Facile Microwave-assisted Method Research Articles

Architecting ultra-thin SiO2 shell for high magnetic performance of Fe3O4 nanoparticles for biomedical applications

This research focuses on the architectural design of the silica shell on the Fe3O4 nanoparticle to precisely control and minimize its thickness, with the aim of achieving a final product with optimal saturation magnetization (Ms) for biomedical applications. A rapid and facile microwave-assisted synthesis method was developed for the synthesis of Fe3O4@SiO2 and Fe3O4@SiO2@NH2 core–shell nanoparticles with ultra-thin SiO2 shells and excellent magnetic performance. The particle size distribution of the Fe3O4@SiO2 nanoparticles was in the range of 15–35 nm, with a mean particle size of approximately 21 nm. The mean thickness of the SiO2 shells on the Fe3O4 cores was found to be 3 nm. FTIR analysis also confirmed the successful silica coating on Fe3O4 nanoparticles and the successful amino-functionalization of silica-coated Fe3O4 nanoparticles. The Ms of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@NH2 nanoparticles were found to be 64.4, 59.8, and 52.4 emu/g, respectively. It has been confirmed that the ultra-thin SiO2 coating has a negligible effect on the magnetic characteristics of the nanoparticles. The developed microwave-assisted synthesis method in this study not only provides an interesting, rapid, and facile synthesis route but also results in a product with a narrow particle size distribution, an ultra-thin SiO2 shell, favorable magnetic properties, and improved cell compatibility, which may be used in several different applications, particularly biomedical applications.

Highly fluorescent nitrogen-doped carbon quantum dots prepared using sucrose and urea: Green synthesis, characterization, and use for determination of torsemide in its tablets and plasma samples.

A simple and facile microwave-assisted method was developed for the synthesis of highly fluorescent nitrogen-doped carbon quantum dots (N-CQDs) using sucrose and urea. The produced quantum dots exhibited a strong emission band at 376 nm after excitation at 216 nm with quantum yield of 0.57. The as-prepared N-CQDs were characterized using Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) images, and ultraviolet-visible (UV-visible) spectra. The average particle size was 7.7nm. It was found that torsemide (TRS) caused an obvious quenching of the fluorescent N-CQDs; so, they were used for its spectrofluorometric estimation. An excellent linear correlation was found between the fluorescence quenching of N-CQDs and the concentration of the drug in the range of 0.10 to 1.0μg/mL with limit of quantitation (LOQ) of 0.08 μg/mL and limit of detection (LOD) of 0.027 μg/mL. The method was successfully applied for the assay of the drug in its commercial tablets and spiked human plasma samples, and the results obtained were satisfactory. Complex GAPI was used for greenness assessment of the analytical procedures and the pre-analysis steps. Interference likely to be introduced from co-administered drugs was also studied.

Microwave-Assisted Rapid Synthesis of MOF-Based Single-Atom Ni Catalyst for CO2 Electroreduction at Ampere-Level Current.

Carbon-based single-atom catalysts (SACs) have attracted tremendous interest in heterogeneous catalysis. However, the common electric heating techniques to produce carbon-based SACs usually suffer from prolonged heating time and tedious operations. Herein, a general and facile microwave-assisted rapid pyrolysis method is developed to afford carbon-based SACs within 3 min without inert gas protection. The obtained carbon-based SACs present high porosity and comparable carbonization degree to those obtained by electric heating techniques. Specifically, the single-atom Ni implanted N-doped carbon (Ni1 -N-C) derived from a Ni-doped metal-organic framework (Ni-ZIF-8) exhibits remarkable CO Faradaic efficiency (96 %) with a substantial CO partial current density (jCO ) up to 1.06 A/cm2 in CO2 electroreduction, far superior to the counterpart obtained by traditional pyrolysis with electric heating. Mechanism investigations reveal that the resulting Ni1 -N-C presents abundant defective sites and mesoporous structure, greatly facilitating CO2 adsorption and mass transfer. This work establishes a versatile approach to rapid and large-scale synthesis of SACs as well as other carbon-based materials for efficient catalysis.

Zn3V2O7(OH)2·2H2O/MXene cathode with fast ion diffusion for highly durable zinc ion batteries.

