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Green nanomaterials have been extensively used in the environmental and agricultural applications due to their advantages of biocompatibility, eco-friendly, and cost-effectiveness. In this study, we have employed P. granatum leaf extract as a capping and stabilizing agent for the biofabrication of nickel oxide (NiO) nanoparticles to remove dyes effectively. The key factors which influenced the removal of Methylene Blue (MB) and Congo Red (CR) dyes under both visible and UV light exposure were identified. The experimental findings demonstrated the significant degradation efficiencies, with MB and CR reaching degradation levels of 91.7 % and 81.2 %, respectively. Furthermore, the face-centered cubic (fcc) structure with a space group of (Fm3m) of NiO was observed from the powder X-ray diffraction (XRD) analysis. Additionally, the morphology of NiO nanoparticles were investigated using scanning electron microscopy (SEM). Morphological analysis using high-resolution transmission electron microscopes (HR-TEM) with energy-dispersive X-ray spectroscopy (EDX), revealed the formation of spherical, cylindrical, and rod-shaped, nanoparticles and their elemental composition respectively. Fourier-transform infrared spectroscopy (FTIR) analysis has provided valuable insights into the molecular vibrations and the formation of Ni-O bonds within the NiO lattice. In the PL spectrum, the observed emission peaks at 484 and 545 nm indicate the presence of defects within the NiO structure. Raman spectroscopy further confirms the 2M vibrational mode and a reduction in antiferromagnetic coupling in the samples. Additionally, investigations on NiO nanoparticles at concentrations ranging from 50 to 500 mg/ml have exhibited their influence on bacterial activity against Bacillus cereus and Bacteroides fragilis. [ABSTRACT FROM AUTHOR]

Metal oxides are recognized as exemplary materials for photocatalytic dye degradation attributed to their unique characteristics such as tunable electronic structure, prolonged stability, and cost-effectiveness. However, the wide band gap inherent to most of these materials often limits their light absorption to the ultraviolet (UV) region. Consequently, the doping of noble metal nanoparticles into the metal oxide nanostructures has been proposed to significantly improve their light-harvesting ability. This enhancement is primarily ascribed to the localized surface plasmon resonance (LSPR) effect associated with noble metal nanoparticles, which facilitates more effective utilization of light. Thus, in this study, we synthesized silver-doped nickel oxide (Ag:NiO) with varying Ag concentrations (0, 1, 2, 4, 6 wt%) to evaluate their photocatalytic performance. The X-ray diffraction (XRD) spectra revealed that NiO possesses a cubic crystalline structure, and a peak shift to a higher angle was noted for Ag doping, indicative of compressive strain. Further analyses of morphological, vibrational, and absorption properties were conducted through the acquisition of scanning electron microscopy (SEM) images, Raman spectra and UV–Vis absorption spectra, respectively. The photocatalytic degradation of methylene blue (MB) and rhodamine B (RhB) dyes was assessed, revealing that NiO with 4.wt.% Ag doping exhibited enhanced photocatalytic activity, achieving 99% degradation of MB and 90% degradation of RhB. Notably, Ag doping significantly enhances the light absorption capabilities and modifies the electronic structure of the NiO, thereby improving its performance in photocatalytic dye degradation. • A novel strategy is proposed to improve the photo-catalytic ability of wide bandgap NiO. • Different concentration of Ag was doped into the NiO lattice. • The LSPR properties of Ag dopants will significantly improve light absorption in the visible region. • Most importantly, 99 % of MB degradation and 90 % of RhB degradation were achieved by Ag dopants. • Catalyst's high degradation efficiency towards MB Dye can be highly useful in wastewater treatment. [ABSTRACT FROM AUTHOR]

In this work, resistive type photodetectors were fabricated using Gd3+ ions doped NiO nanoparticles to improve the detection of ultraviolet (UV) light. The occurrence of the simple cubic phase in NiO systems has been shown by X-ray diffraction patterns. The crystalline size of the NiO nanoparticles doped with different concentrations of Gd3+ at levels of pure, 1 %, 2 %, and 3 % were 6 nm, 8 nm, 9 nm, and 12 nm, respectively. The presence of dopants in the material was established by the Raman spectrum analysis. Transmission electron microscopy (TEM) pictures were used to validate the morphological properties of Gd3+ doped NiO nanoparticles nanoparticles at different degrees of dopant concentration (0 %, 1 %, 2 % and 3 %). The introduction and concentration of dopants alter the shape of NiO material. Based on the findings of UV–visible absorption spectroscopic studies, it can be concluded that the addition of Gd3+ ions to the system improved the absorption characteristics. The measured bandgap values for various degrees of Gd3+ doping, namely 0 %, 1 %, 2 %, and 3 %, are 3.51 eV, 3.45 eV, 3.36 eV, and 3.23 eV, respectively. According to the measured photoluminescence spectrum, Gd3+ ions may efficiently trap and maintain excited electrons within an energy level between the ground and excited states. This process greatly extends the lifespan of excitons from immediate recombination. The use of Gd3+-doped NiO sensors in UV photodetection resulted in a significant increase in conductivity and photocurrent. The photodetector fabricated using a 3 % concentration of Gd3+ doped NiO, has a responsivity of 24 × 10−2 AW−1, a detectivity of 14 × 109 Jones, and an external quantum efficiency (EQE) of 62 %. • Simple cubic phase NiO with Gd3+ doping, crystalline sizes up to 12 nm. • TEM confirms morphological changes, Ni 1-x Gd x O (x = 0 to 3). • Reduced bandgap: 3.51 eV–3.23 eV with Gd3+ doping. • Enhanced photodetection: Responsivity 24 × 10−2 AW−1, EQE 62 %. [ABSTRACT FROM AUTHOR]

Nickel oxide nanoparticles were synthesized via calcination of organometallic chelate. The adsorption of acid yellow 99 (AY99) was examined using produced NiO at temperatures of 450°C, 550°C, and 650°C. Different spectroscopic studies were used to characterize the synthesized NiO as an example (XRD) X-ray diffraction, FTIR, energy-dispersive X-ray spectroscopy (EDX), including the Brunauer–Emmett–Teller (BET) variable surface area, which was 156.036 m2 /g. Scanning electron microscopy (SEM) got accustomed to quantifying the changes on the surface. Initial pH, for example, is variable to consider, the dose of adsorbent, time of contact, temperature, and the point of zero charging (pHPZC) of NiO was designed and established to be 7.3. To discover the best adsorption conditions for extracting (AY99) from aqueous media, researchers looked into a variety of factors. Langmuir isotherm was shown to closely resemble the experimental values. To characterize the dye getting, the pseudo-second-order represents growth was adopted. This was also shown that adsorption has a high activation energy of 24.8 kJ/mol, this indicates that the adsorption obeys the chemisorption process. To determine adsorption equilibrium parameters, the Langmuir isotherm was utilized. Several thermodynamic constraints, for example, ΔG°, ΔH°, and ΔS° were calculated at various temperatures. The thermodynamics of the adsorption mechanism was discovered to be endothermic, random, and spontaneous. Compare the results of adsorption of AY99 over the NiO was 766.35 mg/g with other adsorbents and found it is the best one for removal. [ABSTRACT FROM AUTHOR]

In this study, we described a green, sustainable, and feasible method for synthesizing 5 nm NiO nanoparticles. Eggplant skin was chosen as an appropriate bio-template with a high potential to induce its structure into the desired metal oxide. Two approaches were used and compared to synthesize NiO bio-template: hydrothermal and sol-gel. The morphology and physical properties of the obtained NiO nanoparticles were evaluated using FESEM, TEM, XRD, BET, FT-IR, TGA, and UV–Vis analyses. All these methods confirm that the hydrothermal method is a better approach for synthesizing NiO bio-template nanoparticles than the sol-gel method. UV–Vis analysis revealed that the NiO nanoparticles produced by the hydrothermal method have a low bandgap of 2.88 eV, which is a key factor for photocatalytic applications. [ABSTRACT FROM AUTHOR]

