查看更多>>摘要：Herein, for the first time, macro-porous hydrophobic cryogels of poly(iso-decyl acrylate-co-ethylene glycol dimethacrylate) P(IDA-co-EGDMA) have been successfully fabricated through y-ray radiation-induced cryopolymerization. This synthesis route is highly advantageous over the reported redox and UV-radiation routes for the synthesis of hydrophobic cryogels considering the high energy and the penetrating depth of y-ray, which favours the fabrication of larger cryogels within shorter duration. The effects of radiation time, dose rate, amount of cross-linker, solvent type and solvent amount on the cryo-polymerization were studied in detail, which were based on the measurements of gel fraction and contact angle as well as the characterizations of Fourier transform infrared spectroscopy, thermal gravimetric analysis and scanning electron microscopic examination. The fabricated macro-porous cryogels were used as a sorbent for different organic solvents and oils. Using benzene as a common organic solvent, the absorption equilibrium was reached within only 60 s and the absorption capacity varied in the range of 16-20 g/g depending on the cryogel morphology and crosslinking density. As for the halogenated solvents, P(IDA-co-EGDMA) cryogels absorbed 25-29 g/g of chlorobenzene, bromobenzene, iodobenzene and tetrachloromethane. Those cryogels withstood high temperature (150 degrees C) deprived of any alteration in absorption capability and pore morphology. The cryogels reusability was also confirmed with keeping absorption capacity and cryogel mass up to 10 cycles.
查看更多>>摘要：A novel core-shell structured catalyst (Zn/MZSM-5@S-1) with the microporous silicalite-1 shell and the mesoporous ZSM-5 core (Zn/MZSM-5) was prepared by the epitaxial recrystallization method using tetrapropylammonium hydroxide (TPAOH) as template. Multitechniques including XRD, TEM, N2 adsorption-desorption, XPS, 27Al NMR, IR, NH3-TPD, IG and ICP were employed to investigate the physicochemical properties of the core-shell Zn-MZSM-5@S-1 and the deactivation of carbon deposits. Results revealed that the diffusion capacities of Zn-MZSM-5@S-1 have been dramatically improved after the epitaxial growth of the silicalite-1 shell. In addition, the non-acidic silicalite-1 shell covering on Zn/MZSM-5 core could decrease the external Bronsted acid sites, and thus inhibit the formation of carbon deposits. Applying the protective shell increased the stability of the core-shell catalyst in comparison to Zn/MZSM-5 catalyst without the silicalite-1 shell. However, the overgrowth of the silicalite-1 shell extended the diffusion path of reactants and products, reducing the catalytic properties in methane co-aromatization with propane. In this sense, the controlled formation of desired thickness of the silicalite-1 shell around Zn/MZSM-5 core accounted for the enhanced catalytic properties.
查看更多>>摘要：Due to the importance of the colon-specific disease, its treatment with reduced side effects has become fasci-nating over the last decades. The aim of this study was the synthesis of the nanocomposite based on the pro-tonated aluminum-modified mesoporous silica nanoparticles (H/Al-MSN) and curcumin possesses mesalamine to develop its efficacy and eliminating side effects for enhancing permeability in intestinal tissues. Here, different amounts of mesalamine were loaded and studied under accurate analysis in order to evaluate release quality. The aluminosilicate nanoparticles are encapsulated by the combination of curcumin as an herbal product and also chitosan as a natural biopolymer with the advantages of non-toxicity, biocompatibility, biodegradability, and non-allergenic. The release of mesalamine from the nanocomposite was investigated in different pH included acidic, neutral, and alkaline media. The results showed that the release of mesalamine is dependent on acidity. A colonic drug delivery system was designed based on the release time and pH sensitivity. The drug release was studied at pH 5.5, 7, and 8 a different region of the gastrointestinal tract was simulated. The results showed that the trend of mesalamine release is higher at pH 8 with high efficacy performance of more than 90% at room temperature for about 90 h.
查看更多>>摘要：We combine experiments and simulations to study the adsorption of water in several UiO-66 frameworks (ideal and defect-containing structures). We propose a new set of charges for the frameworks that accurately provides the water-structure interaction at the molecular level. The new set is suitable for predicting water adsorption in the ideal UiO-66 structure, providing for the first time, good agreement between experimental and calculated isotherms. The proposed procedure for tuning the point charges of the framework to achieve agreement with experiments is universal and can easily be extended to other MOFs. We explore the structural characteristics in terms of adsorption of water and the potential application of these materials to water harvesting from air. Our results show that the number of introduced defects significantly affect water sorption properties, which results in shifting steep water uptake and increasing saturation loading. Additional performed experiments, such as Ar sorption and the use of the QE-TPDA method allow for a broad characterization of structure-containing defects and the impact that these defects exert on the properties of the materials.
