Aggregation and thermoresponsive properties of new star block copolymers with a cholic acid core

Poly(allyl glycidyl ether) (PAGE) and poly(ethylene glycol) (PEG) blocks were sequentially grown via anionic polymerization to form four block copolymer arms on a cholic acid (CA) core, yielding star block copolymers (CA(AGE(8)-b-EG(n))(4)) with low polydispersities (ca. 1.05). The introduction of PAGE segments into CA(PEG)(4) significantly reduced their crystallinity. The polymers can aggregate in water at room temperature above their critical aggregation concentration. The copolymers are thermoresponsive; their behavior in aqueous solutions was studied by the use of UV-visible spectroscopy, dynamic light scattering, and transmission electron microscopy. Their cloud points vary from 13 to 55 °C with increasing length of the PEG segments. Double thermoresponsive behavior was observed with short PEG segments because of a two-step transition process: small micelles are formed upon heating and then further aggregate into micellar clusters through the association of PEG chains.     

Preparation and Characterization of Activated Carbon from Sesame Seed Shells by Microwave and Conventional Heating with Zinc Chloride Activation

The preparation of activated carbon from sesame shells as raw precursor was investigated in the study by sequentially applying microwave and conventional heating methods assisted by zinc chloride activation. The optimizisation of experimental parameters including microwave power, microwave treatment time, conventional activation time, conventional activation temperature and zinc chloride concentration ratio for the microwave and conventional heating method was performed. The characterization of the prepared activated carbon was done by thermogravimetric and differential thermal measurements, infrared spectroscopy, scanning electron microscopy and specific surface area analyses. The maximum surface area of 1254?m²/g for the prepared activated carbon was obtained at a microwave power of 750?W, a microwave treatment time of 20?min, an activation time of 45?min, an activation temperature of 500°C and zinc chloride concentration ratio of 1:1. Methylene blue and iodine adsorption capacities for the prepared activated carbon were 103 and 1199?mg/g, respectively.     

Production of ultrahigh temperature composite materials HfB2-SiC and the study of their behavior under the action of a dissociated air flow

Ultrahigh temperature composite materials HfB₂-SiC containing 25, 35, and 45 vol % SiC were produced by spark plasma sintering. Modeling of heating under the action of a dissociated air flow for selected samples using a VGU-4 induction plasma generator showed that these materials do not degrade even while keeping at a surface temperature of more than 2000°C (up to 2600°C) for 11 min. A combination of optical microscopy, scanning electron microscopy (with EDX analysis), and X-ray computed microtomography were used for investigating the microstructure and composition of the oxidized layer before and after heating.     

Silicon dioxide hollow microspheres with porous composite structure: synthesis and characterization

In this paper, a strategy for hollow porous silica microspheres with ideally flower structure is presented. SiO(2)/PAM hybrid composite microspheres with porous were synthesized by the reaction that the porous polyacrylamide (PAM) micro-gels immersed in tetraethoxysilane (TEOS) anhydrous alcohol solution and water in a moist atmosphere, with ammonium hydroxide as a catalyst. The SiO(2) hollow microspheres with porous were obtained after calcination of the composite microspheres at 550 °C for 4 h. The morphology, composition, and crystalline structure of the microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FI-IR), and X-ray diffraction (XRD), N(2) absorption analysis, respectively. The results indicated that the obtained hollow porous SiO(2) microspheres were a perfect flower structure.     

Selective synthesis of zigzag-type aligned carbon nanotubes on SiC (0 0 0 −1) wafers

Zigzag-type carbon nanotubes have been selectively produced by surface decomposition of a well-polished SiC single crystal. The SiC wafer was heated to 1500 °C at a very small heating rate under vacuum. Transmission electron microscopy (TEM) and electron diffraction patterns revealed that almost all the well-aligned carbon nanotubes formed perpendicular to the SiC (0 0 0 −1) surface were double-walled and of zigzag type. The results of high-resolution electron microscopy (HREM) indicate that the zigzag type structure evolves from the Si–C hexagonal networks in the SiC crystal by the collapse of carbon layers remaining after the process of decomposition.     

