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1.
A novel carbon nanotube (CNT)-coated solid-phase microextraction fiber was prepared based on sol–gel technique. Commonly used fragile fused silica fiber was replaced with stainless steel wire, which made the fiber unbreakable. An approach was also proposed for batch producing, and good reproducibilities for fiber to fiber and between fibers were achieved. Experiments showed that the sol–gel-CNT fiber exhibited high thermal stability to resist 350 °C and excellent solvent durability in methanol and acetonitrile. Compared to commercial polydimethylsiloxane (PDMS) fiber, the sol–gel-CNT fiber represented significantly improved extraction efficiencies for both polar (phenols) and non-polar (benzene, toluene, ethylbenzene, and o-xylene) compounds. Meanwhile, no replacement effect, low carry-over and wide linear range demonstrated that the newly prepared sol–gel-CNT coating has liquid properties, which allow a relatively easy quantification procedure. Moreover, the characterization of the sol–gel-CNT coating was also evaluated with McReynold probe solutes. The results showed that the coating has better affinity for all the five types of solutes compared to commercial 7 μm PDMS fiber, which suggested that the coating has the potential to be developed as GC stationary phase.  相似文献   

2.
Uptodate,rapidpurificationofmixedproteininlargescalehasbeenanimportantresearchprojectinbioengineeringproductprocessing.Immobilizedmetalionaffinitychromatography(IMAC)isanefficientmethodextensivelyusedforaffinitypurificationofbiologicallyactivesubstance…  相似文献   

3.
A silica gel composite (denoted as 1–SG) doped with a proton-conductive metal–Schiff-base–POM-MOF, {[Cu3(L)2(H2O)4][Cu(DMF)4(SiW12O40)]·9H2O} n (1) (where L is N, N′-bis[1-(2-methoxyphenol-6-yl)-methylidene] hydrazine hydrate, DMF is dimethyl formamide, POM-MOF is polyoxometalates-based metal–organic framework), was prepared by sol–gel method. The structure of as-synthesized 1–SG was confirmed by infrared spectrometry and X-ray powder diffraction, and its proton conductivity was calculated based on electrochemical impedance spectroscopic measurement. It was found that the structural characteristics of complex 1 are retained successfully in the silica gel skeleton of as-prepared 1–SG. Besides, though 1–SG contains just 6.25 wt% complex 1, it exhibits good proton conductivities of as much as 1.51 × 10?3–1.26 × 10?2 S cm?1 in the temperature range of 25–100 °C under a relative humidity of 98 %; and in particular, it shows better proton conductivity than both complex 1 and silica gel at the same conditions, due to the presence of a large number of micropores and mesopores filled with “liquid”.  相似文献   

4.
In this paper, the crystallization behavior, thermal degradation properties, rheological behavior and the spinnability of poly(β-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fiber were studied. Experimental results indicated that the spherulite growth rate of PHBV was very slow and its size was very large. PHBV began to degrade above 170°C. The flowing curve indicated that the processing temperature and the residential time had important effects on PHBV melts. When the equipment of melting spinning was improved and processing conditions were strictly controlled, the mechanical properties of the PHBV filament can comply with the requirements of the American Pharmacopoeia. __________ Translated from Journal of Donghua University (Natural Science Edition), 2007, 33(4): 425–430  相似文献   

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In this study, we have developed a new method to synthesize mesoporous titanium silicalite-1 (TS-1) with a higher content of active titanium in the framework (more than 5%) than that obtained from the conventional hydrothermal synthesis. The new method combines two methods as follows: (1) a sol-gel method in tetrahydrofuran for the synthesis of TiO2–SiO2 composite with highly dispersed Ti species and (2) a dry gel conversion method for the crystallization to TS-1. This investigation revealed that the dispersion of Ti in the starting materials was quite important to synthesize mesoporous TS-1 with high content of Ti besides dry conversion method. The obtained mesoporous TS-1 with a high content of titanium showed higher catalytic activity in 1-hexene epoxidation than conventional TS-1. This high activity is likely to originate from the high content of titanium in the framework.  相似文献   