V-based materials are considered promising candidates as cathode materials for zinc ion batteries (ZIBs). However, the inherent low conductivity of V-based compounds leads to the sluggish diffusion kinetics of Zn2+ and serious cycling capacity degradation of ZIBs. Herein, 1D Zn3V2O7(OH)2·2H2O (ZVO) nanowires were grown on monodisperse 2D Ti3C2T x MXene nanosheets via a facile microwave-assisted method. The introduction of Ti3C2T x MXenes effectively improved the conductivity and hydrophilicity of ZVO. Furthermore, the Zn2+ diffusion coefficient of ZVO/Ti3C2T x composites was enhanced to 10-7-10-8 cm2 s-1, which was superior to that of pure ZVO nanowires (10-8-10-10 cm2 s-1) and other previously reported typical V-based cathodes. The ZIBs based on the ZVO/Ti3C2T x cathode possessed an excellent discharge specific capacity of 215.2 mAh g-1 at 0.1 A g-1 and cycling stability (84% retention over 14 000 cycles at 10 A g-1). Moreover, the flexible Zn//ZVO/Ti3C2T x ZIBs using a gel electrolyte still exhibited good cycling stability and rate performance.

Tailoring iridium-palladium nanoparticles with Ir-rich skin: a highly durable anode electrocatalyst for acidic water electrolysis via a facile microwave-assisted chemical reduction method.

Electrochemical water splitting under acidic conditions is a clean way towards producing hydrogen fuels. The slow kinetics of the oxygen evolution reaction (OER) at the anode is currently a bottleneck for commercial acceptance of this technology. Therefore, arriving at more efficient and sustainable OER electrocatalysts is highly desirable. We here demonstrate the synthesis of iridium-palladium (IrPd) alloy nanoparticles (2-5 nm) with variable average composition (Ir : Pd = 1 : 0, 1 : 1, 1 : 3, 1 : 6, 1 : 9 and 0 : 1) using a facile one-pot microwave-assisted chemical reduction method. The IrPd nanoparticles show structure- and composition-dependent OER performance in acidic media. Utilizing different reduction strengths and precursor ratios, successful alloy catalysts were prepared with Ir-rich skin and sublayers of different Pd compositions. Their structures were revealed using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen underpotential deposition (Hupd) studies. It turned out that (1) the alloy OER catalyst also has a high electrochemically active surface area for hydrogen adsorption/desorption, (2) the OER performance is strongly dependent on the surface Ir contribution and (3) the intact Ir skin is essential for electrocatalyst stability.

Facile fabrication of Fe3O4@UiO-66-NH2/popcorn-like gold nanoparticles based SERS substrate for selective enrichment and real-time detection of residual enrofloxacin in milk

In this study, a magnetic metal-organic frameworks (MOFs) based hybrid substrate was designed and fabricated for SERS detection of enrofloxacin (ENR) in milk. The magnetic MOF (Fe3O4@UiO-66-NH2) was synthesized by a facile microwave-assisted method, then loaded with popcorn-like Au nanoparticles (NPs) through electrostatic interaction. The as-prepared SERS substrate (Fe3O4@UiO-66-NH2/Au NPs) integrated the abundant hot spots of popcorn-like Au NPs with porous Fe3O4@UiO-66-NH2, which greatly improved its SERS activity and stability. More importantly, benefiting from the fingerprint characteristics of SERS and adsorption performance of Fe3O4@UiO-66-NH2, the SERS substrate exhibited high selectivity and sensitivity in detecting ENR. Under the optimal detection condition, a good linearity (R2 = 0.996) was obtained with ENR concentration of 1.0 × 10−9–1.0 × 10−6 M in spiked milk, the LOD was as low as 5.26 × 10−10 M, and the recoveries were in the range of 76.1–86.1 % at three different spiking levels. The whole detection process including sample pretreatment took about 50 min, which indicating that the prepared substrate has great potential in sensitive and real-time detection of ENR in milk.