Effects of vacuum pyrolysis conditions on the characteristics of activated carbons derived from pistachio-nut shells

Preparation of effective adsorbents from pistachio-nut shells was carried out. Optimization of the vacuum pyrolysis parameters prior to activation was carried out to study the effects of vacuum pyrolysis temperature, hold time, and heating rate on the properties of chars and activated carbons, while CO2 activation conditions were fixed at a temperature of 900 degrees C, an activation time of 30 min, a heating rate of 10 degrees C/min, a CO2 flow rate of 100 cm3/min, and a nitrogen flow rate of 150 cm3/min. The optimum vacuum pyrolysis conditions for preparing activated carbons with high surface area and pore volume were identified. The microstructure and microcrystallinity of the activated carbons prepared were examined by scanning electron microscopy and powder X-ray diffraction techniques respectively while the Fourier transform infrared spectra determined any changes in the surface functional groups produced during different preparation stages. Experimental results show that it is feasible to prepare activated carbons with high BET surface area from pistachio-nut shells.     

Deep eutectic solvents skeleton typed molecularly imprinted chitosan microsphere coated magnetic graphene oxide for solid‐phase microextraction of chlorophenols from environmental water

Novel molecularly imprinted chitosan microspheres were prepared on the surface of magnetic graphene oxide, with deep eutectic solvents both as a functional monomer and template. The prepared molecularly imprinted chitosan microspheres‐magnetic graphene oxide was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area, thermogravimetric analysis were subsequently combined with solid‐phase micro‐extraction for simultaneous separation and enrichment of the extraction of chlorophenols from environmental water. Factors affecting the extraction efficiency of chlorophenols were optimized using response surface methodology. The actual extraction capacities under the optimal conditions (liquid to solid ratio = 3, cycles of adsorption/desorption = 5, 40°C extraction temperature, and extraction time for 35 min) were 86.90 mg/g. Compared to the traditional materials, the molecularly imprinted chitosan microspheres‐magnetic graphene oxide produced higher selectivity and extraction capacity.     

Thermal effectiveness of different IR radiators employed in rheumatoid hand therapy as assessed by thermovisual examination

We conducted a thermovisual comparison of mean hand surface temperature changes upon local heating with two different IR sources. Sixty-six patients with rheumatoid arthritis (47 women and 19 men; average age, 56.1 ± 8.6 years) were subjected to topical heat therapy for one hand with either the standard IR radiator (SIR) or the water filter IRA (wIRA). The surface temperature of the dorsal side of both hands was measured, and thermal images were taken before and up to 2 h after treatment. At 1 min after treatment, SIR application increased the surface skin temperature of the heated hand from 31.5 ± 1.9 to 35.0 ± 1.9 °C (P<0.05), while wIRA increased it from 32.1 ± 1.6 to 34.2 ± 1.1 °C (P<0.05). Constant decline in temperature was observed immediately after treatment, with the temperatures reaching baseline in about 30 and 120 min after wIRA and SIR treatment, respectively. Similar temperature changes were observed in the heated hands for wIRA and SIR, except at 1 min after treatment. Changes in the untreated hands indicated contralateral reaction. The temperature of the warmed hand showed a correlation to the body mass index.     

Carbonization of electrospun poly(acrylonitrile) nanofibers containing multiwalled carbon nanotubes observed by transmission electron microscope with in situ heating

Composite nanofibers with 5% w/w multiwalled carbon nanotubes (MWCNTs) in polyacrylonitrile (PAN) were fabricated using the electrospinning technique. Morphological development during the carbonization process was characterized by transmission electron microscopy (TEM) with in situ heating. It was found that the orientation of graphitic layers increases with temperature and does not change significantly with time during our TEM measurement, except the 750 °C. In the heating stage at 750 °C noticeable enhancement of orientation with time was observed. The presence of embedded CNTs enhances the order of the formed graphitic structures even when the CNTs are irregular or entangled. The results indicate that embedded MWCNTs in the PAN nanofibers nucleate the growth of carbon crystals during PAN carbonization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Thermal stability of functionalized carbon nanotubes studied by in-situ transmission electron microscopy

The thermal stability of funtionalized carbon nanotubes (CNTs) has been studied experimentally by direct in-situ observations using a heating stage in a transmission electron microscope, from room temperature (RT) to about 1000 °C. It was found that the thermal stability of the functionalized CNTs was significantly reduced during the in-situ heating process. Their average diameter dramatically expanded from RT to about 500 °C, and then tended to be stable until about 1000 °C. The X-ray energy dispersive spectroscopy analysis suggested that the diameter expansion was associated with coalescence of the carbon structure instead of deposition with additional foreign elements during the heating process.     