Photocatalytic CO 2 conversion, in general, requires the incorporation of expensive and noble materials to achieve a highly efficient conversion rate. Herein, the TNT/NiO/CQD ternary nanocomposites without any expensive materials and material modification are fabricated for the demonstration of efficient and economically affordable photocatalytic CO 2 conversion, to our best knowledge, for the first time. The TNT-based ternary photocatalysts are successfully prepared by a simple anodization and immersion process. The TNT/NiO/CQD ternary nanocomposites produce 1.47 μmol·cm-2·h-1 (≈ c.a. 2834 μmol·g-1·h-1) of CH 4 as the sole product under AM 1.5 illumination. This is five times higher performance than that of bare TNT and the performance is comparable to that of any other TiO 2 -based unitary, binary, or ternary photocatalysts. This highly enhanced performance results from effective junction formation between TNT and NiO NP, and the dual role of CQDs as a light absorber and charge transporter/collector in the system. The formation of Z-scheme at the TNT/NiO interface leads to efficient charge transfer via a TiO 2 /NiO bond. The light absorption of the photocatalysts is enhanced and extended by decorated CQDs due to their small band gap. The charge transfer and collection are further improved by charge depletion at the TNT/CQD interface and the charge transfer at the NiO/CQD interface. This work provides a possible model for the realization of efficient and economically affordable photocatalytic CO 2 conversion. [ABSTRACT FROM AUTHOR]

The aim of this research was to fabricate active nanocomposite films by incorporation of nickel oxide nanoparticles (NiONPs) (3, 6 and 9% w/w) into the chitosan-based films. The NiONPs were synthesized by solution combustion method and the films were prepared by solvent casting method. The formation of new interactions and increasing of films' crystallinity were confirmed by FT-IR and XRD analyses. Uniform dispersion of NiONPs at lower concentrations and their aggregation at level of 9% was confirmed by FE-SEM observations. Water barrier properties, tensile strength, thermal properties and surface hydrophobicity of films enhanced by addition of 6% NiONPs. Photocatalytic activity of nanocomposites was confirmed by absorption of 72% of methyl orange during 270 min under UV irradiation. The nanocomposite films exhibited good antibacterial activity against gram-positive (S. aureus) and gram-negative (S. typhimurium) bacteria. Therefore, the chitosan-NiONPs nanocomposite films could be used for active food packaging applications and photodecolorization purposes. [Display omitted] • Chitosan/NiONPs nanocomposite films were prepared by incorporating 3–9% synthesized NiONPs. • Incorporation of NiONPs improved thermal stability and crystallinity of chitosan films. • Large aggregates were observed at morphology of films containing high amounts of NPs. • Strong antimicrobial activity was observed against Gram-positive and Gram-negative bacteria. • Good photocatalytic activity of films was approved by more than 72% dye absorption capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simultaneous improvement of H 2 O 2 production and selectivity using NiO nanoparticles. • The presence of NiO nanoparticles promotes CN charge separation and adsorption strength for oxygen. • The loading of NiO nanoparticles greatly reduces the energy barrier for the activation of *O 2 to *OOH. The use of solar photocatalysis to produce H 2 O 2 as a new strategy alternative to the anthraquinone method, is less resource intensive and more environmentally friendly. In this study, carbon nitride (CN) loaded with NiO nanoparticles (CN-NiO) was used as photocatalyst for the generation of H 2 O 2 through two electron oxygen reduction reactions (ORR). The existence of NiO nanoparticles improves both the photoactivity and selectivity of the carbon nitride towards two electron ORR. CN-NiO photocatalyst reaches 86 % selectivity for 2e− ORR, and a yield of 4054.1 μmol g−1h−1 for H 2 O 2 generation under simulated sunlight, which is 2.7 times of that for bare CN. NiO nanoparticles promote the separation efficiency of photogenerated electrons and holes in photocatalysts, and also serve as adsorption sites for O 2 , enhancing the adsorption of O 2. Additionally, DFT calculations show that the loading of NiO nanoparticles greatly reduces the energy barrier for the activation of *O 2 to *OOH, which facilitates the efficient 2e− ORR photocatalysis. This study may advance knowledge regarding the function of metal oxide nanoparticles in the photocatalytic synthesis of H 2 O 2. [ABSTRACT FROM AUTHOR]

Wastewater treatment has always remained a precarious issue in the context of its environmental impacts and tackling of varied nature of contaminants. Plant-mediated NiO nanoparticles (G-NiO NPs) offer a way out to resolve these issues by presenting quick, cost-effective, less tedious and environmentally friendly approach to remove the potentially harmful multi-contaminants like endocrine- disrupting chemicals (for example reactive dyes, pesticides and phthalates) and microbial contaminants effectively. The formation of nanoparticles was confirmed by UV-Vis spectrophotometer, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron scanning electron microscopy, energy-dispersive X-ray spectroscopy and AFM. The adsorption data was applied to various kinetic models, diffusion models and adsorption isotherms. Fitting of experimental data to these models showed best-fit models to be Avrami-fractional kinetic model and Liu adsorption model in all three cases (reactive red dye, bifenthrin and dioctyl phthalate) with adsorption capacities of 374.7, 34.85 and 323.59 mg g-1, respectively. G-NiO NPs also proved potentially viable against E. coli with a 93% reduction in the microbial count. [ABSTRACT FROM AUTHOR]

Quaternary nanocomposite films with favorable electrical and optical properties have been produced by adding nickel oxide nanoparticles (NiO NPs) to polyvinyl alcohol (PVA), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), and polypyrrole (PPy) with a solution casting technique. In this study, different concentrations of NiO NPs were added to pure PVA/PEDOT:PSS/PPy blends and investigated through various characterization methods. From transmission electron microscopy (TEM) and X-ray diffraction (XRD) observations, the synthesized NiO NPs have a cubic phase and a diameter that varies between 6 and 40 nm. XRD analysis also indicates that the filling of PVA/PEDOT:PSS/PPy with NiO NPs results in a decrease in the crystallinity of the nanocomposites prepared. Raman analysis demonstrated the existence of prominent distinctive peaks associated with vibrational groups that characterize the synthesized samples, which change randomly with increasing concentrations of NiO NPs. In the UV/VIS spectrum for the PVA/PEDOT:PSS/PPy blend, there were two absorbance peaks at 202 and 224 nm that may result from π→π* and n→π* transitions. The results show that, by increasing NiO NP concentrations, UV/Vis absorbance increased by about 44 % at wavelength ranges from 190 to 240 nm, while optical band gap energies for indirect transitions decreased from 4.96 to 4.85 eV. The AC electrical conductivity of the films has been investigated via impedance spectroscopy at frequencies from 10−1 to 107 Hz. As the NiO NPs concentration in the blend rises, the AC electrical conductivity increases and is shown to follow Jonscher's rule. Additionally, it has been demonstrated that nanoparticle concentration causes a rise in composite dielectric loss and dielectric constant. The reduction in the optical bandgap energies and the enhancement of electrical properties due to the filling with NiO NPs suggest the possibility of using the prepared nanocomposites in optoelectronic devices. • Quaternary nanocomposites are prepared by solution casting PVA/PEDOT:PSS/PPy/NiO. • NiO concentration allows tunable optical absorbance and energy band gaps. • NiO NPs had a significant effect on the electrical conductivity and dielectric properties of the nanocomposite films. • These nanocomposite films are potential candidates for future optoelectronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiO Nano particles are synthesised by green method using leaf extract of ocimum sanctum in aqueous medium. • For the first time, we have designed a symmetric supercapacitor device using NiO Nano particles. • The supercapacitor device prepared using NiO NPs could successfully glow ten red light emitting diodes for duration of 14 s when charged for 30 s. The nickel oxide nanoparticles (NiO NPs) are synthesized by a green method using the leaf extract of Ocimum sanctum (OS) as a reducing agent. The NiO NPs of different sizes are synthesized using various concentrations of leaf extract of OS. The average crystallite size and particle size of the NiO NPs is measured using XRD and Transmission electron microscope (TEM) respectively. The size of NiO NPs is observed to decrease from ∼ 17 nm to ∼ 13 nm with increase in concentrations of leaf extract of OS. The morphology and elemental analysis of the NiO NPs is carried out using Field emission scanning electron microscope (FE-SEM) and energy dispersive X-ray (EDX) analysis respectively. The cyclic voltammetric (CV) studies on electrode of NiO NPs showed a pseudocapacitive behavior with a specific capacitance of 100 Fg−1 at a scan rate of 100 mV/sec for the particles with the size of ∼ 13 nm. The Galvonostatic charge–discharge studies showed a prolonged discharge time for the electrode of NiO NPs with size of ∼ 13 nm for a current density of 5 A/g. The electrochemical impedance spectroscopy (EIS) studies of electrodes of NiO NPs indicate the electric double layer capacitance (EDLC) and diffusion controlled pseudo capacitance behavior. The synthesized electrode shows capacitance retention of 84 % for 2500 cycles, is chosen for designing a supercapacitor device for glowing 10 red light emitting diodes (LEDs). Therefore, the use of leaf extract of OS is an ecofriendly alternative for synthesis of NiO NPs of different sizes that has applications in energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Increasing laser power shifts the Raman modes and changes their intensities. • Increasing laser power decreases 1LO/2LO intensity ratio. • Laser probe heating effect, lattice expansion, and spin-phonon coupling contribute. • Different polarizations lead to slight intensity fluctuations in first phonon mode. The effect of laser heating on the Raman spectra of pure, (Mg, Cu), and (Mg, Ru) codoped NiO nanoparticles was analyzed. Laser power increase (0.15–4.52 mW) caused Raman shifts and intensity variations that indicated stoichiometry and microstructural deviations. Raman spectra of (Mg, Ru) codoped NiO nanoparticles indicated the presence of RuO 2 secondary phase. At higher laser power, peaks associated with phonon modes of secondary phases were eliminated. The laser power impacted the structure by expanding the lattice, reducing instability, and substituting Ru into the lattice. Polarization-dependent Raman measurements showed symmetrical nature and preferred crystallization orientation of each sample. [ABSTRACT FROM AUTHOR]