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Multivalent ions take a significant role in the sorption of soluble polysaccharides on solid cellulose substrates and thus demonstrate an important principle in structural polysaccharide organisation. Sorption of Fe(III)–alginate complexes on lyocell fibres as model for the insoluble cellulose matrix has been studied between pH 3–13, at 30 and 60 °C. Sorption maximum of the Fe(III)–alginate complex was observed at pH 3 where the sorbed amounts of alginate and iron were 6,600 and 85 mg iron per kg cellulose respectively. Under the experimental conditions used, a concentration of 0.05 mM Fe(III) is sufficient to achieve surface sorption of Fe(III)–alginate complex. The alginate sorption exhibited minor dependence on molar ratio of Fe(III) to alginate. In environmental scanning electron microscopy no deposition of Fe-hydroxides on the fiber surface was detected. The thickness of the adsorbed Fe(III)–alginate layer on the fiber surface was estimated with 12–22 nm. Tensile strength and abrasion resistance of Fe(III)–alginate treated fibers were not reduced through the sorption treatment. Alginate modified cellulose is of interest as material for medical application, as sorbent and textile finish.  相似文献   

10.
Sol–gel coating technology for the preparation of solid-phase microextraction fibers involves a single-step procedure and allows for in situ creation of chemically bonded coatings which are characterized by high thermal and solvent stabilities. A novel titania sol–gel coating was prepared for the first time on a stainless steel fiber and applied for the headspace solid-phase microextraction (HS-SPME) of menthol with gas chromatography and flame ionization detection. Important parameters influencing the efficiency of SPME process, such as extraction time, extraction temperature and ionic strength, were optimized by central composite design. An extraction time of 40 min at 60 °C gave maximum extraction efficiency, when NaCl (10% w/v) was added to the aqueous sample. The analytical characteristics of the proposed method were comparable with other reported fibers. Under optimized conditions, the linearity was between 0.05 and 100 µg mL??1. The relative standard deviations (RSDs) determined at 0.5 µg mL??1 concentration level (n?=?5) were as follows: intra-day RSD 7.26%; inter-day RSD 10.87%; fiber-to-fiber RSD 9.05%. The relative recoveries determined after spiking a mint distillate sample at three concentration levels from 0.067 to 50.0 µg mL??1 varied from 86 to 102%. The proposed method was successfully applied for the analysis of menthol in peppermint samples.  相似文献   

11.
Nanosized zinc aluminate spinel (gahnite, ZnAl2O4) powders were prepared by sol−gel technique at low sintering temperatures. Aluminium-sec-butoxide [Al(OsBu)3] and zinc nitrate hexahydrate Zn(NO3)2 . 6H2O were used as starting materials. Gels with and without chelating agent were prepared. Ethyl-acetoacetate (C6H10O3) was used as a chelating agent in order to control the rate of hydrolysis of Al(OsBu)3. The dried gels and thermally treated samples were characterized by means of Differential Thermal Analysis and Thermo-Gravimetric Analysis (DTA, TGA), X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). The surface area was measured by Brunauer-Emmet-Teller (BET) adsorption–desorption isotherms. It has been established that chelation enables to obtain a transparent gel. The thermal evolution of gels was characterized by two crystallization processes in the range 200–400 °C and 600–700 °C. Both processes yielded pure ZnAl2O4 as evidenced by XRD, i.e. zinc aluminate spinel powders were produced by gel heat-treatment at temperatures as low as 300 °C. The average gahnite crystallite size for the samples sintered in the temperature range of 400–1000 °C has been calculated from the broadening of XRD lines revealing that nanocrystalline powders were prepared. The surface areas measured for the samples fired at 700 °C for 2 h were 43.1 and 62.6 m2 g−1, for sample without and with the chelating agent, respectively. TEM micrographs confirmed the nano-scale size of particles.  相似文献   