Insights into the kinetics–morphology relationship of 1-, 2-, and 3D TiNb2O7 anodes for Li-ion storage

Understanding the influence of electrode material’s morphology on electrochemical behavior is of great significance for the development of rechargeable batteries, however, such studies are often limited by the inability to precisely control the morphology of electrode materials. Herein, nanostructured titanium niobium oxides (TiNb2O7) with three different morphologies (one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D)) were synthesized via a facile microwave-assisted solvothermal method. The influence of the morphological dimension of TiNb2O7 as electrode material on the electrochemical performance in Li-ion batteries (LIBs) and the underlying correlation with the electrochemical kinetics were studied in detail. 2D TiNb2O7 (TNO-2D) shows a superior rate capability and cycling stability, associated with improved kinetics for charge transfer and Li-ion diffusion, compared to the 1D and 3D materials. Operando X-ray diffraction measurements reveal the structural stability and crystallographic evolution of TNO-2D upon lithiation and delithiation and correlate the Li-ion diffusion kinetics with the lattice evolution during battery charge and discharge. Moreover, carbon-coated TNO-2D achieves enhanced rate capability (205 mAh·g−1 at 50 C) and long-term cycling stability (87% after 1000 cycles at 5 C). This work provides insights into the rational morphology design of electrode materials for accelerated charge transfer and enhanced fast-charging capability, pushing forward the development of electrode materials for high-power rechargeable batteries in future energy storage.

Interface engineering of hollow CsPbBr3/Co3O4 p-n heterojunction with rich oxygen vacancy for highly enhanced photocatalytic CO2 reduction

Surface defect or p-n heterojunction is considered as an efficient strategy to fabricate intrinsic built-in electric field and facilitate the charge separation and transfer. Herein, a novel p-n heterojunction photocatalyst CsPbBr3/Co3O4 was constructed by a facile microwave-assisted method, in which CsPbBr3 QDs anchored on ZIF-67 derived Co3O4 nanocage can simultaneously introduce oxygen vacancies and strengthen the interfacial interaction. As a result, the as-prepared CsPbBr3/Co3O4 displays the satisfactory photocatalytic CO2 reduction performance without photosensitizer and sacrificial agent, and the optimal catalyst exhibits that the average electron consumption rate (Relectron) is 158.80 μmol‧g−1‧h−1, which is 12.41 times higher than that of pure CsPbBr3. Photoassisted Kelvin probe force microscopy (KPFM) and experimental characterizations exhibit the formation of strong built-in electric fields probably due to the rich oxygen vacancies in this p-n heterojunction. Besides, DFT calculations confirm that the charge transfer pathway, where the electrons are quickly migrated to the catalytic active sites through the formed Cs-O bonds, thus accelerating the charge separation. This work could establish an effective strategy for the rational design of p-n heterojunctionto achieve high-performance CO2 conversion.

Facile fabrication of Fe-Fe3C nanoparticles decorated with carbon nanotubes for sensitive dopamine detection

In this study, we present an electrochemical sensor with superior sensitivity and selectivity for dopamine (DA) detection. The sensor was created using a nanocomposite of iron-iron carbide nanoparticles decorated with carbon nanotubes (Fe-Fe3C@CNTs) to modify a glassy carbon electrode (GCE). The Fe-Fe3C@CNTs nanocomposite can be synthesized by a facile microwave-assisted synthesis method with just adopting ferrocene and carbon fiber as raw material and heat source, respectively. The electron microscopy (EM) results indicate that the Fe-Fe3C nanoparticles encapsulated with graphitic layer were decorated with CNTs. An investigation of the electrochemical responses of the Fe-Fe3C@CNTs/GCE sensor to DA was performed using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Notably, in ideal experimental settings, the sensor demonstrated a minimal limit of detection (LOD) of 0.01 μM within a range of linearity from 0.05 to 40 μM, even under a high concentration of uric acid (UA) interference. Moreover, the utility of the produced Fe-Fe3C@CNTs/GCE sensor was further validated through successful DA testing in urine samples of human.

Enhanced acetone gas sensing performance of ZnO polyhedrons decorated with LaFeO3 nanoparticles

Since acetone is potentially harmful to humans, it is necessary to develop a high-performance acetone gas sensor. In this study, ZnO polyhedrons decorated with LaFeO3 (LFO) nanoparticles with high acetone-sensing performances were prepared by a facile microwave-assisted hydrolytic reaction method, and the p-n heterojunction was successfully constructed. The crystal structure, surface morphology, and internal composition of the LaFeO3/ZnO composites were analyzed by various characterization methods. The results showed that LaFeO3 nanoparticles were successfully composited with ZnO polyhedra. Compared with the pure ZnO sensor, the LaFeO3/ZnO sensor showed a significant improvement in sensitivity, recovery time, and selectivity. For example, at the optimal operating temperature of 340 °C, the response of the LaFeO3/ZnO sensor to 100 ppm acetone could reach ∼208.7, which was 39 times higher than that of the pure ZnO sensor. And the recovery time of the LaFeO3/ZnO sensor was reduced to 15.4 s. Meanwhile, the LaFeO3/ZnO sensor had the highest selectivity for acetone. The significant improvement of the sensing performance of the LaFeO3/ZnO sensor might be attributed to the formation of p-n heterojunctions and the good catalytic effect of LaFeO3.

