Nanostructured Nickel Oxide Thin Films Research Articles

Effect of annealing temperature on physical properties and photoelectrochemical behavior of electrodeposited nanostructured NiO thin films for optoelectronic applications

Our paper used a low-cost electrodeposition technique to grow Nickel Oxide (NiO) thin films on fluorine-doped tin oxide (FTO) substrate. As-deposited films were annealed at different temperatures (350, 400, 450, and 500 °C). X-ray diffraction (XRD), Raman spectroscopy (RAM), scanning electron microscopy (SEM), UV–vis spectrophotometer, photoluminescence (PL), Cyclic voltammetry (CV), photocurrent (PC), electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis (MS) were used to study and investigate the effect of annealing temperatures on the structural, morphological, electrical, and optical properties of prepared thin films. XRD patterns proved the cubic phase of all NiO samples with the preferential orientation in (111) direction. SEM results showed that the grain size increased with increasing annealing temperature. The optical transmission was studied by a UV–vis spectrophotometer, where high transmittance for NiO thin films was found to vary in the range of 73–84 % in the visible wavelength region, depending on the annealing temperatures. At the same time, UV–visible measurements indicate an absorption band edge at 311 nm, mainly recognized as a characteristic direct band gap for prepared NiO. The optical gap calculated from the Tauc relation showed a decreasing trend from 3.97 to 3.86 eV with increasing annealing temperature from 300 °C to 500 °C. PL spectra of synthesized samples revealed two distinct emission peaks at around 400 nm and 490 nm. RAM analysis confirmed the presence of three characteristic peaks related to the vibration of Ni–O bonds. The NiO film annealed at 500 °C displays the highest specific capacitance value by CV analysis. The P-type conductivity of manufactured arrays and enhanced electrical properties were confirmed by PC, EIS, and MS analysis. The highest carrier concentration values (9.19 × 1018 cm−3) and flat band potential (0.82 V) were obtained for samples annealed at 500 °C. Our outcomes proved that NiO-500 °C thin films are ideal candidates for optoelectronic applications.

Enhanced Electrochemical Based DNA Sensing Platform for the Yellow Rust Detection in the Wheat Using Nanostructured Nickel Oxide Thin Film

Enhanced Electrochemical Based DNA Sensing Platform for the Yellow Rust Detection in the Wheat Using Nanostructured Nickel Oxide Thin Film

Investigation of Nanostructured NiO and Au Doped NiO Thin Films by SPT

Nanostructured Nickel oxide (NiO) and NiO doped with 2% and 4% Au were prepared via spray pyrolysis technique (SPT). Structure, surface morphology, and optical properties were evaluated via XRD, AFM and UV-VIS spectrometer. Results indicate that all thin films polycrystalline and the peaks at 37.28° and 43.29° corresponding to (111), (200). The AFM image shows average diameter 73.5nm and average roughness 0.76 nm. Optical measurements show the band gap decrease with increase doping of Au thin films (2.88, 2.75 and 2.39) eV.

Pseudo n-type behaviour of nickel oxide thin film at room temperature towards ammonia sensing

Sensors are part of a safe laboratory, working space and closed environment. In view of this, a sensing material for ammonia (NH3) vapour, nickel oxide (NiO) has been investigated to improve its quality as a sensor. The transparent nanostructured NiO thin films were deposited on glass substrates by sol-gel spin coating method at different molar concentrations (0.4 M, 0.6 M and 0.8 M). The NH3 sensing studies reveal that 0.6 M film shows admirable response of 403 (75 ppm), and also it has good response and recovery times (110 s and 33 s) for 25 ppm at room temperature. These features of the film are attributed to low surface roughness, small grain size and higher surface to volume ratio compared to other films. In presence of air ambience, the electrons at film surface are chemisorbed by oxygen molecules and thereby cause an increase of the depletion layer. Once the film is exposed to the analyte gas NH3, the depletion layer decreases because of electrons returning back to the conduction band (CB). These electrons are then de-excited to the valence band (VB) and recombine with holes (annihilation of holes). At the same time, the trapping of electrons by Ni(OH)2 and creation of holes by oxidation of Ni2+ into Ni3+ increases the hole concentration at VB, followed by a reduction of recombination rate of electrons and holes. All these processes decrease the potential barrier between the grains and thereby cause the Fermi level (EF) to shift towards VB. These processes remarkably enhance the sensing behaviour of the film. Importantly, the prepared NiO thin film behaves as a n-type sensor at room temperature for NH3; and therefore, termed as pseudo-n-type.

Optimising Aged Nanostructured Nickel Oxide Thin Films for Solar Cells Fabrication

Optimising Aged Nanostructured Nickel Oxide Thin Films for Solar Cells Fabrication

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).

