Microwave-assisted Strategy Research Articles

Defect-Engineered Nanostructured Ni/MOF-Derived Carbons for an Efficient Aqueous Battery-Type Energy Storage Device.

A Ni-based metal–organic framework (Ni-MOF) has been synthesized using a microwave-assisted strategy and converted to nanostructured Ni/MOF-derived mesoporous carbon (Ni/MOFDC) by carbonization and acid treatment (AT-Ni/MOFDC). The materials are well characterized with Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET), revealing that chemical etching confers on the AT-Ni/MOFDC-reduced average nanoparticle size (high surface area) and structural defects including oxygen vacancies. AT-Ni/MOFDC displays low series resistances and a higher specific capacity (Cs) of 199 mAh g–1 compared to Ni/MOFDC (92 mAh g–1). This study shows that the storage mechanism of the Ni-based electrode as a battery-type energy storage (BTES) system can be controlled by both non-faradic and faradic processes and dependent on the sweep rate or current density. AT-Ni/MOFDC reveals mixed contributions at different rates: 75.2% faradic and 24.8% non-faradic contributions at 5 mV s–1, and 34.1% faradic and 65.9% non-faradic at 50 mV s–1. The full BTES device was assembled with AT-Ni/MOFDC as the cathode and acetylene black (AB) as the anode. Compared to recent literature, the AT-Ni/MOFDC//AB BTES device exhibits high energy (33 Wh kg–1) and high power (983 W kg–1) with excellent cycling performance (about 88% capacity retention over 2000 cycles). This new finding opens a window of opportunity for the rational designing of next-generation energy storage devices, supercapatteries, that combine the characteristics of batteries (high energy) and supercapacitors (high power).

Microwave-assisted solvothermal fabrication of hybrid zeolitic–imidazolate framework (ZIF-8) for optimizing dyes adsorption efficiency using response surface methodology

Abstract Herein, an efficient and rapid fabrication procedure for ZIF-8 crystals through microwave-assisted strategy (450 W, 140 °C, and 15 min) was reported. Additionally, the crystallinity, morphology, chemical bonding, and porosity of ZIF-8 was fully characterized by X–ray powder diffraction (XRD), scanning electron microscopes (SEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), and N2 adsorption/desorption isotherm measurement. Response surface methodology approach was established to optimize a series of adsorption conditions: initial concentration (8–92 mg/L), dose (0.6–1.4 g/L), and time (20–220 min) for CR and RhB removals. Many statistical error functions (R2, MRE, χ2, HYBRID, and MPSD) were analyzed to compare the compatibility of nonlinearised kinetic and isotherm models. Particularly, plausible adsorption mechanisms (electrostatic interactions and π–π stacking) were elucidated and isotherm models were rigorously studied by two-parameter equations (Langmuir, Freundlich, Temkin) and three-parameter equations (Redlich-Peterson, Sips, Khan). Through advantageous effectiveness involving good reusability (4 recycles), high removal efficiency (87–99 %), maximum adsorption capacities (95.5–167.0 mg/g), it is recommendable to utilize ZIF-8 as an adequate adsorbent for the dyes remediation.

Iron Nanoparticles Encapsulated in S,N-Codoped Carbon: Sulfur Doping Enriches Surface Electron Density and Enhances Electrocatalytic Activity toward Oxygen Reduction.

Development of highly efficient nonprecious metal (NPM) catalysts for oxygen reduction reaction (ORR) in acidic media is challenging but of great significance. Herein, an effective ORR catalyst based on Fe nanoparticles encapsulated by S,N-codoped few-layer defective carbon (Fe@S,N-DC) was synthesized via a microwave-assisted strategy. The obtained Fe@S,N-DC nanocomposite showed a remarkable electrocatalytic activity toward ORR in acidic media, with a half-wave potential (E1/2) of +0.785 V versus reversible hydrogen electrode, which was 80 mV more positive than that of the sulfur-free counterpart (Fe@N-DC). Furthermore, due to the protection by the S,N-codoped carbon shell, the Fe@S,N-DC nanocomposite displayed apparent stability with only a 13 mV negative shift of E1/2 after 10,000 cycles and excellent tolerance to methanol. X-ray absorption near-edge spectroscopy measurements confirmed the formation of multiple defective sites on the S,N-codoped carbon surface and strong interfacial electron transfer from the Fe core to the outer carbon surface, as compared to the sulfur-free counterpart. The enriched electron density on the defective carbon surface of Fe@S,N-DC, induced by the interfacial electron transfer, facilitated the reduction of O2 to OOH*, leading to enhanced ORR performance. These results shed light on the significance of S doping in Fe-N-C catalysts in the design of high-performance NPM catalysts for ORR in acidic media.