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Novel solid-phase microextraction fibers were prepared based on sol–gel technique. Commonly used fused silica substrate was replaced by titanium wire which provided high strength and longer fiber life cycle. Titanium isopropoxide was employed as the precursor which provides a sol solution containing Ti–OH groups and shows more tendencies to the molecularly similar group on the substrate. Three different polymers, poly (dimethylsiloxane) (PDMS), poly(ethylenepropyleneglycol)-monobutyl ether (Ucon) and polyethylene glycol (PEG) were employed as coating polymer in preparing three different fibers. The applicability of these fibers was assessed for the headspace SPME (HS-SPME) of benzene, toluene, ethylbenzene and xylenes (BTEX) from water sample followed by gas chromatography–mass spectrometry (GC–MS). Effects of different parameters such as fiber coating type, extraction condition, desorption condition were investigated and optimized. Under the optimized conditions, LODs and LOQs of 0.75–10 μg L−1 (S/N = 3) and 1–20 μg L−1 (S/N = 10) were respectively obtained. The method showed linearity in the range of 10–25,000 μg L−1 with correlation coefficient of >0.99. The relative standard deviation was less than 8%.  相似文献   

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Transition Metal Chemistry - In this work, two well-known titanium-type metal–organic framework (MOF) solids named MIL-125 and MIL-125-NH2 were successfully synthesized using a solvothermal...  相似文献   

14.
Polysiloxanes in combination with metal oxides show interesting properties as nanocomposites for optical or medical applications. The formation of covalent connections between the metal oxide and the polysiloxane is an important method to overcome phase separation between the two components, but it also can have an influence on the morphology of the final materials. In this contribution we report a method for the synthesis of hybrid materials based on polysiloxanes and various metal oxides in which both components are tightly connected to each other. Alkoxysilane modified polysiloxanes were obtained by hydrosilation reactions between vinyl triethoxysilane and poly(dimethylsiloxane-co-methylhydrosiloxane) (PDMS-co-PMHS). The thus functionalized polymers were used in a sol-gel process applying Stöber conditions and hybrid nanoparticles were obtained. Following the same pathway, different metal alkoxides (M(OR)4; M = Ti, Zr; R = ethyl, isopropyl) were coordinated to allyl acetoacetate (AAA) and the resulting complexes were applied in a hydrosilation reaction with PDMS-co-PMHS. Metal oxide hybrid nanoparticles were obtained through a sol–gel process.  相似文献   

15.
Reaction of Ti(OPri)4 with 2-methyl-2,4-pentanediol [HOGOH, where G = CMe2CH2CH(Me)] in 1?:?3 M ratio under reflux afforded the monomeric [Ti(OGO)(OGOH)2] (1), which on further reactions with [Al(OPri)3] or [Nb(OPri)5] in 1?:?1 and 1?:?2 M ratios afforded heterometallic derivatives, [Ti(OGO)3{M(OPri)n?2}] and [Ti(OGO)3{M(OPri)n?1}2] [where M = Al (n = 3), Nb (n = 5)], respectively. Similar reactions of Zr(OPri)4?PriOH with a number of glycols [HOGOH, where G = CH(Me)CH(Me), CMe2CMe2, CMe2CH2CH(Me)] yielded dimeric [Zr2(OGO)2(OGOH)4]. [Zr2(OGO)6{M(OPri)n?2}2] and [Zr2(OGO)4(OGOH)2M(OPri)n?2] [M = Al (n = 3), Ti (n = 4), Nb (n = 5)] were prepared by 1?:?2 and 1?:?1 reactions, respectively, of [Zr2(OGO)2(OGOH)4] with Al(OPri)3, Ti(OPri)4, or Nb(OPri)5. Surprisingly, a 1?:?2 reaction of [VO(OPri)3] with 2,2-diethyl-1,3-propanediol in benzene followed a different reaction and produced a neutral tetranuclear derivative [V4(O)4(μ-OCH2CEt2CH2O)2(OCH2CEt2CH2O)4] (18). All of these derivatives were characterized by elemental analysis, molecular weight measurements, FT-IR, and 1H NMR (and wherever possible, by 27Al or 51V NMR) spectroscopic studies. The derivatives [Zr2(OCMe2CH2CH(Me)O)2(OCMe2CH2CH(Me)OH)4] (9 and 18) were additionally characterized by single-crystal X-ray structure analysis.  相似文献   

