溶剂诱导翻转Pickering乳液用于原位循环使用酶催化剂

Separation and recycling of catalysts are crucial for realizing the objectives of sustainable and green chemistry but remain a great challenge, especially for enzyme biocatalysts. In this work, we report a new solvent-induced reversible inversion of Pickering emulsions stabilized by Janus mesosilica nanosheets (JMSNs), which is then utilized as a strategy for the in situ separation and recycling of enzymes. The interfacial active solid particle JMSNs is carefully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption experiments, Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA).The JMSNs are demonstrated to show order-oriented mesochannels with a large specific surface area, and the hydrophobic octylgroup is selectively modified on one side of the nanosheets. Furthermore, the inversion is found to be a fast process that is strongly dependent on the interfacial activity of the solid emulsifier JMSNs. Such a phase inversion is also a general process that can be realized in various oil/water phasic systems, including ethyl acetate-water, octane-water, and cyclohexane-water systems. By carefully analyzing the capacity of JMSNs with different surface wettabilities for phase inversion, a triphase contact angle (θ) close to 90° and a critical oil-water ratio of 1 : 2 are identified as the key factors to achieve solvent-induced phase inversion via a catastrophic phase inversion mechanism. Importantly, this reversible phase inversion is suitable for the separation and recycling of enzyme biocatalysts that are sensitive to changes in the reaction medium. Specifically, during the reaction, the organic substrates are dissolved in the oil droplets and the water-soluble catalysts are dispersed in the water phase, while a majority of the product is released into the upper oil phase and the enzyme catalyst is confined inside the water droplets in the bottom layer after phase inversion. The perpendicular mesochannels of JMSNs provide a highly accessible reaction interface, and their excellent interfacial activity allows for more than 10 rounds of consecutive phase inversions by simply adjusting the ratio of oil to water in the system. Using the enzymatic hydrolysis kinetic resolution of racemic acetate as an example, our Pickering emulsion system shows not only a 3-fold enhanced activity but also excellent recyclability. Because no sensitive chemical reagents are used in this phase inversion process, the intrinsic activities of the catalysts can be preserved even after seven cycles. The current study provides an alternative strategy for the separation and recycling of enzymes, in addition to revealing a new innovative application for Janus-type nanoparticles.     

对BJH方法计算孔径分布过程的解读

This paper introduces the geometric assumptions and neglects of the pore size distribution calculated by BJH method, the arithmetic approximation for simplified calculation, the derivation process of each parameter, the calculation steps and key points of the pore size distribution. This paper also introduces the application scope of BJH method at the current instrument level, and how to further integrate the data. In order to get the required analysis and test report, references are provided for the subsequent adjustment of test parameters and improvement of test methods. Some problems often encountered in reading experimental reports are also discussed.     

Solution-phase synthesis of ordered mesoporous carbon as resonant-gravimetric sensing material for room-temperature H_2S detection

H_2S can cause multiple diseases and poses a great threat to human health.However,the precise detection of extremely toxic H_2S at room temperature is still a great challenge.Here,a facile solvent evaporation induced aggregating assembly(EIAA) method has been applied for the production of ordered mesoporous carbon(OMCs) in an acidic THF/H_2 O solution with high-molecular-weight poly(ethylene oxide)-b-polystyrene(PEO-b-PS) copolymers as the structure-directing agent,formaldehyde and resorcinol as carbon precursors.Along with the continuous evaporation of THF from the mixed solution,cylindrical micelles are formed in the solution and further assemble into highly ordered mesostructure.The obtained OMCs possesses a two-dimensional(2 D) hexagonal mesostructure with uniform and large pore diameter(～19.2 nm),high surface area(599 m~2/g),and large pore volume(0.92 cm~3/g).When being used as the resonant cantilever gas sensor for room-temperature H_2S detection,the OMCs has delivered not only a superior gas sensing performance with ultrafast re s ponse(14 s) and recovery(21 s) even at low concentration(2 ppm) but also an excellent selectivity toward H_2S among various common interfering gases.Moreover,the limit of detection is better than 0.2 ppm,indicating its potential application in environmental monitoring and health protection.     

Functionalized mesoporous silica nanoparticles templated by pyridinium ionic liquid for hydrophilic and hydrophobic drug release application

Chemotherapy is the most common treatment for all cancer patients but this treatment poses many side effects due to lack of drug’s selectivity. To overcome this problem, utilizing a better and more effective delivery agent is the solution. Mesoporous silica nanoparticles (MSNs) emerged as a promising platform in development of drug delivery agent. This is due to its desirable properties such as tunable pores, large surface area, good biocompatibility and easy functionalization. Furthermore, these properties can be tuned through the utilization of alternative template such as pyridinium ionic liquid. Besides, by employing surface functionalization, the effectiveness of MSNs as drug delivery agent may also increase. This work reported the usage of 1-hexadecylpyridinium bromide ionic liquid as template for MSNs production and the surface of MSNs was then further functionalized via post – grafting method in order to obtain MSN – NH₂, MSN – SH and MSN – COOH as drug carrier, respectively. These functionalized MSNs were then used to study the drug loading and drug release of hydrophilic drug, gemcitabine and hydrophobic drug, quercetin. For quercetin, MSN-NH₂ had the highest drug loading percentage (72%) and slowest release (14%) in 48 h while for gemcitabine, it was found that MSN-COOH had the highest drug loading percentage (45%) and slowest release (15%) in 48 h. Based on the results, it is suggested that mesoporous silica nanoparticle with surface functionalization has suitable properties for controlled drug release which gives constant release behavior over a period of time to avoid repeated administration of drug where the drug is administered at a fixed dosage and regular time interval.     

