Microwave Synthesis Method Research Articles

Optimizing the Mechanoluminescent Properties of CaZnOS:Tb via Microwave-Assisted Synthesis: A Comparative Study with Conventional Thermal Methods.

Recent developments in lighting and display technologies have led to an increased focus on materials and phosphors with high efficiency, chemical stability, and eco-friendliness. Mechanoluminescence (ML) is a promising technology for new lighting devices, specifically in pressure sensors and displays. CaZnOS has been identified as an efficient ML material, with potential applications as a stress sensor. This study focuses on optimizing the mechanoluminescent properties of CaZnOS:Tb through microwave-assisted synthesis. We successfully synthesized CaZnOS doped with Tb3+ using this method and compared it with samples obtained through conventional solid-state methods. We analyzed the material's characteristics using various techniques to investigate their structural, morphological, and optical properties. We then studied the material's mechanoluminescent properties through single impacts with varying energies. Our results show that materials synthesized through microwave methods exhibit similar optical and, primarily, mechanoluminescent properties, making them suitable for use in photonics applications. The comparison of the microwave and conventional solid-state synthesis methods highlights the potential of microwave-assisted methods to optimize the properties of mechanoluminescent materials for practical applications.

Magnetically tunable rheological properties of PVDF doped with superparamagnetic Fe3O4 nanoparticles synthesized by rapid microwave method

We report on the surfactant/additives free synthesis of single domain superparamagnetic Fe3O4 nanoparticles (FNPs) by rapid microwave synthesis method. X-Ray diffraction (XRD) and Scanning Electron Microscopy (SEM) studies reveal that FNPs were crystallized in the magnetite (Fe3O4) lattice and have granular shape with average particles size of ∼14 nm. The band gap of FNPs calculated from UV–Visible absorption spectrum is ∼2.3 eV. FNPs exhibit single domain superparamagnetic behaviour as confirmed from magnetic hysteresis loops. The nanocomposites of FNPs and β-phase of PVDF were prepared via mixed solvent approach using THF/DMF with different concentrations of FNPs. The rheological behaviour of the nanocomposites was studied with and without ageing in an applied magnetic field of 3500 Gauss for 3 h. Samples depicts shear thinning to shear thickening transition, decrease in zero shear viscosity and long frequency range viscoelastic behaviour as function of increasing FNP concentration. Increase in CST region, fluidity and complex modulus are the main consequences of magnetic aging. FNP-PVDF nanocomposites with such properties could find applications in flexible magnetic and mechanical films for soft body armor and memory storage.

Application of novel Fe3O4/Zn-metal organic framework magnetic nanostructures as an antimicrobial agent and magnetic nanocatalyst in the synthesis of heterocyclic compounds.

Using the microwave-assisted method, novel Fe3O4/Zn-metal organic framework magnetic nanostructures were synthesized. The crystallinity, thermal stability, adsorption/desorption isotherms, morphology/size distribution, and magnetic hysteresis of synthesized Fe3O4/Zn-metal organic framework magnetic nanostructures were characterized by XRD patterns, TGA curve, BET adsorption/desorption technique, SEM image, and VSM curve, respectively. After confirming the Fe3O4/Zn-metal organic framework magnetic nanostructures, its antimicrobial properties against Gram-positive bacterial, Gram-negative bacterial, and fungal strains based on minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) values were studied. The MIC values in antimicrobial activity for Gram-positive and Gram-negative bacterial strains, between 16–128 μg/ml, and for fungal strain, 128 μg/ml were observed. The results showed that the high specific surface area of Fe3O4/Zn-metal organic framework magnetic nanostructures caused the antimicrobial power of nanoparticles to be high, and the observed antimicrobial effects were higher than some known commercial antimicrobial drugs. Another advantage of the specific surface area of Fe3O4/Zn-metal organic framework magnetic nanostructures was its high catalytic properties in the three-component reaction of isatin, malononitrile, and dimedone. New spiro [indoline-pyranopyrimidines] derivatives were synthesized with high efficiency. The catalytic activity results of Fe3O4/Zn-metal organic framework magnetic nanostructures showed that, in addition to recyclability, derivatives could be synthesized in less time than previously reported methods. The results of investigating the catalytic activity of Fe3O4/Zn-metal organic framework magnetic nanostructures showed that the spiro [indoline-pyranopyrimidines] derivatives were synthesized in the time range of 10–20 min with an efficiency of over 85%. As a final result, it can be concluded that the microwave synthesis method improves the unique properties of magnetic nanostructures, especially its specific surface area, and has increased its efficiency.

