the glass substrate at 350 °C. The presence of Ni and O in the samples was confirmed using Rutherford backscattering spectroscopy (RBS), X-ray diffractometry (XRD) and energy dispersive X-ray spectroscopy (EDX). For the 0.1 M NiO thin films, the thickness was approximately 43 nm, and for the 0.2 M, 0.3 M, and 0.4 M films, the thickness was 46 nm, 47 nm, and 49 nm, respectively. The XRD findings were supported by the increased Raman intensity peaks with increased precursor concentration, which confirmed the films' improved crystallinity. For the same number of passes of films deposition, as the molar concentration increases, the films thickness increases. The amount of nickel in NiO thin films increases as the molarity increases, but the amount of oxygen in NiO thin films decreases as the molarity increases. It was discovered that as molarity increases, the optical transmittance decreases and the optical band gap narrows. The qualities of NiO discovered in this study suggest the films’ potentials for usage as window layer and buffer material in thin film solar cells.

Hydrothermally prepared ultra-stable multilayer nanoflake NiO-based electrochromic films

Electrochromic materials cycle between colored and bleached states under various applied voltage and have applications in smart windows and displays. The formation of a micro–nano structure in electrochromic thin films using hydrothermal methods can improve their properties. However, the conventional constant-temperature hydrothermal method yields films that easily peel from the conductive substrate during electrochromic cycling, resulting in performance losses. Therefore, we investigated the effect of a gradient-temperature hydrothermal protocol on the electrochromic performance of NiO thin films. First, a layer of small, strongly adhered crystal grains was seeded on an indium tin oxide substrate. Thereafter, NiO nanoflake layers were grown by adjusting the reaction temperature. The prepared film could be operated for 14,000 electrochromic cycles, four-times more than those of the conventionally prepared films, without significant performance loss. Therefore, our proposed method enhances the cyclic stability of micro–nanostructured NiO thin films significantly and will aid the development of high-performance electrochromic thin films having broad applications.

Nanostructured NiO Thin Film for Ammonia Sensing at Elevated Temperatures

Nanostructured NiO Thin Film for Ammonia Sensing at Elevated Temperatures

An effect of Fe on physical properties of nanostructured NiO thin films for nonlinear optoelectronic applications

Nanostructured NiO thin films are fabricated with various concentrations of Fe through a simple spin-coating route and studied for its possible nonlinear optoelectronic applications. The grown films are of good crystallinity grown along (111) plane with single phase of NiO approved by X-ray analysis. The crystallite size values were calculated and noticed to be reduced from 36 to 8 nm with increasing Fe-doping content. Furthermore, FT-Raman spectroscopy also confirmed single phase. EDX approves the presence of Ni, O and Fe in final films and SEM elemental mapping shows homogeneous doping of Fe throughout the NiO films. AFM topographic study reveals the grain size and roughness varies with increase of Fe contents into NiO. The optical study reveals that the grown films are of high transparency which is about 70–85%. The estimation of various optical parameters was done, and direct energy gap found in 3.60 to 3.64 eV region for 0.0, 1, 2.5 and 5 wt% Fe:NiO films, correspondingly. The nonlinear properties were investigated and the values of $${\chi }^{1}, { \chi }^{3}$$, and $${n}_{2}$$ were found to be improved from 0.16 to 0.54, 1.3 × 10–13 to 1.25 × 10–11 esu and 2.67 × 10–12 to 1.70 × 10–10 esu, respectively. The enhancement in linear and nonlinear parameters owing to Fe-doping content makes the fabricated films more useful in optoelectronics.

Room temperature detection and modelling of sub-ppm NO2 by low-cost nanoporous NiO film

NiO-based NO2 sensors operating at room temperature are attracting great attentions due to their promising energy and cost saving performances. However, only a few reports showed high sensitivity and selectivity in the sub-ppm concentration range and low limit of detection (LoD). In this work, we designed and fabricated by a low-cost chemical bath deposition (CBD) and thermal annealing a nanostructured and porous NiO thin film (nanoporous NiO film) composed of NiO nanoparticles (30−50 nm). The nanoporous NiO film was then applied as sensing element for the NO2 detection at room temperature, demonstrating a high response to sub-ppm level NO2 (140 ppb), excellent selectivity and stability, and a very low LoD of 20 ppb. The NO2 sensing mechanism was investigated and satisfactorily modelled by two energetically different and independent adsorption sites at room temperature. Both sites contribute to the NO2 detection at room temperature while only one site contributes at higher temperatures. The described low-cost fabrication method and the discussed superior NO2 sensing performances at room temperature make the nanoporous NiO film a promising NO2 sensor for environmental monitoring.

