Centrifugal Microfluidic Synthesis of Nickel Sesquioxide Nanoparticles

Nickel sesquioxide (Ni2O3) nanoparticles were synthesized using centrifugal microfluidics in the present study. The obtained nanoparticles were characterized using SEM to investigate their morphology and microstructure, and XRD was employed to analyze their purity. The nanoparticle size data were measured and analyzed using ImageJ (v1.8.0) software. The flow process and mixing procedure were monitored through computational fluid dynamics simulation. Among the synthesized Ni2O3 nanoparticles, those obtained at the rotation speed of 1000 rpm for 10 min with angular acceleration of 4.2 rad/s2 showed the best performance in terms of high purity, complete shape and microstructure, small diameter, and narrow diameter distribution. The experimental results demonstrate that the rotation speed of the microfluidic chip and reaction time contribute to a decrease in particle diameter and a narrower diameter distribution range. In contrast, an increase in acceleration of the rotation speed leads to an expanded nanoparticle size range and, thus, a wider distribution. These findings contribute to a comprehensive understanding of the effects exerted by various factors in centrifugal microfluidics and will provide new insights into nanoparticle synthesis using centrifugal microfluidic technology.

Application of visible light active photocatalysis for water contaminants: A review

Organic water pollutants are ubiquitous in the natural environment arising from domestic products as well as current and legacy industrial processes. Many of these organic water pollutants are recalcitrant and only partially degraded using conventional water and wastewater treatment processes. In recent decades, visible light active photocatalyst has gained attention as a non-conventional alternative for the removal of organic pollutants during water treatment, including industrial wastewater and drinking water treatment. This paper reviews the current state of research on the use of visible light active photocatalysts, their modified methods, efficacy, and pilot-scale applications for the degradation of organic pollutants in water supplies and waste streams. Initially, the general mechanism of the visible light active photocatalyst is evaluated, followed by an overview of the major synthesis techniques. Because few of these photocatalysts are commercialized, particular attention was given to summarizing the different types of visible light active photocatalysts developed to the pilot-scale stage for practical application and commercialization. The organic pollutant degradation ability of these visible light active photocatalysts was found to be considerable and in many cases comparable with existing and commercially available advanced oxidation processes. Finally, this review concludes with a summary of current achievements and challenges as well as possible directions for further research. PRACTITIONER POINTS: Visible light active photocatalysis is a promising advanced oxidation process (AOP) for the reduction of organic water pollutants. Various mechanisms of photocatalysis using visible light active materials are identified and discussed. Many recent photocatalysts are synthesized from renewable materials that are more sustainable for applications in the 21st century. Only a small number of pilot-scale applications exist and these are outlined in this review.

Observation of Josephson-like Tunneling Junction Characteristics and Positive Magnetoresistance in Oxygen Deficient Nickelate Films of Nd0.8Sr0.2NiO3-δ

Nickelate films have recently attracted broad attention due to the observation of superconductivity in the infinite layer phase of Nd0.8Sr0.2NiO2 (obtained by reducing Sr doped NdNiO3 films) and their similarity to the cuprates high temperature superconductors. Here, we report on the observation of a new type of transport in oxygen poor Nd0.8Sr0.2NiO3-δ films. At high temperatures, variable range hopping is observed while at low temperatures a novel tunneling behavior is found where a Josephson-like tunneling junction characteristic with serial resistance is revealed. We attribute this phenomenon to coupling between superconductive (S) surfaces of the grains in our Oxygen poor films via the insulating (I) grain boundaries, which yields SIS junctions in series with the normal (N) resistance of the grains themselves. The similarity of the observed conductance spectra to the tunneling junction characteristic with Josephson-like current is striking, and seems to support the existence of superconductivity in our samples.

