Microwave Irradiation Technique Research Articles

Two dimensional (2D) reduced graphene oxide (RGO)/hexagonal boron nitride (h-BN) based nanocomposites as anodes for high temperature rechargeable lithium-ion batteries

With lithium-ion (li-ion) batteries as energy storage devices, operational safety from thermal runaway remains a major obstacle especially for applications in harsh environments such as in the oil industry. In this approach, a facile method via microwave irradiation technique (MWI) was followed to prepare Co3O4/reduced graphene oxide (RGO)/hexagonal boron nitride (h-BN) nanocomposites as anodes for high temperature li-ion batteries. Results showed that the addition of h-BN not only enhanced the thermal stability of Co3O4/RGO nanocomposites but also enhanced the specific surface area. Co3O4/RGO/h-BN nanocomposites displayed the highest specific surface area of 191 m2/g evidencing the synergistic effects between RGO and h-BN. Moreover, Co3O4/RGO/h-BN also displayed the highest specific capacity with stable reversibility on the high performance after 100 cycles and lower internal resistance. Interestingly, this novel nanocomposite exhibits outstanding high temperature performances with excellent cycling stability (100% capacity retention) and a decreased internal resistance at 150 °C.

Evaluation of Low and High Surface Area TiO₂ and Al₂O₃ Metal Oxides-Carbon Hybrids in Terms of Polymer Electrolyte Membrane Fuel Cell Catalyst Support.

Support materials are of great interest in order to improve the activity and stability of the polymer electrolyte membrane fuel cell (PEMFC) catalysts. Metal oxides have been reported as promising support materials due to their excellent mechanical resistance and high stability against corrosion emerging at acidic and oxidative environment. In this study, high (250 m₂/g) and low (45 m₂/g) surface area mesoporous TiO₂ and high (220 m₂/g) and low (30 m₂/g) surface area mesoporous Al₂O₃ were investigated as an alternate cathode catalyst support materials for PEMFCs. These semiconducting TiO₂ and Al₂O₃ metal oxides were combined with the carbon black (Vulcan XC 72) at different mass ratios in order to preserve electrical conductivity of catalyst support a certain extent. Pt and TiO₂/C and Pt and Al₂O₃/C catalysts were prepared by means of Pt reduction on support materials via microwave irradiation technique. The as-prepared catalysts were characterized with some physicochemical and electrochemical analyses. The results reveal that two surface areas TiO₂ and Al₂O₃ support materials differ from each other in terms of fuel cell performance and high surface area TiO₂/C (25:75) hybrid supported Pt catalyst gave the best performance.

Microwave irradiation-assisted high-efficiency N-glycan release using oriented immobilization of PNGase F on magnetic particles

Peptide-N-glycosidase F (PNGase F) is the most frequently used enzyme to release N-glycan from glycoproteins in glycomics; however, the releasing process using PNGase F is tedious and can range in duration from hours to overnight. Recently, efforts have been made to accelerate this enzymatic reaction, and they include the use of microwave irradiation, ultrahigh pressure, enzyme immobilization, and other techniques. Here, we developed a novel method combining the oriented immobilization of PNGase F on magnetic particles and microwave-assisted enzymatic digestion techniques to achieve highly efficient release of N-glycans. The oriented immobilization of PNGase F on magnetic particles utilizes the affinity of its co-expressed His-tag towards iminodiacetic acid-Nickel modified magnetic particles. Compared with non-oriented immobilization, the oriented immobilization of PNGase F exhibits several advantages including tolerance to high temperature (52 °C) and the ability to retain strong activity after more than five reuses. When used in combination with microwave irradiation, efficient N-glycan removal from ribonuclease B was achieved within 5 min. The proposed strategy was also used to release glycan from fetuin and human serum and has proven to provide a promising deglycosylation method for the characterization of protein glycosylation.

Surfactant-Free Synthesis of Nb2O5 Nanoparticles Anchored Graphene Nanocomposites with Enhanced Electrochemical Performance for Supercapacitor Electrodes.

