Convenient synthesis of ethylene carbonates from carbon dioxide and 1,2-diols at atmospheric pressure of carbon dioxide

An efficient and convenient synthesis of ethylene carbonates was achieved by the reaction of carbon dioxide with 1,2-diols in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), followed by treatment with 1-bromobutane. This DBU-promoted transformation proceeded at an atmospheric pressure of carbon dioxide at 25 °C and gave ethylene carbonates in good yields.     

Crystalline evolution of various CeO2 morphology via a solvothermal method

Preparation of cerium compounds with different structures and morphology is still a challenge in powder synthesis. CeOHCO₃ and CeO₂ have received widespread attention because of their potential applications. In this study, a solvothermal method with one-step precipitation was used to synthesize CeO₂ with different structures and morphology without use of surfactant. The effects of different experimental conditions on the morphology of CeO₂ were investigated. Both X-ray diffraction and SAED patterns revealed that products changed from a single CeOHCO₃ phase to a mixture of CeOHCO₃ and CeO₂. A single CeO₂ phase could always be obtained from CeOHCO₃ by calcination in air at 673 K for 1 h. Moreover, the morphology of CeOHCO₃ was retained. Thus CeO₂ particles with different morphology, for example rod-like, prism-like, polygon-like, sphere-like, and cube-like, could be synthesized. Possible mechanisms of phase and morphology evolution are discussed.     

Synthesis of double mesoporous core-shell silica spheres with tunable core porosity and their drug release and cancer cell apoptosis properties

In this work, we demonstrate a simple two-pot approach to double mesoporous core–shell silica spheres (DMCSSs) with uniform size of 245–790 nm, shell thickness of 41–80 nm and surface area and total pore volume of 141–618 m² g^?1 and 0.14–0.585 cc g^?1, respectively. First, solid silica spherical particles were synthesized by the Stöber method and used as a core. Second, a mesoporous shell could be formed around the silica cores by using an anionic surfactant and a co-structure directing agent. It was found that mesopores can be anchored within dense silica cores during mesoporous silica shell formation, synchronously the base group with surfactant assistant can etch the dense silica cores to re-organize new mesostructure, so that double mesoporous core–shell silica sphere (DMCSS) structure can be obtained by a single surfactant-templating step. The spherical size and porosity of the silica cores of DMCSS together with shell thickness can be tuned by controlling Stöber parameters, including the concentrations of ammonia, solvent and tetraethoxysilane and the reaction time. DMCSS were loaded with ketoprofen and thymoquinone, which are an anti-inflammatory and a potential novel anti-cancer drug, respectively. Both drugs showed controlled release behavior from the pores of DMCSS. Drug uptakes within DMCSS were ～27 and 81 wt.% for ketoprofen and thymoquinone, respectively. Furthermore, DMCSS loaded with thymoquinone was more effective in inducing cancer cell apoptosis than uncontained thymoquinone, because of the slow release of the drug from the mesoporous structure.     

Palladium-catalyzed intramolecular hydroarylation of 4-benzofuranyl alkynoates. Approach to angelicin derivatives

Intramolecular hydroarylation of 4-benzofuranyl alkynoates using Pd(OAc)(2) as catalyst took place selectively and efficiently, giving angular furocoumarin derivatives in high yields. The parent angelicin was obtained in 80% yield by this method. The starting 4-benzofuranyl alkynoates were easily accessible from readily available 4-hydroxybenzofurans and alkynoic acids.     

Low temperature sintering and color of a new compound Sn1.24Ti1.94O3.66(OH)1.50F1.42

Nanopowder of a new tin(II) titanium(IV) oxide hydroxide fluoride, Sn_1.24Ti_1.94O_3.66(OH)_1.50F_1.42 with the pyrochlore-type structure (cubic a = 10.3777(7) Å, space group Fd-3m) was prepared by using a microwave-assisted solvothermal reaction. The grain size of the nanopowder was 20–30 nm in diameter. Sn_1.24Ti_1.94O_3.66(OH)_1.50F_1.42 decomposed above 300 °C, but could be sintered to relative density greater than 99% by a hydrothermal hot-pressing (HHP) method at 270 °C and 80 MPa for 4 h. The synthesized powder and solidified body obtained using HHP showed significantly different color, probably due to the difference in water content.     

Preparation and characterization of titania/tetratitanate nanocomposites

Nanocomposite titania/tetratitanate particles were prepared by utilizing the electrostatic interaction of the colloidal tetratitanate nanosheets and TiO₂ powders through dispersing TiO₂ into tetratitanate solution at pH4. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, chemical analysis, and photocatalytic activity measurement. The crystallites of Ti₄O₉^2? in the form of tetratitanate nanosheets have lateral size around 100 nm. The visible light responsive photocatalytic activity of rutile nanoparticles could be improved by forming nanocomposite with layered tetratitanate. The high specific surface area of this kind of composite and a certain amount of mesopores in nanocomposite powder could be responsible for better performance in the NO elimination.     

Synthesis of ZnO crystals with unique morphologies by a low-temperature solvothermal process and their photocatalytic deNO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> properties

A series of unique morphologies of ZnO were synthesized by a simple mild solvothermal process using equimolar of Zn(NO₃)₂/Zn(AC)₂–hexamethylenetetramine (HMT) acting as precursors and ethylene glycol (EG) and triethylamine (TEA) as the dispersant and surfactant additive, respectively. When the as-prepared particles were further treated in 0.02 M HMT solution for such a long time as 72 h, screw-like and rose-like crystals with three-dimensional and developed structure could be formed. The deNO _x photocatalytic activity was characterized and the analysis results showed that the modified ZnO crystals possessed a three-dimensionally developed structure and had higher deNO _x photocatalytic activity compared to that of the as-prepared untreated ZnO.     

Effect of carboxyl group on the visible-light photocatalytic activity of SrTiO3 nanoparticles

SrTiO₃ nanoparticles modified with a carboxyl group were successfully prepared by microwave-assisted solvothermal reaction of SrCl₂·6H₂O and Ti(OC₃H₇)₄ in methanol–organic acid solution. The as-prepared products were characterized using X-ray diffraction (XRD), diffuse reflectance spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy. The photocatalytic activity was determined by DeNO _x ability using a mercury arc with filters to control irradiation wavelengths to >290, >400, and >510 nm. Nanoparticles of perovskite-type SrTiO₃ were successfully synthesized above pH 12. The photocatalytic activity of SrTiO₃ under visible-light (>510 nm) irradiation could be promoted by surface modification of SrTiO₃ with the carboxyl group (–COO), especially from oleic acid.     

High performance visible light responsive photocatalysts for environmental cleanup via solution processing

Fabrication of nitrogen-doped titania and/or strontium titanate nanoparticles via soft chemical reactions and their performance for environmental cleanup under visible light irradiation were introduced. Nitrogen-doped anatase, brookite and rutile with high specific surface area can be selectively prepared by the solvothermal reactions in mixed aqueous solution of titanium trichloride-hexamethylenetetramine. Nitrogen-doped strontium titanate can be prepared by mechanochemical reaction of strontium carbonate, titania and hexamethylenetetramine using a planetary ball-mill. Nitrogen-doped titania shows excellent photocatalytic activity for the nitrogen monoxide destruction under visible light irradiation. The photocatalytic activity of nitrogen-doped titania is in the order anatase > brookite > rutile. The photocatalytic activity of nitrogen-doped titania and strontium titanate can be improved by co-doping with higher valence metal ions to reduce oxygen vacancy and/or coupling with Fe₂O₃ and Pt to retard quick recombination of photo-induced electron and hole by the heterogeneous electron transfer.