Microwave-assisted synthesis of nanostructured tin sulfide as a highly efficient visible-light active photocatalyst: Characterization, applications, and theoretical studies

In this study, nanostructured tin sulfide was synthesized using a facile microwave-assisted method. The as-prepared sample was further characterized via X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), UV–Visible Diffuse Reflectance Spectroscopy (DRS), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH) and Mott-Schottky analyses. Based on the results, the synthesized SnS is an n-type semiconductor and has a direct band gap of 1.32 eV. Photocatalytic activity of nanostructured SnS was then evaluated through degrading methylene blue (MB) under visible light in a cylindrical batch reactor. The results show that this highly efficient photocatalyst can degrade almost up to 83.06% of 14 mg/L pollutant within 10 min, which can be attributed to its relatively high specific surface area of 52.819 m2/g. In addition, the photocatalyst performance was studied from the isothermic, thermodynamic, and kinetic points of view. The results suggest that Fritz-Schlunder along with Baudu are the most appropriate models to describe the adsorption process (the first step of photochemical reactions), as they have the lowest error functions and highest correlation coefficients. Based on kinetic studies results, there is a good agreement between the pseudo-second-order adsorption kinetic model and our experimental data. Additionally, the corresponding structural parameters of SnS were compared by size-strain plot (SSP), and Williamson-Hall methods. Furthermore, a density functional theory (DFT) approach was conducted to get more insight into the electronic and structural properties of the SnS. In terms of the band structure, 1.35 eV of band gap energy (Eg) is obtained, which perfectly matches with the results of characterization tests (1.32 eV). Finally, the partial density of states curves indicate that the valence band maximum (VBM) is mainly generated from 3pS, 5sSn, and 5pSn states while the conduction band minimum (CBM) is made of 5pSn states. Consequently, the spin-up and spin-down curves are found to be highly symmetric, indicating the non-magnetic property of tin sulfide.

Facile microwave-assisted synthesis of Pt single atom anchored on poly (ionic liquids) functionalized reduced graphene oxide for ultrasensitive detection of H2O2

Theoretically, Single atoms are providing the maximum atomic efficiency and are very promising to improve the performance of the noble metal catalysts for high-active electrochemical sensors. In this work, Pt single atom anchored on surficial modified, reduced graphene oxides with poly(ionic liquids) (Pt1_rGO@PILs) for detecting hydrogen peroxide (H2O2) was synthesized via a facile microwave-assisted method. Due to the high active sites from PILs, 1.2 wt% isolated Pt atoms were steadily loaded on the surface of rGO@PILs and formed Pt-S4 coordination with the modified PILs layer. Such atomical dispersion of Pt atoms and their unique coordination environment promoted electronic transfer during the electrochemical reaction. The Pt1_rGO@PILs composite presented a detection limitation of 1.5 µM in a liner range from 2.3 to 250 µM with high sensitivity up to 725.95 µA/µM. The catalysts also showed good stability for 30 days while active and the lowest detected concentration of approximately 15 μM for H2O2 in the real commercial samples.

Microwave-assisted synthesis of copper oxide particles and its application for determination of imazapyr in environmental samples

Imazapyr (IMA) is currently applied as pre- and post-emergence herbicide for control of weeds in crops. Because of its extensive use, IMA residues may reach water sources and soils. Consequently, its accurate measurement is demanded for timely actions with minimal involved steps and analysis time. Herein, copper oxide particles (Cu2O PS) were proposed as chemical sensor for determination of IMA residues. Cu2O PS were prepared by a facile microwave-assisted method using glucose as reducing agent and polyvinylpyrrolidone as stabilizer. The effect of main experimental parameters on the conversion rate of the Cu2O PS were analyzed by the response surface methodology. Obtained particles were thoroughly characterized in order to determine the particle size distribution, morphology, surface charge, optical and surface properties for further application. Determination of IMA was only based on the localized surface plasmon resonance band of Cu2O PS at 473 nm. Under optimal conditions, the method was evaluated in the concentration range between 80.0 and 1,000 μg L−1 showing a limit of detection about 101 μg L−1 (R2 >0.98). The applicability of the proposed methodology to determine IMA in soil and water samples was assessed with satisfactory recoveries (104–121.8%) displaying a good implementation prospect in environmental complex matrices.