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.

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.

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

Investigation of the properties of nanostructured nickel oxide NiO thin films irradiated at different γ-doses

Nanostructured thin films of Nickel oxide NiO were synthesized using spray coating method. The samples were irradiated at different γ-doses by Co-60 radioisotope. The obtained films were studied using X-ray diffraction (XRD), scanning electron microscopy, UV–visible spectrophotometry, Raman spectroscopy, photoluminescence (PL) spectroscopy and FT-IR. The experimental results demonstrated that the irradiation of NiO led to significant changes. XRD and Raman spectroscopy demonstrate that the as-deposited NiO samples show a cubic structure with (111) preferred orientation common at all gamma radiation doses. The optical energy gaps of the samples were found to decrease when increasing the γ ray dose, the Eg value decreases from 3.84 eV for as deposited NiO thin film to 3.60 eV for sample irradiated at 50 kGy. Scanning electron microscope (SEM) image of sprayed NiO films shows the high porosity and the presence of microcavities in surface of films.

Development of nanostructured nickel oxide thin film matrix by rf sputtering technique for the realization of efficient bioelectrode

In the present work, RF magnetron sputtering technique has been exploited with varied deposition parameters (optimized parameters: sputtering pressure = 20 mT, 100% O2 gas ambient, without any substrate heating) to develop nanostructured NiO thin film matrix with increased surface roughness (5.09 nm) and good charge transfer properties for efficient detection of cortisol. Electrochemical and electrical studies have been performed to determine charge communication characteristics and conductivity of the prepared NiO thin film that could yield enhanced biosensing response properties. The biosensing response has been studied on the optimized parameters using cortisol as a test analyte and a relatively high sensing response of 14 μA (ug/mL)−1 has been obtained for the optimized NiO matrix-based electrodes (Cortisol-Ab/NiO/ITO).

Impedimetric glucose biosensor based on nanostructure nickel oxide transducer fabricated by reactive RF magnetron sputtering system

As a new performance, nanostructured nickel oxide (Nano-NiO) thin film was considered at the optimized instrumental deposition conditions on the F-doped SnO2 conducting glass (FTO) by reactive radio frequency (RF) magnetron sputtering system. The attained uniform Nano-NiO thin film was successfully exploited to immobilize glucose oxidase enzyme (GOx) for impedimetric glucose quantification. Step by step film monitoring using field emission-scanning electron microscopy (FE-SEM) before and after enzyme immobilization established nanostructured NiO thin film with great isoelectric point (IEP~10.7) was a suitable biosensing media for enzymes with low IEP (4.5). Observing of biosensor fabrication was accomplished using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The impedimetric results for invented FTO/Nano-NiO/GOx biosensor exhibited good sensitivity 4.45kΩ/mM for glucose detection within 0.20–4.0mM range, good electrocatalytic activity, and low detection limit as 24μM via appropriate enzyme activity and stability. The suggested disposable biosensor demonstrated a potential application for real sample analysis with unknown interferences.

Hydrogen Gas Sensing Characteristics of Nanostructured NiO Thin Films Synthesized by SILAR Method

Nanostructured NiO thin films have been synthesized by a facile, low-cost successive ionic layer adsorption and reaction (SILAR) method, and the effects of the film thickness on their hydrogen gas sensing properties investigated. The samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) analysis, and energy-dispersive x-ray analysis. The XRD results revealed that the crystallinity improved with increasing thickness, exhibiting polycrystalline structure. SEM studies showed that all the films covered the glass substrate well. According to optical absorption measurements, the optical bandgap decreased with increasing film thickness. The gas sensing properties of the nanostructured NiO thin films were studied as a function of operating temperature and gas concentration. The samples showed good sensing performance of H2 gas with high response. The maximum response was 75% at operating temperature of 200°C for hydrogen gas concentration of 40 ppm. These results demonstrate that nanostructured NiO thin films synthesized by the SILAR method have potential for application in hydrogen detection.