Since carbon material was used as the electrode of perovskite solar cell (PSC), it has attracted wide attention because of its excellent thermal stability and low cost. However, serious charge recombination at the perovskite/carbon interface can lead to poor performance of carbon-based holeless PSCs. In this work, highly efficient and stable carbon-based PSC uses NiO nanoparticles as hole transport layer, which effectively promotes the separation and extraction of photogenerated carriers and inhibits the charge recombination at the perovskite layer/carbon electrode interface, thus improving the performance of the device. By optimizing the concentration of NiO nanoparticles, the power conversion efficiency (PCE) of carbon-based PSC reaches 13.6%. This work shows adding NiO nanoparticles between the perovskite film and the carbon electrode efficiently improve the hole extraction and the performance of PSC. [ABSTRACT FROM AUTHOR]

This study was aimed to synthesize nickel oxide (NiO) powder and its subsequent use in bactericidal activities by exploring the role of interaction at nanoparticle-bacteria interface of E. coli (gram negative) microorganism as well as water treatment by catalysing the two toxic azo dyes reduction reactions by sodium borohydride. The NiO nanoparticles were synthesized through single-step, residue free, in situ thermal decomposition method. Their size, structural and morphological features were confirmed through various analytical tools. An average size of 7-8 nm, high crystallinity and cubic crystal structure of the synthesized nanoparticles was confirmed by XRD and HR-TEM analyses. The NiO nanoparticles revealed virtuous bactericidal activities against pathogenic E. coli. Field emission scanning electron microscopy images were used as the evidence of the cell wall deterioration. The prepared NiO nanoparticles were also used in the catalytic reduction reactions of methyl orange (MO) and congo red (CR) dyes by sodium tetra-borohydrate. The reaction rate constants for the MO and CR were 0.4989 and 0.298 min-1, respectively. The reaction mechanism, comparison with other catalyst and recyclability of the NiO were discussed. [ABSTRACT FROM AUTHOR]

• Polymorphism of formed NiO nanoparticles with size in 25-50 nm was observed. • High toxicity of nanoparticles was witnessed against MG-63 cancer cells. • NiO nanoparticles revealed high biocompatibility on HEK293 normal cells. • Nanoparticles showed bactericidal activity on various human pathogenic bacteria. The green synthesis of metal oxide nanoparticles is interestingly becoming familiar as the reason of its non-toxicity, economical, eco-friendly, and commerciality. The secondary metabolites and bioactive molecules in biomaterial extract play an important role of reducing, capping, stabilizing and chelating activities to form the nanoparticles as a substitute of hazardous chemical surfactants. Hence this present work concentrated on the biogenic synthesis of NiO nanoparticles using grains extract of Oryza longistaminata (red rice), and their toxicity assessment as well as biomedical applications. The synthesized nanoparticles were widely characterized by using several analytical and biomedical techniques. The reduction mechanism of Ni2+ ions using major active phytocompound in red rice grains extract was stated. UV–visible spectroscopic analysis revealed the formation of NiO nanoparticles by emerging the sharp surface Plasmon resonance band at 326 nm. The absorption peaks of red rice grains extract at 206, 260, 330 and 410 nm stated the presence of phytocompounds in them. X-ray diffraction pattern explicated the high crystallinity of NiO nanoparticles and their average crystallite size was found to be at 36 nm. The diffraction pattern of red rice grains revealed the amorphous characteristic. Fourier transform infrared analysis displayed the different vibrational functional groups of nanoparticles and red rice grains. Dynamic light scattering analysis showed the particle size distribution was in between 30-65 nm. High-resolution transmission electron microscopic analysis showed the hexagonal, rectangular, oval and spherical shaped polymorphism of NiO nanoparticles and their size was in 25-50 nm. Energy dispersive X-ray spectrum and mapping analyses validated the formation of NiO nanoparticles by the major existence of Ni and O elements. The high toxicity of nanoparticles towards MG-63 osteosarcoma cancer cells was revealed at 94.69% in 100 μg/mL concentration. The nanoparticles showed no severe toxicity against HEK293 normal cells and red blood cells till higher concentration. The biomedical analyses such as antioxidant, anti-inflammatory and anti-diabetic activities exposed the potential bio-drug activity of NiO nanoparticles with maximum activity of 86.22, 84.23 and 85.18% in the high concentration of 80 μg/mL. The antibacterial activity divulged the good bactericidal drug nature of NiO nanoparticles against both Gram-positive (S. aureus and B. Subtilis) and Gram-negative (S. typhi and K. pneumonia) bacteria with low MBC/MIC ratio. As per the assessment of results, the biosynthesized NiO nanoparticles have non-carcinogenic, high biocompatible and potent nature and it suggests that they can be used as therapeutic candidates in biomedical, clinical and pharmaceutical fields for treating various diseases. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymer solar cells (PSCs) are limited in their power conversion efficiency (PCE) by trap-assisted recombination caused by localized deep trap states. Therefore, developing efficient hole transport layers (HTLs) for PSCs is essential for facilitating the hole extraction stage from the photoactive layers. As part of this study, an organic/inorganic hybrid HTL was prepared by mixing synthesized nickel oxide (NiO) nanoparticles (NPs) of average size ranging from 16 to 21 nm with poly(3-hexylthiophene) (P3HT). Based on this hybrid HTL, multilayer PSCs with an ITO/ZnO/P3HT:PC61BM/P3HT:NiO NPs/MoO 3 /Ag structure were fabricated and characterized. As a result of the incorporation of the optimum ratio of 5 wt% NiO NPs in the P3HT layer, the PCE obtained 3.73% compared to pristine devices (2.70%) fabricated without the P3HT layer. A charge extraction by increasing voltage (CELIV) measurement confirmed enhanced hole extraction at the active layer/HTL interface. The low fluorescence emission of the P3HT/NiO NPs film enabled efficient hole extraction at the active layer/hybrid HTL interface. Adding NiO NPs beyond 5 wt% to the P3HT layer causes deep trap states to form, which facilitated trap-assisted recombination and slowed down the mobility of the holes. Consequently, we can gain insight into how to improve PSC performance with hybrid HTL. • Multilayer polymer solar cells with an inverted structure were fabricated and characterized. • NiO NPs gradually incorporated into the P3HT layer increased hole mobility to 1.30 10−4 cm2 V−1 s−1. • PCE obtained 3.73% compared to pristine devices without the P3HT layer (2.70%). • Deeper trap levels in P3HT were induced by higher NiO NPs concentration, compromising hole transport mechanisms. [ABSTRACT FROM AUTHOR]