El Sabahy, JulienRicoul, FlorenceJousseaume, Vincent
10页
查看更多>>摘要：The increasing need for on-site and real-time analyses of complex gas mixtures drives the development of several sensing approaches. In case of gravimetric sensors, a chemical sensitive layer is often required to improve the target molecule detection. Numerous materials are studied in the literature but only few are really compatible with the manufacturing of silicon-based sensing devices. This paper is focused on the gas detection ability of porous organosilicates thin films deposited by plasma enhanced chemical vapor deposition that are already used as low-k dielectric in microprocessors. A large panel of porous SiOCH were deposited on quartz crystal micro balances and were studied in the case of toluene and pentane detection. By using three different synthesis approaches, variations in open porosity, mean pore size and chemical composition were investigated. A large affinity to toluene and pentane is observed with partition coefficients higher than 20,000 in the case of toluene. These values are far above those reported for usually known polymers. The kinetic responses are in the range of a few minutes which is fast compared to the literature. Ellipsometry porosimetry (EP) characterizations, performed to obtain adsorption isotherms, highlight the role of porosity and more precisely of microporosity. Materials with smaller pores present higher affinity to pentane and toluene than materials with larger pores. Besides, EP appears to be an efficient technique to classify chemical sensitive layers. Finally, these porous SiOCH that present a good chemical stability and a hydrophobicity are promising sensitive layers for the manufacturing of NEMS-based gravimetric sensors integrated on silicon.
查看更多>>摘要：Porous silicon was widely used in displays, optical sensors, and biological imaging due to its high surface areas, adjustable microstructure, large adsorption capacity and excellent optical performance. Unfortunately, there are numerous reactive silane groups on the freshly etched porous silicon surface, which are susceptible to oxidization in the air, thereby affecting the optical performance and stability of porous silicon. This study provides an efficient strategy of using photocatalytic reaction to graft dodecafluoroheptyl methacrylate to freshly prepared n-type porous silicon surface, thereby generating a fluorine-modified porous silicon with high stability and superhydrophobic surface. The structure and composition of porous silicon before and after modification were analyzed by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). The effects of UV light, reactant mass fraction and reaction time on the surface properties of porous silicon were studied by water contact angle (WCA) and photoluminescence (PL). The results indicated that the dodecafluoroheptyl methacrylate was successfully grafted onto n-type porous silicon surface by photocatalytic reaction. The superhydrophobic and luminescent porous silicon was prepared by reacting 40 min in a dichloride solution containing 10 wt% dodecafluoroheptyl methacrylate under UV light. The WCA of the fluorine-modified porous silicon surface could reach 153 degrees and had good photoluminescence intensity. This modified porous silicon surface had great stability in alkaline and air environment. After treated with alkaline droplets for 30 min, the WCA of modified porous silicon could maintain above 150 degrees and had good photoluminescence. And under room temperature within a week, the porous silicon surface still showed great hydrophobic properties and photoluminescence intensity. In addition, the modified porous silicon has different responsiveness to ethanol solutions of different concentrations, which could be applied to alcohol sensors and has great development prospects.
查看更多>>摘要：Efforts are being made to develop gene therapy delivery systems capable of substituting the viral vectors with comparable efficiency but with fewer biosafety concerns, easier production on large-scale and improved shelfstability. Among the potential delivery systems based on inorganic nanoparticles for plasmid DNA, mesoporous silica has been gaining significance due to its combination of biocompatibility with unique structural and chemical properties. In this study, mesoporous silica nanoparticles were grafted with different alkyl-amino groups to enable the formation of conjugates with the plasmid vector pEGFP-N3. The colloidal properties, cytotoxicity and transfection efficiency of conjugates to HeLa cells were evaluated. Spherical nanoparticles with around 90 nm of diameter were synthesized and then functionalized with propylamine, (2-aminoethyl)(ethyl) propylamine and 3-(diethylenetriamine)propyl groups. Dispersions prepared in different cell culture media and the zeta potential measurements revealed that their aggregation tendency was influenced by their functionalities. Besides, the structural integrity of the functionalized nanoparticles dispersed in Dulbecco's modified Eagle's medium was affected when sterilized in autoclave. The highest efficiency on the pEGFP-N3 conjugation was obtained with 3-(diethylenetriamine)propyl groups while the highest transfection efficiency was achieved with propyl amino groups onto the surface of mesoporous silica nanoparticles. The cytotoxicity of conjugates to HeLa cells was acceptable and the transfection efficiency was low possibly due to the aggregation observed in the cell culture medium.
