Microwave-solvothermal Method Research Articles

Enhanced photocatalytic degradation of methylene blue by WO3/ZnWO4 composites synthesized by a combination of microwave-solvothermal method and incipient wetness procedure

ZnWO4 nanoparticles were successfully synthesized by microwave-solvothermal method. Subsequently, the incipient wetness procedure was used to load WO3 into ZnWO4 matrix and to form the WO3/ZnWO4 composites with different morphologies. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectrophotometry, and electron microscopy (EM) were used to characterize the phase, oxidation state, composites, and morphology. According to the Scherrer formula and the Brunauer–Emmett–Teller (BET) adsorption, average crystallite sizes of the nanoparticles are less than 30nm and 45nm, respectively, larger than the direct measurement by TEM. The 3.23eV direct energy gap (Eg) and the 478nm emission wavelength of 3mol% WO3/ZnWO4 composites were determined by UV-visible absorption and photoluminescence (PL) spectroscopy. The photocatalytic degradation of methylene blue (C16H18N3SCl) was greatly enhanced by WO3 loading in ZnWO4 matrix to form WO3/ZnWO4 composites. In this research, 3mol% WO3-loaded ZnWO4 offered the best photodegradation performance of methylene blue at 36.21% within 300min and 55.54% within 480min under UV light irradiation.

Synthesis of hexagonal wurtzite Cu2ZnSnS4 prisms by an ultrasound-assisted microwave solvothermal method

Wurtzite Cu2ZnSnS4 (CZTS) hexagonal prisms were synthesized by a simple ultrasound-microwave solvothermal method. The product was characterized by XRD, FESEM, EDS, TEM, Raman and UV–vis spectrometer. The hexagonal prisms were 0.5–2μm wide and 5–12μm long. The PVP played an important role in the formation of the CZTS hexagonal prisms. In addition, the ultrasound-assisted microwave process was helpful for synthesis of wurtzite rather than kesterite phase CZTS. A nucleation–dissolution–recrystallization mechanism was also proposed to explain the growth of the CZTS hexagonal prisms.

Energy-efficient, microwave-assisted hydro/solvothermal synthesis of hierarchical flowers and rice grain-like ZnO nanocrystals as photoanodes for high performance dye-sensitized solar cells

Hierarchical ZnO with different morphologies have been synthesized via rapid microwave-solvothermal method. Innovative ZnO nano-hybrid architecture photoanode based DSSCs showed remarkable enhancement in solar power conversion efficiency as high as 5.64%.

LiMnBO₃ nanobeads as an innovative anode material for high power lithium ion capacitor applications.

A novel approach was made to fabricate lithium ion hybrid capacitor (Li-HC) having LiMnBO3 nanobead (LMB-NB) anode and polyaniline nanofiber (PANI) cathode in 1 M LiPF6 organic electrolyte. LMB-NB and PANI nanofibers were synthesized using urea assisted microwave-solvothermal method and chemical polymerization process, respectively. The PANI/LMB-NB cell showed improved electrochemical capacitive behavior as compared to activated carbon (AC)/LMB-NB cell due to the characteristic conductivity and the morphological feature of PANI as well as LMB-NB electrodes. A discharge capacitance (DCcell) of ∼125 F g(-1) was obtained at a current density of 1 A g(-1) between the potential range 0 and 3 V for PANI/LMB-NB cell, while AC/LMB-NB cell delivered only 77 F g(-1) at the same current density. Moreover, PANI/LMB-NB cell exhibited excellent rate performance with the DCcell of about 55 F g(-1) at 2.25 A g(-1) and still retained 94% of the initial value after 30 000 charge-discharge cycles. In addition, maximum energy and power densities of 42 Wh kg(-1) and 5350 W kg(-1), respectively, were achieved from PANI/LMB-NB cell. The obtained DCcell, energy, and power densities along with prolonged cyclic life for PANI/LMB-NB cell are some of the best ever reported values for Li-HC as compared to the cells constructed with various lithium intercalating materials.

Effect of pH on photocatalytic activity of SnO2 microspheres via microwave solvothermal route

Quasi-monodispersed SnO2 microspheres have been successfully synthesised by a microwave solvothermal method, in which polyethylene glycol is used as template, SnCl4.5H2O and urea as raw materials. The products have been characterised by X-ray diffraction, a scanning electron microscope, and a transmission electron microscope. Besides, the thermal behaviour of the products synthesised by solvothermal process has been studied through the thermogravimetry differential scanning calorimetry. Photocatalytic activities of the samples have been evaluated by the degradation of rhodamine B (RhB) in different pH values under UV light illumination. Results showed that these microspheres with diameter about 1·0–1·5 μm were composed of numerous SnO2 nanoparticles with a diameter of ∼9 nm. The SnO2 microspheres exhibited a high effective adsorption and an excellent photocatalystic activity of RhB in a wide range of pH values.

