Nickel Oxide Nanoparticles: A Brief Review of Their Synthesis, Characterization, and Applications

Noncovalent Interactions of Surface Adsorbed Species Control the Self-Assembly of Calcinated Nickel Oxide Nanoparticles

Utilizing state of the art diffraction, imaging and spectroscopic techniques in conjunction with two-dimensional correlation analysis, we provide novel in-depth insights into the physics and chemistry behind the different tendencies towards self-assembling in NiO nanoparticles as function of their surface facets. We demonstrate substantially different temperature dependence of the spectroscopic behavior of the two types of NiO NPs, polar versus non-polar faceted. Temperature-dependent spectroscopy data for NiO NPs obtained by the ammonia route are consistent with the process in which high amount of water molecules that take part in hydrogen-bonding interaction with the surface-adsorbed non-dissociated water molecules on the neutral (100) planes are lost during the thermal treatment and attached back upon cooling. Interactions between water molecules adsorbed on two vicinal NiO NPs are responsible for keeping the self-assembly of the Ni(OH)2 NPs upon heat treatment. In carbamide-based NiO NPs, the self-assembly of initially formed Ni3(OH)4(NO3)2 NPs is not preserved. These NPs are terminated with polar (111) atomic planes, on which water molecules dissociatively adsorb, giving surface hydroxyl groups. As the hydrogen bonding proton - donating and accepting abilities are negligible at OH-polar terminated NiO NPs, only unfavorable inter-NP interactions are possible which leads to disruption of the NP assembly.

Quantification of L-lactic acid in human plasma samples using Ni-based electrodes and machine learning approach

This work presents a robust strategy for quantifying overlapping electrochemical signatures originating from complex mixtures and real human plasma samples using nickel-based electrochemical sensors and machine learning (ML). This strategy enables the detection of a panel of analytes without being limited by the selectivity of the transducer material and leaving accommodation of interference analysis to ML models. Here, we fabricated a non-enzymatic electrochemical sensor for L-lactic acid detection in complex mixtures and human plasma samples using nickel oxide (NiO) nanoparticle-modified glassy carbon electrodes (GCE). This paper presents a data-driven approach for developing transducers that reduce interference effects using ML with a sufficiently large dataset. The interference trends of uric acid, ascorbic acid, and glucose were measured in the presence of L-lactic acid and the complex data set was analyzed using various ML models. Limit of detections of 2.61 μM, 15.99 μM, 11.34 μM, and 3.27 μM for L-lactic acid, uric acid, glucose, and ascorbic acid were obtained, respectively, in a complex mixture using an artificial neural network-based-regression model. Further, the electrochemical signature was recorded for 10 different human plasma samples and analyzed using developed ML models to validate the sensor performance in real samples. The random forest model performance was tested against the L-lactic acid levels in human plasma samples obtained through conventional colorimetric assays which showed a good prediction performance with coefficient of determination (R2), limit of detection (LOD), and limit of quantitation (LOQ) values of 0.99, 1.3 μM, and 4.4 μM respectively. By further miniaturization and integration of such sensors into point-of-care testing devices, metabolic profiles of different redox-active species related to the measurement of the predictive value of sepsis can be managed.

Hsa_circ_0001944 Regulates FXR/TLR4 Pathway and Ferroptosis to Alleviate Nickel Oxide Nanoparticles-Induced Collagen Formation in LX-2 Cells

Nickel oxide nanoparticles (NiONPs) can induce liver fibrosis, and their mechanism may be related to non-coding RNA, nuclear receptor signal transduction and ferroptosis, but the regulatory relationship between them is not clear. In this study, we aimed to investigate the role of hsa_circ_0001944 in regulating the Farnesol X receptor (FXR)/Toll-like receptor 4 (TLR4) pathway and ferroptosis in NiONPs-induced collagen deposition. We observed decreased FXR expression, increased TLR4 expression and alterations in ferroptosis features in both the rat liver fibrosis and the LX-2 cell collagen deposition model. To investigate the regulatory relationship among FXR, TLR4 and ferroptosis, we treated LX-2 cells with FXR agonist (GW4064), TLR4 inhibitor (TAK-242) and ferroptosis agonist (Erastin) combined with NiONPs. The results showed that TAK-242 alleviated collagen deposition by increasing ferroptosis features. Furthermore, GW4064 reduced the expression of TLR4, increased the ferroptosis features and alleviated collagen deposition. The results indicated that FXR inhibited the expression of TLR4 and enhanced the ferroptosis features, which were involved in the process of collagen deposition in LX-2 cells induced by NiONPs. Subsequently, we predicted that hsa_circ_0001944 might regulate FXR through bioinformatics analysis, and found NiONPs reduced the expression of hsa_circ_0001944 in LX-2 cells. Overexpression of hsa_circ_0001944 increased FXR level, reduced TLR4 level, increased the ferroptosis features and alleviated collagen deposition in LX-2 cells. In summary, we demonstrated that hsa_circ_0001944 regulates the FXR/TLR4 pathway and ferroptosis alleviate collagen formation induced by NiONPs.

