Synthesis Of NiO Nanostructures Research Articles

Green structure orienting and reducing agents of wheat peel extract induced abundant surface oxygen vacancies and transformed the nanoflake morphology of NiO into a plate-like shape with enhanced non-enzymatic urea sensing application.

Researchers are increasingly focusing on using biomass waste for green synthesis of nanostructured materials since green reducing, capping, stabilizing and orientation agents play a significant role in final application. Wheat peel extract contains a rich source of reducing and structure orienting agents that are not utilized for morphological transformation of NiO nanostructures. Our study focuses on the role of wheat peel extract in morphological transformation during the synthesis of NiO nanostructures as well as in non-enzymatic electrochemical urea sensing. It was observed that the morphological transformation of NiO flakes into nanoplatelets took place in the presence of wheat peel extract during the preparation of NiO nanostructures and that both the lateral size and thickness of the nanostructures were significantly reduced. Wheat peel extract was also found to reduce the optical band gap of NiO. A NiO nanostructure prepared with 5 mL of wheat peel extract (sample 2) was highly efficient for the detection of urea without the use of urease enzyme. It has been demonstrated that the induced modification of NiO nanoplatelets through the use of structure-orienting agents in the wheat peel has enhanced their electrochemical performance. A linear range of 0.1 mM to 13 mM was achieved with a detection limit of 0.003 mM in the proposed urea sensor. The performance of the presented non-enzymatic urea sensor was evaluated in terms of selectivity, stability, reproducibility, and practical application, and the results were highly satisfactory. As a result of the high surface active sites on sample 2, the low charge transfer resistance, as well as the high exposure to the surface active sites of wheat peel extract, sample 2 demonstrated enhanced performance. The wheat peel extract could be used for the green synthesis of a wide range of nanostructured materials, particularly metal/metal oxides for various electrochemical applications.

Green Approach for the Synthesis of NiO Material and Their Non-Enzymatic Glucose Sensor-Based Applications at Low Potential

ABSTRACTThe study presents a novel route towards the synthesis of NiO nanostructures by using various green amino acids. The nanostructures were obtained by hydrothermal methodology assisted by threonine, arginine, aspartic acid, leucine, isoleucine and serine respectively. The characterization of the synthesized materials was studied by different techniques such as XRD, SEM and TEM. The synthesized structural features were explored for their electro-chemical properties and used for fabrication of glucose sensors based on non-enzymatic functions. The developed sensors demonstrated a promising result in terms of sensitivity, selectivity, and stability. The most important finding in the present study is the oxidation of glucose at low potentials such as 0.125, 0.23, 0.093, 0.26, 0.037, and -0.02 V respectively for the isoleucine, leucine, serine, threonine, arginine, and aspartic acid assisted NiO nanostructures. This unique finding is attributed to the morphology of different nanostructures of NiO grown with the addition of green additives. The glucose sensing ability of glucose was not affected in presence of species such as uric acid, ascorbic acid, and other carbohydrates due to their close oxidation potential compared with glucose. The sensitivities of proposed non-enzymatic glucose sensors were found to be for the isoleucine, leucine, serine, threonine, arginine, and aspartic acid assisted NiO nanostructures as 4930, 3173, 2648, 1724, 1070, and 525 µA/mM/cm2 respectively. The maximum sensing capability was recorded for isoleucine structures which showed higher sensitivity of 4930 µA/mM/cm2, greater stability and excellent anti-interference capability compared to other nanostructures. The limit LOD and LOQ were also found and remain 0.01 (S/N = 3) and 1.9 µM individually, for the newly developed method for the sensor based on NiO grown with isoleucine amino acid. The potential application of isoleucine assisted NiO nanostructures composite material for the blood sample quantities analysis which further it demonstrates the feasibility of developed based for the non-enzymatic glucose sensor.

A facile one-step flash combustion synthesis and characterization on C doped NiO nanostructures

Synthesis of NiO nanostructures in presence of different concentrations of citric acid (CA) was achieved through flash combustion technique. The NiO nanostructures formation was confirmed through X-ray diffraction analysis. At low concentrations of CA no extra peak was observed in XRD patterns, however when the CA concentration was raised to 5 and 10 g, two new extra peaks appeared at 44.6° and 51.9° which may be attributed to the presence of C. The crystallite size was noticed to reduce from 29 to 18 nm with increase in the CA concentration. All observed Raman bands were noticed to be shifted owing to the quantum size effect. EDX and SEM mapping confirm the existence of C. SEM images confirm the cubic nanocrystalline morphology for 0.5 g CA:NiO, however with increasing CA concentration a drastic change in morphology, i.e. from nanocrystals to extended nanosheets, was observed. The energy gap values were determined using Kubelka-Munk theory and found in range of 3.5–4.0 eV. An additional energy gap ∼2 eV was also noticed at higher CA concentration. The values of relative permittivity, εr′, were found in the range of 18–110 for CA concentration upto 5g, however, at 10.0 g CA its value was found to be order of 104 at 2 × 105 Hz.

Synthesis of NiO nanostructures and their catalytic activity in the thermal decomposition of ammonium perchlorate

NiO nanorods and microflowers were successfully achieved via a hydrothermal reaction without any surfactant and then a post heat treatment process. Characterization methods, such as X-ray diffraction, transmission electron microscopy and scanning electron microscopy, were employed to systematically investigate the mechanism for the morphology evolution, as well as the transformation of phase structure. Furthermore, the physicochemical properties of NiO with different morphologies were also examined and it was found that these properties were pretty sensitive to the morphology. Compared with the nanorods, the flower-like NiO nanostructures showed a great enhancement of the ferromagnetic properties. The catalytic activities of NiO with different morphologies were investigated through the thermal decomposition of ammonium perchlorate (AP). AP exhibited relatively low decomposition temperature and fast reaction rate in the catalyzed formations making NiO with microflower structure an effective catalyst. This study provided a facile way to control the morphology of NiO nanostructures, which also indicates the potential application of the nanostructures, with the modified magnetic properties, in modern science and technology.

Preparation and Characterization of Nickel Oxide Nanostructures via Solid State Thermal Decomposition Approach

Pyramidal NiO nanostructures have been prepared via a solid-state thermal decomposition reaction. In the synthesis of NiO nanostructures, a [Ni(phen)2]2+ complex was employed as a novel precursor in solid-state thermal decomposition process at air at 500°C. The products were characterized by elementary analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Synthesized nickel oxide microstructures have a cubic phase with average size of 56 nm via nanoparticles that exists on the surface of the pyramidal microstructure. The present method is both simple and low-cost, which makes it feasible for scale-up production of NiO nanostructures.

Synthesis of NiO nanostructures from 1D to 3D and researches of their gas-sensing properties

We successfully synthesized four kinds of NiO from 1D to 3D as follows: NiO nanowires, nanosheets, nanobulks and nanospheres. With our careful preparation and accurate reagent ratio, different and beautiful morphologies were obtained through the hydrothermal process only by changing the active agent. We mainly chose NiC2O4·2H2O as the precursors of NiO and found that the existence of ethylene glycol (EG), polyethylene glycol (PEG) and glycine played an important role in synthesis of disparate NiO nanostructures. The gas-sensing performances of the as-prepared NiO nanostructures with different dimensions were investigated toward ethanol at 350°C. NiO nanowires present the better gas sensing properties and the corresponding response value (Rg/Ra), response time and recovery time were about 3.4, 4s, and 5s to 50ppm ethanol, respectively.