Controlled Synthesis of Nanostructured Nickel Oxide Thin Film for Supercapacitor Application

In the present work we report the controlled synthesis of NiO thin film with nano-leaves like morphology using reflux method. The synthesized NiO electrode is used as working electrode for supercapacitor application. The deposited NiO thin film was characterized using thermogravimetric (TGA) analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The supercapacitor behaviour of NiO was investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy using 3 M KOH electrolyte. The electrochemical results show specific capacitance of 513 F g−1 at 10 mV s−1 scan rate, power density (10.44 kW kg−1), energy density (14 Wh kg−1) and 85% capacitance retention over 5000 cycles. These remarkable results indicate the importance of the NiO nano-leaves electrode in energy storage device.

Sensing and biosensing with screen printed electrodes modified with nanostructured nickel oxide thin films prepared by magnetron sputtering at oblique angles

This work reports about the sensing and biosensing applications of a novel screen printed electrode (SPE) modified by nanostructured nickel oxide thin films obtained by reactive magnetron sputtering under an oblique angle configuration. Using these films as electrodes we demonstrate their ability to detect hydrogen peroxide under neutral pH conditions. Furthermore, as a proof-of-concept, NiO-modified SPEs have been developed and their cholesterol biosensing properties determined by cyclic voltammetry and chronoamperometry.

Nanostructured NiO-based reagentless biosensor for total cholesterol and low density lipoprotein detection.

Nanostructured nickel oxide (NiO) thin film has been explored as a matrix to develop a reagentless biosensor for free and total cholesterol as well as low density lipoprotein (LDL) detection. The redox property of the matrix has been exploited to enhance the electron transfer between the enzyme and the electrode as well as to eliminate the toxic mediator in solution. X-ray diffraction, scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy were carried out to characterize the NiO thin film. Biosensing response studies were accomplished using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The developed biosensors exhibited a high sensitivity of 27 and 63μA/mM/cm2 over a linear range of 0.12-10.23 and 1-12mM, respectively, for free and total cholesterol. Reagentless estimation of LDL was also achieved over the wide range 0.018-0.5μM with a sensitivity of 0.12mA/μM/cm2. The results are extremely promising for the realization of an integrated biosensor for complete detection of cholesterol in the serum samples. Graphical Abstract Reagentless sensing mechanism of (a) free cholesterol and (b) total cholesterol using nanostructured NiO matrix.

Potentiostatic electrodeposition of nanostructured NiO thin films for their application as electrocatalyst

We report the synthesis of nanostructured nickel oxide (NiO) films, and their implementation as photocathodes in photoelectrochemical (PEC) cells for hydrogen generation by water splitting. NiO nanograins were prepared by electrodeposition of nickel from complexing glycinate solution at different pH from 2 to 13, followed by annealing at 400°C. The characterization of NiO films was carried out by XRD, SEM, UV–vis, PL and electrochemical techniques. XRD study showed that NiO with cubic structure was obtained for all films. SEM micrographs showed a spherical-granular structure for NiO films with a grain size between 400 and 125nm. The measurements carried out on PEC cell with NiO as photocathodes, under simulated solar irradiation, demonstrated a significant increase of cathodic photocurrent as the pH of electrodeposition solution was increased. Analysis of Mott-Schottky plots for each NiO film showed a remarkable increment of the charge carrier density as the grain size was decreasing.

Investigation on structural and electrochemical properties of binder free nanostructured nickel oxide thin film

Here, we report a simple method to achieve binder free nickel oxide (NiO) thin film using an electrohydrodynamic atomization (EHDA) process. The optimization of process parameters to obtain uniform thin film is discussed in detail. The high surface purity of nanostructured NiO film is oriented in the face centered cubic structure. The surface morphology revealed uniform deposition of anisotropic nanoplatelets morphology. The cyclic voltammetry and electrochemical impedance spectroscopy confirm the pseudocapacitance behavior of NiO film with a specific capacitance of 178F/g. The cyclic test exhibits a good cyclic retention of 94% for 1200 cycles.

Preparation and characterization of nanostructured nickel oxide thin films by spray pyrolysis

Transparent crystalline nanostructured nickel oxide (NiO) thin films were prepared using a simple spray pyrolysis technique from hydrated nickel chloride salt solution (NiCl2� 6H2O) onto glass and silicon (n-type) substrates at different temperatures (280, 320, 360, and 400 C) and with different solution concentrations (0.025, 0.05, 0.075, and 0.1 M). Structural and morphological properties of the grown NiO films were studied using X-ray diffraction (XRD) and atomic force microscope. Optical properties and chemical analysis of the films were char- acterized by UV-visible absorption spectra and Fourier transform infrared spectroscopy, respectively. The XRD result showed that the deposited film has an amorphous structure when deposited at temperature of Ts = 280 C and concentration of 0.025 M. At higher temperatures (Ts = 320, 360, 400 C) and solution concentrations (0.05, 0.075, 0.1 M), the deposited films have cubic polycrystal- line structure formed with preferred orientation along (111) plane. The band gap of NiO film increases from 3.4 to 3.8 eV as the molarity decreased from 0.1 to 0.05 M.

