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This study investigated the catalytic CO2 methanation using nickel oxide (NiO) nanoparticles and nickel oxalate (NiC2O4) as catalysts. The NiC2O4 precursor was synthesized through a chemical precipitation reaction between nickel (II) nitrate hexahydrate (Ni(NO3)2.6H2O) and oxalic acid (H2C2O4.2H2O). Nickel oxide (NiO) nanoparticles were synthesized through thermal decomposition of NiC2O4 precursor at 450 °C in air. The samples were characterized by XRD, FTIR, BET, SEM, and EDX. The XRD and FTIR analyses revealed that the NiO nanoparticles were well‐crystallized having size 17.30 nm. The BET analysis of the NiO sample revealed mesoporous NiO nanoparticles with a specific surface area (SBET) of 29.08 m2/g and a narrow distribution of pore sizes. The catalytic performance of NiO and NiC2O4 catalysts studied for the CO2 methanation in tubular packed bed reactor at 150–550 °C and 1 atm. The reduced NiO nanoparticles exhibited more catalytic activity than the decomposed NiC2O4 catalyst. At 380 °C, 1 atm, and gas hourly space velocity (GHSV) of 9000 mL g−1 h−1, the reduced NiO nanoparticle catalyst showed high catalytic activity, with a maximum CO2 conversion of 85.54 %, 99 % CH4 selectivity, and 84.69 % CH4 yield. Furthermore, the NiO nanoparticle catalyst demonstrated excellent stability after 12 h of streaming at 380 °C. [ABSTRACT FROM AUTHOR]

Metal and metal oxide nanoparticles (NPs) embedded in glass matrixes exhibit special optical, electrical, or magnetic properties. Despite various approaches of encapsulating NPs in different kinds of glasses to prepare functional composite materials, there still exist challenges in fabricating efficiency and performance for silica glass made by traditional methods, such as sol–gel or melt quenching. Herein, the authors report a facile way to fabricate metal oxide NP‐doped silica glass by digital light processing (DLP) 3D printing technology for the first time. Different from common ion doping in silica glass, metal acetylacetonates that can be thermally decomposed to corresponding metal oxides innocuously, are chosen as a general precursor. Then, the representative nickel(II) acetylacetonate is introduced during the 3D printing process. The subsequent heat treatment generates a homogeneous distribution of NiO NPs in silica glass and it also exhibits optical nonlinear effect. The results provide a facile method for developing functional metal oxide‐doped glasses as well as the freeform fabrication of optoelectronic devices based on them. [ABSTRACT FROM AUTHOR]

High‐performance composite electrode materials for supercapacitors were developed by two‐step electrochemical deposition of nano‐NiO and poly(3,4‐ethylenedioxythiophene) (PEDOT) on nickel foam (NF). NF is considered an excellent conductive substrate for preparing porous electrode materials due to its high conductivity and porosity. The electrodeposited NiO nanoparticles were uniformly and densely coated on the pore of NF to fill in the internal voids, which provides an abundant active site for the electrodeposition of PEDOT. PEDOT was prepared by simple electrodeposition and was uniformly coated on the substrate surface which has high conductivity and reversible electrochemical redox properties, as well as excellent cyclic stability. The loose surface morphology not only provides abundant redox active sites for electrode material but also contributes the good pseudocapacitance property. As expected, the maximum mass‐specific capacity of PEDOT/NiO@NF composite electrode material can reach up to 129.7 F g−1 at the current density of 1 A g−1. Moreover, the composite electrode material shows excellent electrochemical cycling stability that the specific capacity has no obvious decay compared with its initial capacity after 200 cycles of cyclic voltammetry and 100 cycles of galvanostatic charge–discharge (GCD). This work demonstrates that the composite material PEDOT/NiO@NF could be a candidate flexibility electrode material for high‐performance supercapacitor applications. [ABSTRACT FROM AUTHOR]

To counter the concern of the future availability of fossil fuel due to ever‐increasing energy demand and the emission generated due to its utilization, alternative renewable fuels, such as biogas and fuel additives in the form of nanoparticles emerge as viable alternative fuels. To date, no research has been carried out on the optimization of the co‐addition rate of nanoparticles and biogas. In this study, engine load (0.7–3.5 kW), Nickel oxide (NiO) Nanoparticles doped rate (NDR, 0–50 ppm), and Biogas Flow Rate (BFR, 0.5–1 kg/h) were selected as independent input variables to optimize compression ignition (CI) engine emission and performance outputs through the response surface methodology (RSM) approach. The F‐value of the RSM model indicates that the engine load variable has the greatest impact on engine output responses, with the BFR and NDR variables following in importance. At 2.54 kW engine load, 47.48 ppm NDR, and 0.747 kg/h BFR, the best engine output response was seen when the RSM model including the desirability function was optimized. Based on the optimization results, an assertion can be made that the use of nanoparticles in conjunction with biogas has a substantial impact on the emissions and efficiency of CI engines. [ABSTRACT FROM AUTHOR]