Synthesis and Characterization of ZnO from Thermal Decomposition of Precipitated Zinc Oxalate Dihydrate as an Anode Material of Li-Ion Batteries

Zinc oxide (ZnO) is one of the most promising materials applied in Li-ion batteries. In this research, ZnO was synthesized by the thermal decomposition of zinc oxalate dihydrate. This precursor was obtained from the precipitation process of zinc sulfate with oxalic acid. In-depth studies were carried out on the effect of various heating temperatures of zinc oxalate dihydrate precursors on ZnO synthesis. The as-prepared materials were characterized by XRD, SEM, and FTIR. Based on the XRD analysis, the presence of the ZnO-wurtzite phase can be confirmed in samples heated at temperatures above 400 °C. Meanwhile, SEM-EDX results showed that the ZnO particles have a micron size. Cells with ZnO samples as anodes have low columbic efficiency. In contrast, cells with ZnO/Graphite composite anodes have a relatively large capacity compared to pure graphite anodes. Overall, based on the consideration of the characterization results and electrochemical performance, the optimal sintering temperature to obtain ZnO is 600 °C with a cell discharge capacity of ZnO anode and in the form of graphite composites is 356 mAh/g and 450 mAh/g, respectively. This suggests that ZnO can be used as an anode material and an additive component to improve commercial graphite anodes’ electrochemical performance.

Synthesis and comparative study on the structural and optical properties of ZnO doped with Ni and Ag nanopowders fabricated by sol gel technique

In this work we have tried to prepare Ni and Ag doped ZnO nanopowders using the sol gel technique. The influence of Ni and Ag (1, 3 and 5 mol.%) on the crystalline structure and optical properties of ZnO was investigated. The samples were characterized by XRD, FTIR and UV–visible spectrophotometer. XRD patterns confirmed the wurtzite formation of doped and undoped ZnO nanopowders. The average crystallite sizes of the prepared samples found from XRD were 19 nm for undoped ZnO, from 17 to 22 nm for Ni-ZnO and from 19 to 26 nm for Ag-ZnO. The average crystallite size of Ag-ZnO increased with increasing Ag contents. Different optical properties of Ni-ZnO and Ag-ZnO nanopowders were observed for different Ni and Ag content. The band gaps of Ni-ZnO and Ag-ZnO nanopowders were lower than that of the undoped ZnO (3.1 eV). The band gaps of Ag-ZnO were lower than that of Ni-ZnO. The optical properties of ZnO were enhanced by Ni (mol.%) in the UV region and by Ag (3 and 5 mol.%) in the visible region.

Preparation and characterization of MCM-48/nickel oxide composite as an efficient and reusable catalyst for the assessment of photocatalytic activity

Mesoporous silica (MCM-48) was synthesized and used as a catalyst for supporting the nickel oxide photocatalyst. The loading of nickel oxide on MCM-48 results in a considerable reduction in the bandgap energy to 2.4 eV. MCM-48 was used as a catalyst and back-supporter for the nickel oxide to enhance its photocatalytic properties along with adsorption capacity. Therefore, the adsorption capacity of MCM-48/Ni₂O₃ was enhanced by 17.5% and 32.2% compared to Ni₂O₃ and MCM-48, respectively. Furthermore, the percentage of photocatalytic degradation was improved by approximately 68.2% relative to the free-standing Ni₂O₃. The MCM-48/Ni₂O₃ proved the chemisorption adsorption mechanism that happens in multilayer form through the heterogeneous surface. This through fixing such Ni₂O₃ particles over the nanoporous topography to provide more exposed hot adsorption and photocatalytic sites for the incident light photons. Therefore, supporting Ni₂O₃ catalytic particles onto MCM-48 produces a new category of photocatalytic systems with promising active centers for the efficient degradation of Congo red dye molecules.

Ethanol introduced synthesis of ultrastable 1T-MoS2 for removal of Cr(VI)

Metallic 1T phase of MoS₂ (1T-MoS₂) has aroused great concern for decontamination of heavy metal ions from water. Herein, ultrastable 1T-MoS₂ was successfully achieved via a gentle two-stage solvothermal strategy utilizing water and ethanol as solvent for efficient removal of Cr(VI). Notably, nearly 100 % 1T-MoS₂ was obtained, and it remained highly stable in air even for 360 days. Electron paramagnetic resonance analysis showed that sulfur vacancies were in situ formed on the 1T/2H mixed phase MoS₂ (M-MoS₂) under the induction of ethanol, which is critical to promote the transformation of 2H to 1T phase. Molecular dynamic simulation revealed that there was strong interaction between ethanol and MoS₂ surface, which could decrease the total energy of MoS₂ for strengthening stability of 1T phase. Moreover, 1T-MoS₂ shows superior sorption capacity (200.3 mg·g^-1) for removal of Cr(VI), twice more than that of M-MoS₂ and 2H phase MoS₂ under the same condition. Significantly, the stable phase structure of 1T-MoS₂ and chromium adsorption capacity still remained even after five cycles of chromium adsorption. The study of Cr(VI) adsorption mechanism revealed that the chromium adsorption was attributed to the undercoordinated Mo(IV) as active site and coupled with redox reaction during removal process.