[Display omitted] A NiO/graphene nanocomposite has been prepared via one step electrochemical synthesis using simultaneous pulse alternating current dispersion of both Ni electrode and an electrode of thermally expanded graphite. Electron microscopy and Raman spectroscopy data reveals that the composite consists of graphene sheets with 2–5 layers having 0.5–2 μm size as well as NiO sheets with 200–250 nm dimensions comprising NiO nanoparticles of ∼3.6 nm diameter. The electrochemical capacitance of the nanocomposite is 825 F g−1, with retaining 89% of the initial value after 1000 operation cycles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • NiO doped by different transition elements nanoparticles were successfully prepared by chemical co-precipitation method. • Ferromagnetic behavior was observed for different doped NiO nanoparticles. • The optical band gap was strongly dependent on the doped transition element type. • These nanoparticles can be useful for biomedical applications. Abstract Pure and 2% Mn, Fe and Zn doped NiO nanoparticles were synthesized by co-precipitation method at calcination temperature 550 °C. They were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, proton induced x-ray emission, Rutherford Back Scattering, Fourier transmission infrared spectroscopy, UV-vis spectroscopy, M-H loop and electron paramagnetic resonance. The obtained results indicate that the lattice parameter, crystalline size, direct energy gap and chemical functional group are significantly dependent on the kind of dopant element. Moreover, the dopant elements are not affected by the ferromagnetic nature of NiO nanoparticles while g-factor varies according to the kind of dopant elements. [ABSTRACT FROM AUTHOR]

Abstract Dispersed nickel oxide nanoparticles (NiO-NPs) have been obtained through a "green" co-precipitation method using nickel nitrate hexahydrate and starch as Ni precursor and stabilizing/capping agent, respectively, while ammonia has been applied in the role of a complex agent throughout this procedure. The structural, photocatalyst, optical, and magnetic qualities of the NiO-NPs have been enquired into by FTIR, UV–Vis, XRD, FESEM, EDX, VSM, and TGA/DTG. Magnetic measurement has confirmed the superparamagnetic behavior of NiO-NPs at ambient temperature after calcination procedures. The band gap of NiO-NPs has been calculated to be about 3.55 eV and thus, this sample is a semiconductor that can be utilized as photocatalysts. According to the obtained results, about 80% of methylene blue (MB) degrades in the presence of NiO-NPs under UV light after 270 min. In vitro cytotoxicity investigations on cells has exhibited a dose-dependent toxicity with non-toxic consequences in concentrations below ∼7 μg/mL. The synthesis outcomes have shown that starch can be an interesting material with the potential of being employed as a stabilizer for preparing small nanoparticles, as well as being a bio-template for nanoparticles growth. Graphical abstract Image Highlights • A facile "green" method was developed to synthesize NiO-NPs in starch solutions. • It was observed that the size of spherical shape NiO-NPs is < 40 nm. • The formed NiO-NPs are characterized by FESEM and XRD. • Cytotoxicity of NiO-NPs showed a toxic effect on cancerous cells. [ABSTRACT FROM AUTHOR]

The sol-gel synthesized NiO nanoparticles were characterized and used for the modification of a carbon paste electrode (CPE) in electrocatalytic voltammetric determination of sulfasalazine. Calcination temperature of NiO had an important role on the peak current of the modified NiO-CPE and calcined NiO at 200 °C had the best and maximum peak current for the corresponding electrode. Jahn-Teller and a Z-out effects for the singlet electrons in their 3d z 2 orbital for calcined NiO at 200 °C relatively instable such electrons and hence they can easily participate in the electro-oxidation process. The electrochemical impedance spectroscopy (EIS) results confirmed that the modified CPE by calcined NiO at 200 °C has lower charge transfer resistance. In interaction effects study between the experimental variables by using the response surface methodology (RSM) approach, the optimized run included the 17.5% of NiO modifier, 0.5 M NaOH, amplitude of 295 mV, step potential of 7 mV and frequency of 15 Hz. A calibration plot in the range of 0.009–1.6 μM with limits of detection (LOD) and quantification (LOQ) of 0.002 and 0.006 μM was obtained, respectively. The modified electrode showed good selectivity and applicability for SSZ determination in complex matrixes. [ABSTRACT FROM AUTHOR]

The NiO/Nitrogen doped carbon sphere (NiO/NCS) composites were successfully achieved via an easy one pot synthetic method with urea acting as both nitrogen source and Ni precipitator. The electrocatalytic performances of the obtained NiO/NCS modified glass carbon electrodes showed superior activity for direct electrocatalytic oxidation of glucose than that of nitrogen free NiO/carbon sphere (NiO/CS), which might be due to the synergistic effect of the properties of NCS and NiO nanoparticles. The introduce of nitrogen can improve the conductivity of the NiO/NCS and accordingly accelerate the electron transport within the composites, which was very beneficial to improve the sensitivity to glucose detection for NiO/NCS modified electrodes. The NiO/NCS electrodes exhibited two corresponding linear regions of 1–800 μM and 4–9 mM with the sensitivity of 398.57 μA mM −1  cm −2 and 17.81 μA mM −1  cm −2 , and the detection limit of 0.25 μM and 0.05 mM respectively. Moreover, the NiO/NCS composites have also exhibited good selectivity by adding certain amount of urea, NaCl, l -proline, l -valine, l -Leucine and ascorbic acid into the 0.1 M NaOH solution, respectively. The high sensitivity, wide glucose detection range and good selectivity of the electrodes may ensure its potential applications in the clinical diagnosis of diabetes. [ABSTRACT FROM AUTHOR]

We have designed the solid-state electrochemical mixed potential type NiO and yttrium-stabilized zirconia (YSZ) composite based sensing electrode for selective detection of NO x at elevated temperatures. The planner NiO-YSZ composite sensing electrode could detect NO x even at 400 °C, with acceptable response/recovery rates. The change in emf values of the sensor varied linearly with NO x concentrations on a logarithmic scale in the range of 5–100 ppm. The response characteristic of the sensor was improved by modifying the surface with different vol% of pore former. As a result, obtained porous electrodes showed better response characteristics concerning speed and response owing to higher porosity. To improve response kinetics of porous NiO-YSZ electrode, NiO nanoparticles are infiltrated into an optimized NiO-YSZ sensing electrode surface by controlled urea/cation infiltration method. The experimental results demonstrated that NiO nanoparticles infiltrated NiO-YSZ sensor electrode reveal remarkably high emf response to NO x compared that of planar electrode, suggesting that NiO nanoparticles introduction can significantly enhance catalytic activity and electrochemical performance of NiO-YSZ electrode. Finally, the porosity effect of electrode subtracts (YSZ) with NO x gases response and recovery kinetics was examined under the optimum operating temperature at 400 °C. The sensing mechanism based on the mixed potential for the surface modified NiO-YSZ composite sensing electrode was discussed based on the obtained result of sensing characterizations. [ABSTRACT FROM AUTHOR]

Carbon-based hole conductor-free perovskite solar cells (PSCs) have attracted great attention due to the simple process, low cost and relatively high stability. However, the power conversion efficiency (PCE) is considerably lower than that of the standard PSCs using spiroOMeTAD as hole-conductor material and Au (or Ag) as counter electrodes. Herein, by means of incorporating p-type NiO nanoparticles into carbon electrodes, the PCE of the hole conductor-free PSCs was significantly boosted to 13.26% from 10.29% of that based on pure carbon electrode, because of the enhancement of hole transfer. In addition, the carbon-based hole conductor-free PSCs showed 85% of the initial efficiency after 800 h in ambient atmosphere. The results indicate that the p-type NiO nanoparticles can enhance hole transfer from perovskite into carbon electrodes, and the carbon electrodes can prevent the water in the air to improve stability. While the PSCs using Spiro-OMeTAD as hole conductor and Ag as electrodes have slightly lower PCE of 13.24% and lower stability. Hence, it is an effective strategy of incorporating p-type nanomaterials into carbon electrodes to enhance the carbon-based hole conductor-free PSCs. [ABSTRACT FROM AUTHOR]