Calzaferri, GionGallagher, Samuel H.Bruehwiler, Dominik
11页
查看更多>>摘要：The adsorption of simple gases begins with the formation of a monolayer on the pristine surface, not always followed by the formation of a second or more monolayers. Subsequently, cluster formation or cavity filling occurs, depending on the properties of the surface. The characteristically different shape of the isotherms related to these processes allows to clearly differentiate them. We analyzed argon and N-2 adsorption isotherms quantitatively over the entire relative pressure range for adsorbents bearing different properties: the nonporous Stober-type particles, the microporous zeolite L (ZL) and zeolite L filled with indigo (Indigo-ZL), and three mesoporous silica adsorbents of different pore size. The formal equilibria involved in cluster formation and in cavity filling have been derived and successfully applied to quantitatively describe the isotherms of the adsorbents. No indication regarding formation of a second monolayer on top of the first one was observed for the Stober-type particles. Instead, cluster generation, which minimizes surface tension, starts early. The behavior of microporous ZL and of Indigo-ZL is different. A second monolayer sets up and cluster formation starts with some delay. The enthalpy of cluster formation is, however, practically identical with that seen for the Stober-type particles. The difference between the experimental and the calculated inflection points is very small. The shapes of the isotherms seen for the mesoporous adsorbents differ significantly from those seen for the nonporous and for the microporous adsorbents. The quantitative analysis of the data proves that formation of a second monolayer is followed by filling of cavities which ends as soon as all cavity sites are filled. The sum of the individual fractional contributions, namely the monolayer formation Theta(mL), the appearance of a second monolayer Theta(2L) on top of the first one, and the cavity filling Theta(cav), yields a calculated adsorption isotherm Theta(calc) which describes the experimental data Theta(exp) well. The experimental and the calculated first inflection points are in excellent agreement, which is also the case for the second inflection points. The value of the cavity filling enthalpy is roughly 10% larger than that for the cluster formation seen in the nonporous and the microporous adsorbents. The volume for cavity filling is significantly smaller than the monolayer volume for the mesoporous adsorbent with a pore diameter of 2.7 nm, while it is the same or larger for pore diameters of 4.1 nm and 4.4 nm, respectively. We conclude that understanding the adsorption isotherms as signature of several sequential chemical equilibrium steps provides additional information data for clusters, cavities, and position of the inflection points, not accessible by means of the conventional models. The theory reported herein covers type I, II, IV and to some extent also type VI isotherms.
查看更多>>摘要：Liquid-phase separation of cyclohexane and benzene is both demanded and challenging, and the use of selective sorbents, such as metal-organic frameworks (MOFs), for extraction of one component from the mixture is the most promising solution. We report new mechanistic insights into diffusion of benzene and cyclohexane in well-known MOF ZIF-8 using recently developed methodology of encapsulated spin probes detected by Electron Paramagnetic Resonance (EPR). We demonstrate unambiguously that only one component of the hydrocarbons mixture, benzene, can penetrate into ZIF-8 particles, and these EPR-based conclusions are confirmed by high values of sorption selectivity measured by gas chromatography. However, systematic analysis of the mixtures containing small fractions of benzene (e.g. similar to 1%) shows noticeable decrease in separation efficiency and only partial removal of benzene from diluted benzene/cyclohexane mixtures. This occurs due to the reverse diffusion of benzene from MOF particles into solution in equilibrium. At the same time, our diffusion study clearly points out that the membrane separation of benzene/cyclohexane using ZIF-8 should be highly perspective and pursued in the future.
查看更多>>摘要：Selective hydrogenation of alpha,beta-unsaturated aldehyde catalyzed by supported Pd nanoparticles (NPs) is challenging, especially under harsh reaction conditions. Here, we report a facile method to prepare a catalyst composed of highly dispersed Pd NPs (similar to 2.6 nm) confined in zeolite ZSM-5 crystals. When used in the hydrogenation of cinnamaldehyde, the prepared catalyst (Pd@SG-ZSM-5) exhibited excellent performance for the selective production of hydrocinnamaldehyde (HCAL) due to the confinement effect. Compared with the traditional supported Pd catalyst prepared by impregnation, Pd@SG-ZSM-5 showed a 2.5-fold enhancement in the HCAL selectivity (73% vs. 30%). Liquid adsorption combined with infrared spectroscopy characterization revealed that compared with the traditional catalyst, Pd@SG-ZSM-5 adsorbed much less reactant as well as product molecules and desorbed the generated HCAL quickly, thereby suppressing the formation of by-products and leading to high selectivity of HCAL.
NSTL
Elsevier