Microwave-assisted Solvothermal Route Research Articles

Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures

We report the synthesis of metastable cobalt oxide (CoO) nanostructures via the low-temperature microwave-assisted solvothermal (MAS) process. An alcoholic solution of cobalt (II) acetylacetonate in a sealed vessel was irradiated with microwaves at a temperature <150 °C and a pressure below 100 psi. As-synthesized powder material was characterized in terms of its structure and morphology. X-ray diffractometry (XRD) indicates the formation of well-crystallized CoO nanoparticles without the need for post-synthesis annealing. The mean crystallite size of the nanoparticles was estimated to be 41 nm. The morphology of the as-prepared powder sample was evaluated by field-emission scanning electron microscopy (FESEM), which revealed the formation of densely packed nanospheres of diameter <100 nm. The CoO nanospheres were obtained without the need for any surfactants or capping agents; they were found to be quite resistant to oxidation in ambient air over several months. We attribute the stability of CoO nanospheres to their dense packing, the driving force being the minimization of surface energy and surface area. Fourier-transform infrared (FT-IR) spectroscopy and Raman spectroscopy confirm the formation of phase-pure CoO nanostructures. The deconvolution of the active modes in Raman spectra obtained at room temperature reveals the Oh symmetry in rock-salt CoO produced by the MAS route. We have analyzed its effect on the magnetic characteristics of the CoO nanostructures. Isothermal field-dependent magnetization (MH) and inverse magnetic susceptibility measurements show a phase transition from antiferromagnetic to ferromagnetic interactions in the CoO nanostructures at around 10 K. The results indicate that the phenomenon of magnetic phase transition as a function of temperature is unique to CoO nanoparticles. This finding reveals the magnetic behavior of CoO nanostructures and presents opportunities for its possible application as an anisotropy source for magnetic recording.

Switching the locus of oxygen reduction and evolution reactions between spinel active phase and carbon carrier upon heteroatoms doping

Multi-walled carbon nanotubes (MWCNTs) doped with nitrogen and sulfur atoms and with deposited manganese–cobalt spinel catalysts were studied to reveal the role of active centers in the oxygen reduction and evolution reactions (ORR and OER) in alkaline media. Commercial MWCNTs were oxidized by boiling in concentrated nitric acid and then double-doped with N and S heteroatoms using thiourea precursor. Manganese-cobalt spinels supported on the MWCNTs were synthesized by a microwave-assisted solvothermal route. The catalysts were comprehensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and X-ray fluorescence spectroscopy. The deposited mixed spinel active phase consists of well-dispersed nanocrystals with sizes in the range of 5–8 nm. The electrocatalytic activities of the synthesized catalysts in ORR (the onset potential and the number of transferred electrons) and OER (the overpotential required to reach the 10 mA cm−2 current density) were examined in alkaline media by rotating ring-disc electrode (RRDE) and rotating disc electrode (RDE) techniques, respectively. It was found that N and S doped MWCNT catalysts exhibit high activity in ORR with Eonset = 0.890 ± 0.013 V, and a number of electrons exchanged n = 3.83 ± 0.03, which remained essentially the same, within experimental error, upon spinel deposition. The addition of the spinel phase does not improve the electrocatalytic properties. The advantage of the dispersed spinel active phase was observed in OER, the activity of these samples was comparable to that of the RuO2 benchmark catalyst. In the case of ORR, the observed reactivity was accounted for by the incorporation of nitrogen and sulfur to the MWCNTs, whereas for OER the locus of the active centers is moved towards the manganese-cobalt spinel nanocrystals dispersed on the carbon nanotubes matrix. Functionalization of the latter with N and S atoms is then catalytically redundant.

Investigation of Fe3O4/SBA-15 magnetic nanocomposite synthesized by microwave-assisted solvothermal route as multi-therapeutic agent

In the current study, a facile and in situ synthesis route for the preparation of mesoporous SiO2-Fe3O4 magnetic nanocomposite using iron (III) acetylacetonate via microwave-assisted solvothermal method is proposed. To characterize the samples, XRD, EDS, SEM, TEM, BET, and VSM were applied, and their potential applications as drug carriers, hyperthermia, and MRI contrast agents were investigated. The results confirmed that the magnetic nanocomposite could be used as a drug carrier, and its drug release rate is affected by the magnetic field. Also, the product applications as both hyperthermia and MRI contrast agent for T2 weighted images were approved.

