Microwave Methodology Research Articles

Cellulose Modified with Polyethylenimine (PEI) Using Microwave Methodology for Adsorption of Chromium from Aqueous Solutions.

A large amount of agricultural waste was used to prepare cellulose (Cel) and then the surface was modified with PEI (Cel-PEI) using the microwave method. To be used as a metal adsorbent, the adsorption of Cr (VI) from an aqueous solution by Cel-PEI was measured using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) techniques. The parameters of Cr (VI) adsorption in solution by the Cel-PEI adsorbent were as follows: the pH of the solution was 3, the concentration of the chromium solution was 100 mg/L, and the adsorption time was 180 min at 30 °C using 0.01 g of adsorbent. Cel-PEI had a Cr (VI) adsorption capacity of 106.60 mg/g, while the unadjusted Cel was 23.40 mg/g and the material recovery showed a decrease in efficiency of 22.19% and 54.27% in the second and third cycles, respectively. The absorption isotherm of chromium adsorption was also observed. The Cel-PEI material conformed to the Langmuir model with an R2 value of 0.9997. The kinetics of chromium adsorption showed that under pseudo-second-order analysis, with R2 values of 0.9909 and 0.9958 for Cel and Cel-PEI materials, respectively. The G° and H° values of the adsorption process were negative, indicating that the adsorption is spontaneous and that the adsorption process is exothermic. The efficient preparation adsorbent materials for Cr (VI) was achieved using a short microwave method that is low-cost and environmentally friendly for use in the treatment of Cr-contaminated wastewater.

Green synthesis of novel magnetite mixed metal oxides with cationic surfactant nanocomposite: Investigation of its effective removal of Azorubine E122 food dye and antimicrobial activity

Design and assembly of novel nanocomposites with multi‐purpose activities including efficient adsorption behavior toward different pollutants and microbial growth inhibition of various active biological species is a challenging aspect. Therefore, the current study is devoted to fabricating a novel nanocomposite of mixed metal oxides (ZrO2 and SiO2) with magnetite (Fe3O4) and cationic surfactants (cetyltrimethyl ammonium bromide [CTAB] and dodecyltrimethyl ammonium bromide [DoTAB]) via a solvent free microwave methodology to yield ZrSiO4 NPs‐CTAB@Fe3O4 NPs‐DoTAB. The as‐prepared nanocomposite was characterized by SEM to confirm the existence of homogeneous particles (~32.45 nm). The chemical structure of nanocomposite was also confirmed from the energy dispersive X‐ray spectroscopy (EDX), Fourier‐transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD) analyses. The surface area of this nanocomposite was also determined by the Brunauer‐ Emmett‐ Teller (BET) method and found to correspond to 6.319 m2 g−1. Remediation of Azorubine E122 food dye was optimized in the presence of a number of controlling parameters. The maximum adsorption capacity was characterized as 66.55 mg g−1 using 50 mg nanocomposite at 20 min. Kinetics and isotherm modeling evaluations referred to the best fitting with pseudo‐second order and Freundlich model, respectively. The antibacterial activity of ZrSiO4 NPs‐CTAB@Fe3O4 NPs‐DoTAB nanocomposite was assessed against Escherichia coli ATCC® 25922™ and Staphylococcus aureus ATCC® 25923™, and the collected data proved efficient growth inhibition (p < 0.05) at considerably low concentrations of the investigated nanocomposite. Therefore, the evaluated ZrSiO4 NPs‐CTAB@Fe3O4 NPs‐DoTAB nanocomposite was concluded to afford excellent antibacterial activity and efficient magnetic removal behavior of organic dyes. Hence, it is recommended as a talented material for purification of water resources containing multi‐chemical and biological pollutants as well. Finally, this study is expected to open new prospects for manufacturing other new nanocomposites with the aim of future applications in the removal of different chemical pollutants as well as viruses and bacteria.

Synthesis and biological evaluation of some benzothiazole-2-thiol derivatives as potent quorum sensing inhibitors

QS is a well-known mechanism of bacteria cell-to-cell communication. By inhibiting the quorum sensing pathway, compounds can prevent the aggressive activity of bacteria, including virulence production, biofilm formation, and other pathogenesis. Herein, the authors reported the synthesis and biological evaluation of several benzothiazole-2-thiols toward quorum sensing activities. As a result, five compounds are successfully synthesised using microwave methodology in good yields. In terms of bioactivity, compounds 2, 5 showed moderated quorum sensing inhibitory activity with IC50 of 212.03±2.17 and 198.11±3.48 μg/ml, respectively, in comparison to that of reference compound 4NPO. This research provides a novel template for future drug discovery and development.