(NiO) x (Bi 1.6 Pb 0.4 )Sr 2 Ca 2 Cu 3 O 10-δ composite, where 0.0 ≤ x ≤ 0.2 wt%., were prepared using solid state reaction method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). Vickers microhardness measurements (H V ) were carried out at room temperature under different applied loads varying from 0.49 to 9.8 N, and dwell times (40 and 59 s). It was noted that dwell time and Vickers microhardness were inversely proportional. H V values increase as x increases up to 0.1 wt%, and then they decrease with further increases in x. All samples exhibit indentation size effect (ISE) with normal trend, as Vickers microhardness decreases by increasing the applied loads. Also, Vickers microhardness measurements of the prepared samples were done during both loading forces up to 9.8 N and unloading downwards to 0.49 N. It was noted that unloading values of Vickers microhardness are slightly greater than loading values. The elastic/plastic deformation model (EPD) was used to interpret the loading and unloading Vickers microhardness results. It is clearly noted that values of d o, the added elastic component the measured plastic indentation semi-diagonal (d),in the unloading results are much higher than those for loading data. The effect of liquid nitrogen immersion for 16 h on Vickers microhardness values was examined. A significant improvement in the Vickers microhardness of (Bi, Pb)-2223 samples immersed in liquid nitrogen was observed. Such behavior is attributed to the fact that nitrogen immersion increases the volume contraction of the superconductor matrix, causing the shrink of the pores and voids present in the samples. Different models were used to analyze the obtained results such as Meyer's law, Hays–Kendall (HK) approach, elastic/plastic deformation (EPD) model, and modified proportional specimen resistance (MPSR) model. The experimental results of Vickers microhardness of both samples without and with liquid nitrogen immersion are well fitted according to the MPSR model. [ABSTRACT FROM AUTHOR]

New nanocomposites, containing nickel oxide nanoparticles (NiONPs) and Nile blue@reduced graphene oxide (NB/rGO), were synthesized. Nile blue was decorated on the surface of rGO by covalent bonds (using diazonium reaction). Then, NiONPs was immobilized on the surface of the functionalized rGO. The electrocatalytic and electrochemical behaviors of NiO@rGO and NiO@Nile/rGO nanocomposites for HER were investigated using cyclic voltammetry and electrochemical impedance spectroscopy in acidic and alkaline media. From them, NiO@rGO has shown long-term stability for HER in acidic solution at room temperature. The electrocatalytic activity of NiO@rGO (vs. NiO@Nile/rGO) for HER was greatly improved and its behavior was close to the behavior of platinum. In the next stage of our study, due to the importance of oxygen as an energy source, the production of oxygen molecules through electrochemical oxidation of water at NiO@rGO and NiO@Nile/rGO were studied too. For this purpose, the electrochemical behaviors of the nanocomposites for oxygen evolution reaction were investigated using cyclic voltammetry and electrochemical impedance spectroscopy in acidic and alkaline media. The results of them confirmed that NiO@Nile/rGO acts as an excellent electrocatalyst with good long-term stability for oxygen evolution reaction in 0.5 mol L −1 KOH solution at room temperature. Therefore, NiO@rGO and NiO@Nile/rGO can be used as powerful cathode and anode, respectively in an electrochemical cell for water splitting. [ABSTRACT FROM AUTHOR]

NiO nanoparticles have emerged as ideal candidates in various fields due to their magnetic, electrical and optical properties. The coupling of plant extracts that have anticancer and antibacterial properties with NiO nanoparticles has increased their usage in the biomedical field. In this work, we report on the novel synthesis of NiO nanoparticles using a local medicinal plant, Monsonia burkenea . The nickel nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), Energy dispersive X-ray analysis (EDX), Scanning electron microscope (SEM), High-resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD). FTIR showed that the extraction of the plant phytochemicals was successful and the green synthesized nanoparticles from plants contained the phytochemical groups that are found in the Monsonia burkeana plant. XRD and HRTEM confirmed the successful formation of NiO nanoparticles with an average particle size range of 20 nm. These results were also corroborated by elemental mapping and EDX, where the dominant groups were identified.The Monsonia burkeana NiO particles exhibited selective bactericidal activity against Gram-negative strains, such as E. coli and P. aeruginosa. Additionally, cytotoxicity studies showed the materials did not have any anti proliferative effect against A549 lung cancer cells but could be used as potential drug delivery vehicles against human cancers. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiONPs enhanced biogas and biomethane production from green algae C. linum. • The Box-Behnken design was applied to define the optimum biomass and NiONPs levels. • The supreme biomethane generation (94.86 mL/g VS) was achieved by the addition of NiONPs. • LCA was used to estimate the environmental influence of NiONPs on biogas generation. The optimization of the three parameters process was assessed as a controlling factor for the optimum generation of biogas and biomethane by Response Surface Methodology (RSM) using green algae Cheatomorpha linum (C. linum) as the substrate. The three factors, biomass amount, Nickel oxide nanoparticles (NiONPs) dosage and digestion time, were assessed and optimized by RSM using Box-Behnken design (BBD) to define their optimum level. The effectiveness of NiONPs with different concentrations as an improver for biogas and biomethane generation from C. linum was studied. BET, FTIR, TGA, XRD, and TEM were used to characterize the NiONPs. To evaluate the sustainability of using NiONPs for biomethane production, the environmental influences accompanying the process were computed from a life cycle assessment (LCA) perspective. Furthermore, the energy balance of biogas generation via co-digestion of C. linum and cow-manure using different dosages of NiONPs was estimated. The kinetic investigation proved that the modified Gompertz model fit the working results satisfactorily, with R 2 ranging between 0.983 and 0.995 and 0.837 to 0.972 for biogas and biomethane production, respectively. The results recommended that adding NiONPs at doses of 5 mg/L and 15 mg/L to C. linum (1 and 1.5 g) gives rise to a significant increase in biogas yield compared to all other treatments (384 and 380 mL/g VS). The maximum biomethane generation (94.86 mL/g VS) was achieved by the addition of NiONPs at doses of 15 mg/L to C. linum (1.5 g). LCA and energy analysis results showed that incorporating NiONPs with cow manure and C. linum remarkably reduced the negative environmental impacts, including global warming potential (GWP), and enhanced energy recovery compared to the case without NiONPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiO nanoparticles were successfully prepared from watermelon seed shell extract by the green synthesis method. • NiO nanoparticles were applied for the first time in the photocatalytic reduction of methylene blue and H 2 production from NaBH 4 hydrolysis. • 98 % of methylene blue was reduced in 13 min in the presence of NiO nanoparticles. • The H 2 production rate, activation energy and reaction order were found to be 660 mL H2 min−1 g cat −1, 39.8 kJ mol−1 and 0.59, respectively. In the study, NiO nanoparticles were successfully prepared from watermelon seed shell extract as a reducing agent by the green synthesis method. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) were used for the characterization of NiO nanoparticles to evaluate the structural and morphological identifications. The NiO nanoparticles were applied for the first time as a photocatalyst in the photocatalytic reduction of methylene blue and as a catalyst in H 2 production from NaBH 4 hydrolysis. In the photocatalytic reduction of methylene blue with NaBH 4 as a reducing agent, it was observed that there was no colour change for 24 h without catalyst, and 98 % of methylene blue was reduced in 13 min in the presence of NiO nanoparticles. The photocatalytic reduction kinetics of methylene blue was investigated using the pseudo-first-order model, and the rate constant was found to be 0.382 min−1. H 2 production from NaBH 4 hydrolysis using the NiO nanoparticles was investigated in terms of the effect of microwave radiation ambient and temperature. The kinetics of H 2 production from NaBH 4 hydrolysis was studied by applying the nth-order kinetic model. The H 2 production rate (r H2), activation energy (Ea) and reaction order (n -value) were found to be 660 mL H2 min−1 g cat −1 (at 70 °C), 39.8 kJ mol−1 and 0.59, respectively. This study revealed that NiO nanoparticles prepared by an eco-friendly green synthesis method can be used as an alternative potential catalyst for the photocatalytic reduction of methylene blue and H 2 production from NaBH 4 hydrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • A strong Raman intensity enhancement of the two-magnon (2 M) mode was observed in the NiO nanoparticles annealed in vacuum. • The increased 2 M peak intensity is microscopically explained by the increasing proportion of octahedral NiO 6 symmetry. • Varied oxygen environment underlie both the change in the 2 M intensity and the splitting of TO phonon of NiO nanoparticles. Nanostructured antiferromagnetic (AFM) NiO has attracted much attention from both the fundamental and applied perspectives. Understanding the two-magnon (2 M) is of great significance in NiO applications such as spin valves and next-generation magnetic random access memories (MRAM). We investigated the phonon modes and antiferromagnetically ordered states of NiO nanoparticles prepared by empirically controlled measurements. An intensity enhancement of the 2 M mode was observed by Raman spectroscopy as the NiO nanoparticles were vacuum annealed at 650 ℃. The increased 2 M peak intensity in NiO nanoparticles is explained by the local symmetry conversions from NiO 5 to NiO 6 configurations due to the oxygen redistribution during the vacuum annealing. The change of the splitting of anisotropic transverse optical (TO) phonon with different oxygen contents was also revealed by the Raman spectroscopy. We have shown that the changes in the oxygen environment underlie both the change in the 2 M intensity and the splitting of TO phonon in the NiO nanoparticles. Our work offers an efficient avenue to strengthen the AFM ordering and emphasizes the effect of vacuum annealing of the NiO nanoparticles, opening the interesting possibility of individual parameter control in practical applications. [ABSTRACT FROM AUTHOR]