Electrochemical Reduction of CO2 With Good Efficiency on a Nanostructured Cu-Al Catalyst.

Carbon monoxide (CO) and formic acid (HCOOH) are suggested to be the most convenient products from electrochemical reduction of CO2 according to techno-economic analysis. To date, tremendous advances have been achieved in the development of catalysts and processes, which make this research topic even more interesting to both academic and industrial sectors. In this work, we report nanostructured Cu-Al materials that are able to convert CO2 to CO and HCOOH with good efficiency. The catalysts are synthesized via a green microwave-assisted solvothermal route, and are composed of Cu2O crystals modified by Al. In KHCO3 electrolyte, these catalysts can selectively convert CO2 to HCOOH and syngas with H2/CO ratios between 1 and 2 approaching one unit faradaic efficiency in a wide potential range. Good current densities of 67 and 130 mA cm−2 are obtained at −1.0 V and −1.3 V vs. reversible hydrogen electrode (RHE), respectively. When switching the electrolyte to KOH, a significant selectivity up to 20% is observed for C2H4 formation, and the current densities achieve 146 and 222 mA cm−2 at −1.0 V and −1.3 V vs. RHE, respectively. Hence, the choice of electrolyte is critically important as that of catalyst in order to obtain targeted products at industrially relevant current densities.

Boosting exciton dissociation by regulating dielectric constant in covalent organic framework for photocatalysis

Polymer semiconductor photocatalysts usually suffer from the high exciton binding energy because of the low dielectric constant. Herein, two crystalline polymer photocatalyst prototypes, neutral covalent organic framework (COF) and ionic covalent organic framework ( i COF), were employed to investigate the exciton effect. After polarization by the ionic sites with high dipole moment, the i COF endows a greatly increased dielectric constant to reach the low exciton binding energy of 23 meV, below the thermal energy under room temperature ( k B T, 26 meV). Thus, enhanced generation, separation, and transport of photogenerated charge carriers over the i COF catalyst resulted in a hydrogen peroxide production rate of 10.01 mmol g -1 h -1 in the photocatalytic oxygen reduction coupling with water oxidation reaction, which is almost 7 times higher than the neutral COF under identical conditions. This work demonstrates a promising way to tune the dielectric properties of polymer photocatalysts in order to regulate the exciton effect and related photocatalytic behavior. • Highly crystalline i COF was obtained in a microwave-assisted solvothermal route • The highly polar ionic sites enhanced the dielectric constant of the COF matrix • Low exciton binding energy was reached to allow spontaneous exciton dissociation • Rapid H 2 O 2 production was observed under visible-light irradiation in pure water Photocatalytic production of high-energy chemicals such as H 2 O 2 plays an essential role in seeking sustainable energy. Organic polymeric semiconductors that can be prepared from the earth’s abundant elements are preferential photocatalysts with advantages such as tunability. Nonetheless, the inherent low dielectric properties of organic polymers result in high exciton binding energies that inhibit the spontaneous exciton dissociation and thus restrict photocatalytic activity. Herein, we demonstrated that polarizing the covalent organic framework by integration of ionic moieties, fabricating i COF, can greatly increase the dielectric constant and thus reduce the exciton binding energy down to k B T (26 meV). The spontaneous exciton dissociation was obtained, accelerating the separation and transport of photogenerated carriers and thus a high H 2 O 2 production rate. This work opens a new avenue to boost the efficiency of organic semiconductors for solar-fuel production. The high polarization of the ionic sites greatly increases the dielectric constant of the COF matrix and thus reduces the exciton binding energy, effectively accelerating the H 2 O 2 production rate under visible-light irradiation.

Enhancement of compatibility between covalent organic framework and polyamide membrane via an interfacial bridging method: Toward highly efficient water purification