Photocatalytic decolorization of ZnO/Fe for the removal of methylene blue by new microwave methodology

Photocatalytic decolorization of ZnO/Fe for the removal of methylene blue by new microwave methodology

New bimetallic adsorbent material based on cerium-iron nanoparticles highly selective and affine for arsenic(V)

Bimetallic oxy(hydroxides) have gain great interest in water treatment systems based on adsorption processes. Their high OH groups density, in addition to inheriting the oxides properties make them highly promising adsorbents of anions. In this work, highly affine and selective bimetallic oxyhydroxides of cerium and iron (Ce:Fe–P's) for arsenic(V) were synthesized by implementing an assisted microwave methodology. The Ce:Fe–P's were characterized by various techniques (SEM, FTIR, XRD and XPS) and the As(V) adsorption capacity and kinetics as well as the effect of pH and the presence of coexisting anions were determined. The results showed that Ce:Fe–P's have an outstanding As(V) adsorption capacity (179.8 mg g−1 at Ce = 3 mg L−1) even at low concentrations (120 mg g−1 at Ce = 37 μg L−1). Moreover, the adsorption equilibrium was reached very fast, just in 3 min, with an adsorption rate of 0.123 mg min−1, that is, 80% of the initial As(V) concentration of 5 mg L−1 was removed in the first 3 min. The arsenic adsorption capacity decreased only up to 20% at pH above 7, attributed to electrostatic repulsions due to the adsorbent's pHPZC, which was 6.8. On the other hand, the arsenic adsorption capacity of Ce:Fe–P's decreased just 21% in the presence of 10 mg L−1 of each of the following competing anions: F−, Cl−, SO42−, NO3−, PO43− and CO32−, which usually coincide in contaminated water with As(V). Ce:Fe–P's has proven to be one of the most promising As(V) adsorbent materials reported so far in the literature, because it presented an outstanding adsorption capacity and at the same time a very fast adsorption speed. Furthermore, the pH and the concentration of coexisting anions caused little interference in the adsorption processes. Due to the above, the Ce:Fe–P's is already in the process of intellectual protection.

Microwave assisted processing of X8R nanocrystalline BaTiO3 based ceramic capacitors and multilayer devices

BaTiO3 based multilayer ceramic capacitor (MLCC) is an important component in electronic devices. Achieving high dielectric performance, miniaturisation and cost effectiveness are still challenging. Co-sintering ceramic layers with metal electrodes and use of expensive Pt and high-Pd content compositions as electrodes are other key issues. Thus, the major factors that could lead to cost effectiveness of MLCCs are reduction in sintering temperature and using less expensive metal electrodes without compromising dielectric performance and these traits could auger well for the next generation low-cost high performance electroceramic devices – this is the subject matter of the present study.In this work, initially we have fabricated and analysed the dielectric performance of BaTiO3 (BT) ceramics with different BT particle sizes (50 nm, 100 nm and 200 nm). Based on results, 200 nm BaTiO3 was used for further studies due to its superior dielectric performance. Then, to reduce the sintering temperature and improve the dielectric performance of 200 nm BaTiO3 ceramics, Bi2O3 was used as a dopant which acts both as a sintering aid and helps to improve the dielectric performance. A combination of rare earth dopant system (proprietary from the industrial partner Knowles, UK) with Bi2O3 was also added to tune the defect chemistry of BaTiO3 for enhancement in dielectric performance further. A homogeneously mixed BT-based ceramic slurry system (containing the above dopants) with optimum rheology was developed using a non-aqueous medium, dispersant and a binder system. Addition of glass frits for lowering the sintering temperature and its effect on dielectric performance was also investigated on both discs (made using dry pressing of the powders obtained via drying of the slurry) as well as multilayer ceramic capacitors (MLCCs) fabricated through screen printing. Conventional, microwave and hybrid sintering procedures were employed for the densification of the electroceramic devices and these were characterized for density, microstructure, composition and dielectric performance systematically. Conventional sintering resulted in undesired large micron sized surface features which are detrimental to device durability, whereas formation and growth of these features have been demonstrated to be significantly minimised using the rapid microwave assisted sintering procedures for the first time. Further efficient co-sintering of ceramic layers with less expensive (Ag/Pd) alloy has also been accomplished using the microwave methodology. The resultant BaTiO3 based capacitive devices exhibited high dielectric permittivity, superior X8R performance and low dissipation factor, asserting their massive potential for widespread high temperature applications in automotive, sensing and space sectors.