Functionalisation of mesoporous silica nanoparticles with 3-isocynatopropyltrichlorosilane

The functionalisation of Mesoporous Silica Nanoparticles (MSN) with the isocyanate group was carried out. The excellent reactivity of 3-isocynanatopropyltrichlorosilane allowed its grafting on the surface of MSN in mild conditions. Further reaction with different nucleophiles bearing primary amino groups led to the formation of a urea linkage and thus the covalent grafting of the nucleophiles to the MSN surface.     

Sol-gel technique for the generation of europium-doped mesoporous and dense thin films: A luminescent study

In this paper, a series of europium-activated titania mesoporous and dense thin films were prepared by sol-gel process. Structural characterizations show that high europium ion loadings can be incorporated into titanium dioxide walls without destroying the mesoporous arrangement. However, high europium content locks the titanium dioxide crystallization process. Upon 10% europium ions loading, mesoporous thin films are mainly amorphous, whereas dense ones are still partially crystallized. Eu³⁺ ion luminescence has been investigated by exciting through the semiconductor host lattice. Emission features reveal that europium ions adopt similar environments (nanocrystalline and glassy-like ones) in both dense and mesoporous thin films. Fluctuations of europium emission under continuous UV excitation have been observed. One observes that the effect strongly depends on the thin films’ crystalline character which is strongly related with the texturation and existence at the mesoscopic length scale.     

Synthesis and characterization of submicron-sized mesoporous aluminosilicate spheres

Mesoporous aluminosilicate spheres of 0.3–0.4 Μm diameter, with different Si/Al ratios, have been prepared by surfactant templating. Surface area of these materials is in the 510–970 m² g^-1 range and pore diameter in the 15–20 ? range.     

Green approaches via nanocatalysis with nanoporous materials: Functionalization of mesoporous materials for single site catalysis

Among the various green keys, catalysis, especially using heterogeneous catalysts, has been powerfully applied to achieve greener chemical processes. Here are presented nanoporous materials which have mesoporosity with the functional groups on the inner pore walls. The materials were synthesized via a rather greener process, such as microwave synthesis, and over these nanocatalysts some of the green chemical reactions were carried out with high activities and selectivities. Cobalt species has been successfully functionalized and stabilized as a Co(III) complex onto SBA-15 support and proven to be an active catalyst in alkylaromatic oxidation with molecular oxygen, styrene epoxidation with tert-butyl hydroperoxide (TBHP), and allylic oxidation of cycloolefins with H₂O₂. Short-channeled amino-functionalized SBA-15 catalyst with hexagonal plate morphology was synthesized directly by using microwave synthesis from the co-condensation of aminopropyl triethoxysilane (APTES) and sodium metasilicate under a strong acidic condition. The catalyst showed high catalytic activity in liquid-phase Knoevenagel condensation reactions, due to easy diffusion and mass transfer of substrates into the short mesopore channel. The HO₃S–SBA-15 was prepared by grafting of mercaptopropyl trimethoxysilane onto the calcined mesoporous silica surface and subsequently oxidized with H₂O₂. The resulting catalyst was applied as a Bronsted solid-acid catalyst for the esterification of oleic acid with methanol.     

Structural change of mesoporous silica with sonochemically prepared gold nanoparticles in its pores

Ultrasonic irradiation of mesoporous silica soaked in a mixture of chloroauric acid and isopropanol for 120 min in Ar atmosphere at room temperature yielded Au/SiO₂ mesoporous composite, which was characterized by high resolution transmission electron microscopy and optical absorption measurement. The structure of mesoporous silica after sonochemical preparation of gold (Au) nanoparticles within its pores was studied by nitrogen adsorption technique. It has been shown that the structural parameters, such as specific surface area (SSA), porosity (P), the mean pore diameter (l_p) were increased significantly after ultrasonic irradiation. It is suggested that the collision of Au nanoparticles with pore walls and localized erosion induced by the asymmetric implosive collapse of cavities on the extensive liquid–solid interface that are responsible for the structural change in the mesoporous solid.     

Enhanced cycling properties of transition metal molybdates, Li x M2(MoO4)3 {0?≤ x

K. M. Begam  M. S. Michael  S. R. S. Prabaharan 《Ionics》2007,13(6):467-471