جستجوی مقالات مرتبط با کلیدواژه "metal oxide" در نشریات گروه "شیمی"

This study presents the development of a highly efficient NiCoMn@N,Co-rGO electrocatalyst designed to facilitate electrochemical water electrolysis, specifically addressing both the Oxygen Evolution and Hydrogen Evolution Reactions. This catalyst features a novel hybrid nanostructure comprising Co-Ni-Mn oxides integrated onto nitrogen- and cobalt-co-doped reduced graphene oxide (N,Co-rGO). The synthesis involved the improved Hummers’ method for graphene oxide preparation, followed by nitrogen and cobalt doping via calcination, and deposition of Co-Ni-Mn oxides through a solvothermal process. Physicochemical and electrochemical characterizations confirmed the successful formation of a mesoporous structure and efficient synergy between the metal oxides and graphene substrate. The NiCoMn@N,Co-rGO composite exhibits superior catalytic efficiency in facilitating the Oxygen Evolution Reaction in alkaline media, achieving a potential of 1.58 V at 10 mA/cm² (overpotential: 0.27 V), compared to 1.62 V (overpotential: 0.50 V) for NiCoMn oxide. For the Hydrogen Evolution Reaction, it achieves a potential of -0.50 V at -10 mA/cm² (overpotential: 0.49 V), similar to NiCoMn oxide. The improved efficiency is ascribed to the synergistic effects of nitrogen and cobalt doping in the reduced graphene oxide framework, improving conductivity, active site accessibility, and structural stability. These findings establish NiCoMn@N,Co-rGO as a more efficient electrocatalyst for OER.

Biodiesel production from waste cooking oil (WCO) holds promise as a renewable and sustainableenergy source. However, high levels of free fatty acids (FFAs) in WCO require efficient pre-treatment before transesterification. Utilizing solar energy for heterogeneous catalytic reactionsoffers an alternative to thermal-driven processes. TiO2EFBA, synthesized via the wet impregnationmethod, exhibits distinctive physicochemical properties confirming the successful incorporationof titanium dioxide (TiO2) onto the metal oxides of empty fruit bunches ash (EFBA), thereby en-hancing the catalyst’s performance and stability. Results showed that TiO2EFBA exhibits superiorFFA conversion compared to TiO2alone. Under optimized reaction conditions, employing 4 wt%TiO2EFBA catalyst, 20:1 methanol to oil molar ratio, and 2 h reaction time at room temperatureunder Ultra Violet (UV) light, achieves a remarkable 78% conversion rate of FFAs in WCO.Mechanistic investigation reveals the crucial role of electron/hole (e−/h+) species in reducingFFAs by suppressing the e−/h+mechanism. Notably, TiO2EFBA facilitates easy separation andcan be reused for 10 cycles, demonstrating its stability as a heterogeneous photocatalyst.

Non-edible vegetable oils have garnered significant research attention in recent years due to their enhanced tri-bological characteristics as biolubricants. Jatropha Curcas oil, in particular, shows promising potential as a feedstock for lubricant production. In this study, Jatropha biolubricant was synthesized through a two-step transesterification process: first converting Jatropha seed oil to methyl ester and then further transesterifying the methyl ester with sodium methoxide in the presence of ethylene glycol. The synthesis achieved a yield of 83.21-90% of Jatropha biolubricant using sodium methoxide as the catalyst. To enhance its performance, the synthesized biolubricant was blended with copper oxide (CuO) and zinc oxide (ZnO) as metal additives. Viscosity tests revealed that the blended biolubricant at 1 wt% additive concentration exhibited optimal viscosity characteristics: 52.952 cSt at 40 ℃ and 8.767 cSt at 100 ℃, compared to 31.58 cSt and 6.547 cSt, respectively, for the biolubricant without additives. Furthermore, blended biolubricant exhibited improved thermal degradation resistance and enhanced oxidative stability across different additive concentrations. Key lubricating properties such as pour point (10 ℃), viscosity at 40 ℃ (52.951 cSt), viscosity at 100 ℃ (8.767 cSt), and viscosity index (165.54) were analysed and found comparable to SAE 40 petroleum lubricants and other plant-based biolubricants.