Nb2O5/graphene nanocomposites without any surfactant are synthesized by an in situ microwave irradiation technique. Structural and morphological studies revealed that the prepared composites were composed of Nb2O5 nanoparticles intercalated into the graphene sheet. The thermal stability of graphene oxide, Nb2O5, and Nb2O5/graphene nanocomposite was studied by the TGA. The electrochemical properties are assessed by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy analyses. The specific capacitance of Nb2O5/graphene nanocomposites is greater (633 Fg−1) than pure Nb2O5 nanoparticles (221 Fg−1) and graphene (290 Fg−1) at a current density of 1 Ag−1. The long-term cyclic measurement confirms higher cyclic stability of the nanocomposite with capacitance retention of 99.3% after 5000 cycles without performance degradation. The composites exhibit higher electrochemical conductivity and allow effective ions and charge transport over the entire electrode surface with aqueous electrolyte. The electrochemical study suggests that Nb2O5/graphene nanocomposites have the potential to be an effective electrode for superior performance supercapacitor applications.

Enhanced electrochemical performance of α-MoO3/graphene nanocomposites prepared by an in situ microwave irradiation technique for energy storage applications.

Nanoparticles of α-molybdenum oxide (α-MoO3) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method. The prepared α-MoO3 and α-MoO3/G nanocomposites are analysed by different characterization techniques to study their structural, morphological and optical properties. Transmission electron microscope images reveal the intercalation of three dimensional (3D) α-MoO3 nanoparticles into 2D graphene sheets without any agglomeration. The electrochemical results exhibit improved performance for the α-MoO3/G composite electrode compared to pristine α-MoO3 owing to its structural superiority. The specific capacitance (Cs) values of the α-MoO3/G composite and pristine α-MoO3 are measured to be 483 and 142 F g−1 respectively at a current density of 1 A g−1. The α-MoO3/G composite maintains a very strong cyclic performance after 5000 cycles. The capacitance retention of the composite electrode shows stable behavior without any degradation confirming its suitability as an enduring electrode material for high-performance supercapacitor applications.

The construction of fluorophoric thiazolo-[2,3-b]quinazolinone derivatives: a multicomponent domino synthetic approach

Acid-mediated one-pot domino reactions of substituted 2-amino thiazoles, substituted benzaldehydes and cyclic diketones have been developed for the synthesis of novel and architecturally unique thiazolo[2,3-b]quinazolinone derivatives under microwave irradiation. In this protocol, a series of thiazolo[2,3-b]quinazolinone derivatives have been synthesized and the excellent fluorescence behaviors of some of the molecules have been reported based on the incorporation of different electron-donating and electron-withdrawing substituents on the aryl moieties of the target molecules.

Microwave-Assisted Palladium-Catalyzed Cross-Coupling Reactions: Generation of Carbon–Carbon Bond

Cross-coupling reactions furnishing carbon–carbon (C–C) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Negishi, Heck, Kumada, Sonogashira, Stille, Suzuki, and Hiyama, utilizing palladium or its salts as catalysis have, for decades, attracted and inspired researchers affiliated with academia and industry. Tremendous efforts have been paid to develop and achieve more sustainable reaction conditions, such as the reduction in energy consumption by applying the microwave irradiation technique. Chemical reactions under controlled microwave conditions dramatically reduce the reaction time and therefore resulting in increase in the yield of the desired product by minimizing the formation of side products. In this review, we mainly focus on the recent advances and applications of palladium catalyzed cross-coupling carbon–carbon bond formation under microwave technology.