The blooming requirement of high‐performance energy storage systems has aroused the thirst for advanced energy storage materials. As a high capacity anode, however, the application of NiO nanoparticles (NiO NPs) is hindered by intractable issues of dramatic volume change, intrinsic low electronic conductivity, and severe aggregation tendency during lithiation/delithiation. Herein, a polydopamine (PDA) assisted bi‐functionalization strategy for fabricating of PDA@NiO‐CNT composites for fast and durable lithium storage is reported. In this composite, CNTs intertwine to form a network to ensure sufficient electrolyte infiltration and act as a highly conductive system to motivate fast charge transmission. The strong binding affinity of PDA facilitates bonding between NiO NPs and CNTs, which not only forms uniform and flexible PDA coating but also ensures homogeneous distribution of NiO NPs on CNTs network. Therefore, the bi‐functional modified PDA@NiO‐CNT electrode possesses high conductivity, alleviates volume change and aggregation of NiO NPs during cycling, achieves a reversible capacity of 1326 mAh g−1 at 100 mA g−1, a rate capability of 215 mAh g−1 at 2000 mA g−1 and a cycling stability with 78% capacity retention after 250 cycles. This bi‐functional modification approach manifests its prospective potential for architecting other electrode materials toward high‐performance electrochemical devices. [ABSTRACT FROM AUTHOR]

4‐Nitrophenol (4‐NP) is a hazardous organic pollutant with detrimental effects on plants, animals, and humans. Detection of 4‐NP in the environment is therefore a necessary requirement. We demonstrate a facile green synthesis of nickel‐oxide (NiO) nanoparticles employing Brassica oleracea vegetable extract (cauliflower) as a green stabilizing and reducing agent. Green synthesized NiO nanoparticles were used as an efficient electrode material for the highly sensitive electrochemical detection of 4‐NP. The abundant polyphenolic component in the vegetable extract of Brassica oleracea is capable of reducing and stabilizing C2NiO4 into NiO nanoparticles. The as‐synthesized NiO nanoparticles were characterized by UV‐Vis spectroscopy, FTIR spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, and X‐ray photoelectron spectroscopy (XPS), and the structural phase of NiO nanoparticles was confirmed using powder X‐ray diffraction technique. The surface morphology of the NiO nanoparticles was analyzed using scanning electron microscopy (SEM). Linear sweep voltammetry (LSV) and Differential pulse voltammetry (DPV) techniques were adopted to for the electrochemical determination of 4‐NP after drop casting the NiO nanoparticles onto the screen‐printed carbon electrode (SPCE). The developed sensor (NiO/SPCE) showed a high sensitivity of 1.055 μA/nM over a wide linear‐range from 1 to 10 nM with a detection limit of 0.519 nM for the detection of 4‐NP using DPV technique. [ABSTRACT FROM AUTHOR]

p‐Nitrophenol (p−NP) is a high priority toxic pollutant and that has harmful effects on human, animals and plants. Thus, the detection and determination of p−NP present in the environment is an urgent as well as highly important requisite. The present article, therefore focused on the construction of a novel electrochemical sensor based on NiO nanoparticles/α‐cyclodextrin functionalized reduced graphene oxide modified glassy carbon electrode (NiO−NPs‐α‐CD‐rGO‐GCE) for the selective and sensitive detection of p−NP. UV‐vis, high resolution transmission electron microscopy (HR‐TEM), selected area electron diffraction pattern (SAED) and X‐ray diffraction (XRD) analysis confirms the formation of highly pure NiO nanoparticles. Field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray spectroscopy (EDS), and cyclic voltammetry (CV) were used to characterize the step‐wise electrode modification process. DPV was carried out to quantify p−NP within the concentration range of 1−10 μM and found the detection limit of 0.12 nM on the basis of the signal‐to‐noise ratio S/N=3. The electrode can able to detect different isomers of nitrophenols. Interferences of other pollutants such as phenol, p‐aminophenol, o‐ and m‐ nitrophenol, 4‐chlorophenol, 2,6‐dichlorophenol and ions like K+, Cd2+, Cl−, SO42− did not affect the sensing of p−NP. The newly developed sensor exhibited diffusion controlled kinetics and had excellent sensitivity, selectivity and reproducibility for the detection of p−NP. The electrode showed good recoveries in real sample analysis. [ABSTRACT FROM AUTHOR]

