Preparation and characterization of NiO nanoparticles from thermal decomposition of the [Ni(en)3](NO3)2 complex: A facile and low-temperature route

NiO nanoparticles with an average size of 15 nm were easily prepared via the thermal decomposition of the tris(ethylenediamine)Ni(II) nitrate complex [Ni(en)₃](NO₃)₂ as a new precursor at low temperature, and the nanoparticles were characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV-Vis spectroscopy, BET specific surface area measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and magnetic measurements. The magnetic measurements confirm that the product shows a ferromagnetic behavior at room temperature, which may be ascribed to a size confinement effect. The NiO nanoparticles prepared by this method could be an appropriate photocatalytic material due to a strong absorption band at 325 nm. This method is simple, fast, safe, low-cost and also suitable for industrial production of high purity NiO nanoparticles for applied purposes.     

Simple and low-temperature synthesis of NiO nanoparticles through solid-state thermal decomposition of the hexa(ammine)Ni(II) nitrate, [Ni(NH3)6](NO3)2, complex

NiO nanoparticles with an average size of about 12 nm were easily prepared via the thermal decomposition of hexa(ammine)Ni(II) nitrate complex, [Ni(NH₃)₆](NO₃)₂, at low temperature of 250 °C. The product was characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV-Vis spectroscopy, BET specific surface area measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and magnetic measurement. The magnetic measurement revealed a small hysteresis loop at room temperature, confirming a superparamagnetic (weak ferromagnetic) nature of the synthesized NiO nanoparticles. Indeed, the NiO nanoparticles prepared by this method could be an appropriate semiconductor material due to the optical band gap of 3.35 eV which shows a red shift in comparison with the previous reports. This method is simple, fast, safe, low-cost and also suitable for industrial production of high purity NiO nanoparticles for applied purposes.     

A Simple Chemical Method for Synthesis of NiFe2O4 Nanoparticles and Polystyrene-Based Magnetic Nanocomposites

Magnetic NiFe₂O₄ (NiFe) nanoparticles were synthesized via a facile chemical reaction between Ni(NO₃)₂ and Fe(NO₃)₃. Different percents of NiFe nanoparticles were then added to polystyrene (PS) matrix. Nanoparticles were characterized using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The magnetic properties of the samples were also investigated using an alternating gradient force magnetometer. The nanoparticles exhibit ferromagnetic behaviour at room temperature, with a saturation magnetization of 20.8 emu/g and a coercivity of 99.6 Oe. Preparation of NiFe₂O₄ -PS nanocomposite leads to decrease in the coercivity.     

Hydrothermal and sonochemical synthesis of a nano-sized nickel(II) Schiff base complex as a precursor for nano-sized nickel(II) oxide; spectroscopic, catalytic and antibacterial properties

The Ni(II) complexes [Ni(L)₂](ClO₄)₂ (1) and [Ni(L)₂(NO₃)₂] (2), where L is the Schiff base ligand of 4,5,9,13,14-pentaaza-benzo[b] triphenylene, were synthesized and characterized by physico-chemical and spectroscopic methods. Nano-sized particles of (1) were prepared both by sonochemistry (3) and solvothermal (4) methods. NiO nanoparticles were obtained by calcination of the nano-structure complexes at 500 °C. The structures of the nano-sized compounds were characterized by X-ray powder diffraction and scanning electron microscopy. The thermal stabilities of the bulk complexes (1–2) and nano-sized particles (3–4) were studied by thermogravimetric and differential scanning calorimetry. The catalytic activities of complexes of (1–4) are reported. The free Schiff base and its Ni(II) complexes have been screened for antibacterial activities against three Gram-positive bacteria. The metal complexes are more active than the free Schiff base. Electrochemical studies show that the Ni complexes undergo irreversible reduction in MeCN solution.     

Synthesis of high surface area NiO nanoparticles through thermal decomposition of mixed ligand Ni(II) Complex, [Ni(binol)(bpy)]∙CH<Subscript>3</Subscript>OH

The present work focuses on the synthesis of high surface area NiO nanoparticles through thermal decomposition of [Ni(binol)(bpy)]?CH₃OH complex as a new precursor. [Ni(binol)(bpy)]?CH₃OH (where binol = racemic-1,1′-bi-2-naphtholate and bpy = 2,2′-bipyridine) was synthesized from reaction of NiCl₂(bpy) with rac-Na₂(binol). The complex was characterized by elemental analysis and spectroscopy techniques of IR, UV-Vis, mass, ¹H and ¹³C NMR. The results revealed that [Ni(binol)(bpy)]?CH₃OH was a paramagnetic tetrahedral complex. The physicochemical properties of the nanoparticles were characterized by various analysis techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and BET specific surface area. The used synthetic rout is facile and economic that makes it suitable for large scale production of pure nickel oxide nanoparticles.     