Spray Coated Nanostructured Nickel Oxide Thin Films for Ethanol Sensing

Spray Coated Nanostructured Nickel Oxide Thin Films for Ethanol Sensing

Synthesis and characterization of nanostructured nickel oxide thin films prepared with chemical spray pyrolysis

Nickel oxide thin films have been deposited in an open atmosphere onto glass substrates by chemical spray pyrolysis using aqueous nickel acetate solutions and air as driving gas. The films show a strong variation in the surface morphology depending on the substrate temperature and the precursor solution flux. At 350 °C substrate temperature, a reticular tissue-like film morphology is obtained, becoming the reticular nickel oxide fibres of the film thicker with increasing precursor solution flux. At 450 °C substrate temperature, the film growth rate is 4 times slower and a highly symmetric self-ordering of the material at nanometer length scale occurs. These films consist of interconnected grains separated by pores, both of about 100 nm in size. XRD and TEM revealed that the films are cubic NiO, being the crystallite size around 10 nm. The optical band gap of the films decreases strongly for increasing film thickness from 4.3 eV to 3.65 eV.

Electrochromic properties of nano-structured nickel oxide thin film prepared by spray pyrolysis method

In this study, we present a simple method to improve the electrochromic properties of a nickel oxide thin film. The method involves a three-step process—(a) conducting indium tin oxide (ITO) nano-particles were first sprayed onto a conducting substrate to form a porous nano-structured ITO layer, (b) nickel oxide film was then deposited onto the nano-structured ITO layer by a spray pyrolysis technique, and (c) the substrate, ITO nano-particles layer and nickel oxide film were annealed at high temperature of 300 °C to improve adhesion of these three layers. The microstructure of the resulting electrochromic cell was investigated using scanning electron microscopy. It is evident that the nickel oxide film covers the surface of the ITO nano-particle layer and forms a nano-structured nickel oxide (NSNO) film. The switching time and contrast were characterized by Autolab PGSTAT12 potentiostat and Jasco V-570 spectrophotometer. The results suggest that the transmittance contrast and switching time of NSNO are slightly superior to those of a conventional nickel oxide (CNO) film. However, the cycling durability of NSNO can be much better than that of CNO.

Preparation and characterization of nanostructured NiO thin films by reactive-pulsed laser ablation technique

Nanostructured nickel oxide (NiO) thin films were prepared using pulsed laser ablation technique on heated quartz substrates under an oxygen partial pressure of 2×10 −3 mbar. X-ray diffraction (XRD) studies indicate enhancement in growth along (1 1 1) and (2 0 0) crystal planes with increase of substrate temperature. The atomic force microscopic (AFM) studies indicate a self-assembly of NiO nanocrystals having size ∼84 nm, with a uniform height profile along the assembly for films prepared at a substrate temperature of 673 K. Formation of arrays of confined two-dimensional NiO layers in the films prepared at a substrate temperature of 473 K is also reported. The optical band gap and electrical resistivity of the films synthesized under different deposition conditions are also discussed.

Nanostructured mesoporous nickel oxide thin films

Nanostructured nickel oxide thin films were prepared by the pulsed laser ablationtechnique. The effects of annealing on the structural, morphological, electrical and opticalproperties are discussed. Phase imaging was used to examine the surface contaminants,adhesion and hardness and height imaging to evaluate the height profile of the films.Morphological investigations using atomic force microscopy and scanning electronmicroscopy indicate a strong influence of the annealing process on the surfaceroughness and particle size. A self-assembly of nanocrystals agglomerating togetherto form an island-like structure is observed in films annealed at 773 K. X-raydiffraction and x-ray photoelectron spectroscopy investigations indicate the presence ofNi2O3 in the as-deposited films. A transformation to cubic NiO with growth along (111) and (200)planes with increase of annealing temperature is also observed.

Preparation and characterization of Eosin B- and Erythrosin J-sensitized nanostructured NiO thin film photocathodes

Nickel oxide (NiO) thin films were prepared onto ITO/glass substrates by spin-coating, dipping and electrochemically. Studies of the morphological and structural properties of the films were done by atomic force microscopy (AFM). Photoelectrochemical and optical experiments were carried out in order to characterize the semiconductor properties of the nanostructured NiO thin films. The experiments were also done for Eosin B- and Erythrosin J-sensitized nanostructured NiO films, with the aim to visualize their potential application as photocatodes in tandem dye-sensitized solar cells (TDSSC). The NiO grown by dipping was the one presenting the best morphological properties. The photoelectrochemical results for all the bare NiO, NiO–Eosin B and NiO–Erythrosin J/electrolyte (I 2/I −) systems showed a p-type behavior. An enhancement in the photocurrent has been observed for the systems sensitized with the dyes. For the NiO/Erythrosin J system the enhancement of the current under illumination in comparison to the dark current was about 200%.