Microwave-assisted Amination Reactions: An Overview

C-N coupling reactions were found to be attractive among researchers owing to the importance of C-N bond formation in heterocyclic synthesis. Hence C-N bond formation via amination reaction with the assistance of microwave radiations gained significant attraction recently. Microwave-assisted reactions are greener, faster and generally efficient compared to the conventional thermal reactions offering better purity of the product with enhancement in the yield. It was surprisingly revealed that several new advancements in amination reactions were highly influenced by this greener technology. This first review on microwave-assisted amination reaction focuses on the novel amination strategies that emerged with the help of microwave methodology, and covers literature up to 2019.

Microwave-Assisted Dry and Bi-reforming of Methane over M–Mo/TiO2 (M = Co, Cu) Bimetallic Catalysts

Microwave (MW) methodology has opened up new opportunities for chemical reactions by providing novel routes that are not practical by conventional heating. This paper reports on M–Mo bimetallic cat...

Innovative Three-Step Microwave-Promoted Synthesis of N-Propargyltetrahydroquinoline and 1,2,3-Triazole Derivatives as a Potential Factor Xa (FXa) Inhibitors: Drug Design, Synthesis, and Biological Evaluation.

The coagulation cascade is the process of the conversion of soluble fibrinogen to insoluble fibrin that terminates in production of a clot. Factor Xa (FXa) is a serine protease involved in the blood coagulation cascade. Moreover, FXa plays a vital role in the enzymatic sequence which ends with the thrombus production. Thrombosis is a common causal pathology for three widespread cardiovascular syndromes: acute coronary syndrome (ACS), venous thromboembolism (VTE), and strokes. In this research a series of N-propargyltetrahydroquinoline and 1,2,3-triazole derivatives as a potential factor Xa (FXa) inhibitor were designed, synthesized, and evaluated for their FXa inhibitor activity, cytotoxicity activity and coagulation parameters. Rational design for the desired novel molecules was performed through protein-ligand complexes selection and ligand clustering. The microwave-assisted synthetic strategy of selected compounds was carried out by using Ullmann-Goldberg, N-propargylation, Mannich addition, Friedel-Crafts, and 1,3-dipolar cycloaddition type reactions under microwave irradiation. The microwave methodology proved to be an efficient way to obtain all novel compounds in high yields (73–93%). Furthermore, a thermochemical analysis, optimization and reactivity indexes such as electronic chemical potential (µ), chemical hardness (η), and electrophilicity (ω) were performed to understand the relationship between the structure and the energetic behavior of all the series. Then, in vitro analysis showed that compounds 27, 29–31, and 34 exhibited inhibitory activity against FXa and the corresponding half maximal inhibitory concentration (IC50) values were calculated. Next, a cell viability assay in HEK293 and HepG2 cell lines, and coagulation parameters (anti FXa, Prothrombin time (PT), activated Partial Thromboplastin Time (aPTT)) of the most active novel molecules were performed to determine the corresponding cytotoxicity and possible action on clotting pathways. The obtained results suggest that compounds 27 and 29 inhibited FXa targeting through coagulation factors in the intrinsic and extrinsic pathways. However, compound 34 may target coagulation FXa mainly by the extrinsic and common pathway. Interestingly, the most active compounds in relation to the inhibition activity against FXa and coagulation parameters did not show toxicity at the performed coagulation assay concentrations. Finally, docking studies confirmed the preferential binding mode of N-propargyltetrahydroquinoline and 1,2,3-triazole derivatives inside the active site of FXa.

Synthesis and characterization of microwave‐assisted biologically active triazole silanes