Date Fruits-Assisted Synthesis and Biocompatibility Assessment of Nickel Oxide Nanoparticles Anchored onto Graphene Sheets for Biomedical Applications

Nanographene- and graphene-based nanohybrids have garnered attention in the biomedical community owing to their biocompatibility, excellent aqueous processability, ease of cellular uptake, facile surface functionalization, and thermal and electrical conductivities. NiO nanoparticle-graphene nanohybrid (G-NiO) was synthesized by first depositing Ni(OH)₂ onto the surface of graphene oxide (GO) sheets. The Ni(OH)₂-GO hybrids were then reduced to G-NiO using date palm syrup at 85 °C. The prepared G-NiO nanohybrids were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy (EDX). The NiO nanoparticles, with a diameter of approximately 20–30 nm, were uniformly dispersed over the surface of the graphene sheets. The G-NiO hybrids exhibit biocompatibility in human mesenchymal stem cells (hMSCs) up to 100 μg/mL. The nanohybrids do not cause any significant changes in cellular and nuclear morphologies in hMSCs. The as-synthesized nanohybrids show excellent biocompatibility and could be a promising material for biomedical applications.     

Different morphologies of ZnO nanostructures via polymeric complex sol–gel method: synthesis and characterization

Various morphologies of ZnO nanostructures, such as nanoparticles, nanorods and nanoflowers have been achieved controllably by polymeric sol–gel method. In this approach, zinc nitrate Zn(NO₃)₂·6H₂O, citric acid and ethylene glycol were used as the source of Zn²⁺, the chelating agent and the solvent agent, respectively. The microstructure of the ZnO nanostructures was characterized by X-ray diffractometry, scanning electron microscopy with the energy dispersive X-ray spectroscopy, transmission electron microscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy. The effect of ethylene glycol to citric acid mole ratio on the morphology and structure of the products was discussed. The ZnO nanoparticles with diameter between 24 ± 2 nm was obtained with EG:CA mole ratio equal to 2:1. The optical properties of as-obtained power were investigated by ultraviolet–visible spectroscopy.     

Enhanced electrochemical performance of carbon-coated LiMPO<Subscript>4</Subscript> (M = Co and Ni) nanoparticles as cathodes for high-voltage lithium-ion battery

Olivine LiMPO₄ (M = Co and Ni) nanoparticles have been synthesized by the polyvinylpyrrolidone (PVP) assisted polyol method and adopted the resin coating process for carbon coating on the surface of the nanoparticles. The X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies confirmed the phase and structural co-ordination of bare and carbon-coated LiMPO₄ (M = Co and Ni) nanoparticles, respectively. The formation of uniform carbon layer of nanometer-measured thickness over nanoparticles is confirmed by the high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS). Wagner’s polarization study explains an improved electronic transport number (t _e) for carbon-coated LiMPO₄ (M = Co and Ni) cathodes as compared to bare samples. The electrochemical study of the Li-ion cells shows the first cycle discharge capacities of 180 and 97 mAh/g at 0.1 C for the cathodes LiCoPO₄/C and LiNiPO₄/C, respectively, which is an improvement of 21.2 and 25.8 % as compared to bare samples. The enhancement of electrochemical performance of the cells is attributed to the improved electronic properties of cathode materials due to the presence of carbon on the surface of nanoparticles.     