Selective synthesis of TiO2 nanocrystals with morphology control with the microwave-solvothermal method

In this paper, a method to synthesize anatase TiO2 nanorods by hydrolysis of titanium(IV) isopropoxide (TTIP) in the presence of benzyl alcohol and acetic acid at 210 °C was tested. The novelty of the present approach relies on the evaluation of the shape-controlled synthesis of anatase TiO2 nanocrystals via a microwave-solvothermal method in 45 min. The different TiO2 nanocrystals were obtained by tuning the TTIP/acetic acid ratio under optimized synthetic conditions and were characterized in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), micro Raman (together with microphotoluminescence) and FT-IR spectroscopies. The acetic acid coordinated on the nanocrystal surface was removed by the reduction of its carboxyl group via a “super-hydride reaction”, and the photocatalytic activity of bare TiO2 nanocrystals, under visible light irradiation, was also evaluated: the best performing TiO2 anatase nanocrystals exhibited a discrete photoactivity, completely degrading Rhodamine B solution in five hours.

Synthesis of flower-like nanoparticles of anatase titania by microwave solvo-hydrothermal method

Anatase titania nanoparticles with an average size of about 14 nm were synthesized by microwave solvothermal method from TiCl4 and ethanol as a precursor and solvent respectively. The shapes of as prepared samples were modified by microwave hydrothermal treatment in strongly alkaline medium at 100 °C for 2 h, the agglomerate particles can be converted to the nanorods then to flower-like sphere. The structure, morphology and optical properties of as-prepared powders were investigated by X-ray diffraction, scanning electron microscopy and UVvis absorption spectroscopy, the quality of the samples was examined by IR absorption spectroscopy and room temperature photoluminescence (PL). The results showed that the synthesized TiO2 revealed the formation of the nanorods and the flower-like shape of titania after post treatment in 5 mol/L and 10 mol/L NaOH solution, respectively. IR absorption spectra showed that the as-prepared TiO2 nanocrystals were highly pure and strongly surface hydrated, The photoluminescence measurement showed that five main emission peaks appeared in UV, violet, blue and green regions.

Towards an Understanding on the Role of Precursor in the Synthesis of ZnS Nanostructures

Wurtzite-structured ZnS nanostructures have been synthesized by means of a microwave-solvothermal method at 140°C using three precursors (chloride, nitrate and acetate). Different techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements have been employed to characterize this material. The structure, surface morphology, chemical composition and optical properties were investigated as function of precursor. In order to complement experimental results, first principles calculations at DFT level were carried out in order to obtain the relative stability of the proposed intermediates along the formation mechanism. Keywords: ZnS, Microwave-solvothermal method, precursors, first principle calculations.

Synthesis of Bi2Te3 Urchin-like Nanorods by a Microwave–Solvothermal Method

Abstract Nanocrystalline Bi2Te3 (nanospheres with diameters of 50–500 nm, urchin-like nanorods with diameters ranging from 5 to 15 nm and lengths ranging from 40 to 100 nm) has been successfully synthesized by a microwave–solvothermal method using TeO2, Bi(NO3)3·5H2O, and HNO3 in a solvent of poly(ethylene glycol) (PEG-400). Compared with other reaction systems, less reagents and reductant-free conditions were important factors to simplify the reaction process.

Photoluminescence properties of the Eu-doped alpha-Al2O3 microspheres

Abstract Al 2 O 3 :Eu 3+ samples were synthesized via microwave solvothermal method and thermal decomposition of Eu 3+ doped precursors. The sample characterizations were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL) spectra. XRD results indicated that Eu 3+ doped samples were most of α-Al 2 O 3 phase after being calcined at 1473 K. SEM results showed that the obtained α-Al 2 O 3 based powders via microwave solvothermal method were microspheres with an average diameter about 1.6 μm. PL spectra showed that upon excitation at 393 nm, the orange–red emission bands at the wavelength longer than 560 nm were from 5 D 0 → 7 F J ( J = 1, 2) transitions. The asymmetry ratio of ( 5 D 0 → 7 F 2 )/( 5 D 0 → 7 F 1 ) intensity is about 1 and this value suggests that Eu 3+ ions occupy the same ratio of symmetry and asymmetry sites. It is shown that the 0.7 mol% of doping concentration of Eu 3+ ions in α-Al 2 O 3 :Eu 3+ is optimum. According to Dexter’s theory, the critical distance between Eu 3+ ions for energy transfer was determined to be 18 A.