Electrocatalytic Conversion of Methane to Ethylene Utilizing Highly Durable Barium Niobate Perovskites

Pursuing efficient conversion of methane to value-added products such as olefins and aromatics is a prospective use of natural methane feedstocks. The demand for on-site methane conversion has further increased due to the recent discoveries of shale gas reserves. Electrochemical methane conversion provides a means to control the surface oxide ion concentration, aiming to eliminate the over-oxidation of methane while also aiding in methane activation via applied potential. High temperature electrolysis processes provide improved reaction kinetics. Unfortunately, high temperature operation also leads to material degradation via sintering, crystal structure disproportion to thermodynamically more stable phases, and interfacial reactions that reduce performance. We demonstrated that the Sr2Fe1.5Mo0.5O6- d (SFMO) perovskite which was reported with desirable methane activation properties had poor chemical and electrochemical stability as it formed carbonates and coke under methane rich environments.[1][2] Here we present an exciting class of barium niobate perovskite materials with varying levels of Mg and Fe co-doping that show promising catalytic activity towards methane activation in the electrochemical and conventional heterogeneous oxidative coupling environment. The perovskite material was prepared by conventional solid-state methods and by microwave synthesis methods to compare the role of surface area. Thermogravimetric analysis and temperature programmed reaction measurements under methane show superior chemical stability in comparison to SFMO perovskites. These catalysts’ electrochemical properties are evaluated by cyclic voltammetry, impedance spectroscopy, and chronoamperometric measurements coupled with mass spectra analysis that demonstrate durable operation for five continuous days. A maximum ethylene production of 277 mmolcm-2h-1 with a faradaic efficiency of 20% at 1V was obtained. Stability determinations of our perovskite oxide electrocatalysts for EC-OCM offer an excellent example of our approach towards evaluation of materials durability under the highly carburizing environments. These perovskite materials could also serve as a support for a wide variety of catalyst materials for high temperature applications thus opening new possibilities.

Nanocomposites of Carbon Quantum Dots and Graphene Quantum Dots: Environmental Applications as Sensors

Carbon-based quantum dots and their nanocomposites have sparked immense interest for researchers as sensors due to their attractive physico-chemical properties caused by edge effects and quantum confinement. In this review article, we have discussed the synthesis and application of nanocomposites of graphene quantum dots (GQDs) and carbon quantum dots (CQDs). Different synthetic strategies for CQDs, GQDs, and their nanocomposites, are categorized as top-down and bottom-up approaches which include laser ablation, arc-discharge, chemical oxidation, ultrasonication, oxidative cleavage, microwave synthesis, thermal decomposition, solvothermal or hydrothermal method, stepwise organic synthesis, carbonization from small molecules or polymers, and impregnation. A comparison of methodologies is presented. The environmental application of nanocomposites of CQDs/GQDs and pristine quantum dots as sensors are presented in detail. Their applications envisage important domains dealing with the sensing of pollutant molecules. Recent advances and future perspective in the use of CQDs, GQDs, and their nanocomposites as sensors are also explored.