The alliance of new drug, green technology and public health initiatives is essential for the ecosystem. The microwave technique is used to synthesize new drugs cognate to metronidazole. A new family of triethoxysilanes (3a–3e) was synthesized after reconnaissance with terminal alkynes (2a–2e) as an array using the Huisgen 1,3‐dipolar cycloaddition. All products were obtained in excellent yield with recovery of the catalyst as well as the solvent, and in a short time span. The design feature of these compounds is the tailoring of two unsymmetrical triazole nuclei into a single scaffold. The pharmacokinetic profiles of the triazole scaffold were analyzed using MOLINSPIRATION and ADMET toolkits, which gave promising results that prompted the investigation of these compounds for anti‐parasitic activity against parasites (Giardia lamblia and Trichomonas vaginalis) in contrast to standard drug (metronidazole). Compound 3d manifested good efficacy against both strains amongst all the synthesized triazole analogs.Highlights By using microwave methodology, a series of triazole functionalized alkynes and triazole organo silanes were synthesized. This involves tailoring of the 1,2,4‐triazole nucleus to 1,2,3‐triazole moiety. The protocol afforded excellent yield in a short time span under eco‐friendly conditions. The hybrid molecules were screened for their physicochemical properties using MOLINSPIRATION software and ADMET web server. All the synthesized compounds were investigated for their antioxidant activity, anti‐giardial and anti‐trichomonal activities. Tris triazole silane (3d) was found to be the most significant against Giardia lamblia and Trichomonas vaginalis, respectively, and this low‐price, versatile drug will hopefully lead to the eventual elimination of parasitic disease from the human population. Thermal gravimetric analysis has been performed for compounds (2a–2e) and (3a–3e).

Optimization of the synthesis of quinoline-based neutral cyclometalated iridium complexes via microwave irradiation: design of light harvesting and emitting complexes using bulky quinolines

We report a fast, simple, and robust microwave methodology for the synthesis of quinoline-based neutral heteroleptic cyclometalated iridium complexes: photophysical and computational characterization of the new complexes.

One-pot synthesis of benzopyranophenazines using graphene oxide dichlorotriazine (GO-DCT) under microwave irradiations

An efficient synthesis of benzopyranophenazines has been presented by one-pot four-component reaction of hydroxynaphthoquinone, o-phenylenediamine, benzaldehydes and malononitrile with graphene oxide dichlorotriazine (GO-DCT) as an efficient nanocatalyst under microwave irradiation in ethanol. The catalyst has been characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Atomic force microscopy (AFM) and scanning electron microscopy (SEM). Atom economy, experimental simplicity, wide range of products, low amount of catalyst loading, the reusability of the catalyst, excellent yields in short reaction times and applying the microwave methodology as an efficient and green method are some of the substantial features of this method.

Role of alkyl silatranes as plant growth regulators: comparative substitution effect on root and shoot development of wheat and maize

The present investigation reports the stimulating effects of different substituted alkyl silatranes (3a-3e) on the early seedling growth of wheat (Triticum aestivum) and maize (Zea mays). Seeds of these plants were exposed to six different concentrations (0, 10, 50, 100, 200 and 500 µmol L-1 ). The results revealed that different substitutions (3a-3e) had different effects on root and shoot elongation. Silatranes (3a-3e) were synthesized employing microwave irradiation by a solvent-mediated transesterification reaction, thereby reducing reaction times from several hours under conventional reflux conditions to 15 min under microwave irradiation. It was of interest that the effect of these silatranes did not show a dose-dependent relationship but an optimum concentration, which was 100 µmol L-1 for maize and 200 µmol L-1 for wheat. γ-Aminopropyl silatranes (3b and 3e) gave the best results in maize, whereas γ-chloropropyl silatrane (3a) was most efficient for wheat at these optimum concentrations. All the synthesized silatranes were effective in promoting root and shoot growth of wheat and maize. Furthermore, an efficient green microwave methodology was successful for the synthesis of silatranes. These observations pave the way for silatranes as efficient plant growth regulators for crops. © 2018 Society of Chemical Industry.

Peroxynitrite and Hypochlorite Fluorescence Quantification by S,N and P,N co-Doped Carbon Dots

Carbon Dots (CDs) responding to Peroxynitrite (ONOO-) and Hypochlorite (ClO-) were synthesised by microwave methodology. To improve the quantum yield, selectivity an sensitivity, CDs were doped with Sulphur, Nitrogen and Phosphorous, Nitrogen (S,N-CDs/P,N-CDs) using urea, cysteine and sodium phosphate.

Wastewater treatment by catalytic wet air oxidation process over Al-Fe pillared clays synthesized using microwave irradiation

Microwave irradiation has been used to prepare Al, Fe-pillared clays from a natural Tunisian smectite from the El Hicha deposit (province of Gabes). Chemical analysis, XRD spectra and surface properties evidenced the success of pillaring process. The obtained solids present higher surface area and pore volume than conventionally prepared Al-Fe pillared clays. The main advantages of the microwave methodology are the considerable reduction of the synthesis time and the consumption of water. The microwave-derived Al-Fe pillared clays have been tested for catalytic wet air oxidation (CWAO) of phenol in a stirred tank at 160°C and 20 bar of pure oxygen pressure. These materials are efficient for CWAO of phenol and are highly stable despite the severe operating conditions (acidic media, high pressure, high temperature). The catalyst deactivation was also significantly hindered when compared to conventionally prepared clays. Al-Fe pillared clays prepared by microwave methodology are promising as catalysts for CWAO industrial water treatment.