A facile and rapid approach to synthesize uric acid-capped Ti3C2 MXene quantum dots for the sensitive determination of 2,4,6-trinitrophenol both on surfaces and in solution.

Herein, uric acid@Ti3C2 quantum dots (UA@Ti3C2 QDs) were synthesized via a microwave-assisted strategy on the basis of acid etching and stripping. The UA@Ti3C2 QDs have bright blue emission. Intriguingly, the fluorescence emission of the UA@Ti3C2 QDs was significantly quenched after the addition of 2,4,6-trinitrophenol (TNP), due to inner-filter effect (IFE). Based on these findings, a novel environmentally friendly and water-soluble fluorescence probe based on UA@Ti3C2 QDs was demonstrated for the sensitive and selective detection of TNP. The method presented a wide linear range for TNP detection in the 0.01-40 μM range, with a low detection limit of 9.58 nM. Furthermore, the probe was successfully used for the sensitive detection of TNP in real water and smartphone-based colorimetric (SPBC) detection of TNP on surfaces with the linear range from 10.0 to 100.0 ng. On the whole, this work provides an effective strategy for the synthesis of UA@Ti3C2 QDs and an alternative fluorescence probe for detecting TNP both on surface and in solution.

Bimetallic Pd/SnO2 Nanoparticles on Metal Organic Framework (MOF)-Derived Carbon as Electrocatalysts for Ethanol Oxidation

Bimetallic Pd/SnO2 nanoparticle electrocatalysts on metal organic framework-derived carbon (MOFDC) were successfully synthesized using microwave-assisted strategies and explored for ethanol oxidation reaction (EOR) in alkaline solution. The materials were thoroughly characterized using XRD, XPS, TEM, and Raman. TEM showed that Pd/SnO2/MOFDC gave the least average particle size of 5.5 nm compared to its counterparts on carbon black (CB). The Pd/SnO2/MOFDC gave the best electrocatalytic performance in terms of high electrochemical active surface area (ECSA) of 962 cm2 mg−1, low onset potential and overpotential for EOR, and high current density (j) of four times more than those of the Pd/CB electrocatalyst. In addition, Pd/SnO2/MOFDC showed superior kinetic parameter (in terms of the Tafel slope (b) = 216.1 ± 8 mV dec−1) and least combined resistance (R = Rs + Rct). These results show that the Pd/SnO2/MOFDPC nanoparticle electrocatalyst is promising for EOR with improved electrocatalytic properties for application in direct ethanol fuel cell (DEFC).

Pick your precursor! Tailoring the size and crystal phase of microwave-synthesized sub-10 nm upconverting nanoparticles

The influence of precursor chemistry on thermal decomposition and particle growth in a rapid microwave-assisted strategy was investigated, demonstrating the selective synthesis of small and ultrasmall luminescent lanthanide-doped NaGdF4 nanoparticles.

Microwave-assisted synthesis of cobalt phosphide using ionic liquid as Co and P dual-source for hydrogen evolution reaction

Cobalt phosphide nanoparticles (Co2P) were synthesized via microwave radiation or pyrolysis at 400 °C, and two ionic liquids (IL) were applied as the phosphorus and cobalt dual-source for fabricating Co2P. In the microwave radiation method, tetrabutylphosphonium tetrachlorocobaltate(II) ([P4,4,4,4]2[CoCl4]) with carbon nanotubes (CNTs) was utilized to obtain the Co2P/CNTs-1 via one step phosphidation within 6 min. These as-prepared materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The electrocatalytic performance of microwave-prepared Co2P/CNTs-1 toward hydrogen evaluation reaction was investigated in acidic solution, which shows a good catalytic activity with onset overpotential of 80 mV, Tafel slope of 58 mV dec−1, current densities of 10 and 20 mA cm−2 at overpotentials of 135 and 170 mV, respectively. This microwave-assisted strategy for synthesis of Co2P provides a remarkable advantage of preparation process in a quite short time, which also is a simple operation and energy efficient method.

Topochemical Synthesis of 2D Carbon Hybrids through Self-Boosting Catalytic Carbonization of a Metal-Polymer Framework.

