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Cu3(BTC)2 (BTC = benzene-1,3,5-tricarboxylate) nanoflakes, synthesized in an ionic liquid/water binary solvent, exhibit a high catalytic performance for benzyl alcohol oxidation.

Pickering emulsion is a heterogeneous system consisting of at least two immiscible liquids, which are stabilized by solid particles, in which organic solvent or water is dispersed into other phase in form of micrometre-sized droplets. Compared to traditional emulsions stabilized by surfactant, solids are cheap and can be easily separated and recycled by centrifugation or filtration after use. Moreover, the properties of Pickering emulsions can be adjusted by using different types of solid particles. Up to now, Pickering emulsions have been applied in a wide range of areas such as material science and catalysis. Here we review recent studies on Pickering emulsions stabilized by metal-organic framework, graphitic carbon nitride and graphene oxide.

To construct the heterojunctions of TiO2 with other compounds is of great importance for overcoming its inherent shortages and improving the visible-light photocatalytic performance. Here we propose the construction of TiO2/covalent organic framework (COF) heterojunction with tight connection by a supercritical CO2 (SC CO2) method, which helps bridging the transformation paths for photo-induced charge between TiO2 and COF. The produced TiO2/COF heterojunction performs a H2 evolution of 3,962 µmol·g−1·h−1 under visible-light irradiation, which is ∼ 25 times higher than that of pure TiO2 and 4.5 folds higher than that of TiO2/COF synthesized by the conventional solvothermal method. This study opens up new possibilities for constructing heterojunctions for solar energy utilization.

The electroreduction of CO2 to valuable chemicals and fuels offers an effective mean for energy storage. Although CO2 has been efficiently converted into C1 products (e.g., carbon monoxide, formic acid, methane and methanol), its convention into high value-added multicarbon hydrocarbons with high selectivity and activity still remains challenging. Here we demonstrate the formation of multi-shelled CuO microboxes for the efficient and selective electrocatalytic CO2 reduction to C2H4. Such a structure favors the accessibility of catalytically active sites, improves adsorption of reaction intermediate (CO), inhibits the diffusion of produced OH− and promotes C—C coupling reaction. Owing to these unique advantages, the multi-shelled CuO microboxes can effectively convert CO2 into C2H4 with a maximum faradaic efficiency of 51.3% in 0.1 M K2SO4. This work provides an effective way to improve CO2 reduction efficiency via constructing micro- and nanostructures of electrocatalysts.

Multi-component photocatalysts can take advantage of each component and overcome their shortcomings at the same time by synergetic effect, providing a great promising future for high activity photocatalyst. In this work, P3HT/Ag/TiO2 ternary photocatalyst was constructed to further promote the separation of photogenerated carriers and enhance the photocatalytic activity as much as possible by introduction of Ag nanoparticles into the conjugated polymers/TiO2 heterojunction. The results showed that different amount of Ag nanoparticles were successfully photodeposited on the surface of TiO2 to form Ag/TiO2 composites, which were subsequently hybridized with P3HT, obtaining P3HT/Ag/TiO2 ternary photocatalytic system. The ternary photocatalyst exhibit remarkably enhanced photocatalytic activity for degradation of MO compared to the single- and two- component systems under both visible light and ultraviolet illumination by varying Ag content. This should be ascribed to the favored separation of photogenerated carriers resulted from the synergistic effect of P3HT, Ag and TiO2, as confirmed by the results of photocurrent tests. However, the influence of Ag content on photocatalytic activity under various light conditions was totally different. P3HT/Ag/TiO2-1, with a very small amount of Ag, showed the highest visible light photocatalytic activity, which was 2.1 and 9.7 times that of P3HT/TiO2 and TiO2 respectively and then the photocatalytic activity decreased with Ag loading amount. For the photocatalytic experiments performed under ultraviolet light, the activity continuously increased with the Ag content within our conditions, reaching the maximum for P3HT/Ag/TiO2-4, which was 4.5 and 1.8 times that of P3HT/TiO2 and Ag/TiO2-4 respectively. This might be resulted from the different role of Ag nanoparticles, probably electron sink under visible irradiation and Z-scheme bridge between P3HT and TiO2 under ultraviolet light.