Pure and (Mg, Cu) codoped NiO nanoparticles were prepared via the co-precipitation method. The prepared nanoparticles were investigated by XRD, TEM, SEM-EDX, XPS, FTIR, Raman, UV–vis, PL and VSM. NiO cubic structure forms with no impurities or secondary phases. (Mg, Cu) codoping of NiO lowers its crystallite size and causes variation in the Ni stoichiometry as well as formation of O vacancies. The optical transmittance is enhanced up to 87% for x = 0.08, becoming beneficial for transparent electrodes. The bandgap and Urbach energies increase from 3.51 to 3.66 eV and 0.43–0.54 eV, respectively, whereas the optical dielectric constant decreases from 7.72 to 7.25 with enhancement of the electron-phonon interaction. Weak ferromagnetic contribution exists, and the ferromagnetic origin is explained by the BMP model. Coercivity and saturation magnetization decrease from 438.42 to 30.12 Oe and 0.267 to 0.178 emu/g, respectively, which is beneficial for data storage applications. • Mg and Cu were codoped successfully in NiO nanoparticles by coprecipitation method. • Optical transmittance, bandgap energy and electron-phonon interaction were enhanced. • Weak ferromagnetism was modified by codopants' concentration and surface effects. • (Mg, Cu) codoping was found beneficial in optoelectronic and data storage devices. [ABSTRACT FROM AUTHOR]

The influence of band-gap on the non-linear absorption mechanism in nickel oxide nanoparticles synthesized by the chemical precipitation method was investigated. The NiO nanoparticles with different optical band-gaps were prepared by varying the calcination temperature from 200 to 400°C. The open aperture Z-scan technique estimated the two-photon absorption coefficients (2PA) and two-photon absorption cross-sections (σ 2 P A ) of NiO nanoparticles at an excitation of 532 nm. The 2PA coefficient has undergone an increase with a reduction in the band-gap. The 2PA coefficient, 2PA cross-section and optical limiting threshold were estimated to be 41.77 cm/GW, 1.93 × 106 GM and 157.91 MW/cm2, respectively. The significant 2PA coefficient and 2PA cross-section values suggest that the NiO nanoparticles could be a promising material for developing optical limiting devices with a relatively low threshold value. All the inferences were validated with structural, elemental and stoichiometric analysis. • The structural and optical properties of nickel oxide nanoparticles synthesized by different calcination temperatures have been studied. • This paper investigates the effect of the band gap on the nonlinear absorption coefficient and cross-section of nickel oxide nanoparticles at 532 nm. • The nonlinear absorption coefficient is obtained to be 41.77 cm/GW. • The nonlinear absorption cross-section is estimated in the range of 106 GM, which is higher than that of other semiconductors reported. • This low limiting threshold value makes the nickel oxide nanoparticles suitable for optical limiters at this wavelength. [ABSTRACT FROM AUTHOR]

Current attention has been given on health effects of combined exposure of nanoscale materials and organic pollutants. Nickel (II) oxide nanoparticles (NiO NPs) displays exceptional properties and is being used in various areas such as batteries, diesel–fuel additives, and biomedicals. Benzo[a]pyrene (BaP) is a ubiquitous pollutant. Cigarette smoke, diesel exhaust, and grilled foods are main sources of BaP exposure. Therefore, combined exposure of NiO NPs and BaP to humans is unavoidable. There is a dearth of knowledge on combined effects of NiO NPs and BaP in humans. This study was aimed to investigate co-exposure effects of NiO NPs and BaP in human liver cells (HepG2) and primary rat hepatocytes. We observed that individual and co-exposure of NiO NPs and BaP induced cytotoxicity, lactate dehydrogenase leakage, lipid peroxidation, depletion of mitochondrial membrane potential, and activation of caspases (-3 and -9) in both types of cells. Individual and co-exposure of NiO NPs and BaP further accelerated the generation of free oxygen radicals (reactive oxygen species and hydrogen peroxide) and depletion of antioxidants (glutathione and various antioxidant enzymes). Remarkably, NiO NPs and BaP exerted synergistic toxicity to both HepG2 cells and primary rat hepatocytes. Moreover, combined toxicity of NiO NPs and BaP in both cells was mediated through free oxygen radicals induced oxidative stress. This work warrants further research on risk assessment of co-exposure effects NiO NPs and BaP in an appropriate in vivo model. [ABSTRACT FROM AUTHOR]

To address the plight of huge volume change and low intrinsic conductivity of NiO as anodes for lithium ion batteries (LIBs), we construct carbon-encapsulated NiO nanoparticles (NiO@C) on porous reduced graphene oxide (pRGO) matrix (NiO@C/pRGO). This is achieved by a smartly programmed annealing process using Ni(OH) 2 /RGO hybrid aerogel as precursor. It is noteworthy that our synthetic strategy unifies the formation of pores on RGO and inner carbon shell on NiO nanoparticles simultaneously and realizes the application of pRGO in such dual-carbon armored electrodes for the first time. When used as anodes for LIBs, NiO@C/pRGO electrode displays a high rechargeable specific capacity of 1003 mAh g −1 at a current density of 200 mA g −1 , superior rate capability, and good cycling performance up to 1000 cycles. Such outstanding electrochemical performance is mainly ascribed to the dual-carbon decoration, which can not only accommodate large volume changes of NiO, but also stabilize the NiO against self-agglomeration and greatly improve the charge transfer efficiency of the electrode. It is expected that such dual-carbon protection and porous carbon matrix can be extended to prepare other electrodes with well-defined nanoarchitecture and high efficiency for lithium transition. [ABSTRACT FROM AUTHOR]

In this paper, NiO nanoparticles were prepared by hydrothermal synthesis of Ni(OH) 2 precursors using different alkalis (NH 3 and NaOH) followed by a calcination at different temperatures (400 °C and 600 °C) and characterized by XRD and SEM. Their electrochemical and optical properties were probed by cyclic voltammetry and reflectance spectroscopy and related to the structural and morphological properties. It was found that the smallest peak-to-peak separations and band gaps attain to the NiO nanoparticles prepared at 400 °C, which are smaller and more porous. The preparations at 600 °C correspond to larger nanoparticles, with a larger size distribution and in one case (preparation with NaOH) a compact structure. The associated band gaps are larger and the electrochemical performances worse. [ABSTRACT FROM AUTHOR]