PSt种子与“花瓣”形PSt/PAN复合颗粒的制备

以过硫酸钾为引发剂,在乙醇/水的混合介质中使苯乙烯进行无皂乳液聚合,得到了单分散亚微米级聚苯乙烯(PSt)微球.用扫描电子显微镜研究了引发剂浓度、单体浓度、反应温度和溶剂组成对PSt微球粒径的影响.结果表明,改变上述条件能明显影响其粒径.以所得单分散聚苯乙烯微球为种子,在丙烯酸单封端聚乙二醇大分子单体存在的条件下,使丙烯腈和少量苯乙烯进行新的无皂种子乳液聚合,在合适的条件下制得到了“花瓣”形的聚合物复合颗粒,为深入探讨这类特殊形态聚合物颗粒的形成机理提供了新的佐证.     

BiOBr microspheres for photocatalytic degradation of an anionic dye

BiOBr microspheres were obtained using a solvothermal synthesis route in the presence of ethylene glycol and KBr at 145 °C, for 18 h. BiOBr microspheres were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), nitrogen adsorption-desorption isotherms analysis, diffuse reflectance spectroscopy (DRS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Additionally, the theoretical and experimental isoelectric points (IEP) of BiOBr nanostructured microspheres were determined, and pH's influence on the degradation of an anionic dye (methyl orange) under simulated solar radiation was analyzed. Results show that 97% of methyl orange is removed at pH 2 after 60 min of photocatalytic reaction. Finally, DRIFTS studies permit the proposal of a surface reaction mechanism of the photocatalytic oxidation of MO using BiOBr microspheres.     

Biodegradable heparin-loaded microspheres: carrier molecular composition and microsphere structure

Microspheres of amphiphilic triblock polymers PLLA-PEG-PLLA were investigated as carriers for heparin delivery. Two series of PLLA-PEG-PLLA triblock were synthesized and prepared into microspheres with heparin loaded. The microspheres were hollow and the surface morphology varied from smooth to porous. The pore size increased with increasing PEG content. The microsphere size distribution showed that higher PEG content increased the average microsphere size. The release rate of heparin was closely related to the surface morphology of the microspheres. DSC spectra showed that both cold crystalline temperature (Tc) and crystalline melting temperature (Tm) of heparin-loaded microspheres were related to the copolymer composition and the Tc was lower than those of corresponding pure microspheres. [IMAGES: SEE TEXT]     