Microwave irradiation technique: Green potent energy source for sustainable applications

Synthesis of organic and inorganic compounds is a foundational concept in the preparation of bioactive material for drug development as well as provision of materials for other applications in everyday life of man. Conventional synthetic approach by heating under reflux has been in use since antiquity. This usually take a longer time to complete, it is not void of release of toxic chemical and could lead to decomposition of envisaged compounds some time. In recent time, microwave assisted reaction have been adopted in synthesis of numerous compounds which are essential templates in many industrial processes and various application. This present review deals with the recent advances of microwave irradiation techniques as sustainable and ecofriendly means of preparing compounds of interest to man. Microwave assisted technique approach is noted to be remarkably useful towards the synthesis of bioactive materials for drug design, polymeric materials for composite matrix, donor molecules for corrosion inhibition, material for battery application, nanomaterials as perovskites for supercapacitance electrodes, high wavelength compounds as solar cell sensitizers, dye materials in textile industries among others. Thus, microwave irradiation is an unavoidable technique for the accelerated eco-friendly synthesis of organic compounds which must be well explored for the benefit of man and his environment.

Triazolothiadizepinylquinolines as potential MetAP-2 and NMT inhibitors: Microwave-assisted synthesis, pharmacological evaluation and molecular docking studies

The enzymes MetAP-2 and NMT play a crucial role in the process of myristoylation of oncoproteins which is deregulated in many types of cancers. Execution of both these enzymes is considered as strategy for the intervention of various cancers and relative fungal infections, and hence the discovery of novel MetAP-2 and NMT inhibitors necessitate their high relevancy. In this investigation, we have synthesized a series of novel seven-membered triazolothiadiazepinyl quinolines 10(a–m) distinctively under microwave irradiation technique and identified as selective MetAP-2 and NMT inhibitors. Amongst the functionalized derivatives when evaluated for the in vitro antifungal assay, compounds 10b, 10c, 10e and 10f were considered promising due to notable inhibitory effects (MIC = 0.2 mg/mL) on Aspergillus fumigatus. Screening of the anticancer activity against NCI-60 Human tumor cell lines portrayed that conjugates 10b, 10c, 10e and 10f were found to be moderately effective against the Renal Cancer cell line UO-31. The data acquired from biological studies was further validated by molecular docking studies and pharmacokinetic evaluation.

Effect of metal-based nanoparticles decorated graphene hybrids on flammability of epoxy nanocomposites

To overcome the flammability of epoxy resins (EPs), metal-based nanoparticlesdecorated reduced graphene oxide (rGO) hybrids including Ag@rGO, Cu2O@rGOand TiO2@rGO, were synthesized through microwave irradiation technique and subsequently incorporated into EPs. The structure and morphology of the metal-based nanoparticlesdecorated rGO hybrids were characterized by XRD, XPS, TEM and SEM, which confirmed successful synthesis of the hybrid materials. The metal-based nanoparticles were uniformly deposited to the rGO nanosheets, which could avoid re-stacking of graphene nanosheets. The addition of metal-based nanoparticlesdecorated rGO hybrids significantly diminished the flammability of epoxy nanocomposites. Specifically, the Cu2O@rGO/EP nanocomposite showed 50% and 29% reduction in peak heat release rate and total smoke production, respectively. The reduced flammability was attributed to the improved char yield that restrained the heat and smoke release during combustion. It is prognosticated that metal-based nanoparticles decorated graphene hybrids will provide an efficient solution to improve fire safety of polymeric materials.

Host-guest complex of β-cyclodextrin and pluronic F127 with Luteolin: Physicochemical characterization, anti-oxidant activity and molecular modeling studies

The purpose of this investigation was to ameliorate the solubility and dissolution rate of luteolin (LUT) in aqueous phase by LUT: β-cyclodextrin (β CD) binary and LUT: β-cyclodextrin (β CD) : Pluronic F127 (PLF) ternary complex. Phase solubility study was performed with β CD as well as with β CD-PLF to assess the solubilizing efficiency. The solid complexes were prepared by solvent evaporation (SE), and microwave irradiation (MI) techniques. The in-vitro dissolution study was performed for the developed systems. The selected ternary complex was evaluated for solid state characterization, anti-oxidant effect and further molecular docking study was performed to provide structural insights and to identify the favorable role of β CD in improving the solubility of LUT. The key results of phase solubility studies indicated that 6.23 fold and 10 folds increase in LUT solubility with β CD and β CD-PLF respectively in comparison to pure LUT solubility. The formulation TIC-MI showed maximum drug release 97.06 ± 4.23% followed by TIC-SE (83.679 ± 3.78%) > BIC-MI (76.35 ± 3.57%) > BIC-SE (57.39 ± 2.11%) > TNPM (42.72 ± 2.45%) > BNPM (26.16 ± 1.71%). Most importantly IR, NMR study results revealed that there is no interaction was observed between LUT and used excipients. The antioxidant effect of the complex was found higher than that of LUT. The docking results demonstratethat LUT is completely embedded into the β CD cavity. Therefore, LUT: β CD: PLF ternary complex prepared by MI method found to be efficient with improved solubility, dissolution and antioxidant effect.