Synthesis of nanostructured Li2MnSiO4/C using a microwave assisted sol–gel process with water as a base solvent

Microwave assisted sol–gel method is used to fabricate nanostructured Li2MnSiO4/C composites. Our process has the advantages in homogenous heating and reduced reaction time. In addition, the water is used as a base solvent while the conventional microwave-solvothermal method use the organic solvent as the base solvent, which makes our process much more safe and economical. Here, our prepared Li2MnSiO4/C composite exhibits an enhanced discharge capacity of 173.1 mAh g−1, compared to the conventional processes.

Microwave-solvothermal synthesis of Fe3O4 magnetic nanoparticles

Fe3O4 magnetic nanoparticles were successfully synthesized by the microwave-solvothermal method in a simple reaction system during significantly shorter time than traditional solvothermal or hydrothermal methods. In this synthetic system, ethylene glycol acts as solvent, microwave mediate, and reductant; trisodium citrate works as assistant reductant and electrostatic stabilizer, which makes the Fe3O4 nanoparticles well dispersed in the solution; NH4Ac is the nucleating agent. In the process, a burst of “hot-spots” induced by quick microwave irradiation can create a condition for uniform seeding in the precursor solution, and accelerate the formation of Fe3O4 nanocrystals. F43O4 nanoparticles prepared by the microwave-solvothermal method showed a higher saturation magnetization than the sample synthesized by the conventional solvothermal method, which can be ascribed to the fact that the former has smaller particle sizes than the later.

Synthesis and characterization of zinc borophosphates with ANA-zeotype framework by the microwave method

Abstract Zinc borophosphate (NH 4 ) 16 [Zn 16 B 8 P 24 O 96 ] (denoted as ZnBP-ANA) with ANA-zeotype structure has been synthesized by employing microwave-assisted solvothermal synthesis in the reaction system ZnCl 2 ∙6H 2 O-(NH 4 ) 2 HPO 4 –H 3 BO 3 using ethylene glycol as a co-solvent. The influences of various experimental parameters, such as reaction temperature, solvent ratio, zinc precursors and reactive power, have been systematically investigated. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), and so on. Small and homogeneous ZnBP-ANA single crystal with regular cube morphology are crystallized by using microwave solvothermal synthesis method within a shorter time, and its grain size decreases with power.

Magnetic Iron Oxide Nanoparticles for High Frequency Applications

Magnetic properties of iron oxide nanoparticles synthesized by microwave solvothermal method are reported. The effect of the nucleating agent on the composition, size, morphology and microstructure of nanoparticles was studied with a view to their correlation with magnetic properties. It is shown that a soft magnetic material with high value of magnetization saturation and high-frequency dispersion of complex permeability can be obtained by an appropriate choice of the nucleating agent.

Synthesis, Characterization, and Activity of Tin Oxide Nanoparticles: Influence of Solvothermal Time on Photocatalytic Degradation of Rhodamine B

The SnO2 spheres-like nanoparticles have been successfully synthesized by a microwave solvothermal method, in which SnCl2·2H2O, poly(vinylpyrrolidone) PVP, H2O2 and NaOH as raw materials. The as-synthesized products have been characterized by X-ray diffraction, scanning electron microscope, and UV/Vis/NIR spectrophotometer. Photocatalytic activities of the samples have been evaluated by the degradation of rhodamine B (RhB) under UV-light illumination. Results showed that these products with diameter about 1 - 2 μm, and when the reaction time prolong, the surface of the SnO2 spheres will change to rough and then smooth when the time even longer. The product with nanorods on its surface shows the higher photocatalytic activity and red shift in the UV-vis absorption, which are relative to the unique structure. At last we studied the electron transfer reactions during photo-oxidation of RhB.