Comparative performance of bare and functionalize ZnO nanoadsorbents for pesticide removal from aqueous solution

The present study focus on the naphthalene adsorption from aqueous solution by using ZnO nanoparticles (NPs) synthesized via microwave methodology. This study reveals that the adsorption capacity depends not only on the textural features of the material but also on the functionalization of the nanoparticles. It was found that 1-butyl-3-methylimidazolium tetrafluoroborate (BMTF-IL) functionalized Zinc oxide nanoparticles show maximum adsorption capacity (148.3mgg−1) towards naphthalene removal as compared with CTAB functionalized (89.96mgg−1) and bare ZnO (66.80mgg−1) nanoparticles. To obtain a good picture of the surface and best interpretation of the adsorption process various isotherms were applied. To find out the rate constant of adsorption process, the well-known kinetics models i.e. pseudo first order and pseudo second order model were applied as a function of time and it was found that pseudo-second order model fits best in the adsorption process. Further the adsorption studies were performed in real water samples and in different salts to ensure that nanoparticles work well in presence of real water samples and different ions respectively. Recovery technique of the nanoparticles using a simple methodology is also described.

Rapid synthesis of high purity gold nanorods via microwave irradiation

A versatile method to rapidly synthesize high quality gold nanorods through the use of a microwave terminated growth process is presented. Traditional nanorod growth procedures require lengthy growth periods in addition to the use of additional materials/steps to terminate growth, including extra reagents, precise control of reagent concentrations, and tuning of environmental factors such as temperature or pH. Utilizing brief, high power microwave irradiation exposure, one can improve the nanorod monodispersity and achieve a significant reduction in the level of nanoparticle impurities within the sub-30 min growth regime without the need of additional reagents or pH adjustments. In addition to the increased synthesis efficiency, microwave-terminated gold nanorods yielded an increase in the longitudinal:transverse plasmon peak ratios, signifying a reduction in nanoparticle impurities with samples treated at 24 min versus traditional 24 h growth procedures without microwave termination. Utilizing the microwave methodology also yields an improved homogeneity of the produced rods as shown with a narrower spectral full width at half maximum compared to traditionally grown gold nanorods.

Microwave-assisted deep eutectic-solvothermal preparation of iron oxide nanoparticles for photoelectrochemical solar water splitting

Iron oxide nanoparticles, prepared using a new, efficient deep eutectic-solvothermal microwave methodology, were cast as photoanodes, showing competitive photocurrent performance.

Surface modification of poly(ethylene-butyl acrylate) copolymers by microwave methodology and functionalization with 4-dimethylamino-N-(2-hydroxyethyl)-1,8-naphthalimide for acidity sensing

A new procedure was developed for functionalization in the solid phase by using microwave irradiation. Heterogeneous chemical modification of poly(ethylene-butyl acrylate) copolymer (EBA), hydrolysis, chlorination, and Schotten–Baumann reactions were monitored by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. EBA was superficially functionalized by a previously synthesized fluorescent dye, 4-dimethylamino-N-(2-hydroxyethyl)-1,8-naphthalimide, and the depth profile of the functionalized polymer was determined by confocal Raman spectroscopy. The new functionalized materials were also evaluated as an acidic pH sensor by determining the change in the spectroscopic properties of absorption and fluorescence with pH of the solution and vapor phases. To improve the wettability of the EBA surface, oxygen plasma treatment was used and the response time of the solid sensor was analyzed.

Gallium and Functionalized-Porphyrins Combine to Form Potential Lysosome-Specific Multimodal Bioprobes.

A water-soluble bimetallic normal ("cold") and radiochemical ("hot") gallium-porphyrin-ruthenium-bipyridine complex (GaporRu-1) has been synthesized by microwave methodology in short reaction times with good (>85%) yields. (68)GaporRu-1 is demonstrated to be a potential multimodal and functional bioprobe for positron emission tomography (PET), lysosome specific optical imaging, and photodynamic therapy.