Non-enzymatic Glucose electrochemical sensor made of porous NiO thin films prepared by reactive magnetron sputtering at oblique angles

Porous nanostructured NiO thin films have been prepared in one step by magnetron sputtering in an oblique angle configuration (MS-OAD) and used as electrodes for the non-enzymatic detection of glucose. The films have been thoroughly characterized by different complementary techniques and their performance for the analysis of glucose in basic solutions determined by electrochemical methods. These electrodes presented four times higher sensitivity that equivalent compact thin films prepared by MS in a normal configuration and were superior in terms of sensitivity than majority of nickel based electrodes prepared by other methods. Finally, a high sensitivity towards detection of glucose in blood, insensitivity to common interferences, a long term stability and high reproducibility confirmed the good performance and reliability of these electrodes for practical analytical purposes.

Tailoring the textured surface of porous nanostructured NiO thin films for the detection of pollutant gases

Abstract In the present article, an experimental approach to detect pollutant gases in presence of humidity was applied for gas sensors based on p-type NiO thin films. NiO thin films were deposited by radio frequency magnetron sputtering in inert atmosphere using a NiO target. Thin films were investigated by scanning electron microscopy to observe their surface morphology. Crystal structure and vibrational study were investigated by X-ray diffraction and micro-Raman spectroscopy, respectively. It was observed that deposition temperature played a crucial role in the structural and surface morphology of NiO thin films. Sensing response of the nanostructured thin films to reducing and oxidizing gas was studied as a function of gas concentration and operating temperature. A double digit (12.3) response was observed towards ozone at 200 °C, while maximum response to ethanol and acetone was recorded at 400 °C. A correlation was established between sensing response and crystalline dimension for ozone sensing. The result showed that NiO thin films can be used as p-type metal oxide material for the fabrication of solid state gas sensors to detect low concentrations of ozone (70 ppb).

One-step fabrication of nanostructured NiO films from deep eutectic solvent with enhanced electrochromic performance

Nanostructured NiO thin films were directly prepared by simple and efficient electrodeposition in a choline chloride-based ionic liquid. Uniform granules and some open voids between these granules are observed in the film deposited at 70 °C, while the film becomes compact and the NiO particles are 2–6 nm in size when the electrodeposition temperature is 90 °C. The optical transmittance of the film increased with the increase of the electrodeposition temperature. Although the electrochromic switching and reaction kinetics of the NiO film deposited at low temperature are fast due to the presence of metallic Ni and some voids, little transmittance modulation occurs in the wavelength range of 300–900 nm. In contrast, the NiO film deposited at high temperature exhibits high optical modulation of 67% at 550 nm, high coloration efficiency (98 cm2 C−1 at 400 nm, 92 cm2 C−1 at 550 nm and 51 cm2 C−1 at 750 nm), good memory effect and cycling durability.

Resistance switching properties of planner Ag/Li:NiO/Ag structures induced by swift heavy ion irradiation

We report on the resistance switching induced by swift heavy ion (SHI) irradiation in lithium doped nanostructured NiO thin films grown on MgO (100) substrates by chemical solution deposition. Hysteresis in current-voltage curves were observed for the Ag/Li:NiO/Ag planner structures irradiated with 100 MeV Ag+14 ions, whereas pristine samples showed only linear I-V characteristics. No preferential oxygen loss from the film surface has been detected in on-line elastic recoil detection analysis. This suggests that change in the defect density created by SHI irradiation that may contribute to the metallic filaments play a major role as compared to the interfacial oxygen vacancies in resistance switching of NiO.

NiO Thin Film Fabricated by Electrophoretic Deposition and Formaldehyde Gas Sensing Property Thereof

In the present work, nanostructured NiO thin films were prepared from a facile method based on electrophoretic deposition (EPD) using NiOOH sols as the starting material. The scanning electron microscope (SEM) and atomic force microscopy (AFM) observations revealed that the films were comprised of 40-80 nm particles with a thickness of about 100 nm. When using the obtained NiO film as formaldehyde gas sensor, it was found that such kind of nanostructured films have contributed and modified remarkably the sensing properties such as shorter response and recovery time (approximately 10 s and 5 s), higher sensitivity (approximately 3/10 ppm) at lower working temperature (approximately 300 degrees C).

NiO nanostructured films with Pt coating prepared by magnetron sputtering

Nanostructured NiO thin films were prepared by dc reactive magnetron sputtering in a mixture of oxygen and argon and subsequently coated by Pt on an NiO film surface. Pt very thin overlayers with a thickness of about 3 and 5 nm have been deposited by magnetron sputtering. The microstructure and surface morphology of the samples have been analysed by XRD and by SEM and AFM, respectively. The electrical responses of the NiO-based sensors towards hydrogen concentration have been also considered. The thickness of the Pt thin layers seems an important parameter in determining the properties of the NiO films as hydrogen sensors.