An octahedral metal oxide nanoparticle-based dual-signal sensing platform for simultaneous detection of histidine and lysine in human blood plasma and urine

Histidine and lysine serve as essential amino acids in physiological processes and biomarkers for specific diseases, requiring precise detection methods in a variety of samples. This study presents an affordable single colorimetric probe that employs nickel oxide nanoparticles (NiONPs) as an artificial enzyme to detect histidine and lysine, improving conventional analytical limitations. The characterization of NiONPs was executed using SEM-EDX, FE-SEM, FTIR and XRD. The NiONPs demonstrated peroxidase-like catalytic activity on the conversion of TMB to oxidized TMB (oxTMB) in the presence of H2O2, utilizing optimization parameters like pH value (3), TMB concentration (10 mM), H2O2 concentration (60 mM), and incubation time (18 min). The study revealed that Ni and O atoms are present on the surface of NiONPs, allowing for specific interactions with essential amino acids and temporarily hindering the catalytic activity of oxidized TMB. The method exhibited a low limit of detection (LOD) of 0.07 μM (10-100 μM) for histidine and 1.1 μM (15-150 μM) for lysine with good stability. The proposed strategy was validated with urine and plasma samples, yielding favorable recoveries of 93.6-98.2% in urine and 90.5-96.0% in plasma for histidine and 91.2-94.8% in urine and 88.4-93.3% in plasma for lysine, supporting its selectivity, feasibility, and reliability for practical applications. In the future, this methodology will facilitate the integration of histidine and lysine detection into microfluidic systems using NiONPs as a colorimetric probe.

Tailoring the Heterointerfaces of Earth-Abundant Transition-Metal Nanoclusters on Nickel Oxide Nanosheets for Enhanced Overall Water Splitting through Electronic Structure Optimization

Evolving highly competent and economical electrocatalysts for alkaline water electrolysis is crucial in renewable hydrogen energy technologies. The slow hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) kinetics under alkaline electrolytes, still, has troubled developments in high-performance green hydrogen production systems. Herein, we demonstrate the tailoring of the interface of earth-abundant transition-metal nanoclusters (MNCs), including iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) nanoclusters on nickel oxide nanosheets (M NCs|NiO NS) through metal-support interaction for enriched overall water splitting under an alkaline electrolyte. The strong metal-metal oxide interaction allows alteration of the binding capabilities of hydrogen ions (*H) and hydroxyl ions (*OH) on Ni electrodes. Specifically, the robust interaction between Fe and NiO reveals optimized binding of H* and OH* energies, facilitating the water-splitting reaction under an alkaline electrolyte. In addition, the improved HER/OER catalytic activity is attained with the Fe NCs|NiO NS with small overpotentials of ∼62.0 and ∼380.0 mV for the HER and OER, respectively, a high mass activity of ∼90.0 A g-1, a turnover frequency of ∼5.94 s-1, and long-lasting stability via offering abundant electrochemical active sites, three-dimensional (3D) morphologies, and high dispersion of nanoclusters that provide effective charge and mass transport processes. This study provides a promising strategy for the effective design of efficient bifunctional electrocatalysts based on earth-abundant materials for alkaline water electrolyzers.