Oil emulsions and the different recent demulsification techniques in the petroleum industry - A review

The emulsions are formed during the production of crude oil, which is often accompanied by water. These emulsions are undesirable and should treat to remove the dispersed water and accompanying inorganic salts. so, many researchers have over the years focused to probe of the appropriate demulsification techniques in the petroleum sector in order to meet production and transportation requirements, and to reduce corrosion and catalyst poisoning and to maximize the overall profitability of the crude oil production. Therefore, this study presents an overview of the emulsions, formation, classification, Stability, and properties. practical demulsification techniques in the petroleum sector, including chemical, microwave irradiation, biological, thermal, membrane, electrical, and ultrasonic techniques for both oilfield and synthetic emulsions. Amongst these techniques, chemical demulsification has been the most widely applied and reported in the literature. Moreover, a more effective demulsification process could be attained by leveraging synergistic effects by combining one or more of these techniques

Influence of nature of surfactant and precursor salt anion on the microwave assisted synthesis of barium carbonate nanoparticles

Barium carbonate nanoparticles of rod and bean shaped morphologies were synthesized by microwave irradiation technique and the influence of the surfactants cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and Tween 80 having different co-anions were studied on the morphology and size of the as-prepared nanoparticles. The nanoparticles were characterized by X-ray powder diffraction (XRD) technique, field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), and thermogravimetric analysis (TGA). The transmission electron microscopy (TEM) of the BaCO3 nanoparticles showed that different interesting images such as rod-like, flower-like, bean-like and peanut-like are formed when SDS was used with different barium salts. The purity of prepared product was confirmed by energy dispersive X-ray spectroscopy (EDS). Thermogravimetric analysis (TGA) was done to determine the thermal behavior of the as-prepared BaCO3 nanoparticles.

Microwave heating temperatures and pharmaceutical powder characteristics

Abstract Temperature is an important factor that has a significant influence on the physical and chemical characteristics of the dried materials, mainly in the pharmaceutical solid powders. Pharmaceutical solids can be dried using different conventional drying techniques. However, in the present work, the technique of microwave irradiation was used to dry the moisturized formulation of naproxen-sodium drug. The exploitation of the microwave irradiation energy in the pharmaceutical field is limited, and the available information about the interaction between the electromagnetic radiations and the pharmaceutical material is still scarce. Therefore, this work aimed to explore the effects of the microwave irradiation temperatures on the elimination of the moisture, the morphology, the crystalline structure, the size of the dried particles, and the chemical groups of the naproxen-sodium drug. In the present research, a formulation of the naproxen-sodium drug was prepared and wetted by a wet granulation process. The prepared wet granules were dried at different heating temperatures using microwave irradiation energy. Powder X-ray diffraction, Fourier-transform Infra-red spectroscopy, moisture analyzer, and scanning electron microscopy were used to characterize the non-moisturized drug powder (the reference powder), the wet granules, and the dried granules. The results of this study exhibited that the use of the high microwave irradiation drying temperatures was more effectual in the removal of the moisture from the formulated naproxen-sodium drug than that at the low temperatures. Even though there was no significant variation in the chemical structure of the dried granules, crystallinity, morphology and particle size were relatively reformed with the variation in the microwave heating temperatures.