低温熔盐法制备球状多孔 La1-xSrxMn0.8Fe0.2O3（0≤x≤0.6）及其催化 CO氧化性能

汽车尾气中 CO, HC, NOx,硫化物及其颗粒粉尘严重危害人们身体健康和大气环境,是大气环境的主要污染源之一.目前,尾气净化是其减排的最主要方式.汽车尾气催化剂的发展经历了几代的研究,一直以来广泛采用 Pt, Pd和 Rh等贵金属,但因其资源匮乏,价格昂贵,容易被 S和 P中毒,因此人们逐渐将目光投向非贵金属催化剂的研发.钙钛矿复合氧化物因具有独特的物理化学性质以及灵活的“化学剪裁”特性而在材料研究等领域颇受青睐,有望成为贵金属催化剂的替代品.一般而言,催化剂的比表面积越大,表面活性位点越多,其催化活性越高,且会明显降低起燃温度.目前,一些制备工艺,如水热法、共沉淀法、微乳液法和硬模板法,虽可在一定程度上提高催化剂的比表面积,但却存在费时、耗能及制备工艺复杂等缺点.因此,如何简单有效地制备出大比表面积的钙钛矿型催化剂依然是一个难题.本文以合成的分级多孔δ-MnO2微球为模板,采用熔盐法制备出球状多孔 La1-xSrxMn0.8Fe0.2O3(0≤x≤0.6)钙钛矿氧化物,研究了球状多孔钙钛矿氧化物的形成过程和合适的制备温度,以及 B位 Fe3+掺杂量为20%时 A位 Sr2+掺杂量对钙钛矿催化剂结构和催化活性的影响.采用 X射线粉末衍射、扫描电子显微镜、透射电子显微镜、N2吸附-脱附、傅里叶红外光谱(FT-IR)和 X射线能谱(XPS)等方法对催化剂进行了表征.在固定床石英管反应器上评价了催化剂催化 CO氧化活性及稳定性,采用气相色谱联接氢火焰离子化检测器检测了产物和反应物的组成.结果表明,以分级多孔δ-MnO2微球为模板,采用熔盐法在450oC反应4 h制备出的球状多孔 La1-xSrxMn0.8Fe0.2O3(0≤x≤0.6)钙钛矿氧化物具有良好的结晶性、较大的比表面积(55.73 m2/g)和孔体积(0.37 cm3/g).其球状多孔结构的形成可分为两个阶段：原位形成钙钛矿相和纳片表面析出钙钛矿晶粒及钙钛矿晶粒的再生长.另外, FT-IR光谱表明, Fe3+和 Sr2+成功进入 A, B位.同时, CO转化曲线表明, B位 Fe3+的掺杂量为20%时, A位 Sr2+的掺杂量高于30%时可以明显改善催化剂催化 CO氧化活性： La1-xSrxMn0.8Fe0.2O3(0≤x≤0.3)的T50和T90分别在180和198oC左右;而 La0.55Sr0.45Mn0.8Fe0.2O3和 La0.4Sr0.6Mn0.8Fe0.2O3的T50均低于125oC; La0.55Sr0.45Mn0.8Fe0.2O3的T90为181oC,而 La0.4Sr0.6Mn0.8Fe0.2O3却仍低于125oC. XPS结果则证明,较高的催化活性得益于 La0.4Sr0.6Mn0.8Fe0.2O3表面存在较多的 Mn4+、氧空位及吸附氧.最后, La0.55Sr0.45Mn0.8Fe0.2O3和 La0.4Sr0.6Mn0.8Fe0.2O3的稳定性测试结果表明,采用熔盐法以δ-MnO2为模板在450oC焙烧4 h制备的多孔球状钙钛矿具有较好的催化稳定性.虽然催化剂制备工艺简单,周期短,但比表面积最大只有55.73 m2/g,为硬模板法的1/2,因此提高比表面积将是今后研究的方向.     

Synthesis of indium nanoparticles: digestive ripening under mild conditions

Here we report the synthesis of monodispersed indium nanoparticles by evaporation/condensation of indium shot using the solvated metal atom dispersion (SMAD) technique, followed by digestive ripening in low boiling point (BP 38 °C) methylene chloride and in a high boiling point (BP 110 °C) toluene solvent. The as-prepared SMAD indium nanoparticles are polydispersed with particle size ranging from 25 to 50 nm, but upon digestive ripening (heating of colloidal material at the boiling point of solvent in presence of excess surface active ligands) in methylene chloride, a remarkable reduction of particle size was achieved. In higher boiling solvent (toluene), where the indium nanoparticles at reflux temperature are probably melted, it does not allow the best result, and less monodispersity is achieved. We employed different surface active ligands (amine, phosphine, and mixed ligands) to passivate these indium nanoparticles. The temporal evolution of the surface plasmon of indium nanoparticles was monitored by in situ UV-vis spectroscopy, and particles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The merits of this synthesis procedure are the use of bulk indium as starting material, tuning the particle size in low boiling point solvent, particle size adjustment with the choice of ligand, and a possible scale up.     

Biodegradable microspheres containing poly(epsilon-caprolactone)-Pluronic block copolymers for temperature-responsive release of proteins

Temperature-responsive microspheres were fabricated for the purpose of releasing protein in responsive to surrounding temperature changes. Temperature-responsive polymer, Pluronic was synthesized into block copolymers of poly(epsilon-caprolactone)-Pluronic with two different chain lengths of poly(epsilon-caprolactone). Microspheres loaded with proteins were prepared by a W/O/W emulsion method. The surface morphology was examined by scanning electron microscopy, showing that microspheres with diblock copolymers had porous structures due to hydrophilicity of Pluronic blocks. After incubating the microsphere at 37 degrees C for 7 days, temperature-responsive protein release was monitored with alternating temperature changes between 20 and 37 degrees C. The protein release was attenuated when the microsphere was incubated at 20 degrees C but the release rate was recovered at 37 degrees C, confirming variable release rate according to the temperature changes. The variable release rate of protein was dependent on the length of poly(epsilon-caprolactone) blocks attached to Pluronic.     