3D self-assembled polar vs. non-polar NiO nanoparticles nanoengineered from turbostratic Ni3(OH)4(NO3)2 and ordered β-Ni(OH)2 intermediates

A surfactant-free ammonia and carbamide precursor-modulated engineering of self-assembled flower-like 3D NiO nanostructures based on ordered β-Ni(OH)2 and turbostratic Ni3(OH)4(NO3)2 nanoplate-structured intermediates is reported. By employing complementary structural and spectroscopic techniques, fundamental insights into structural and chemical transformations from intermediates to NiO nanoparticles (NPs) are provided. FTIR, Raman and DSC analyses show that the transformation of intermediates to NiO NPs involves subsequent loss of NO3- and OH- species through a double-step phase transformation at 306 and 326 °C corresponding to the loss of free interlayer ions and H2O species, respectively, followed by the loss of chemically bonded OH- and NO3- ions. Transformation to NiO NPs via the ammonia route proceeds as single-phase transition, accompanied with a loss of OH- species at 298 °C. The full transformation to NiO NPs of both intermediates is achieved at 350 °C through annealing in the air atmosphere. Ammonia-derived NPs maintain nanoflower morphology by self-assembling into nanoplates, which is enabled by H2O-mediated adhesion on the NiO NPs' {100} neutral surfaces. Structural transformations of turbostratic Ni3(OH)4(NO3)2 nanoplates result in the formation of NiO NPs dominantly shaped by inert polar OH-terminated (111) atomic planes, leading to the loss of the initial self-assembled 3D structure. DFT calculations support these observations, confirming that H2O adsorbs dissociatively on polar {111} surfaces, while only physisorption is energetically feasible on {100} surfaces. NiO NPs obtained via two different routes have overall different properties: carbamide-derived NPs are 3 times larger (15.5 vs. 5.4 nm), possess a larger band gap (3.6 vs. 3.2 eV) and are more Ni deficient. The intensity ratio of surface optical (SO) modes to transversal and longitudinal optical modes is ∼40 times higher in the NiO NPs obtained from β-Ni(OH)2 compared to Ni3(OH)4(NO3)2-derived NPs. The SO phonon lifetime is an order of magnitude shorter in NiO obtained from β-Ni(OH)2, reflecting a much smaller NP size. The choice of a precursor defines the size, morphology, crystallographic surface orientations and band gap of the NiO NPs, with Ni deficiency providing pathways for utilizing them as p-type materials, allowing for the precise nanoengineering of polar and neutral surface-dominated NiO NPs, which is of exceptional importance for use in catalysis.

Rapid Growth of Metal-Metal Oxide Core-Shell Structures through Joule Resistive Heating: Morphological, Structural, and Luminescence Characterization

The aim of this study is to prove that resistive heating enables the synthesis of metal/metal oxide composites in the form of core-shell structures. The thickness and morphology of the oxide layer depends strongly on the nature of the metal, but the influences of parameters such as the time and current profiles and the presence of an external field have also been investigated. The systems chosen for the present study are Zn/ZnO, Ti/TiO2, and Ni/NiO. The characterization of the samples was performed using techniques based on scanning electron microscopy (SEM). The thicknesses of the oxide layers varied from 10 μm (Zn/ZnO) to 50 μm (Ni/NiO). In the case of Zn- and Ti-based composites, the growth of nanostructures on the oxide layer was observed. Micro- and nanoneedles formed on the ZnO layer while prism-like structures appeared on the TiO2. In the case of the NiO layer, micro- and nanocrystals were observed. Applying an external electric field seemed to align the ZnO needles, whereas its effect on TiO2 and NiO was less appreciable, principally affecting the shape of their grain boundaries. The chemical compositions were analysed using X-ray spectroscopy (EDX), which confirmed the existence of an oxide layer. Structural information was obtained by means of X-ray diffraction (XRD) and was later checked using Raman spectroscopy. The oxide layers seemed to be crystalline and, although some non-stoichiometric phases appeared, the stoichiometric phases were predominant; these were wurtzite, rutile, and cubic for Zn, Ti, and Ni oxides, respectively. The photoluminescence technique was used to study the distribution of defects on the shell, and mainly visible bands (2-2.5 eV), attributed to oxygen vacancies, were present. The near-band edges of ZnO and TiO2 were also observed around 3.2-3.3 eV.

Marine carrageenan‐based NiO nanocatalyst in solvent‐free synthesis of polyhydroquinoline derivatives