Selective hydrogenation of phenol to cyclohexanone over small amount of Ru-promoted Pd/ZrHP catalysts

Selective hydrogenation of phenol to cyclohexanone is a vital step in the manufacture of fiber (nylon), which is currently carried out over expensive Pd catalyst with low productivity. In this work, a series of Ru-promoted Pd catalysts were synthesized in a facile microwave-assisted method and tested in the hydrogenation of phenol to cyclohexanone. It was found that small amount of Ru in Ru-Pd alloy can increase the conversion of phenol obviously without loss of cyclohexanone selectivity. The selectivity of cyclohexanone over Ru0.15Pd4.85/ZrHP remained higher than 99%, while the conversion of phenol increased from 20.5% (over Pd5/ZrHP) to 97.9% at 100 °C and 1 MPa. And the highest turnover frequency (TOF) of surface metal in Ru0.15Pd4.85/ZrHP at 100 °C and 2 MPa reached 1605 h−1. Characterization results revealed that the addition of Ru can improve the dispersion of Ru-Pd alloy and enhance its electron density. In addition, the activated hydrogen on Ru-Pd alloy and acid sites in ZrHP played a synergistic effect for the selective formation of cyclohexanone from phenol.

Enhanced Li storage properties of nickel oxalate microtubes with manganese doping and graphene oxide for lithium-ion batteries

Nowadays, metal oxalates with high discharge/charge capacities were chosen as new anode materials for batteries. Here, novel nickel oxalates microtubes with manganese doping and graphene Oxide (Ni0.8Mn0.2C2O4∙2 H2O/GO) are synthesized at low temperature through a facile microwave-assisted solvothermal method. The X-ray diffraction confirmed a formation of a pure binary compound of Ni0.8Mn0.2C2O4∙2 H2O/GO without contamination by other compounds of Nickel or Manganese. Furthermore, the formed product shows a good crystallinity and has a high surface area of 24.3 m2 g−1. With the assistance of graphene, the material delivers a high discharge capacity of 1781 mA h g−1. Even at high current densities of 5.0 and 10.0 A g−1, discharge capacities of 1138.1 and 891.0 mA h g−1 can be obtained. Encouraged by the superior rate performance, the long-term cycling performance at 10 A g−1 and 20 A g−1 was tested showing a discharge of 676.6 mA h g−1 after 300 cycles and 346.4 mA h g−1 after 1000 cycles. The remarkable electrochemical performance can be attributed to the doping of Mn in the structure of NiC2O4 ∙2 H2O and the contribution of graphene.

Simultaneous adsorption of ciprofloxacin drug and methyl violet dye on boron nitride nanosheets: experimental and theoretical insights.

In this study, hexagonal boron nitride (BN) with a sheet-like morphology is successfully synthesized by reacting borax (Na2B4O7·10H2O) and urea (CO(NH2)2) powders in air via a facile microwave-assisted method within a short reaction time (15 min). The as-prepared product is structurally characterized via Fourier transformation infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersion X-ray analyzer (EDX), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The adsorption process of methyl violet (MV) as a model of organic dyes and ciprofloxacin (CIP) as a model of antibiotics onto the boron nitride nanosheets has been experimentally and theoretically studied. The BN nanosheets exhibit the maximum adsorption capacity of 320.94 mg g-1 for MV dye and 266.29 mg g-1 for CIP antibiotic. The Freundlich isotherm model was suitable to describe the adsorption equilibrium isotherm data and the pseudo second-order model reflected the adsorption kinetics well. The calculated thermodynamic parameters show that the adsorption process is spontaneous under the measured conditions. The adsorption of CIP, MV and CIP + MV molecules on the surface of BN has been investigated through DFT calculations. The charge transfer and high adsorption capacity demonstrate the potential of BN nanosheets as an adsorbent for the simultaneous removal of MV dye and CIP drug from contaminated water.

Au-modified α-Fe2O3 nanoparticles for ultrasensitive isopropanol detection

The Au-modified α-Fe2O3 was prepared using facile microwave-assisted method. The sensor based on 7% mol Au-modified α-Fe2O3 presented the highest sensitivity. Electron transfer from Au NPs to α-Fe2O3 increases the number of oxygen-active species.