Highly porous silica-polyaniline nanocomposite as a novel solid-phase microextraction fiber coating

A highly porous fiber-coated SBA-15/polyaniline material was prepared for solid-phase microextraction (SPME). The SBA-15/polyaniline nanocomposite was synthesized via chemical polymerization. The prepared SBA-15/polyaniline particles were analyzed by scanning electron microscopy analysis. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography-mass spectrometry (GC-MS). In optimum conditions (extraction temperature 60°C, extraction time 40 min, ionic strength 20%, stirring rate: 500 rpm, desorption temperature 260°C, desorption time 2 min), the repeatability for one fiber (n=3), expressed as relative standard deviation (RSD%), was between 5.3 and 8.6% for the test compounds. For deionized water, spiked with selected PAHs, the detection limits for the studied compounds were between 2 and 20 pg/mL.     

Impact of the state of water on the dispersion stability of a skin cream formulation elucidated by magnetic resonance techniques

This study investigated the relationship between the state of water and the dispersion stability of a skin cream formulation. Hydrophilic ointments treated with a high-pressure wet-type jet mill were used as model formulations. Spin-lattice relaxation times (T(1)) were measured by magnetic resonance techniques to estimate the state of water in samples. A shorter T(1) relaxation time was obtained from samples with higher surfactant content, whereas the processing pressure of the jet mill and 1-week storage at 40 °C did not influence the T(1) relaxation time. Observations using scanning electron microscopy (SEM) showed that coalescence occurred in samples with lower surfactant contents (1.0% by weight) following 1-week storage at 40 °C. We also investigated samples prepared using a hydrophilic surfactant with a short polyethylene glycol (PEG) chain and with PEG-4000. From the change in T(1) relaxation times after removing the oil phase from samples by centrifugation, it was clarified that most of the surfactant was located on the surface of oil droplets. Furthermore, SEM observations showed that phase separation was facilitated as the PEG chain length of the surfactant shortened. Thus, a thin water layer over oil droplets is the most important factor for stabilizing their dispersion. This study provides proof-of-principle results on the contribution of the state of water to the dispersion stability of a skin cream formulation.     

In situ synthesis of platelet graphite nanofibers from thermal decomposition of poly(ethylene glycol)

Platelet graphite nanofibers (PGNFs) were synthesized by in situ thermal decomposition from a mixture containing poly(ethylene glycol) (PEG) serving as the carbon source and nickel chloride (NiCl(2)) serving as the catalytic precursor. The mixture was conducted by thermal treatment under a nitrogen atmosphere at 750 degrees C and results found PGNFs with high purity and a uniform diameter distribution formed without hydrocarbon gases in the process. Observations using field-emission scanning electron microscopy and high-resolution transmission electron microscopy revealed PGNFs with a high degree of graphitization, well-ordered graphene layers, and uniform diameters of 10-20 nm. Thermogravimetry-differential scanning calorimetry-mass spectrometry was employed to study the thermal decomposition phenomena of the mixture (PEG/NiCl(2)) before the thermal process. The analysis clarified the in situ synthesis growth mechanism of PGNFs from the mixture.     

Preparation of monodispersed microporous SiO2 microspheres with high specific surface area using dodecylamine as a hydrolysis catalyst

A novel and simple method for the synthesis of monodispersed microporous SiO₂ microspheres with high specific surface area was developed by hydrolysis of tetraethoxysilane (TEOS) in a water-ethanol mixed solution and using dodecylamine (DDA) as hydrolysis catalyst and template. The as-prepared products were characterized with differential thermal analysis-thermogravimetry, scanning electron microscopy, high-resolution transmission electron microscopy, small angle X-ray diffraction and nitrogen adsorption. The effects of experimental conditions including hydrolysis temperatures, calcination temperature and concentrations of TEOS and DDA on the morphology and pore parameters of the as-prepared SiO₂ microspheres were investigated and discussed. The results showed that hydrolysis temperature and concentrations of TEOS and DDA are important parameters for the control of size and morphology of particles. The specific surface area and specific pore volume of the as-prepared SiO₂ microspheres increased with increasing DDA concentration and calcination temperature. DDA may act not only as a good hydrolysis catalyst but also as a template for the formation of monodispersed SiO₂ microspheres with high specific surface area. This research may provide new insight into the synthesis of monodispersed microporous SiO₂ microspheres.