A key challenge in polyamide (PA) based nanocomposite membranes is to achieve non-accumulation filler and defect-free features, based on proper compatibility and great dispersion between the particles in the matrix. To address this issue, herein, an interfacial bridging strategy was introduced to fabricate the nanocomposite membrane. A covalent organic framework (COF), TAPB-BPTA (TAPB = 1,3,5-tris(4-aminophenyl)benzene and BPTA = 1,4-benzenedicarboxaldehyde), containing alkynyl was synthesized by a microwave-assisted solvothermal route and preliminarily grafted with the cysteine (CYS) bridge via a click reaction. Furthermore, the short chain of amine moieties in TAPB-BPTA not only makes more amine groups and carboxy groups in the COF pore wall, thereby elevating its hydrophilicity and improving its dispersion in the polyethyleneimine coating solution, but also presumably brings further free motion for amine groups to react with acyl functions in trimesoyl chloride (TMC). The COF was copolymerized using TMC to finally obtain the crosslinked top skin layer without the defect formation between filler and polymer during the interfacial reaction. The pure water permeance of the optimized nanocomposite membrane is higher than that of the pristine PA membrane. Accordingly, the optimized membrane exhibited good permeability and competitive selectivity for dyes and antibiotics. Meanwhile, it had a highly rejection of 92% for methylene blue after multi-cycle separation test, showing excellent industrial wastewater treating capability.

Microwave-Assisted Solvothermal Route for One-Step Synthesis of Pure Phase Bismuth Ferrite Microflowers with Improved Magnetic and Dielectric Properties.

The prototypical plum-free, one-phase multiferric ferrite BiFeO3 (BFO) is solid, parallel, with a high ferroelectric Curie temperature and Neel temperature and antiferromagnetic and ferroelectric propagation. This work aims to synthesize pure-phase BFO in the quickest possible way. We followed the microwave-assisted solvothermal (MWAST) method to achieve pure-phase BFO in the shortest duration of 3 min. The experiment involves simple optimizations with KOH concentration and microwave power levels. The surface morphology along with magnetic properties of BFO synthesized via the MWAST method are altered with varying KOH concentrations and microwave (MW) power levels. Our X-ray diffraction findings reveal that the pure-phase BFO is formed at 800 W MW power, and the structural characterizations like transmission electron microscopy, field emission scanning electron microscopy with energy-dispersive X-ray analysis have displayed the formation of uniformly distributed spherical microflowers of pure-phase BFO exhibiting a single-crystalline nature. Besides, the magnetic measurements affirmed a reliable weak ferromagnetic behavior (magnetization ∼1.25 emu/g) in BFO synthesized at 800 W MW power. In addition, good dielectric behavior with low dielectric loss was accompanied by frequency-dependent dielectric studies indicating an excellent frequency response of the material, and also the room-temperature ferroelectric properties were studied using a ferroelectric analyzer. The polarization of pure-phase BFO increases with the applied electric field and exhibits unsaturated polarization–electric field loops due to leakage current. Moreover, the Fourier transform infrared spectrum of the synthesized material has indicated the pure-phase BFO, and the Raman data have elucidated the vibrational modes of BFO. Further, the analysis of X-ray photoelectron spectroscopy data has confirmed the presence of fewer Fe2+ ions and oxygen vacancies in the pure-phase BFO. Therefore, the collective characterizations and detailed analysis of BFO material have revealed the uniqueness of the MWAST method in producing the pure-phase BFO in 3 min with improved magnetic and dielectric properties, and hence the BFO synthesized via the MWAST method can be a potential candidate for multiferroic applications.

Novel Insights into Sb-Cu Catalysts for Electrochemical Reduction of CO2

Catalysts play a vital role in electrochemical reduction of CO2 to valuable products. Only based on effective catalysts, CO2 electrolysis process can be advanced toward industrial application. In this work, we present a Sb-Cu2O material synthesized via one-pot microwave-assisted solvothermal route. The Sb-Cu2O derived bimetallic catalyst achieves a highest CO selectivity of 96% and good CO partial current densities of 37.3 and 74.0 mA cm−2 at − 0.8 and − 1.2 V vs. reversible hydrogen electrode (RHE), respectively. The Sb-Cu catalyst also displays good stability at current densities ranging from 5.6 to 100 mA cm−2. Additionally, for the first time, a complete theoretical study reveals the critical roles of Sb in selective CO2 conversion to CO on this bimetallic material, including stabilizing stepped Cu surfaces selective for the reaction, lowering energy barriers for the formation of key intermediate and favouring CO desorption.