Two-dimensional (2D) carbon hybrids have promise in various areas such as energy storage and catalysis. Simple methods for controllable fabrication of 2D graphitic carbon hybrids in a scalable manner remains challenging. Now, a microwave-assisted strategy for mass production of 2D carbon hybrids based on self-boosting catalytic carbonization of a metal-agarose framework is demonstrated. Hybrids including hollow Fe3 C nanoparticles, Ni/Co nanoparticles, and hollow FeOx nanoparticles uniformly embedded in 2D graphitic carbon nanosheets (GCNs) are obtained, demonstrating the generality of the approach. Metal-polymer coordination and microwave-enabled fast catalytic decomposition of precursors play vital roles in facilitating the formation of the nanosheet structure. The resulting FeOx -GCNs hybrid exhibits superior lithium-storage performance (1118 mAh g-1 at 500 mA g-1 and 818 mAh g-1 at 2000 mA g-1 after 1200 cycles).

Nitrogen and sulfur co-doped highly luminescent carbon dots for sensitive detection of Cd (II) ions and living cell imaging applications

In this work, we have developed a green, simple and fast one-pot microwave-assisted strategy for synthesis of nitrogen and sulfur co-doped fluorescent carbon dots (CDs) using scallion (SL) as the carbon source. Optical properties of the SL-CDs have been measured by UV-visible and fluorescent spectroscopy. The morphology of the prepared SL-CDs has been performed by transmission electron microscopy (TEM). Surface functionality and elemental composition of SL-CDs was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra. The photoluminescent (PL) quantum yield of the obtained scallion carbon dots (SL-CDs) can reach as high as 18.6%. We further demonstrated that the SL-CDs can be used as fluorescent probes for detection of Cd2+ ions with a high sensitivity and an excellent selectivity. Linear relationships between the variation of the luminescent intensity of the SL-CDs before and after exposing the Cd2+ ions versus the concentration of Cd2+ ions in the range of 0.1–3.0 μM and 5.0–30.0 μM. The detection limit of Cd2+ ions can reach 15.0 nM. Moreover, the as-prepared SL-CDs exhibit negligible or extremely low cytotoxicity, which makes them be able to be used as fluorescent probes for living cell imaging. Overall, the prepared SL-CDs have promising applications in sensing of Cd2+ ions and in vivo or in vitro bioimaging.

Green synthesis of silver nanoparticles using Nervalia zeylanica leaf extract and evaluation of their antioxidant, catalytic, and antimicrobial potentials

ABSTRACTHere we report a simple, one-pot, inexpensive, and eco-friendly method for the synthesis of silver nanoparticles. The leaf extract of a medicinal plant Nervalia zeylanica was used as reducing and stabilizing agent for the synthesis of nanoparticles by microwave-assisted strategy. The nanoparticles show characteristic surface plasmon peak at 468 nm in UV–vis absorption spectrum. The involvement of phytochemicals in the reduction and stabilization of nanoparticles was confirmed by FTIR analysis. Using X-ray diffraction analysis, the crystalline nature of the nanoparticles was demonstrated. Transmission electron microscopic analysis shows that the nanoparticles were in spherical shape with average particle size of 34.2 nm. The antioxidant studies were performed by the 1,1-diphenyl-2-picryl hydrazyl method. The nanoparticles show excellent scavenging activities than the leaf extract. The IC50 values of silver nanoparticles and the leaf extract, respectively, were 15.20 and 92.83 µg mL−1. The catalytic activities of synthesized nanoparticles were examined by using them in the reduction of organic dyes. The nanoparticles show excellent catalytic activities and follow pseudo-first-order kinetics. The antimicrobial activities of nanoparticles were analyzed by an agar well diffusion method against six microbial strains and found that the nanoparticles were highly toxic against all the tested microbial strains.

Microwave-assisted exfoliation strategy to boost the energy storage capability of carbon fibers for supercapacitors

Carbon fibers, with reduced oxidized graphite layers on the surface obtained using a facile method, were developed as one-dimensional electrodes. The oxidized layers directly formed from the surface of the carbon fibers had a strong interconnectivity with the fiber core, and their conductivity was apparently improved after reduction by hydrazine hydrate. With an abundance of oxygen functional groups induced by oxidation, the one-dimensional electrodes showed a specific capacitance of 213.3 F g−1 at a current density of 0.1 A g−1, which was forty times more than that of the original carbon fibers when tested in a three-electrode configuration. The innately stability in aqueous solutions and the graphite layers from the carbon fibers themselves made the electrodes based on the carbon fibers endowed optimal cycling ability without a decline in specific capacitance after 10000 cycles. The device made of CF-R had a good energy density performance. This strategy provided a facile way to obtain a one-dimensional electrode with a high specific capacitance and good durability for energy storage systems.