Análise bibliométrica e bibliográfica sobre técnicas de tratamento/recuperação de óleo cru de resíduos sólidos produzidos na cadeia produtiva do petróleo

Em decorrência da intensa atividade de exploração e produção, a cadeia produtiva da indústria de petróleo tem sido responsável pela geração de grande parte de resíduos sólidos produzidos no mundo. Dentre estes resíduos, a borra oleosa (BO) encontra-se em lugar de destaque, visto que é produzida em quase todas as etapas de produção e refino do petróleo. Devido à elevada toxicidade destes materiais, o descarte inadequado é considerado um risco ao meio ambiente. Assim, o desenvolvimento de tecnologias capazes de recuperar o óleo presente na borra tem sido objeto de diversos estudos. Diante disso, este trabalho teve como objetivo investigar a produção científica relacionada ao tratamento/recuperação do óleo da borra de petróleo por meio da utilização de métodos de pirólise, extração por solvente e irradiação por micro-ondas. A análise dos resultados revelou que a China é o país que apresenta maior número de publicações a respeito das técnicas de tratamento de BO. Este fato pode estar relacionado ao volume significativo de BO gerada anualmente na China, tendo atingido 5 milhões de toneladas em 2018. Apesar de não haver uma tecnologia industrial pré-estabelecida para tratamento/recuperação de BO, os trabalhos publicados apontam a pirólise como rota eficiente, principalmente quando associada com o emprego de catalisadores (pirólise catalítica). A técnica de irradiação por micro-ondas também é destacada nos trabalhos como aliada da pirólise. Com o emprego conjunto foi possível obter melhores resultados de recuperação de óleo da BO em menores temperaturas. Já a técnica de extração por solvente apresentou a vantagem de se trabalhar em condições amenas de temperatura (25 oC a 80 oC), utilizando solventes como n-hexano, ciclohexano, xileno, tolueno, triclorometano, metiletilcetona, condensado de gás liquefeito de petróleo e Na-AES. Embora a técnica se mostre eficiente na remoção de óleo da borra, não é possível recuperar 100% do solvente no final do processo de extração. Isto tem sido apontado como uma desvantagem desta rota. De forma geral, observou-se que a heterogeneidade da BO é um dos fatores que dificulta tratamento/recuperação do óleo. O setor da cadeia produtiva de petróleo de onde a borra é extraída, bem como a sua manipulação e forma de condicionamento são fatores que poderão interferir em seu tratamento. Logo, a escolha de uma das rotas aqui apresentadas, bem como as condições operacionais a serem utilizadas estará condicionada não somente ao custo/benefício do processo como também às características intrínsecas e de armazenamento da borra.

A facile microwave synthesis of rGO, ZrO2 and rGO–ZrO2 nanocomposite and their room temperature gas sensing properties

Microwave irradiation technique provides a simple and quick synthesis route for nanomaterials at controlled experimental conditions. In this view, nanostructures of rGO, ZrO2, and rGO–ZrO2 composite were synthesized using microwave synthesis technique. Herein, we experimented the preparation of rGO using optimized conditions using convection mode at 373 K in a commercial microwave oven. Structural properties revealed the formation of mixed phases of the orthorhombic and rhombohedral crystal structure of ZrO2. The preferential plane orientation was found to be in c-axis (002) for rGO–ZrO2 nanocomposite, which revealed the predominance of rGO in the nanocomposite. Morphology of the prepared nanostructures exhibited agglomerated sheets, denser nanograins and randomly aggregated nanosheets for rGO, ZrO2, and mixed nanocomposite respectively. Room temperature gas sensing properties of the prepared nanostructures were investigated and reported. rGO showed responses of 5.3 and 5.2 towards 200 ppm of trimethylamine (TMA) and methanol. ZrO2 nanostructure showed a response of 35 towards 200 ppm of ammonia with response–recovery times of 91 and 6 s.