This study presents the preparation of nickel oxide nanoparticles (NiO NPs) in the presence of marine seaweed kappa‐carrageenan (κ‐carrageenan) polysaccharide as a green stabilizer and coating agent under optimal conditions. Thermal gravimetric analyzer (TGA) and Fourier transform infrared (FTIR) results revealed thermal stability and the presence of functional groups of κ‐carrageenan‐coated NiO (NiO@κ‐Car) NPs. The color change of the solution from green to black and advent peak at 320 nm primitively confirmed the formation of NiO NPs. Further, transmission electron microscopy (TEM) images of NiO@κ‐Car demonstrate rather irregular spherical and cubic morphology, showing an average size of 18 ± 1.5 nm. Further, X‐ray diffraction (XRD) analysis confirms that NiO NPs appear as cubic crystal structures with a crystallite size of 23.7 nm. According to the turnover number (TON) and turnover frequency (TOF) results, green NiO@κ‐Car exhibits superior catalytic efficiency in one‐pot multicomponent synthesis of polyhydroquinoline derivatives under free‐solvent conditions. Hydrogen‐1 (1H) and carbon‐13 (13C) nuclear magnetic resonance (NMR) spectra indicated the successful synthesis of various organic products. The key advantages of the proposed efficient synthetic protocol include reusability of the catalyst (four runs), simple workout, high yield of the products, environmental sustainability, and solvent‐free reaction condition. A possible mechanism was also suggested, indicating the role of NiO@κ‐Car as a proficient heterogeneous nanocatalyst in the reaction.

Biomedical Applications of Biosynthesized Nickel Oxide Nanoparticles

Nickel oxide nanoparticles have gained tremendous attention recently in a variety of scientific domains thanks to their characteristic chemical, physical, optical, and biological properties. Due to the diversity of applications in various fields, different physicochemical methods have been used to synthesize nickel oxide nanoparticles. However, most conventional methods use hazardous chemicals during synthesis and become liable for potential health risks, while others are expensive and require a lot of energy to synthesize nanoparticles. As a result, the nanoparticles become less biocompatible and biologically inefficient. Biogenic synthesis of nanoparticles is currently proposed as a valuable alternative to the physical and chemical methods, as it is a simple, non-toxic, cheap, green and facile approach. This synthetic method uses biological substrates such as plant extracts, microorganisms, and other biological products to synthesize nickel oxide nanoparticles. The various phytochemicals from plant extracts, enzymes or proteins from microorganisms, and other biological derivatives play as reducing, stabilizing, and capping agents to provide bioactive and biocompatible nickel oxide nanoscale material. This review discusses current findings and trends in the biogenic synthesis of nickel oxide nanoparticles and their biological activities such as antibacterial, antifungal, antileishmanial, and anticancer, with an emphasis on antimicrobial and anticancer activity along with their mechanistic elucidation. Overall, this thorough study provides insight into the possibilities for the future development of green nickel oxide nanoparticles as therapeutic agents for a variety of ailments.

Metal Oxide Nanoparticles: Review of Synthesis, Characterization and Biological Effects

In the last few years, the progress made in the field of nanotechnology has allowed researchers to develop and synthesize nanosized materials with unique physicochemical characteristics, suitable for various biomedical applications. Amongst these nanomaterials, metal oxide nanoparticles (MONPs) have gained increasing interest due to their excellent properties, which to a great extent differ from their bulk counterpart. However, despite such positive advantages, a substantial body of literature reports on their cytotoxic effects, which are directly correlated to the nanoparticles' physicochemical properties, therefore, better control over the synthetic parameters will not only lead to favorable surface characteristics but may also increase biocompatibility and consequently lower cytotoxicity. Taking into consideration the enormous biomedical potential of MONPs, the present review will discuss the most recent developments in this field referring mainly to synthesis methods, physical and chemical characterization and biological effects, including the pro-regenerative and antitumor potentials as well as antibacterial activity. Moreover, the last section of the review will tackle the pressing issue of the toxic effects of MONPs on various tissues/organs and cell lines.

Enhancement of Surface and Interface Properties of Low Carbon Steel by Hybrid ZnO and NiO Nanoparticles Reinforced Tin Coating

Tin matrix nanocomposite coatings containing ZnO and NiO nanoparticles, both individually and combined, were deposited on low carbon steel substrates. The aim was to investigate the effect of reinforcement of nanoparticles on microstructural morphology and thickness of tin coatings, modification in the interfacial layer between coating and substrate, and the corrosion resistance of low carbon steel substrate. Optical and scanning electron microscopy were employed for microstructural observation, while potentiostat-galvanostat was utilized for electrochemical investigation. It was found that the tin nanocomposite coatings with nanoparticles significantly modified the coating thickness, intermetallic layer thickness, and surface corrosion resistance. Coatings through the direct tinning process are considered to be a simple and low-cost route for protecting metallic materials from corrosion, and the presence of ZnO and NiO nanoparticles in tin coatings further increases the corrosion resistance of low carbon steels.