CuS, In2S3 and CuInS2 nanoparticles by microwave-assisted solvothermal route and their electrochemical studies

The synthesis of CuS, In2S3 and CuInS2 nanoparticles by microwave irradiation of single source precursors is reported. Monodispersed nanoparticles with spherical morphology, whose average particle size were 2.3 nm (CuS) and 15.2 (In2S3) were obtained for the binary sulphides, while the ternary nanoparticles (CuInS2) displayed spindle shape morphology with some degree of agglomeration. The CuS, In2S3 and CuInS2 exhibited hexagonal, orthorhombic and wurtzite crystalline phases respectively. The electrochemical properties of the nanoparticles were studied using electronic impedance spectroscopy (EIS), cyclic and square wave voltammetry (CV and SWV). Results from the cyclic voltametric measurement showed that the modified electrodes exhibited a reversible redox reaction and typical faradic pseudo capacitance behaviour in 5 mM [Fe(CN)]4–/[Fe(CN)]3– aqueous electrolyte. The evaluated anodic current density of each electrode on a glassy carbon electrode (GCE) was found to follow the order: CuS (2.24 A/m2) > GCE (1.17 A/m2) > CuInS2 (0.699 A/m2) > In2S3 (0.632 A/m2), while the electroactive surface areas were 0.034, 0.0832 and 0.057 0 cm2 for GCECuS, GCEIn2S3 and GCECuInS2 respectively. The electron lifetimes of GCEbare, GCECuS, GCEIn2S3 and GCECuInS2 were also estimated, which gave 0.398, 0.275, 0.730 and 0.433 ms respectively. The lower charge transfer resistance and longer electron lifetime observed for the CuS nanoparticles compared to In2S3 and CuInS2 nanoparticles indicated a more efficient controlled surface for electrochemical process. Therefore, the nanoparticles could be employed as photoanodes in photovoltaic application to undergo oxidation on the electroactive species. EIS analysis of GCEIn2S3 and GCECuInS2 showed that the indium containing materials possess good electrocatalytic activity.

Enhancement of the electrochemical performance of LiCoPO4 by Fe doping

LiCoPO4 is an attractive cathode material, but it undergoes poor electronic conductivity and electrochemical performance. This performance is enhanced by substituting iron antisite Cobalt to reduce the direct interaction between the cathode and the electrolyte. Thus, LiCoPO4 doped with Fe was synthesized by the microwave-assisted solvothermal route at 220 °C. According to X-ray diffraction analysis, a single orthorhombic Pn21a phase (a = 10.02 Å, b = 6.71 Å and c = 4.96 Å) was obtained, which transited to Pnma phase (a = 10.21 Å b = 5.92 Å and c = 4.76 Å) after annealing at 700 °C in air. The morphology and particle size of the sample changed after annealing, as shown by TEM. The electrochemical cycling of an annealed sample showed the initial discharge capacity of 125mAh g−1 compared to 12 mAh g−1 for the non-annealed sample, which can be regarded as a partial coating by FePO4 as obtained from X-ray absorption spectroscopy analysis.

Microwave-Assisted Solvothermal Synthesis of Covalent Organic Frameworks (COFs) with Stable Superhydrophobicity for Oil/Water Separation.

COFs were synthesized by a microwave-assisted solvothermal route, with the building blocks containing 1,3,5-tris(4-aminophenyl) benzene and 2,3,5,6-tetra-fluoroterephthalaldehyde (or 1,4-phthalaldehyde). The -F groups introduced into the benzene ring promoted hydrophobicity and stability of the COFs. The universality and long effectiveness of oil adsorption can be realized when applying COFs as adsorbent. The powder also exhibited excellent water-in-oil emulsions separation performance, with the separation efficiency no lower than 99.5%. In this work, the use of microwave solvothermal synthesis of superhydrophobic COFs is potential to replace the conventional synthesis process and more suitable for industrial scale-up production. Furthermore, the findings provide a new strategy for solving the problem of oil spill treatment and industrial water-in-oil emulsions separation by using the emerging 2D COFs.

Weak antilocalization in Sb2Te3 nano-crystalline topological insulator

Microwave-assisted solvothermal route has been followed to synthesize Sb2Te3 nanomaterial. The morphology and topography of the material have been studied in FESEM and AFM measurements respectively. The optical band gap of the material is found to be ~ 0.25 eV as measured in IR spectroscopy. Temperature dependent resistivity of the nanostructure shows thermal activation behavior in the high temperature region as well as it follows 3D Variable Range Hopping mechanism in the moderate temperature region. Electron-electron interaction and quantum interference dominated upturn in the resistivity is observed at T < 24 K. Low field magnetoconductivity (MC) shows disorder induced weak localization (WL) which makes over to weak antilocalization (WAL) at T ≥ 4 K. MC after post annealing of the sample shows WAL behavior at T < 4 K also. Quantum correction to the low field magnetoconductivity of the material follows Hikami-Larkin-Nagaoka (HLN) equation. The obtained parameters of the HLN equation indicate that the system follows the 2D conduction mechanism and presence of a single conduction channel at low temperature. High field MR exhibits linear and positive magnetoresistance (LPMR) which suggests the survival of robust topological surface state conduction in the nanostructured bulk Sb2Te3 topological insulator.