Progress of Monodispersed Nano-Hydroxyapatite-Based Biological Tracing

Nano-hydroxyapatite (nHAp)-based dual-/multi-modal bioimaging systems have received significant attention due to their excellent bioactivity and biocompatibility. However, it is difficult to obtain highly sensitive imaging results. On the one side, the high surface energy of nHAp tends to enable the agglomerations of nHAp, which could further limit the clinical applications. On the other side, the main strategy for the construction of co-doped nHAp nanocrystals depends on high temperature and techniques of post-modification, resulting in inevitable nHAp crystal polymerization and increased particle size. In order to overcome the current shortcomings of nonmonodispersed nHAp, such as uneven distribution and easy aggregation, the construction of monodispersed nHAp is expected to ensure the imaging performance of traceable nHAp by reducing the aggregation of nHAp in vivo and improving the imaging sensitivity. Thus, in this review, the approaches of monodispersed nHAp based on hydrothermal, biomimetic and microwave synthesis methods are summarized. Furthermore, the development of single/multi-mode traceable monodispersed nHAp for biological imaging applications is also discussed.

Microwave-Assisted Synthesis of Schiff Base Metal–Ligand Complexes with Copper and Nickel Centres for Electrochemical In Vitro Sensing of Nitric Oxide in an Aqueous Solution

Nitric oxide (NO), the smallest signalling molecule known in the human body, keeps blood vessels dilated, controls blood pressure, and has numerous other health regulatory effects. The use of Schiff base complexes incorporated onto electrodes to make electrochemical sensors has been explored as an effective method for the determination and quantification of nitric oxide in aqueous solutions. Schiff base ligands were complexed with Cu and Ni metal centres using the microwave synthesis method to produce metal–ligand complexes with enhanced capabilites for NO detection. The electrical current generated at the anode is directly proportional to NO concentrations in the solution through its oxidation to HNO3. Various characterisation techniques were implemented to verify the integrity of each step of metal–ligand synthesis as well as the final product produced, using FT-IR, UV-VIS, and TGA. The as-synthesised Schiff base complexes were electrodeposited on screen-printed carbon electrodes (SPCE) and electrochemically evaluated in a 0.1 M PBS. Furthermore, metal complexes were screened for their in vitro activity towards NO detection in an aqueous solution (PBS). The results show that the investigated sensors (SPCE/Ni-BPND and SPCE/Cu-BPND) respond positively toward NO detection. It was, therefore, identified that the two sensors also do not differ significantly in terms of precision, sensitivity, and lowest detection limit. The sensor strategies demonstrate the NO limits of detection of 0.22 µM and 0.09 µM, and they also demonstrate sensitivity values of 16.3 µA/µM and 13.1 µA/µM for SPCE/Cu-BPND and SPCE/Ni-BPND sensors, respectively.

Ferroelectric switching and current characteristics dependence on ferroelectric polarization direction of microwave synthesized BiFeO3 nanocubes

Herein, we studied the ferroelectric switching and current characteristics of BiFeO3 (BFO) nanocubes dispersed on the surface of a Nb-doped SrTiO3 (Nb:STO) substrate based on the ferroelectric polarization orientation. The microwave synthesis method afforded BFO nanocubes with an average size of ∼50 nm, which were dispersed on the Nb:STO substrate surface and the substrate was subsequently subjected to heat treatment at 500 °C for 1 h. The piezoelectric d33 hysteresis loop, ferroelectric domain structure, and ferroelectric polarization switching characteristics of the 50-nm-sized BFO nanocubes were examined using piezoresponse force microscopy. Finally, atomic force microscopy confirmed the dependency of current characteristics on the ferroelectric polarization orientation of the BFO nanocubes, verifying the applicability of BFO nanocubes as storage media for ferroelectric polarization information.