Fast Production of High Performance LiNi0.815Co0.15Al0.035O2 Cathode Material via Urea-Assisted Flame Spray Pyrolysis

The high throughput and rapid flame-assisted spray pyrolysis method has been adapted to synthesize cathode materials LiNi0.apCo0.15Al0.035O2 (NCA). This method is considered low cost and simple. By varying the precursor solution concentration and sintering temperature, the optimal condition was established at temperature sintering of 800 °C and precursor solution concentration of 1 M. X-ray diffraction patterns showed the as-prepared NCA particles exhibit a pure well-ordered hexagonal layer structure with high crystallinity. Polyhedral shaped micro-sized particles are confirmed by SEM images. Galvanostic charge–discharge tests were conducted using cylindrical full-cell utilizing artificial graphite as the anode. The highest specific initial discharge capacity measured between 2.7 and 4.3 V is 155 mAh g−1 with capacity retention of 92% after cycled at 0.2 C for 50 cycles. Thus, this method is considered as a satisfying approach for NCA mass production.

Synthesis and Characterization of Nitrogen-doped Carbon Nanotubes Derived from g-C3N4

Here, nitrogen-doped carbon nanotubes (CNT-N) were synthesized using exfoliated graphitic carbon nitride functionalized with nickel oxides (ex-g-C₃N₄-NixO_y). CNT-N were produced at 900 °C in two steps: (1) ex-g-C₃N₄-Ni_xO_y reduction with hydrogen and (2) ethylene assisted chemical vapor deposition (CVD). The detailed characterization of the produced materials was performed via atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The possible mechanism of nanotubes formation is also proposed.

A ternary nanocomposite based on nickel(iii) oxide@f-CNF/rGO for efficient electrochemical detection of an antipsychotic drug (Klonopin) in biological samples

The formation of the Ni₂O₃@f-CNF/rGO composite for the electrochemical detection of KNP.

Self-doping synthesis of trivalent Ni2O3 as a hole transport layer for high fill factor and efficient inverted perovskite solar cells

We present a novel self-doping method to obtain trivalent nickel oxide (Ni₂O₃) as an HTL, and its excellent optical transmittance and hole extraction efficiencies lead to a PCE of 17.89% and high FF of 82.66%.

Efficient photocatalytic removal of safarnin-O dye pollutants from water under sunlight using synthetic bentonite/polyaniline@Ni2O3 photocatalyst of enhanced properties

This study involves a synthesis of bentonite/polyaniline composite (BE/PANI) of enhanced physicochemical properties as catalyst support for Ni₂O₃ photocatalyst. The change in the structural properties, morphological features, and optical behavior was addressed utilizing several analytic techniques. The characterization results reflected considerable enhancement in the specific surface area after the integration between bentonite and polyaniline (127 m²/g) and after loading of the campsite by Ni₂O₃ forming bentonite/polyaniline@Ni₂O₃ composite (BE/PANI@Ni₂O₃) (231 m²/g). Additionally, the band gap energy was reduced to 2.41 eV and 1.61 eV for BE/PANI and BE/PANI@Ni₂O₃, respectively, as compared to that of 3.4 eV for pure Ni₂O₃. The photocatalytic removal of safranin-O dye under sunlight exposure using BE/PANI@Ni₂O₃ as catalyst revealed great enhancement in the removal percentages by 63%, 75%, and 72.35% higher than bentonite, polyaniline, and Ni₂O₃, respectively. Five milligrams per liter of safranin-O dye can be completely removed from 100 ml water using 0.05 g of the composite after 90 min. The catalyst also was applied effectively in the removal of safranin-O dye from raw water samples as a realistic application of the synthetic composite. Synthetic BE/PANI@Ni₂O₃ as photocatalyst showed very high stability and can be used seven times as photocatalytic at amazing removal percentages.