Electrochemical preparation of α-Ni(OH)2 ultrafine nanoparticles for high-performance supercapacitors

Well-dispersed nanoparticles of nickel hydroxide were prepared via a simple electrochemical method. Electrodeposition experiments were performed from 0.005 M Ni(NO₃)₂ bath at a constant current density of 0.1 mA cm^?2 on the steel cathode for 1 h. Recording the potential values during the deposition process revealed that the reduction of water has major role in the base electrogeneration at the applied conditions. The obtained deposit was characterized by the X-ray diffraction (XRD), infrared (IR), differential scanning calorimeter–thermogravimetric analysis, carbon–nitrogen–hydrogen (CHN), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The CHN, XRD, and IR analyses showed that the obtained deposit has α phase of Ni(OH)₂ with intercalated nitrate ions in its structure. Morphological characterization by SEM and TEM revealed that the prepared α-Ni(OH)₂ is composed of well-dispersed ultrafine particles with the size of about 5 nm. The supercapacitive performance of the prepared nanoparticles was analyzed by means of cyclic voltammetry and galvanostatic charge–discharge tests. The electrochemical measurements showed an excellent supercapacitive behavior of the prepared α-Ni(OH)₂ nanoparticles. It was also observed that the α-Ni(OH)₂ ultrafine particles have better electrochemical characteristic and supercapacitive behavior than β-Ni(OH)₂ ultrafine nanoparticles, including less positive charging potential, lower E _a???E _c value, better reversibility, higher E _OER???E _a, higher utilization of active material, higher proton diffusion coefficient, greater discharge capacity, and better cyclability. These results make the α-Ni(OH)₂ nanoparticles as an excellent candidate for the supercapacitor materials.     

Synthesis and characterization of nanosized NiO2 and NiO using Triton® X-100

Nanosized NiO₂ particles with an average diameter of 15 nm are prepared by treating of Ni(NO₃)₂ · 6H₂O with an aqueous solution of KClO in the presence of Triton® X-100. This black fine powder of nickel peroxide was characterized by XRD diffraction, energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The as-prepared NiO₂ can be easily transformed to nanosized NiO merely by washing it with acetone. The obtained NiO has an average diameter of 40 nm and was characterized by the same means used for NiO₂. The nanoparticles of NiO₂ and NiO were obtained in high yields and purities.      

Surfactant-assisted low-temperature thermal decomposition route to spherical NiO nanoparticles

Thermal decomposition has been employed to access spherical nickel oxide (NiO) nanoparticles from a new precursor, nickel-salicylate, [Ni(C₇H₅O₃)₂(H₂O)₄]. Surfactants, triphenylphosphine ((C₆H₅)₃P), and oleylamine (C₁₈H₃₅NH₂) were added to control the particle size. The products were characterized by X-ray diffraction, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, and thermogravimetric analysis. TEM images showed particles nearly spherical having sizes 5–15?nm. The magnetism of NiO nanoparticles was studied with a vibrating sample magnetometer. Due to smaller particle size and increased surface uncompensated spins, a superparamagnetic behavior is observed. The synthetic process is simple and affords high-purity material at a relatively lower calcination temperature.     

Preparation and Characterization of NiO Nanoparticles Via Solid-State Thermal Decomposition of Nickel(II) Schiff Base Complexes [Ni(salophen)] and [Ni(Me-salophen)]

This study focuses on the preparation and characterization of nickel oxide nanoparticles from nickel(II) Schiff base complexes as new precursors. At first nickel(II) complexes [Ni(salophen)] and [Ni(Me-salophen)] were synthesized and characterized by elemental analyses and FT-IR spectroscopy. Then NiO nanoparticles were prepared by solid-state thermal decomposition at 550 ºC for 3.5 h. The FT-IR spectrum confirmed the composition of products. The crystalline structures and morphology of products were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD results revealed that the obtained products were nickel oxide. SEM and TEM images demonstrated that the NiO nanoparticles have uniform shape with size between 35 and 70 nm.     

Microwave-assisted sol-gel synthesis of CeO2–NiO nanocomposite based NO2 gas sensor for selective detection at lower operating temperature

The progress in the development of gas sensors has considerably grown using some novel nanomaterials of metal, metal oxide and composite. In the current study, we intended and evaluated the properties of nanomaterials like CeO₂, NiO, and CeO₂–NiO composite and its application as NO₂ gas sensor. Sensing of low concentration of NO₂ gas at optimum functional temperature was succeeded using CeO₂–NiO nanocomposites (NCs) film. The working temperature ranges in between 100 and 225 ?°C. Highly crystalline nanomaterials (CeO₂, NiO and CeO₂–NiO) have been prepared by applying microwave-assisted sol-gel route. The as-prepared nanomaterials are characterized for their structure, size, morphology and constitution by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis. XRD studies of nanoparticles reveal the formation of nanoscale CeO₂ and NiO with crystallite size 26, 23 ?nm, respectively. Both are having a face centered cubic structure. The nanocomposite (NC) Ce:Ni ?= ?60:40 has crystallite size of 13 ?nm. XRD study of NCs shows assimilation of Ni metal into the ceria and proves physical similarities of two phases. It can be observed from SEM that prepared NC has a porous surface which enables more surface active sites for adsorbing oxygen. The optical properties are measured with the help of UV–Vis. Spectroscopy. Optical band gaps of 3.19, 3.41 and 2.9 ?eV were observed for CeO_2, NiO nanoparticles (NPs) and CeO₂–NiO NC, respectively. Gas sensing properties state that the NC material shows a higher gas response % of 67.34% for NO₂ gas (25 ?ppm) at comparatively low operating temperature (125 ?°C). It gives response time as (～28 ?s) and the recovery (～54 ?s). NiO incorporation in CeO₂ results in a decline of operating temperature of NC and improves the sensing features.     