Effects of Cr content and morphology on the luminescence properties of the Cr-doped alpha-Al2O3 powders

Al2O3:Cr3+ samples were synthesized via hydrothermal and microwave solvothermal methods and thermal decomposition of Cr3+ doped precursors. The sample characterizations were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and decay curves. XRD results indicated that Cr3+ doped samples were pure α-Al2O3 phase after being calcined at 1573 K. SEM results showed that the length and diameter of these Cr3+ doped alumina microfibers by hydrothermal route were about 2–5 μm and 100–300 nm, respectively; the obtained α-Al2O3 based powders via the microwave solvothermal method were microspheres with an average diameter about 1–2 μm. PL spectra showed that the Al2O3:Cr3+ samples presented a broad R band at 696 nm. It is shown that the 0.3 mol% of doping concentration of Cr3+ ions in α-Al2O3:Cr3+ is optimum. According to Dexter's theory, the critical distance between Cr3+ ions for energy transfer was determined to be 24 Å. It is found that the curve followed the single-exponential decay. Furthermore, the luminescence properties of the samples are also dependent on the morphology.

Simple and Rapid Synthesis of LiFePO<sub>4</sub>/C Composite for Lithium Rechargeable Batteries by Microwave-Solvothermal Method Assisted with Short Time Post-Treatment Process

A simple and rapid technique to synthesize LiFePO4 by microwave-solvothermal method assisted a short time post-treatment was described. The crystal structure and the charge-discharge performance of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic charge-discharge testing. The results indicated that this rapid synthesis technique by microwave-solvothermal method combined short time post-treatment was an effective way to obtain LiFePO4 with a single olivine-type crystal structure and small particle size. The electrochemical research indicated that the resulting LiFePO4/C composite could deliver 141.7mAh•g-1 at 0.1C at 25 °C and showed good stability retaining 97% after 45 cycles.

Correlation of structural and magnetic properties of Fe3O4 nanoparticles with their calorimetric and magnetorheological performance

Magnetic particles based on Fe3O4 were prepared by means of the microwave solvothermal method under different reaction conditions with the intention of their utilization as a mediator in magnetic hyperthermia and material for reducing blood flow in the tumor area. The synthesized particles were characterized in terms of their structure, size, shape, and magnetic properties with an emphasis on the correlation between particle morphology and magnetic properties. Most importantly, their heat development when exposed to an alternating magnetic field was determined, as well as the rheological behavior of their suspensions under static magnetic field. Reasonable heat development and substantial flow resistance under the effect of magnetic field indicate their potential for applications such as hyperthermia mediators or substances for temporary embolization.

Novel NiO nanodisks and hollow nanodisks derived from Ni(OH)2 nanostructures and their catalytic performance in epoxidation of styrene

A microwave-solvothermal (MS) method combining a calcination process was conducted to synthesize nickel oxide (NiO) nanodisks and hollow nanodisks. First, Nickel hydroxide (Ni(OH)2) nanodisks and hollow nanodisks had been synthesized through the MS method in the presence of oleylamine or sodium oleate. The X-ray powder diffraction (XRD) results of the products illustrate that the as-prepared nanostructures have a Ni(OH)2 and NiO phase. The transmission electron microscopy (TEM) images of the products illustrate that Ni(OH)2 nanodisks prepared in the presence of oleylamine have a thickness of ~10nm and diameter of ~100nm, while Ni(OH)2 hollow nanodisks synthesized in the presence of sodium oleate have a hole in the middle with a thickness of ~10nm and diameter of ~250nm. Second, the NiO nanodisks and hollow nanodisks could be obtained from the precursor without changing their morphologies by a simple calcination procedure. The as-synthesized NiO nanostructures displayed efficient catalytic epoxidation of styrene with conversion (60%) and selectivity (60–80%).

Synthesis of Quasi-monodispersed SnO<SUB>2</SUB> Microspheres via Micro-wave Solvothermal Method

以聚乙二醇(PEG, Mn=6000)为模板剂, 结晶四氯化锡(SnCl 4 ·5H 2 O)和尿素为原料, 采用微波溶剂热法在180℃、添加0.12 mmol PEG的条件下制备出了单分散性良好的SnO 2 微球. 通过XRD、SEM、TEM和FT-IR等分析手段对产物进行表征, 并结合光致发光(PL)谱研究了产物的发光性能. 结果表明: SnO 2 微球是由大量细小晶粒堆积而成的, 微球直径约1.3 um. 经400℃煅烧2 h后, 微球表面致密光滑且直径未发生明显变化. FT-IR谱图中550 cm -1 处吸收峰应为表面结构改变引起的表面振动模式. PL谱表明煅烧前SnO 2 微球在320~450 nm处具有宽而强的发射带, 煅烧后发射带强度大幅下降, 说明产物的晶格缺陷对近带边发射有重要影响.