WITHDRAWN: Synthesis of sulfur-rich nitrogen dots through microwave-assisted strategy for cell imaging

WITHDRAWN: Synthesis of sulfur-rich nitrogen dots through microwave-assisted strategy for cell imaging

Synchronous and rapid preparation of lignin nanoparticles and carbon quantum dots from natural lignocellulose

A rapid one-pot microwave-assisted strategy toward the synchronous preparation of two nano-biomaterials with different scales: lignin nanoparticles and carbon nanodots.

Green Synthesis, Characterization and Applications of Noble Metal Nanoparticles Using Myxopyrum serratulum A. W. Hill Leaf Extract

In this study, we introduce a facile, green, one-pot and eco-friendly method for the synthesis of silver and gold nanoparticles using microwave-assisted strategy. The aqueous leaf extract of a medicinal plant Myxopyrum serratulum A. W. Hill was used as both stabilizing and reducing agents for this preparation. The synthesized nanoparticles were characterized by using UV-vis spectroscopy, FTIR spectroscopy and XRD, TEM and EDAX analyses. The silver and gold nanoparticles respectively show SPR band at 441 and 539 nm in UV-vis spectrum. The involvement of phytochemicals in the reduction and stabilization of nanoparticles was confirmed by FTIR spectroscopy. The crystalline fcc structure of nanoparticles was assured from XRD analysis. The size and morphology of nanoparticles were obtained from the TEM images. The presences of silver and gold elements were confirmed from their respective EDAX spectrum. The antimicrobial effects of leaf extract and synthesized silver and gold nanoparticles were tested against both bacterial and fungal strains by employing agar well diffusion method. The nanoparticles show high antimicrobial properties. The antioxidant properties were studied by simple DPPH assay. The nanoparticles exhibited better DPPH scavenging activities compared to leaf extract. In addition, it has been shown that the synthesized silver and gold nanoparticles functioned as an effective catalyst for the reduction dyes viz. 4- nitrophenol, methylene blue and Congo red by sodium borohydride.

Coffee-Ground-Derived Quantum Dots for Aqueous Processable Nanoporous Graphene Membranes

Carbon-based quantum dots (QDs) with ultralow dimensions and controllable surface chemistry have unique properties appealing to diverse applications. Here, we disclose a high-throughput transformation of spent coffee grounds into uniform QDs assembled by few-layer graphene oxide nanosheets, employing a microwave-assisted strategy under aqueous reaction conditions. Given the low dimensions (30 nm) and high structural integrity, the highly oxygenated QDs exhibited excellent dispersibility in water with tunable fluorescence. The structural attributes of QDs conferred excellent affinity to graphene nanosheets, permitting aqueous processing of nanoporous graphene membranes applicable to removing a broad spectrum of water pollutants ranging from organic compounds to heavy metals while sustaining a high flux rate. The proposed “trash-to-treasure” strategy opens up new possibilities for aqueous processing of nanoporous graphene membranes with great potential in the environmental field.

Efficient microwave-assisted synthesis of fused benzoxazepine–isoquinoline derivatives via an Ugi reaction/tautomerization/intramolecular SNAr reaction sequence

A series of compounds containing the benzoxazepine-isoquinoline scaffold was synthesized in a one-pot procedure via an Ugi reaction followed by tautomerization reaction between the keto and enol forms and intramolecular nucleophilic substitution. The microwave-assisted strategy allowed the facile synthesis of a library of target compounds and is applicable to the construction of diverse libraries of related compounds for high throughput screening in medicinal chemistry.

Microwave-assisted synthesis of high-quality “all-inorganic” CsPbX3 (X = Cl, Br, I) perovskite nanocrystals and their application in light emitting diodes

A fast and efficient microwave-assisted strategy is developed to prepare high-quality CsPbX3 nanocrystals with controllable morphologies (nanoplate, nanocube, and nanorod).