The fabrication of sustainable and efficient metal oxide-based semiconductor materials for effective degradation of environmental pollutants and other applications are currently attracting major interest from researchers. For this reason, magnetic iron oxide (Fe3O4) and zinc incorporated magnetic iron oxide (Zn@Fe3O4) nanoparticles were successfully synthesized by a co-precipitation method and tested for their physical properties and also as a photocatalysts for the degradation of toxic dye from the environment. The photocatalyst were analyzed by the use of scanning electron microscopy (SEM), x-ray diffraction (XRD) and Ultra-Violet Visible spectrophotometer to evaluate their morphology, crystallinity and band gap properties, respectively. The photocatalytic degradation performance of synthesized Fe3O4 and Zn@Fe3O4 was studied for their degradation efficiency on methylene blue (MB) dye. The photocatalytic activity of Fe3O4 was affected by doping with Zn ion. The highest methylene blue degradation (83.80 % and 70.50 %) for Fe3O4 and Zn@Fe3O4 were obtained at 0.5 g dose. The XRD and SEM results approved the existence of Fe3O4 and Zn@Fe3O4, and also highlighted the successful entrance of zinc ion onto Fe3O4. The introduction of zinc dopant into Fe3O4 lattices increases the band gap from 2.77 eV to 2.80 eV. The study of electronic structure of methylene blue was examined through quantum chemical calculations using density functional theory method (DFT) in order to give an insight on the nature of MB interaction with synthesized photocatalyst. The DFT results revealed that the nitrogen atom of the MB molecule is the favorite sites of interaction with the metal oxide surface. Furthermore, the experimental findings showed that magnetic iron oxide demonstrated a good photocatalyst in degradation of methylene blue as compared to the zinc doped magnetic iron oxide particle.

Carbon nanotubes (CNTs) have gained massive attention given their special and unique features including high surface area, suitable chemical and electrochemical stability, unique mechanical and electronic features, as well as unidimensional structure. Two groups of CNT-based hybrids that have received much attention include nanotube/metal nanoparticles and nanotube/oxide nanoparticles hybrids. There are two major methods for preparing such hybrids: (I) in situ formation of nanoparticles in the presence of nanotubes, (II) use of prefabricated nanoparticles and binding them to the nanotube surface. In the CNTs decoration, the aim is to deposit nanoparticles with adhesivity on the nanotubes surface and a suitable bonding should be established between these two materials. Meanwhile, to achieve a hybrid with improved properties, the initial nanotube features should be kept as much as possible. Three principal methods have been evaluated for CNTs decoration: (I) electrochemical deposition and electroless, (II) chemical deposition, and (III) physical deposition. In this study, the aim is to examine different methods of CNTs decoration and to present the mechanism of methods. For this purpose, different examples related to each method and the effective parameters have been evaluated and discussed. Likewise, recent advances in CNTs decoration with metal and metal oxide nanoparticles have been explored in different applications.

Nowadays, with the expanded radar (Radio Detection and Ranging) systems, the investigation of various materials with the capability to reduce or block reflected electromagnetic radiation has developed sharply. In this study, graphene quantum dots-decorated metal-oxide magnetic composites were fabricated as electromagnetic absorber materials because of their light weight, and good electric and magnetic properties. Furthermore, to investigate morphology engineering, a hydrothermal route was applied to fabricate nanostructures. Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and elemental mapping (EDS-mapping). Also, the magnetic moment and electromagnetic interference shielding were tested by Vibrating-sample magnetometer (VSM) and reflection loss (RL), respectively.

Nanotechnology is an emerging discipline for biomedical application. Nanoparticles (NPs) research is one of the most studied and rapidly evolving field with its wide range of diagnostic and therapeutic applications, particularly in antimicrobial development. Following the improvement of the biomaterial’s functionality, the new area of ‘nanocomposites’ which often refers to the combination of NPs with other biomaterials such as hydrogel, polymers or other stabilizers, has swiftly followed. In the past decades, bacterial infections have caused negative impacts on human health, social and economic development in the globe. These problems are further aggravated by antibiotic resistance issues caused by drug-resistant microbes. With this, the development of antibacterial NPs has become an important field to alternate for the discovery of novel antibacterial agent. This review aims to discuss the key features of NPs, primarily derived from metal and metal oxide, for their antibacterial use in the clinic, the mechanisms of bacterial killing, and to cover some of the key challenges towards the Food and Drug Administration (FDA) approval for clinical use.

Numerous metal oxide nanomaterials, such as titanium dioxide (TiO2</sub>), tin oxide (SnO2</sub>), and zinc oxide (ZnO), are highly suitable for the fabrication of effective humidity sensors. Comparatively, ZnO is considered as metal oxide with the highest potential due to its unique properties, such as the enormous excitation binding energy of 60 meV, a direct wide bandgap (3.37eV), and the ability to be synthesized and grown at low temperatures. To further enhance the sensing performance of ZnO structure for humidity sensing, parameters such as the morphology and crystallinity of the ZnO structure can be optimized through control of synthesis conditions, such as precursor concentration, reaction time, temperature, and pH. Although various fabrication and characterization of ZnO nanostructures composited with other metal oxides have been published, there are insufficient investigations that highlight the performance of humidity sensors using ZnO alone. Therefore, this study provides a comprehensive analysis of the application of ZnO nanostructure in developing humidity sensors. The discussion in this review includes a summary of the recent development of humidity sensors and the parameters used to measure their sensing performances such as doping and compounding method. The study also highlighted the unique features of ZnO and the numerous methods used to synthesis ZnO, including sol-gel immersion, two-step solution, hydrothermal synthesis, and spin-coating process. In short, the intriguing development of ZnO-based humidity sensors would offer an alternative option to employ effective humidity-sensing devices in thin-film solar cells and ultraviolet (UV)-based applications.</em>