Microwave Synthesis of Blue Emissive N-Doped Carbon Quantum Dots as a Fluorescent Probe for Free Chlorine Detection

Blue emissive N-doped carbon quantum dots (N-CQDs) were prepared through a convenient and sustainable microwave synthesis method using citric acid monohydrate (CA) and urea as carbon and nitrogen sources, respectively, with an optimum molar ratio of 1:3 (CA:Urea). The surface functional groups, morphology, and hydrodynamic characteristics of N-CQDs were analysed with Fourier-transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS). The as-synthesised N-CQDs with a quantum yield of 14.8%, exhibited excitation-independent fluorescence emission at 443 nm due to surface-state-induced fluorescence, with an optimum excitation wavelength at 360 nm. The N-CQDs were spherical, with an average particle size of 7.29 ± 3.91 nm based on HRTEM analysis. However, DLS analysis showed that the hydrodynamic size (293.0 ± 110.8 nm) was larger than the average particle size due to the presence of hydrophilic polymer chains and abundant surface groups on the N-CQDs. The free chorine-induced fluorescence quenching of N-CQDs at pH 9 denotes the sensitivity of N-CQDs towards detection of free chlorine in the form of hypochlorite (ClO-) ion, providing the limit of detection (LOD) of 0.4 mM and limit of quantification (LOQ) of 1.2 mM. The fluorescence quenching effect in the N-CQDs caused by the quencher (ClO-) is attributed to the dynamic quenching mechanism, via an intersystem crossing. The low selectivity of N-CQDs towards various ions justified N-CQDs' selectivity as a free chlorine fluorescent probe that can be used for wastewater testing due to its high range sensitivity.

Application of imine covalent organic frameworks in sample pretreatment

亚胺类共价有机骨架(I-COFs)是有机单体根据席夫碱(Schiff-base)反应原理缩合形成的一类新型多孔晶体有机材料。I-COFs具有骨架密度低、比表面积大、孔隙率高、单体种类丰富、孔径尺寸可控、结构可功能化、合成方法多样和物化稳定性好等优点。近年来,I-COFs已成为材料科学领域的研究前沿,并广泛用于气体吸附、存储、催化、传感、光电材料等方面。I-COFs材料优异的物理化学性能使其非常适于用作复杂样品中痕量目标物的分离富集介质,其高比表面积、高孔隙率性能赋予了它极高的吸附负载量,这些性能使得目标分析物可被高效富集;通过控制有机单体的链段长度、几何结构、掺杂元素、取代基团等方面精确调控I-COFs的孔洞结构和功能化基团,从而实现目标痕量物质的选择性富集。目前,I-COFs材料在样品前处理领域作为新型萃取介质已引起了极大关注。该文综述了近年来I-COFs材料的主要类型、合成方法及其在固相萃取、磁性固相萃取、分散固相萃取和固相微萃取方面的研究进展,同时展望了I-COFs在样品前处理领域的发展前景。

Microwave-assisted facile synthesis of N, P co-doped fluorescent carbon dot probe for the determination of nifedipine.

A simple and fast microwave synthesis method was applied for the preparation of several carbon dots (CDs) from various combinations of urea, phosphoric acid, and B-alanine as nitrogen, phosphorus, and carbon precursors. The maximum quantum yield (44%) was obtained for nitrogen and phosphorus co-doped carbon dots (N, P-CDs) prepared from urea, B-alanine, and phosphoric acid. Furthermore, N, P-CDs were exploited to synthesize a simple and sensitive fluorometric probe to determine nifedipine (NFD). We determined that the analytical response of the designed sensor could be affected by the kind of dopant and synthesis precursors. It is worth mentioning that the fluorescence intensity of N, P-CDs was weakened by NFD, and no fluorescence quenching was observed for other prepared CDs. The NFD-developed sensor demonstrated a linear response range of 3.3 × 10-8-3.2 × 10-5mol/L, with the detection limit of 1.0 × 10-8mol/L. The sensor was successfully applied to measure NFD in human biological fluids.