In this work, high-performance electrochemical energy storage electrodes were developed based on nickel oxide (NiO)-coated nickel (Ni) foams prepared by a sparking method. NiO nanoparticles deposited on Ni foams with varying sparking times from 45 to 180 min were structurally characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. In addition, the electrochemical energy storage characteristics of the electrodes were evaluated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. It was found that NiO nanoparticles sparked on Ni foam with a longer time would be agglomerated and formed a foam-like network with large pore sizes and a lower surface area, leading to inferior charge storage behaviors. The NiO/Ni foam electrode prepared with the shortest sparking of 45 min displayed high specific capacities of 920 C g -1 (1840 F g -1 ) at 1 A g -1 and 699 (76% of 920) C g -1 at 20 A g -1 in a potential window of 0-0.5 V vs. Ag/AgCl as well as a good cycling performance with 96% capacity retention at 4 A g -1 after 1000 cycles and a low equivalent series resistance of 0.4 Ω. Therefore, NiO/Ni foam electrodes prepared by the sparking method are highly promising for high-capacity energy storage applications. [ABSTRACT FROM AUTHOR]

Abstracts Our previous work demonstrated the fabrication of the NiO nanoparticle-nanographitic flake composite through a direct current (DC) electrophoretic deposition (EPD) process. The composite was used as a catalyst layer having a low onset voltage in ethanol electro-oxidation. This paper presents a new catalyst material fabricated through pulsed EPD, which permitted to acquire a higher efficiency of ethanol electro-oxidation when compared to the catalyst layer fabricated by the DC EPD. The reason behind the enhancement of the performances of the catalyst layers fabricated using the pulsed EPD is the selective deposition of low-weight NiO nanoparticles on nanographitic flakes causing a reduction in the deposition of agglomerated NiO nanoparticles and therefore an enhancement in the efficiency of the ethanol electro-oxidation. [ABSTRACT FROM AUTHOR]

• NiO and NiO metal-doped nanoparticles (NPs) were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption desorption. • Dielectric properties and electrical conductivity were conducted. • Optical properties (e.g. refractive index, optical energy gap, the molar refractivity) were investigated. NiO and NiO metal-doped nanoparticles (NPs) were synthesized using a two-step process. These NPs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption desorption. The cubic structure of the NiO was validated from the similarity of the X-ray diffraction peaks and that all the metallic dopants (Cu and Cr) were stabilized in their sites within NiO structure. TEM revealed the configuration whereby the NiO NPs were arranged side by side and aligned along the same direction, forming a small array shaped agglomerates with around 500 nm length and 50–70 nm diameter. Adsorption-desorption isotherms for N 2 indicated that NiO NPs could be characterized by type IV isotherms with a hysteresis loop at relative pressures between 0.5 and 1.0. The Hysteresis loop's pattern was of H2 type which is a characteristic pattern for inckbottle shaped pores. Dielectric properties and electrical conductivity were conducted at 25 °C – 110 °C and within the frequency range between 100 Hz and 0.3 MHz. Optical properties (e.g. refractive index, optical energy gap, the molar refractivity) for NiO, NiO:Cu, and NiO:Cr NPs were investigated. The data reveal that, the energy gap and the metallization criterion were the lowest for the NiO:Cu NP sample. On the contrary, the refractive index, molar refractivity were the highest for NiO:Cu NP sample. [ABSTRACT FROM AUTHOR]

Current research focuses on the effects of nanomaterials on the human reproductive system. Nanostructures can cross the epithelial and blood-testicular barriers and pose risks to the reproductive organs. Oxidative stress has been proposed as a possible mechanism of reproductive toxicity caused by nanomaterials. Dietary curcumin could be a therapeutic drug for nanomaterial-induced reproductive toxicity. Studies on effect of commonly used nickel (II) oxide nanoparticle (NiO NPs) on male reproductive organs and their attenuation by natural antioxidant curcumin is scarce. This work intended to study the attenuating potential of curcumin against NiO NPs-induced toxicity in mouse spermatogonia GC-1 spg cells. Plausible mechanisms of alleviating effect curcumin against NiO induced reproductive toxicity was explored through oxidative stress pathway. NiO NPs was synthesized via chemical co-precipitation route and characterized by SEM, TEM, and XRD. NiO NPs was found to induce dose-dependent cytotoxicity in GC-1 spg cells (10–320 µg/ml for 24 h) whereas curcumin did not exert any effect in concentration range of 1–80 µg/ml. Interestingly, cytotoxic response of NiO NPs in GC-1 spg cells was significantly attenuated by curcumin. The higher expression of caspase-3 gene and loss of mitochondrial membrane potential after treatment with NiO NPs were effectively alleviated by curcumin. The increase in intracellular pro-oxidant levels (hydrogen peroxide, malondialdehyde, and reactive oxygen species) after exposure to NiO NPs was also mitigated by curcumin. Moreover, glutathione depletion and lower activity of several antioxidant enzymes (GPx, SOD, and CAT) after NiO NPs were further almost reverted by curcumin. We believe, this is the first preliminary study showing that NiO NPs induced cytotoxicity in mouse spermatogonia cells was mitigated by curcumin via oxidative stress. The therapeutic effect of dietary antioxidant curcumin against nanomaterial-induced reproductive toxicity is warranted further research. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenides possess fascinating properties due to their direct bandgap, strong spin-orbit coupling, and promising electronic/mechanical properties. In this work, we synthesized pure tungsten disulfide (WS 2) nanolayers and NiO nanoparticles (NPs) decorated in few-layered WS 2 and measured the third-order nonlinear optical properties using femtosecond Z-scan measurements. The open aperture Z-scan data illustrated that the inclusion of NiO nanoparticles into the WS 2 layers increases the nonlinear absorption at 800 and 400 nm wavelengths. Furthermore, we observed the switchability of the nonlinear absorption from saturable absorption to two-photon absorption or reverse saturable absorption by changing the pump intensity. Thus, the embedded NiO NPs played a crucial role in the variation of intensity-dependent nonlinear absorption mechanism of WS 2 nanolayers and thus can be helpful for various optical applications such as laser pulse compression and optical limiting to prevent over-exposure of protective photosensitive sensors by intense ultrashort laser pulses. [Display omitted] • Synthesized pure tungsten disulfide (WS 2) nanolayers and NiO nanoparticles decorated few-layered WS 2. • Measured the third-order nonlinear optical properties via femtosecond Z-scan measurements at 800 and 400 nm wavelengths. • Observed the switchability of the nonlinear absorption from saturable absorption to two-photon absorption or reverse saturable absorption. • The measured nonlinear optical properties revealed for applications such as laser pulse compression and optical limiting. [ABSTRACT FROM AUTHOR]

Nano-scaled transition metal oxides are massively gaining an exciting horizon of research interest among material scientists by triggering scientific attention due to its prime advancements in physico-chemical, magneto-optical, electro-chemical, bio-medical and bio-compatible characteristics. The current work highlights the fabrication and formalisation of pure and X 0.06 Ni 0.94 O (X = Co, Fe, Cu) nanoparticles via bottom-up sol-gel pathway employing citric acid as the gelling factor. The crystallite size evaluated from X-Ray Diffraction (XRD) analysis decreased with respect to doping were estimated by successive systems among which Halder-Wagner (H-W) and Wagner-Agua (W-A) approach delivered prime results. Fourier Transform Infra-Red (FTIR) spectroscopy analysis regulated at room temperature in the mid infrared frequency continuum 400–4000 cm−1 confirmed the cubic conformation and the presence of predicted functional groups in the as-synthesized nanoparticles. The bandgap energy calculated from Ultra Violet-visible (UV–vis) spectroscopy is found to decrease for Co-NiO and Cu-NiO nanoparticles and increased for Fe doped NiO nanoparticles in comparison with the bandgap of pure NPs reasoned out by the Burstein-Moss shift. The device dependent parameter Urbach energy, and other pivotal optical parameters crucial in the fabrication of optoelectronic devices were evaluated. Surface morphological features and porous network of doped nanoparticles were investigated from Scanning Electron Microscopy (SEM) technique. Energy Dispersive X-ray (EDX) spectra ascertained the molecular matrix array and elemental composition in synthesized samples. The surface area measured from Brunauer-Emmett-Teller (BET) analysis revealed higher surface area (42 m 2 / g) for Fe-doped NiO nanoparticles than other counterparts. The thermal decomposition and stability of the pure and doped samples were analysed by Thermo-Gravimetric (TG) studies. The fundamental kinetic and thermodynamic parameters such as entropy, enthalpy, activation and Gibb's free energy were elucidated through six different models viz., Coats-Redfern (CR), Piloyan-Novikava (PN), Horowitz-Metzger (HM), Van-Krevelen (VK), MacCallum-Tanner (MT) and Broido methods. Vibrating Sample Magnetometer (VSM) analysis coupled with the Law of Approach to Saturation (LAS) operandi extracted two critical magnetic criteria and the saturation magnetization is noticed to reduce with doping. The antibacterial and antifungal efficacies of the as-synthesized NPs were deeply discussed by portraying the nanoparticles-microbes interface. Iron and copper doped nickel oxide nanoparticles encountered favorable antimicrobial activity against pathogenic organisms. Furthermore, the bio-compatibility nature of the NPs was examined through hemolytic activity and the samples exhibited non-toxic behavior towards human cells till 50 μ g / ml. [Display omitted] • Ni 0.94 X 0.06 O (X = Co, Fe, Cu) NPs were synthesized via sol-gel citrate method. • Fe and Cu doped NiO particles exhibited better antibacterial and antifungal activity. • Bio-compatibility nature of NiO NPs was examined via hemolytic activity. • The thermal stability of all the samples was examined and the results are compared with various models and the results are elaborately discussed. • Ferromagnetic behavior was encountered in all doped samples. [ABSTRACT FROM AUTHOR]