In this study, a green process for the synthesis of Mn and Cu oxides in chitosan membranes is reported. The process consists of two steps: (1) synthesis of Mn/Mn2O3 nano/microstructures in the presence of onion via hydrothermal method, (2) synthesis of Mn/Cu/O/chitosan nanocomposites using chitosan, CuO powder, and Mn/Mn2O3 prepared in the first step. The SEM images showed formation of the bundles of spherical Mn/Cu/O/chitosan nanocomposites. The XRD patterns confirmed the formation of the nanocomposites. The problem of water pollution is of a great concern and adsorption is one of the most efficient techniques for removing the pollution from the solvent phase. The nanocomposites synthesized in this work can help us to solve the waste disposal problem. They are effective adsorbents for MB and phenol removal from aqueous solution. In UV-Vis spectra, the intensity of peaks of MB and phenol are decreased after their adsorption on the surface of the nanocomposite.

Titanium dioxide is an important metal oxide semiconductor (MOSs) used in many electronic applications, the most famous of which are gas sensor applications. This review discusses the techniques used for preparing the TiO2 thin films and the effect of the crystalline phases in which this compound forms, on the gas sensing properties. There are three phases to crystallize titanium dioxides, brookite, anatase, and rutile phase. Amongst these varied phases of crystal, the greatest steady main phase is rutile. The phase of anatase and brookite are usually more stable than the rutile phase as the surface energy of them is less than that of the rutile. Therefore, the applications of sensing by anatase TiO2 and rutile TiO2 were fully studied. TiO2 characterizations were established on surface reactions using oxidizing or reducing gases, which; therefore, influences the conductivity of the film. Titanium dioxide gas sensors have healthier steadiness and sensitivity at high temperature compared with that of the other metal oxides. Surveys on titanium dioxide thin film applied in gas sensor devices used in a varied range of applications such as sensor devices, dye-sensitized solar cells, and catalysis. The gas sensor is a function of the crystal structure, particle size, morphology, and the method of synthesis. In this work, characteristic of the titanium dioxide films investigated using various techniques, as reported by many researchers. The aim of this study was to review previous studies through which the best properties can obtained to manufacture TiO2 gas sensor thin films with high sensitivity.

In this research, inorganic material type and content influence on coating of commercially available polypropylene (PP) separator were studied for improving its performance and safety as lithium ion battery separator. Heat-resistant nanopowders of Al2O3, SiO2 and ZrO2 were coated using polyvinylidene fluoride (PVDF) binder. Coating effects on the separators morphology, wettability, high temperatures dimensional stability and electrochemical properties were investigated via their scanning electron microscopy images, electrolyte contact angles, electrolyte uptakes, thermal shrinkages analysis and ion conductivities. Furthermore, their performances were studied as the lithium ion batteries separator. All the coated separators have lower thermal shrinkages compared to the commercial neat PP separator. In addition, almost all of the coated separators have shown higher porosities and electrolyte uptakes than those of the commercial neat PP separators. The coated separator with Al2O3 / binder ratio of 8 (MOA8) revealed highest improvement in electrolyte contact angle of 0 °, electrolyte uptake of 218 % (2.04 times increment), ion conductivity of 1.685 mS/cm (1.89 times increment), 52 % porosity compared with the neat PP separator due to proper coating surface morphology, interstitial cavities and a higher Al2O3 dielectric constant than SiO2. In terms of assembled battery discharge capacity reduction after 100 cycles, MOA8 separator showed better cyclic performance as 8.89 % compared with that of the neat PP separator as 16.6 %.

Ultrafine M(OH)n (M=La, Gd, Ni and Co) nanoparticles were electrochemically deposited from an additive–free M(NO3)n (0.005 M) low-temperature bath on a steel substrate at the constant current density of 1 mA cm−2. Heat–treatment of the prepared M(OH)n nanoparticles at 700oC led to formation of the oxide nanoparticles. The morphologies, crystal structures and compositions of the prepared products were determined by means of scanning (SEM) and transmission (TEM) electron microscopy as well as X-ray diffraction (XRD) and FT-IR spectroscopy. The results showed that the prepared M(OH)n samples are composed of ultrafine particles with the size of about 5 nm. After heat–treatment, the obtained products were well–crystallized phases of oxide nanoparticles with a size of around 10 nm. It was concluded that low-temperature cathodic electrodeposition offers a facile and feasible way for the preparation of ultrafine particles of metal oxides and hydroxides.