Triggering excitation independent fluorescence in zinc(II) incorporated carbon dots: Surface passivation of carbon dots with zinc(II) ions by microwave assisted synthesis methods

Carbon dots (CDs), versatile nanomaterials with unique photophysical and structural properties, often have excitation-dependent fluorescence due to the presence of carboxylic groups on the surface of the nanostructure. The excitation-dependent fluorescence of CDs is valuable for bioimaging, but considered undesirable for applications where monochromatic emission is required. Here in this paper, we demonstrate a green, fast and simple way to control the excitation-dependent fluorescence of CDs by passivating carboxylic groups on the surface of CDs with zinc (II) ions through a microwave synthesis method. Conventional CDs without surface passivation had excitation-dependent fluorescence, whereas zinc(II) ion-passivated CDs had excitation-independent fluorescence. Also, the surface passivation of CDs led to an increase in the quantum yield of CDs. The present work provides an inexpensive and user-friendly way to develop carbon dots with controllable emission properties by incorporating a metal ion into carbon dots through simple microwave-assisted synthesis.

Microwave synthesis of silver sulfide near-infrared fluorescent quantum dots and their detection of dopamine

In this work, NIR-emitting silver sulfide quantum dots (Ag2S QDs) with outstanding aqueous dispersion and superior stability can be directly prepared by a simple microwave synthesis method using D-penicillamine and silver nitrate (AgNO3) in different ratios in pure water. The fluorescence intensity of the prepared near-infrared fluorescent silver sulfide quantum dots was quenched in the presence of dopamine, which was used as an ultrasensitive sensing probe for DA detection. The developed sensing probe based on Ag2S QDs showed a linear response over a wide range of 0–140 μM. The detection limit was 0.77 μM.

Recent advances in the application of metal organic frameworks using in advanced oxidation progresses for pollutants degradation

Metal-organic frameworks (MOFs) materials with highly ordered and porous crystalline structure, have excellent performance in advanced oxidation progresses (AOPs) for organic contaminants degradation in water treatment. This review intends to summarize the timely references and insights for the recent advances in MOFs that are used in AOPs. Starting with the preparation methodologies, including conventional hydrothermal method, electrochemical method, sol-gel method, and emerging microwave and ultrasound assisted synthesis methods. Application and mechanism for MOFs using in various AOPs of Fenton-like, photocatalysis, catalytic ozonation, persulfate catalysis and other emerging oxidation methods are emphatically discussed. We hope this review can comprehensively summarize the research and application progress of MOFs in AOPs, deepen the understanding of the catalytic mechanisms. Application and mechanism of MOFs in emerging AOPs such as Fenton-like, photocatalysis, catalytic ozonation and persulfate catalysis is reviewed in detail.

Microwave-assisted NixFe1-x nanoclusters ultra-stable to oxidation in aqueous media.

Metal alloy nanoparticles, and, in particular, permalloy, still hold an untapped potential in nanotechnology, although their poor stability against oxidation due to environmental exposure limits their use in many technological applications, and even more in life sciences. We propose a scalable single-step microwave-assisted method to produce water suspensions of Ni1-xFex nanoparticles without the need for an inert atmosphere, either organic solvents or any type of post-processing. We use hydrazine as a reducer, iron(II), iron(III) and nickel(II) chloride as precursors, 1,12-dodecanediol as a surfactant and water as a reaction medium. The mixture is heated at 160 °C for 10 minutes to obtain uniform alloy nanoparticles with sizes of around 24.5 nm for Ni (0% Fe) and 5.5 nm for 35% Fe that are forming uniform aggregates with sizes between 200 nm for Ni and 65 nm for iron oxide NPs. A linear increase of saturation magnetization is observed with an Fe content of up to 25%, whereas for larger percentages a sudden drop takes place due to the formation of iron oxides. X-ray diffraction measurements rule out the formation of any oxides after more than one year of storage at 4 °C, surely due to the presence of 1,12-dodecanediol at the surface, as evidenced by infrared spectroscopy.