Despite the increasing use of nickel oxide (NiO) nanoparticles (NPs), limited information is available on their toxicological effects. Health consequences of 28 days repeated oral exposure to NiO NPs have not been explored thoroughly. Hence, toxicity investigations were performed after 28‐day daily exposure in albino Wistar rats with NiO NPs following Organization for Economic Co‐operation and Development test guideline 407. Histopathology, biochemical indices including oxidative stress and biodistribution patterns were evaluated to decipher the toxicological impact of NiO NPs. NiO NP characterization by transmission electron microscopy showed an average size of 12.9 (±3.4) nm. Histological studies depicted a prominent impact on the vital organs of the rats. A dose‐dependent rise in both aminotransferase enzyme values was recorded in the homogenates of liver and kidney tissues. A significant decrease in superoxide dismutase activity and increase in catalase activity was noted. Further, a dose‐dependent decrease in reduced glutathione content was recorded in rats, which suggested generation of reactive oxygen species and oxidative stress. Increase in the malondialdehyde levels was observed with an increase in the dose substantiating the antioxidant enzyme activity profiles. Biodistribution studies indicated maximum accumulation of Ni content in liver followed by kidney. Excretion of Ni was predominantly through feces and a little through renal clearance. Our study indicated that NiO NPs adversely alter the biochemical profile of the rats and cause histological damage. Further investigations are warranted to address the mechanism by which physiological path these NiO NPs exhibit their toxic nature in in vivo. Despite increasing utilization and release of NiO NPs, consequences of repeated oral exposure are limited. Histopathological and biochemical estimations of NiO NPs after repeated oral treatment on Wistar rats showed severe histological damage and alterations in the biochemical profiles. Biodistribution study showed significant accumulation of nickel content in the vital organs. The results of the present study indicated that the NOAEL concentration for NiO NPs is <50 mg/kg, when exposed repeatedly via the oral route in rats. [ABSTRACT FROM AUTHOR]

A convenient, low cost, and sensitive electrochemical method, based on a disposable graphene nanosheets (GR) and NiO nanoparticles modified carbon screen printed electrode (NiO/GR/SPE), is described for the simultaneous determination of dopamine (DA) and uric acid (UA). The modified electrode exhibited good electrocatalytic properties toward the oxidation of DA and UA. A peak potential difference of 150 mV between DA and UA was large enough to determine DA and UA individually and simultaneously. The anodic peak currents of DA were found to be linear in the concentration range of 1.0-500.0 μM with the detection limit of 3.14×10−7 M. [ABSTRACT FROM AUTHOR]

Nickel oxide (NiO) nanoparticles are distributed uniformly in the vertically aligned carbon nanotube arrays (VACNTs) with millimeter thickness by an effective supercritical carbon dioxide-assisted method. The as-prepared VACNT/NiO hybrid structures are used as electrodes without binders and conducting additives for supercapacitor applications. Due to the synergetic effects of NiO and VACNTs with nanoporous structures and parallel 1D conductive paths for electrons, the supercapacitors exhibit a high capacitance of 1088.44 F g−1. Furthermore, an asymmetric supercapacitor is assembled using the as-synthesized VACNTs/NiO hybrids as the positive electrode and the VACNTs as the negative electrode. Remarkably, the energy density of the asymmetric supercapacitor is as high as 90.9 Wh kg−1 at 3.2 kW kg−1 and the maximum power density reaches 25.6 kW kg−1 at 24.9 Wh kg−1, which are superior to those of the NiO or VACNTs-based asymmetric supercapacitors. More importantly, the asymmetric supercapacitors exhibit capacitance retention of 87.1% after 2000 cycles at 5 A g−1. The work provides a novel approach in decorating highly dense and long VACNTs with active materials, which are promising electrodes for supercapacitors with ultrahigh power density and energy density. [ABSTRACT FROM AUTHOR]

BMAP calculator is a simplified software tool to obtain microstructure characteristics and to investigate their isotropic and anisotropic nature using some common broadening methods. The Scherrer and Stokes-Wilson methods as well as the Williamson-Hall plot (microstructure isotropy) and modified Williamson-Hall models (strain anisotropy) are implemented in the calculations. The BMAP input data are the X-ray diffraction peak parameters (the full width at half-maximum or integral breadth and peak position) of a measured line profile and of a reference one. The components of the measured line profile or corrected broadening are based on several approximations (Cauchy, Gauss or Voigt). The linear least-squares fit is used to calculate the size-strain values, and the correlation coefficient for accepting the results. The calculator is applied to an X-ray diffraction experiment of NiO nanoparticles prepared by a sol-gel method for testing. The results of BMAP calculator and the MAUD program, combined with an anisotropic Popa rules approach, are compared. The uniform stress model based on the Cauchy approximation is the most suitable one in cubic nanostructure nickel oxide, with an average crystallite size of 24 nm and anisotropic strains of 1.54 × 10−3, 0.61 × 10−3, 1.77 × 10−3 and 1.49 × 10−3 using the {111}, {200}, {220} and {311} reflections, respectively. Generally, for non-Rietveld users, it is useful to collect different methods into one program to depict the anisotropic nature of materials. [ABSTRACT FROM AUTHOR]