Enhanced photocatalytic removal of Safranin-T dye under sunlight within minute time intervals using heulandite/polyaniline@ nickel oxide composite as a novel photocatalyst

Natural zeolite heulandite/polyaniline composite (Hu/PANI) was synthesized for the first time as catalyst support for nickel oxide photocatalyst (Hu/PANI@Ni₂O₃). The structural, chemical, morphological, textural and optical properties were investigated using different techniques. The synthetic Ni₂O₃ crystals showed well developed flaky habits with diameter range 200-400 nm and length range 1-4 µm. The estimated band gap energies of Hu/PANI composite and Hu/PANI@Ni₂O₃ composite are 1.8 eV and 1.46 eV, respectively, which are remarkably smaller than the recorded value for pure nickel oxide. The photocatalytic properties of Hu/PANI@Ni₂O₃ composite for efficient degradation of safranin-T dye were evaluated under sunlight as a function of irradiation time, initial dye concentration, catalyst mass, solution pH, and the catalyst stability. Hu/PANI@Ni₂O₃ composite exhibits amazing photocatalytic degradation efficiency for safranin dye, whereas 80%, 98%, and ~ 100% of 5 mg/l dye were removed after only 1 min of solar irradiation using 0.025, 0.03, and 0.035 g of Hu/PANI@Ni₂O₃, respectively. The higher concentrations of the dye (10-50 mg/L) can be fully removed within minutes by increasing the solution pH or using higher doses from the Hu/PANI@Ni₂O₃ catalyst. The removal percentage achieved the maximum value at the alkaline conditions. Also, the Hu/PANI@Ni₂O₃ displayed high stability and remain 84.5% of the initial photocatalytic efficiency after 5 runs. Additionally, the composite can be used effectively in the removal of different types of dyes and mixed dyes within the same time intervals. Thus, loading of nickel oxide onto hybrid Hu/PANI composite as a catalyst support achieved amazing photocatalytic degradation capacity.

Surfactant-free one-pot synthesis of CeO2, TiO2 and Ti@Ce oxide nanoparticles for the ultrafast removal of Cr(vi) from aqueous media

Cerium oxide (CeO2), titanium oxide (TiO2) and titanium oxide impregnated with cerium oxide (Ti@Ce oxide) nanoparticles were synthesized using a simple one-pot surfactant-free method. The synthesized adsorbents were tested against the removal of Cr(vi) from aqueous medium. Comprehensive characterization methods like BET, XRD, SEM, EDAX, HR-TEM, SAED, HR-XPS and FT-IR were performed at different stages of the adsorption process and synthesis. A N2-BET study revealed the large surface area (268 m2 g-1) and pore size (6.8 nm) of CeO2 nanoparticles, which decreased after impregnation of titania. An XRD study demonstrated the phase transformation of TiO2 from the anatase phase to the rutile phase after the impregnation with CeO2 by lowering the phase transformation temperature from >550 °C to 400 °C. Ti0.3@Ce0.7 oxide nanoparticles showed 81% removal of Cr(vi) within 2.5 min of initiating the adsorption process while more than 92% removal of Cr(vi) was achieved within 10 min of adsorption. A HR-XPS study indicated the dual oxidation states of ceria and titania metals, which helped to convert the more toxic Cr(vi) ions to less toxic Cr(iii) ions during the adsorption process. The adsorption pattern depicted the monolayer behavior of Cr(vi) obeying the Redlich-Peterson isotherm and followed pseudo second-order kinetics. An intraparticle diffusion model disclosed the surface and pore resistance diffusion of Cr(vi) on the surface of adsorbents.

Facile synthesis of hierarchical nickel (III) oxide nanostructure: A synergistic remediating action towards water contaminants