Evaluation of structural, morphological and optical properties of CdO nanostructures

Microwave synthesis method was adopted to prepare CdO nanoparticles using polyethylene glycol (PEG), NH 3 and NaOH as a co-reagent. A systematic investigation by XRD, SEM, TEM and EDS has been undertaken to evaluate the role of co-reagents on the microstructural and morphological study of the metal oxide nanostructure obtained. The pH of the solution, determined by the co-reagent used, was the main parameter addressing the morphology of CdO nanostructures obtained. By using NH 3 the growth of individual CdO particle is favored at the low pH of 9, likely due to low Cd supersaturation rate at this pH. On the other hand, the presence of NaOH as co-reagent increases pH to 11, enhancing Cd supersaturation and leading mainly to formation of nanowire aggregates. The optical and photoluminescence characteristics of the different CdO nanostructures synthesized have been also evaluated.

Photocatalytic degradation of paracetamol by semiconductor oxides under UV and sunlight illumination.

In this study, photocatalytic degradation of paracetamol (acetaminophen), an analgesic and antipyretic drug, was investigated in using semiconductors under UV-B and sunlight irradiation. Semiconductor materials, Bi2O3, ZnO, TiO2, and ZrO2, were prepared using simple sol-gel, coprecipitation, and microwave synthesis methods. These photocatalyts were characterized by various spectroscopic and other techniques. As a result of the reactions, 25 ppm paracetamol with Bi2O3 and ZnO photocatalyst, total degradation was achieved with UV-B irradiation in 90 min. The results of photocatalytic activities showed that the highest degradation rate was obtained with the Bi2O3 photocatalyst. In the light of all findings, the nanorod-shaped Bi2O3 semiconductor which has a low band gap energy and high quantum efficiency exhibited significant effect on the activity despite of its low surface area.

Microwave processing of carbon doped Nickel-Cobalt composites for high-performance supercapacitors

A facile and rapid microwave synthesis method was used to make Co/Ni-carbon black (CB) nanocomposites. Several sophisticated techniques confirm the formation and the effects of carbon nanoparticles incorporated into Co/Ni-CB composites. Carbon engrafted Co/Ni composite demonstrates excellent morphology, more significant area, and higher conductive region, thus improving electrode/electrolyte accessibility to enhance electrochemical kinetics. The interaction and combination of CB with Co/Ni composite shows excellent capacitive behavior, assessed by galvanostatic discharge method, cyclic voltage voltammetry, and electrochemical impedance spectroscopy. CB plays a crucial role in stimulating the formation of robust structures, surface activity, and specific capacitance through enhancing electron transport and catalytic properties. This electrode material (NX3) has the highest specific capacitance of 748 Fg−1 at scan rates of 5 mVs−1 and was found to have excellent cycle stability (92.8%) over 5000 cycles. Solid-state supercapacitors fabricated from developed electrodes are highly effective for brightening LEDs. In this study, we demonstrated for the first time a single-step technique that is both quick and efficient for the synthesis of Co/Ni-carbon black heterostructure by using microwave irradiation. The present work suggests that low-cost electrodes can be used in a wide range of future energy storage systems as a potential hybrid material.

Nitrogen Tailored Activated Carbon via Microwave Synthesis Method for High Removal of Hydrogen Sulfide

In this work, commercialized palm shell activated carbon was modified into nitrogen-functionalized carbon via urea impregnation method, followed by heat treatment via microwave irradiation at 950 °C.

Novel microwave synthesis of copper chromite nanoparticles

Here, a novel microwave synthesis method has been used to prepare copper chromite nanoparticles. Effect of capping agents viz; citric acid, oleic acid, coconut oil, and urea on crystal structure and size of copper chromite nanoparticles (CuCr2O4 NPs) are presented. Impact of calcination temperature on the formation of pure phase CuCr2O4 has also been observed. The key feature of this research is to reduce the overall reaction time required in the preparation of copper chromite NPs. The samples were characterized with X-ray Diffraction (XRD), Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy(SEM), and Energy Dispersive X-Ray (EDX) analysis techniques.