A microwave-assisted solvothermal method to synthesize BiOCl microflowers with oxygen vacancies and their enhanced photocatalytic performance

The photocatalytic performance of the catalysts are highly dependent on their morphology and the separation efficiency of photo-generated carriers. In this work, the self-assembled BiOCl microflowers with oxygen vacancies (OVs) were synthesized by facile microwave-assisted solvothermal method. The ethylene glycol was applied as solvent, reductant and soft templates of microflowers. As the preparation temperature increased from 100 ℃ to 160 ℃, the morphology of BiOCl was transformed from microflowers to nanosheets, and the concentration of OVs increased gradually. The photocatalytic performance of BiOCl was evaluated by photocatalytic degradation of Rhodamine B (RhB), Methylene blue (MB) and Ciprofloxacin (CIP) under visible light irradiation. It is indicated that the excessive OVs would inhibit the separation and migration of photo-generated carriers. Benefiting from the optimum OVs concentration and enhanced specific surface area, the BiOCl-100 microflowers exhibited a superior photocatalytic performance. The degradation constants for RhB, MB and CIP by BiOCl-100 were estimated to be 0.512, 0.022 and 0.022 min−1, which were 4.3, 1.7 and 5.5 folds higher than BiOCl-100-w nanosheets (with no OVs), respectively. This work demonstrated the superior photocatalytic performance of BiOCl microflowers with optimum OVs, which could be also applied to design of other highly efficient photocatalysts.

Microwave-assisted preparation of Mn3O4@sepiolite nanocomposite for highly efficient removal of uranium

Nuclear energy is an important alternative energy source to non-renewable fossil fuels. Nevertheless, the nuclear contamination associated with nuclear activities and wastes is a formidable concern worldwide. Uranium is one of the most commonly used and discharged radionuclides, and hexavalent uranium [U(VI)] has significant mobility owing to its good solubility in water, leading to serious environmental and health risks. However, facile and economical solutions to effectively treating U(VI)-contaminated water are still limited. Herein, Mn3O4 nanoparticles were dispersedly anchored on sepiolite nanofibers via a facile microwave-assisted method for adsorbing U(VI) from aqueous solutions. Batch adsorption experiments showed that the nanocomposite possessed faster removal kinetics and greater removal capacity than the individual sepiolite and Mn3O4, as well as better removal performance than many reported inorganic and organic adsorbents. The nanocomposite can also reduce the U(VI) concentrations to far less than the standard of drinking water. Furthermore, a systematic investigation of the adsorption mechanism revealed that the nanocomponents Mn3O4 and sepiolite were responsible for the high-affinity U(VI) capture through the bonding of ≡Mn–O–U(VI) and ≡Si/Mg–O–U(VI), respectively, but the loaded Mn3O4 nanoparticles dominated the adsorption. Given that the simple synthesis and excellent U(VI) removal performance, the Mn3O4@sepiolite nanocomposite holds great promise for practical applications in radioactive uranium treatment.

Microwave-Assisted Solvothermal Synthesis of Nanocrystallite-Derived Magnetite Spheres.

The synthesis of magnetic particles triggers the interest of many scientists due to their relevant properties and wide range of applications in the catalysis, nanomedicine, biosensing and magnetic separation fields. A fast synthesis of iron oxide magnetic particles using an eco-friendly and facile microwave-assisted solvothermal method is presented in this study. Submicron Fe3O4 spheres were prepared using FeCl3 as an iron source, ethylene glycol as a solvent and reductor and sodium acetate as a precipitating and nucleating agent. The influence of the presence of polyethylene glycol as an additional reductor and heat absorbent was also evaluated. We reduce the synthesis time to 1 min by increasing the reaction temperature using the microwave-assisted solvothermal synthesis method under pressure or by adding PEG at lower temperatures. The obtained magnetite spheres are 200–300 nm in size and are composed of 10–30 nm sized crystallites. The synthesized particles were investigated using the XRD, TGA, pulsed-field magnetometry, Raman and FTIR methods. It was determined that adding PEG results in spheres with mixed magnetite and maghemite compositions, and the synthesis time increases the size of the crystallites. The presented results provide insights into the microwave-assisted solvothermal synthesis method and ensure a fast route to obtaining spherical magnetic particles composed of different sized nanocrystallites.