16.
Nanocomposite Me–C–N:H coatings (Me is TiNb, TiZr or TiAl), with relatively high non-metal/metal ratios, were prepared by cathodic arc method using TiNb, TiZr and TiAl alloy cathodes in a CH4 + N2 atmosphere. For comparison purposes, a-C–N:H films were also produced through evaporating a graphite cathode in a similar atmosphere. The films were characterized in terms of elemental and phase compositions, chemical bonds, texture, hardness, adhesion and friction behavior by GDOES, XPS, Raman spectroscopy and XRD techniques, surface profilometry, hardness and scratch adhesion measurements, and tribological tests. The nanocomposite films consisted of a mixture of crystalline metal carbonitride and amorphous carbon nitride. The non-metal/metal ratio in the films composition was found to range between 1.8 and 1.9. For the metal containing nanocomposites, grain size in the range 7–23 nm, depending on the metal nature, were determined. As compared with the a-C–N:H, the Me–C–N:H films exhibited a much higher hardness (up to about 39 GPa for Ti–Zr–C–N:H) and a better adhesion strength, while the coefficients of friction were somewhat higher (0.2–0.3 for Me–C–N:H and 0.1 for a-C–N:H).  相似文献   

17.
The lifting of cuttings has been a challenging phenomenon in the petroleum industry for a long period, given the complexity of different cuttings types and their high tendency to gravitate to the low side of the hole. Although many additives have been applied to improve the efficiency of water-based muds (WBMs) for cuttings transport, only a few success was recorded in the application of these additives once evaluated under different field situations. In this study, a new WBM formulated by nanocomposites was proposed to lift cuttings out of the annulus during drilling. Series of characterization, rheological, filtration loss, and cuttings transport tests were performed on the drilling muds formulated by (3-Aminopropyl) triethoxysilane modified polypropylene-silica nanocomposite (PP-SiO2 NC-NH2). The cuttings transport test was conducted in a 16-ft. annulus using 9.5 ppg muds, a 60°-hole angle, and annular velocities between 66.1 and 138.6 ft/min at different PP-SiO2 NC-NH2 concentrations of 0.4, 0.5, 0.8, and 1.2 ppb. The performance of 0.5 ppb PP-SiO2 NC-NH2 + WBM on CTE was evaluated and compared with that of WBM + 0.5 ppb of partially hydrolyzed polyacrylamide (PHPA) at five different hole angles from 90 to 0°. The results of zeta potential showed that the PP-SiO2 NC-NH2 was stable. The rheological and filtration properties were enhanced by the inclusion of PP-SiO2 NC-NH2 in the WBM. There exists a better enhancement in the CTE of PP-SiO2 NC-NH2 + WBM over that of PHPA + WBM at 0.5 ppb. The highest cuttings lifted to the surface occurred in a vertical well, followed by 90°, 30°, 60°, and 45° wells. An increase in annular velocity and the orbital motion of the drill pipe by mechanical action increased the CTE of the nanocomposite more than the rest mud samples. It seems the PP-SiO2 NC-NH2 can be more effective than the PHPA for the drilling process and can improve the cuttings lifting performance of WBMs but caution should be exercised to ensure its proper dispersion in drilling muds.  相似文献   

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A reagentless d-sorbitol biosensor based on NAD-dependent d-sorbitol dehydrogenase (DSDH) immobilized in a sol–gel carbon nanotubes–poly(methylene green) composite has been developed. It was prepared by durably immobilizing the NAD+ cofactor with DSDH in a sol–gel thin film on the surface of carbon nanotubes functionalized with poly(methylene green). This device enables selective determination of d-sorbitol at 0.2 V with a sensitivity of 8.7?μA?mmol?1?L?cm?2 and a detection limit of 0.11 mmol?L?1. Moreover, this biosensor has excellent operational stability upon continuous use in hydrodynamic conditions.
Figure
Reagentless D-sorbitol biosensor based on NAD-dependent D-sorbitol dehydrogenase (DSDH) immobilized in sol-gel/carbon nanotubes/poly(methylene green) composite  相似文献   

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