Morphology-controlled microwave-assisted solvothermal synthesis of high-performance LiCoPO4 as a high-voltage cathode material for Li-ion batteries

Abstract High-performance particles of the high-voltage cathode material LiCoPO 4 for Li-ion batteries are synthesized by a simple and rapid one-step microwave-assisted solvothermal route at moderate temperatures (250 °C). Using a variety of water/alcohol 1:1 (v:v) solvent mixtures, including ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (TTEG), polyethylene glycol 400 (PEG), and benzyl alcohol (BA), the focus of the study is set on optimizing the electrochemical performance of the material by controlling the particle size and morphology. Scanning electron microscopy studies reveal a strong influence of the co-solvent on the particle size and morphology, resulting in the formation of variations between square, rhombic and hexagonal platelets. According to selected area electron diffraction experiments, the smallest crystal dimension is in the [010] direction for all materials, which is along the lithium diffusion pathways of the olivine crystal structure. The anisotropic crystal orientations with enhanced Li-ion diffusion properties result in high initial discharge capacities and gravimetric energy densities (up to 141 mAh g −1 at 0.1 C and 677 Wh kg −1 for LiCoPO 4 obtained from TEG), excellent rate capabilities, and cycle life for 20 cycles.

Statistical optimization of Reactive Red 141 removal by heterogeneous photo–Fenton reaction using ZnFe2O4 oxide prepared by microwave irradiation

A statistical optimization of Reactive Red 141 (RR141) removal by heterogeneous photo–Fenton reaction using ZnFe2O4 particles was performed. ZnFe2O4 oxide was synthesized by microwave-assisted solvothermal route and characterized by X–ray diffraction, Fourier transform infrared spectroscopy, and N2 adsorption–desorption isotherms. This material was used as a catalyst for the removal of RR141 dye from aqueous solution. Statistical optimization for the RR141 removal was performed using a 24−1 fractional experimental design, followed by the response surface methodology. Effects of pH, reaction time, dye concentration, and H2O2 concentration were evaluated. ZnFe2O4 particles presented a mesoporous structure with surface area of 65 m2 g−1. It was found that the more adequate conditions for the RR141 dye removal were pH 2.0, reaction time of 60 min, dye concentration of 60 mg L−1, and H2O2 concentration of 10 mM. In these conditions, 90% of color removal was achieved. The results demonstrate that the ZnFe2O4 oxide is an efficient catalyst for the removal of RR141dye from aqueous solution through the heterogeneous photo–Fenton reaction.

Phase-controlled synthesis of Cu2ZnSnS4 powders via the microwave-assisted solvothermal route

Cu2ZnSnS4 was successfully prepared via the microwave-assisted solvothermal route at the reaction temperature as low as 180°C. In comparison with the conventional solution process for preparing Cu2ZnSnS4 powders, the reaction time was significantly reduced to 1h, and the preparation procedures were simplified with the incorporation of microwave irradiation technique. The mobility of ions and dipoles are suggested to have been accelerated via the microwave, thereby enhancing the reaction rates. Kesterite and wurtzite Cu2ZnSnS4 powders were formed via adjusting the volume fraction of ethylenediamine in the microwave-solvothermal process. The amount of ethylenediamine affected the morphology of the derived powders due to the selective passivation of ethylenediamine on Cu2ZnSnS4. The microscopic analysis revealed that the samples prepared with high ethylenediamine concentrations had large particle sizes. The enhanced grain size reduced the surface recombination and increased the photoluminescence intensity of Cu2ZnSnS4 particles. During the microwave-assisted solvothermal process, Cu2S was formed first and reacted with the constituent ions and hydrogen sulfide ions to form Cu2ZnSnS4 powders.