Fly ash supported NiO as an efficient catalyst for the synthesis of xanthene and its molecular docking study against plasmodium glutathione reductase

A novel fly ash supported NiO (FA–NiO) nanocomposite solid heterogeneous catalyst has been prepared by impregnation of Ni(NO₃)₂ · 6H₂O on thermally activated fly ash (FA) support. FT-IR spectroscopy, X-ray diffraction analysis, scanning electron microscopy, TEM and BET techniques were employed to characterize the catalyst. The catalytic adeptness of FA–NiO was tested and optimized in xanthene formation. Catalyst gave very high yield and good purity. Stability of the catalyst could be promising as it easily recovered and reused giving a similar yield up to four cycles. FA–NiO is an efficient catalyst providing an environmentally clean process for xanthene formation and for developing a revolutionary way to use the majority of waste fly ash. Further, we have also performed docking simulation between 1ONF and a xanthene molecule to evaluate binding orientation and affinity of the ligand.     

Preparation, characterization, and catalytic activity of rare earth metal oxide nanoparticles

In present study, a series of rare earth metal oxide (CeO₂, Pr₂O₃, and Nd₂O₃) nanoparticles have been prepared by sol–gel route using Ce(NO₃)₃·6H₂O, Pr(NO₃)₃·6H₂O and Nd(NO₃)₃·6H₂O, and citric acid as precursor materials. Powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy are employed to characterize the size and morphology of the nano oxide particles. The particles are spherical in shape and the average particle size is of the order of 11–30 nm. Their catalytic activity was measured on the thermal decomposition of ammonium perchlorate and composite solid propellants (CSPs) by thermogravimetry (TG), TG coupled with differential thermal analysis (TG–DTA), and ignition delay measurements. The ignition delays and activation energies are found to decrease when rare earth metal oxide nanoparticles were incorporated in the system. Addition of metal oxide nanoparticles to AP led to shifting of the high temperature decomposition peak toward lower temperature and the burning rate of CSPs was also found to enhance. However, E _a activation energy for decomposition was also found to decrease with each catalyst.     

Synthesis and Characterization of CdS Nanoparticles via Cyclic Microwave from Cadmium Oxalate

The present study reports synthesis and characterization of CdS nanoparticles prepared by cyclic microwave route with the use of [Cd(C₂O₄)·3H₂O] powder as a precursor. The products, with an average size ~15 nm, were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, thermogravimetric analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. Optical property of obtained product was investigated by photoluminescence spectroscopy. The prepared nanostructures displayed a very strong luminescence at 528 nm (2.34 eV) at room temperature.     

The obtaining of NiCr2O4 nanoparticles by unconventional synthesis methods

This paper presents a study regarding the obtaining of NiCr₂O₄ by two new unconventional synthesis methods: (i) the first method is based on the formation of Cr(III) and Ni(II) carboxylate-type precursors in the redox reaction between the nitrate ion and 1,3-propanediol. The thermal decomposition of these complex combinations, at ~300 °C, leads to an oxide mixture of Cr₂O_3+x and NiO, with advanced homogeneity, small particles and high reactivity. On heating this mixture at 500 °C, Cr₂O₃ reacts with NiO to form NiCr₂O₄, which was evidenced by FT-IR and X-ray diffractometry (XRD) analysis; (ii) the second method starts from a mechanical mixture of (NH₄)₂Cr₂O₇ and Ni(NO₃)₂·6H₂O. On heating this mixture, a violent decomposition at 240 °C with formation of an oxides mixture (Cr₂O₃ + CrO₃) and NiO takes place. On thermal treatment up to 500 °C, an intermediary phase NiCrO₄ is formed, which by decomposition at ~700 °C leads to NiCr₂O₄, evidenced by FT-IR and XRD analysis. NiCr₂O₄ is formed, in both cases, starting with a temperature higher than 400 °C, when the non-stoichiometric chromium oxide (Cr₂O_3+x ) loses the oxygen excess and turns to stoichiometric chromium oxide (Cr₂O₃), which further reacts with NiO.     