Heavy metal ion removal from consumable water is an indispensable need to maintain healthy life. Therefore cost effective and highly efficient sorbents are strongly needed to pose threat to real water pollution. Nanomaterials are widely used to maintain clean aqueous system in a very cost effective way with high removal efficiency. In this present work, pure coral like Ni₂O₃ nanostructures were prescribed for Cr(VI) remediation which were prepared by two step synthesis procedure at room temperature. The single hierarchical morphology as confirmed from HRTEM (size∼200 nm) were subjected to toxic Cr(VI) ion removal experiments. They were found to remove ∼65% Cr(VI) ions that was higher than that of pure Ni₂O₃ nanoparticles of comparable size. The enhanced properties were explained on the basis of the defect states present within the nanostructure, investigated by positron annihilation lifetime spectroscopy (PALS). It was found that the hierarchical nanostructure had more number of di-vacancies and vacancy-clusters as compared to the particles. On performing isotherm fitting, it was found that the coral like morphology had a high heterogeneity factor that aided to a high adsorption rate when compared to the pure Ni₂O₃ nanoparticles (which had a homogenous surface). The synthesized nanostructure was severely toxic to bacterial community having minimum inhibitory concentration (MIC) of ∼300 μg/L. Also the nanostructure exhibited dual functionality towards Cr(VI) and bacteria contaminated water at 200 μg/ml. The maximum Cr(VI) removal efficiency for this dual system is found to be 39% whereas antibacterial activity was turned out to be 30% which was extensively higher than that of toxic Cr(VI) ions. A plausible mechanism for the dual functionality was also predicted.

Photocatalytic removal of Congo red dye using MCM-48/Ni2O3 composite synthesized based on silica gel extracted from rice husk ash; fabrication and application

MCM-48 mesoporous silica was successfully synthesized from silica gel extracted from rice husk ash and loaded by nickel oxide (Ni₂O₃). The resulted composite was characterized using X-ray diffraction, scanning electron microscope, and UV-vis spectrophotometer. The role of MCM-48 as catalyst support in enhancing the photocatalytic properties of nickel oxide was evaluated through the photocatalytic degradation of Congo red dye under visible light source. MCM-48 as catalyst support for Ni₂O₃ shows considerable enhancement in the adsorption capacity by 17% and 29% higher than the adsorption capacity of MCM-48 and Ni₂O₃, respectively. Additionally, the photocatalytic degradation percentage increased by about 64% relative to the degradation percentage using Ni₂O₃ as a single component. The adsorption mechanism of MCM-48/Ni₂O₃ is chemisorption process of multilayer form. The using of MCM-48 as catalyst support for Ni₂O₃ enhanced the adsorption capacity and the photocatalytic degradation through increasing the surface area and prevents the nickel oxide particles from agglomeration. This was done through fixing nickel oxide particles throughout the porous structure which providing more exposed active adsorption sites and active photocatalyst sites for the incident photons. Based on the obtained results, supporting of nickel oxide particles onto MCM-48 are promising active centers for the degradation of Congo red dye molecules.

Application of Fe-Cu binary oxide nanoparticles for the removal of hexavalent chromium from aqueous solution

The adsorption process has been used as an effective technique for the removal of metal ions from aqueous solutions. Groundwater remediation by nanoparticles has received interest in recent years. In the present study, a binary metal oxide of Fe-Cu was prepared and used for the removal of hexavalent chromium from aqueous solution. Batch experiments were performed to investigate the effects of initial Cr (VI) concentration, dose of adsorbent, and pH of solution on the removal efficiency of Cr (VI). The prepared nanostructured Fe-Cu binary oxides were able to reduce the concentration of Cr (VI) in aqueous solution. Binary metal oxides nanoparticle exhibited an outstanding ability to remove Cr (VI) due to high surface area, low particle size, and high inherent activity. The percentage removal efficiency of Cr (VI) increased with nanoparticles doses (0.1 g L(-1)-2.5 g L(-1)), whereas it decreased with initial Cr (VI) concentration (1 mg L(-1)-25 mg L(-1)) and with pH (3-9). The Freundlich model was found to be the better fit for adsorption isotherm. The prepared nanomaterial was characterized using powder X-ray diffraction, scanning electron microscopy (SEM), and ultraviolet (UV)-visible spectroscopy. It showed that the Fe-Cu binary oxides were formed in single phase. SEM micrograph showed aggregates with many nano-sized particles. UV-visible spectroscopy showed quantum confinement effect.

Cauliflower-like Ni/NiO and NiO architectures transformed from nickel alkoxide and their excellent removal of Congo red and Cr(vi) ions from water

Cauliflower-like nickel alkoxide, Ni/NiO and NiO architectures were synthesized via a reflux route using NaBH₄–EG as alkaline precipitant.