Innovative biofilm inhibition and anti-microbial behavior of molybdenum sulfide nanostructures generated by microwave-assisted solvothermal route

The incessant use of antibiotics against infectious diseases has translated into a vicious circle of developing new antibiotic drug and its resistant strains in short period of time due to inherent nature of micro-organisms to alter their genes. Many researchers have been trying to formulate inorganic nanoparticles-based antiseptics that may be linked to broad-spectrum activity and far lower propensity to induce microbial resistance than antibiotics. The way-out approaches in this direction are nanomaterials based (1) bactericidal and (2) bacteriostatic activities. We, herein, present hitherto unreported observations on microbial abatement using non-cytotoxic molybdenum disulfide nanostructures (MSNs) which are synthesized using microwave assisted solvothermal route. Inhibition of biofilm formation using MSNs is a unique feature of our study. Furthermore, this study evinces antimicrobial mechanism of MSNs by reactive oxygen species (ROS) dependent generation of superoxide anion radical via disruption of cellular functions.

About MX 3 and MX 2 (M n+ = Mg 2+, Al 3+, Ti 4+, Fe 3+; X p− = F −, O 2−, OH −) nanofluorides

Several nanosized fluoro-compounds have been prepared by microwave-assisted solvothermal routes: Al 3+-, Fe 3+- and Ti 4+-based oxyfluorides with the hexagonal tungsten bronze (HTB) framework, Ti 4+-based fluorinated anatase, and rutile MgF 2. The structural features have been determined using XRD and TEM analyses. The presence of OH − groups substituted for F − ions has been demonstrated for all of these nanofluorides. In Al- and Mg-based nanofluorides, the OH rate can be reduced by F 2-direct fluorination. Furthermore, the higher the polarizing power of the cation, the higher the oxygen content. For cation with high formal charge, such as Ti 4+ stabilized in a distorted octahedral site, the occurrence of O 2−/OH −/F − anions in its vicinity as well as vacancies have to be mentioned. Finally coupling the microwave-assisted solvothermal route with the F 2-direct fluorination allow preparing high surface area metal fluorides where the amount of oxygen is noticeable and contribute to create under-coordinated cationic species at the surface which can induce high Lewis acidity.

Generation and photocatalytic activities of Bi@Bi2O3 microspheres

Composite Bi@Bi2O3 microspheres have been synthesized via a microwave-assisted solvothermal route. The Bi@Bi2O3 microspheres had a narrow size distribution in the range 1.2–2.8 mm. Glucose was selected as the reductant, BiCl3 as the bismuth source, and ethylene glycol (EG) as the solvent in the synthesis system. The as-synthesized sample was characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle diameter distribution, energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV-vis) spectroscopy, and photoluminescence (PL) spectroscopy. The photocatalytic activities of the Bi@Bi2O3 microspheres were evaluated by the photodegradation of rhodamine B (RhB) and methyl orange (MO) dyes under UV light irradiation. The degradation reached ∼96.6% for RhB and 100% for MO after 4 h reaction in the presence of the as-synthesized Bi@Bi2O3 microspheres.

BiOBr hierarchical microspheres: Microwave-assisted solvothermal synthesis, strong adsorption and excellent photocatalytic properties

Two kinds of BiOBr nanosheets-assembled microspheres were successfully prepared via a facile, rapid and reliable microwave-assisted solvothermal route, employing Bi(NO 3) 3·5H 2O and cetyltrimethylammonium bromide (CTAB) as starting reagents in the absence or presence of oleic acid. The phase and morphology of the products were characterized by powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). Experiments indicated that the formation of these building blocks of microspheres could be ascribed to the self-assembly of nanoparticles according to mesocrystal growth mode. Interestingly, both samples exhibited not only strong adsorption abilities, but also excellent photocatalytic activities for methyl orange (MO), rhodamine B (RhB) and phenol. The resulting BiOBr hierarchical microspheres are very promising adsorbents and photocatalysts for the treatment of organic pollutants.

Preparation and Characterization of Microwave Solvothermally Derived SnO2:Sm3+ Phosphors

Spherical SnO2:Sm3+ phosphors were successfully synthesized via a microwave-assisted solvothermal route. The developed microwave solvothermal process greatly reduced the required reaction time, and controlled the particle size and morphology of SnO2:Sm3+ phosphors. SnO2:Sm3+ phosphors can be excited at 318 nm, and emit a red light at 623 nm. When the microwave power was increased, the urea hydrolysis rate was accelerated, and the number of nuclei increases, thereby causing the particle size to reduce. The luminescence properties of prepared phosphors can be tailored via adjusting the irradiation power in the microwave solvothermal process.