Synthesis,crystal structure and DFT calculations of octahedral nickel(II) complexes derived from N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide

The two new nickel(II) complexes, [Ni(HL)(L)](NO₃)?H₂O (1) and [Ni(L)₂] (2) (where HL/L = N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide), have been synthesized and characterized by elemental analysis, spectroscopic, magnetic susceptibility, and cyclic voltammetric measurements. Single-crystal X-ray analysis of [Ni(HL)(L)](NO₃)?H₂O (1) and [Ni(L)₂] (2) has revealed the presence of a distorted octahedral geometry around nickel(II). The X-ray and spectral characterizations have confirmed the existence of the keto-enol form of the ligands in the complexes. The electronic structures and spectral properties of the ligands and the complexes have been explained by DFT and TDDFT calculations. Superoxide dismutase activity of these complexes has also been measured.     

Performance studies of electrolyte-supported solid oxide fuel cell with Ni–YSZ and Ni–TiO2–YSZ as anodes

Redox cycling of Ni-based anode induces cell degradation which limits the cell's lifetime during solid oxide fuel cell operation. In the present study, the redox testing of electrolyte-supported cells has been investigated with TiO₂-added NiO–YSZ anode matrix. Button cells were fabricated by die-pressing YSZ powder as electrolyte, and onto which NiO–YSZ or NiO–TiO₂–YSZ anode and LSM–YSZ composite cathode were painted. The electrochemical performance and stability have been evaluated by measuring current–voltage characteristics followed by impedance spectroscopy after each redox cycling. Anode matrices before and after cell operation have been characterized by X-ray diffraction (XRD), elemental dispersive X-ray (EDX), and scanning electron microscopy (SEM). During cell operation the peak power density decreases from 111 mW cm^?2 (239 mA cm^?2) to 84 mW cm^?2 (188 mA cm^?2) between 23 and 128 h with five redox cycles for cell having NiO–YSZ (40:60) anode. But for cell with NiO–TiO₂–YSZ (30:10:60), the anode peak power density was constant and stable around 85 mW cm^?2 (194 mA cm^?2) throughout the cell run of 130 h and five redox cycles. No loss in the open circuit voltage was observed. SEM and XRD studies of NiO–TiO₂–YSZ (30:10:60) anodes revealed formation of ZrTiO₄, which may be responsible for inhibition of Ni coarsening leading to stable cell performance.     

Microstructure and Magnetic Properties of Carbon‐Coated Nanoparticles

Abstract

In the present work, microstructure and superparamagnetic properties of two types of carbon‐coated magnetic Ni and Fe nanoparticles [Ni(C) and Fe(C)] are reviewed. High‐resolution transmission electron microscopy (HRTEM), electron diffraction (SAED), and x‐ray diffraction (XRD) analyses have been used to reveal the distinct structural morphologies of Ni and Fe nanoparticles. Moreover, novel carbon‐coated Ni nanoparticle assemblies offer us great opportunities for studying the mechanism of superparamagnetism in particle assemblies. Magnetization measurements [M(T) and M(H) curves] for assemblies of Ni nanoparticles indicate that modified superparamagnetic properties at T > T _B, have been found in the assemblies of Ni(C) particles. The blocking temperature, T _B, is determined to be near 115K under a certain applied field. Above T _B, the magnetization M(H, T) can be described by the classical Langevin function L using the relation, M/M _s (T = 0) = coth (μH/kT) ? kT/μH. It is suggested that these assemblies of carbon‐coated Ni nanoparticles have typical single‐domain, field‐dependent superparamagnetic relaxation properties. Finally, Mössbauer spectra and hyperfine magnetic fields at room temperature for the assemblies of Fe(C) nanoparticles confirm their distinct nanophases that were detected by structural analysis. Modified superparamagnetic relaxation is observed in the assemblies of Fe(C) nanoparticles, which is attributed to the nanocrystalline nature of the carbon‐coated nanoparticles.