The Synthesis of RGD-functionalized Hydrogels as a Tool for Therapeutic Applications

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and functionalize polymer chains with compounds that are able to improve biocompatibility, mechanical properties, or cell viability allows the design of novel materials to meet new challenges in the biomedical field. With the polymer functionalization strategies, click chemistry is a powerful tool to improve cell-compatibility and drug delivery properties of polymeric devices. Similarly, the fundamental need of biomedicine to use sterile tools to avoid potential adverse-side effects, such as toxicity or contamination of the biological environment, gives rise to increasing interest in the microwave-assisted strategy. The combination of click chemistry and the microwave-assisted method is suitable to produce biocompatible hydrogels with desired functionalities and improved performances in biomedical applications. This work aims to synthesize RGD-functionalized hydrogels. RGD (arginylglycylaspartic acid) is a tripeptide that can mimic cell adhesion proteins and bind to cell-surface receptors, creating a hospitable microenvironment for cells within the 3D polymeric network of the hydrogels. RGD functionalization occurs through Huisgen 1,3-dipolar cycloaddition. Some PAA carboxyl groups are modified with an alkyne moiety, whereas RGD is functionalized with azido acid as the terminal residue of the peptide sequence. Finally, both products are used in a copper catalyzed click reaction to permanently link the peptide to PAA. This modified polymer is used with carbomer, agarose and polyethylene glycol (PEG) to synthesize a hydrogel matrix. The 3D structure is formed due to an esterification reaction involving carboxyl groups from PAA and carbomer and hydroxyl groups from agarose and PEG through microwave-assisted polycondensation. The efficiency of the gelation mechanism ensures a high degree of RGD functionalization. In addition, the procedure to load therapeutic compounds or biological tools within this functionalized network is very simple and reproducible.

Microwave-Assisted Syntheses of Benzimidazole-Containing Selenadiazole Derivatives That Induce Cell-Cycle Arrest and Apoptosis in Human Breast Cancer Cells by Activation of the ROS/AKT Pathway.

The use of selenium-containing heterocyclic compounds as potent cancer chemopreventive and chemotherapeutic agents has been well documented by a large number of clinical studies. In this study we developed a new approach to synthesize four benzimidazole-containing selenadiazole derivatives (BSeDs). The method uses a combination of peptide coupling reagents and microwave irradiation. This strategy features milder reaction conditions, higher yields, and shorter reaction times. The synthetic BSeDs were identified as potent antiproliferative agents against the human MCF-7 and MDA-MB-231 breast cancer cell lines. Compounds 1 b (5-(6-methyl-1H-benzo[d]imidazol-2-yl)benzo[c][1,2,5]selenadiazole), 1 c (5-(6-chloro-1H-benzo[d]imidazol-2-yl)benzo[c][1,2,5]selenadiazole), and 1 d (5-(6-bromo-1H-benzo[d]imidazol-2-yl)benzo[c][1,2,5]selenadiazole) were found to show greater cytotoxicity against the triple-negative breast cancer cell line MDA-MB-231 than MCF-7, and to exhibit dose-dependent inhibition of cell migration, in which a significant decrease in the zone of cell monolayer wound closure was observed relative to untreated controls. Our results demonstrate that BSeDs can cause cell-cycle arrest and apoptosis in MDA-MB-231 cells by inducing DNA damage, inhibiting protein kinase B (AKT), and activating mitogen-activated protein kinase (MAPK) family members through the overproduction of reactive oxygen species (ROS). Taken together, the results of this study provide a facile microwave-assisted strategy for the synthesis of selenium-containing organic compounds that exhibit a high level of anticancer efficacy.

Rational Design of a Unique Ternary Structure for Highly Photocatalytic Nitrobenzene Reduction

The rational design and controllable synthesis of TiO2 and noble metal composite photocatalysts represent an unprecedented challenge for developing the solar-driven reduction of nitrobenzene (NB) to aminobenzene (AB), owing to the recombination over the interface between the noble metals and TiO2, which is harmful to the conversion efficiency of NB to AB. Here, we design a unique ternary structure (the high separation of TiO2 and Pt nanoparticles on the surface of reduced graphene oxide (RGO)) through the sol–gel and microwave-assisted strategies. The substrate of RGO can be used as an “electric wire” to effectively transfer the photogenerated electrons from the isolated TiO2 nanocrystals to the isolated Pt nanoparticles, which greatly decreases the interface recombination between TiO2 and Pt and further improves the conversion efficiency of NB to AB under the solar light irradiation. We anticipate our research provides a new way to overcome the interface recombination on the binary photocatalysts in the ...