Morphological effects on the photocatalytic properties of SnO2 nanostructures

The photocatalytic properties of SnO2 nanocrystals are tuned by varying their morphology and microstructure. SnO2 nanoparticles and nanowedges have been synthesized using hydrothermal methods, while microwave irradiation techniques have given nanospheres. Detailed structural and chemical characterization of these different morphologies has been accomplished. The influence of SnO2 morphology on photocatalytic activity has been examined by monitoring the degradation of aqueous methylene blue dye. Results demonstrate that changing the morphology of the SnO2 modulates both surface area and levels of surface defects and that these alterations are reflected in the photocatalytic properties of the materials. The degradation of methylene blue dye (98%) in the presence of SnO2 nanoparticles under simulated solar irradiation is superior to previously reported photocatalyst performance and is comparable to that of standard TiO2 (Degussa P-25). The SnO2 nanoparticles perform better than both the nanowedges and nanospheres and this is attributed to the number of surface defects available to the high surface area material. They also reveal outstanding recyclability and stability.

Understanding the phase dependent energy storage performance of MnO2 nanostructures

We demonstrate charge storage mechanisms of four kinds of MnO2 polymorphs (α, β, γ, and δ) both in micro- and nanodimensions successfully synthesized by hydrothermal and microwave irradiation techniques. We observed that layered δ-MnO2, comprised of self-assembled nanoflakes oriented in different directions, shows a significantly improved capacitive behavior. The maximum achieved specific capacitance is 518 F/g at a current density of 3 A/g in a 3M KOH electrolyte solution, exhibiting a large capacity retention of 83.95% over 2000 consecutive charge/discharge cycles at a current density of 10 A/g. State of the art Density Functional Theory (DFT) simulations have also been performed to support experimental data. The quantum capacitance presented from DFT simulations predicts that the δ phase exhibits highest quantum capacitance, whereas it is lowest for the β phase supporting the experimental trend. Also, the structural features of wide tunnel size (∼7 Å) for the δ phase facilitates favorable insertion of cations, whereas narrow tunnel size (∼1.89 Å) for the β phase restricts the diffusion of charge particles yielding poor capacitance performance.

Microwave Assisted Synthesis and Antimicrobial Study of Some Novel 2-Azetidinones Derived from 2-(1-Phenylimino-ethyl)-naphthalen-1-ol

Several substituted 2‐azetidinone derivatives 2a-q have been synthesized from halogenohydroxy substituted imines 1a-q under microwave irradiation technique. The reactions were carried out using 2-methoxyethanol as an efficient reaction media to afford high yield of product. The structures of newly synthesized compounds have been established on the basis of elemental analysis, IR, 1 H NMR, 13 C NMR, GC-MS and elemental data. Further, all newly synthesized compounds were screened for their in vitro antimicrobial activity. The antifungal and antibacterial effects of the tested compounds are due to their molecular structure and substituent present. DOI: http://dx.doi.org/10.17807/orbital.v11i3.1393

Evaluation of anticorrosive behaviour of ZnO nanotetra-pods on a AZ91-grade Mg alloy

Highly cross-linked zinc oxide (ZnO) with the nanorod morphology of tetra-pods was successfully prepared using a microwave irradiation (MWI) technique. In comparison with the available conventional techniques, the MWI technique has the advantage of producing different morphological structures with high purity and in a shorter reaction time. These tetra-pods consist of a ZnO core in the zinc blende from which four ZnO arms emerge in the wurtzite structure. In this investigation, the effects of irradiation times and the growth mechanism of ZnO nanotetra-pods were discussed. The structural, morphological and optical properties of ZnO nanorods were investigated by field emission scanning electron microscopy, X-ray diffraction, an ultra violet visible spectrometry and energy-dispersive spectroscopy. The electrochemical corrosion behaviours of an AZ91-grade Mg alloy and a ZnO/PN nanotetra-pod-coated Mg alloy were investigated. The Tafel plot revealed that the corrosion of Mg drastically decreased on coating with a thin layer of ZnO nanotetra-pods and PN (Mg/PN/ZnO) compared to Mg in a KOH electrolyte.