• The crystallite size is directly proportional to the calcination temperature. • The size of the nanocrystals influenced their structural, morphological, optical and electrocatalytic properties. • UV–vis-NIR measurements show that optical properties are dependent on the crystallite size and lattice imperfections/defects. • The simulation of the electronic and optical properties was satisfactory, despite the difficulty in reproducing the dynamics of the system due to its strongly correlated states. • The electrochemical evaluation shows that the samples are promising electrocatalysts for the oxygen evolution reaction in an alkaline medium. The study of nanoparticles becomes increasingly fascinating since their size can give them unusual behaviors, changing their properties. Due to their outstanding properties, nickel oxide nanoparticles have been applied in several research fields, such as catalysis and optical electronics. In this work, we have investigated the influence of particle size on the optical and electrocatalytic properties of NiO obtained through coprecipitation synthesis (Cp). Thermogravimetric analysis (TG/DTG) measurements reveal that the total decomposition of the precursors occurs at ≈ 545 °C. The X-ray diffraction measurements (XRD) show that it is possible for the formation of only one phase of NiO at 350 °C. Rietveld refinement indicates an increase in crystallite size with the rise of temperature and negative strain values associated with shrinkage of the crystalline lattice. Vibrational spectroscopy (infrared and Raman) data showed a symmetry break and imperfections/defects in the synthesized NiO nanoparticles. The optical properties of these samples were studied by spectrophotometry in the ultraviolet–visible and near-infrared region measurements (UV–vis-NIR). Band gap values decreased with increasing nanoparticle size. The Urbach tail energy estimates corroborate the vibrational spectroscopy measurements, indicating the presence of imperfections/defects in the samples. Density Functional Theory (DFT) studies have been applied from the XRD parameters implemented by the Spanish Initiative for Electronic Simulations with Thousands of Atom (SIESTA) to understand the experimental results better. Despite the computational limitations and the difficulty of describing the dynamic effect presented by the 3d orbitals of Ni, it was possible to obtain satisfactory results within the order of magnitude desired. Also, under the effect of the size of the nanoparticles, all samples present excellent electrocatalytic performance (overpotential of 312–335 mV for a current density of 10 mA/cm2) for Oxygen Evolution Reaction (OER) in alkaline medium. [ABSTRACT FROM AUTHOR]

Nickel oxide nanoparticles were synthesized using low cost sol-gel method. The structure of as prepared NiO nanoparticles has been confirmed from X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray (SEM and EDX) spectroscopic analysis. The electrical and dielectric properties were characterized by complex impedance spectroscopy as a function of frequency at different temperatures. To study the dielectric behavior of the nanoparticles different plots like Nyquist plot, modulus plot and Bode plot were used. Also the frequency dependent ac conductivity is analyzed and the activation energy is calculated. The dielectric constant and dielectric loss as a function of frequency at various temperatures are also studied. [ABSTRACT FROM AUTHOR]

Glass containing metal nanoparticles (NPs) is a promising candidate for application in nonlinear optical devices. Hence, transparent sodium borosilicate (NBS) glass incorporated into NiO nanoparticles (NPs) was fabricated by sol-gel processes plus a controlled atmosphere. Fourier transform infrared (FTIR) analysis was applied to identify the formation mechanism of the NBS glass network. X-ray powder diffraction (XRD), Transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS) analysis were performed to confirm that spherical and well dispersed NiO NPs did exist in the glass host. Z-scan technique was used to investigate third-order nonlinear optical properties (NLO) of the as-obtained glass in the femtosecond (fs) and picosecond (ps) regimes. The results revealed that the glass displayed no nonlinear absorption and moderately strong self-focusing performance in the fs regime, while it exhibited a reverse saturable absorption (RSA) effect in the ps regime. [ABSTRACT FROM AUTHOR]

A dopamine biosensor has been developed using nickel oxide nanoparticles (NPs) and tyrosinase enzyme conjugate. Nickel oxide (NiO) NPs were synthesized by sol–gel method using anionic surfactant, sodium dodecyl sulphate (SDS), as template to control the size of synthesized nanoparticles. The structural and morphological studies of the prepared NPs were carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. Afterwards, tyrosinase enzyme molecules were adsorbed on NiO NPs surface and enzyme coated NPs were deposited on indium tin oxide (ITO) coated flexible polyethylene terephthalate (PET) substrate by solution casting method. The formation of enzyme–NPs conjugate was investigated by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) techniques and used in selective detection and estimation of neurochemical dopamine by electrochemical method. The fabricated Tyrosinase/NiO/ITO electrode exhibits high sensitivity of 60.2 nA/µM in linear detection range (2–100 μM) with a detection limit of 1.038 μM. The proposed sensor had a response time of 45 s, long shelf life (45 days) with good reproducibility and selectivity in presence of interfering substances and was validated with real samples. The tyrosinase enzyme functionalized NiO platform has good bio-sensing efficacy and can be used in detection of other catecholamines and phenolic neurochemicals. [ABSTRACT FROM AUTHOR]

A new method for determination of methyldopa in the presence of folic acid has been described in this work. This method is based on modification of carbon paste electrode with NiO nanoparticles and an ionic liquid (1-Butyl-3-methylimidazolium hexafluorophosphate). Electrochemical studies showed that on the surface of modified electrode, oxidation current of methyldopa has been enhanced and shifted to negative potentials. The fabricated electrode exhibited a linear response to concentration of methyldopa from 0.1 to 700.0 μmol L −1 . The sensitivity of the modified electrode to methyldopa not changed in the presence of folic acid and simultaneous or independent measurements of them are possible. The performance of proposed method was investigated by determination of methyldopa in real samples. [ABSTRACT FROM AUTHOR]

In this study, a high sensitive electrochemical sensor for 4-chlorophenol (4-CP) was established based on graphene oxide NiO/NPs-ionic liquid (IL) ( n -hexyl-3-methylimidazolium hexafluoro phosphate) carbon paste electrode. The proposed sensor exhibited strong enrichment effect on 4-CP and gave superior catalytic activity towards the electro-oxidation of 4-CP. On the other hand, the novel sensor was used for determination of 4-CP in the presence of nitrite for the first time. The anodic peaks of 4-CP and nitrite in their mixture can be well separated. At pH 7.0 the two peaks are separated ca. 0.57 and 0.82 V, respectively. Applying square wave voltammetry (SWV), a good linear relationship of the oxidation peak current with respect to concentration of 4-CP cross the range of 1.0–550.0 μM was achieved. The detection limit was evaluated about 0.7 μM. The novel sensor has been successfully applied for the assay of 4-CP in real samples. [ABSTRACT FROM AUTHOR]