It is of great importance to develop facile strategies to synthesize catalysts with desirable compositions and structures for high-performance photocatalytic hydrogen generation. In this work, we put forward an ionic liquid assisted one-pot route for the synthesis of heteroatom-doped Pt/TiO2 composite material. This route is simple, environmentally benign and adjustable owing to the designable properties of ionic liquids. The as-synthesized Pt/TiO2 nanocrystals exhibit high activity and stability for the photocatalytic hydrogen generation under simulated solar irradiation. This method can be easily applied to the synthesis of various kinds of metal/TiO2 composites doped with desirable heteroatoms (e.g., F, Cl, Br, etc).

The application of nickel in electrocatalytic reduction of CO2 has been largely restricted by side reaction (hydrogen evolution reaction) and catalyst poisoning. Here we report a new strategy to improve the electrocatalytic performance of nickel for CO2 reduction by employing a nitrogen-carbon layer for nickel nanoparticles. Such a nickel electrocatalyst exhibits high Faradaic efficiency 97.5% at relatively low potential of -0.61 V for the conversion of CO2 to CO. Density functional theory calculation reveals that it is thermodynamically accomplishable for the reduction product CO to be removed from the catalyst surface, thus avoiding catalyst poisoning. Also, the catalyst renders hydrogen evolution reaction to be suppressed and hence reasonably improves catalytic performance.

Aiming at developing highly efficient photocatalysts by broadening the light-harvesting region and suppressing photo-generated electron-hole recombination simultaneously, this work reports rational design and fabrication of donor-acceptor (D-A) conjugated polymer/TiO2 heterojunction catalyst with strong interfacial interactions by a facile in-situ thermal treatment. To expand the light-harvesting window, soluable conjugated copolymers with D-A architecture are prepared by Pd-mediated polycondensation of diketopyrrolopyrrole (DPP) and t-butoxycarbonyl (t-Boc) modified carbazole (Car), and used as visible-light-harvesting antenna to couple with TiO2 nanocrystals. The DPP-Car/TiO2 composites show wide range absorption in 300–1000 nm. To improve the interfacial binding at the interface, a facile in-situ thermal treatment is carried out to cleave the pendant t-Boc groups in carbazole units and liberate the polar amino groups (–NH–) which strongly bind to the surface of TiO2 through dipole–dipole interactions, forming a heterojunction interface. This in-situ thermal treatment changes the surface elemental distribution of TiO2, reinforces the interface bonding at the boundary of conjugated polymers/TiO2 and finally improves the photocatalytic efficiency of DPP-Car/TiO2 under visible-light irradiation. The interface changes are characterized and verified through Fourier-transform infrared spectroscopy (FT-IR), photo images, UV/Vis (solution state and powder diffuse reflection spectroscopy), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fluorescence, scanning electron microscopy(SEM) and transmission electron microscopy (TEM) techniques. This study provides a new strategy to avoid the low solubility of D-A conjugated polymers and construct highly-efficient conjugated polymer/TiO2 heterojunction by enforcing the interface contact and facilitating charge or energy transfer for the applications in photocatalysis.

Here we report the first synthesis of nearly pure-phase Cu3Si alloy that can be a highly efficient catalyst in the hydrochlorination of silicon reaction. This material was prepared by a high-temperature (1050 ​°C) calcination method in which copper and silicon powders were used as the reactants. The X-ray photoelectron spectroscopy (XPS) study revealed that the Cu and Si atoms in the Cu3Si alloy carried part of positive and negative charge, respectively. When employed as the catalyst in the silicon hydrochlorination to SiHCl3 (TCS) for the production of Si polycrystals for Solar cell, the sample Cu3Si exhibited excellent low-temperature catalytic performance: the Si conversion and TCS selectivity respectively achieved 41.1% and 96.1% at 250 ​°C. Notably, its TCS yield at 250 ​°C was 1.2 times higher than that of the industrial catalyst-free system at 350 ​°C. Detailed analysis of the reaction process showed that the positively charged Cu atoms and negatively charged Si atoms in Cu3Si alloy could cleave the H–Cl bond in the reactant HCl and make the combination of H and Cl atom with Si atoms easier. Meanwhile, the reaction between the remaining Cu atom and Si was accelerated, leading to the generation of more active Cu6.69Si and ultimately superior catalytic performance. This work deepens the fundamental understanding of the hydrochlorination of silicon reaction, and provides an avenue for the synthesis of Si-based alloy catalysts.

Herein we propose an interfacial assembly and hydrolysis route for fabricating TiO2/UiO-67 composites. The UiO-67 assembles at the water–oil interface serving as a stabilizer of the emulsion. TiO2 nanoparticles are loaded on UiO-67 by hydrolysis of the precursor TBT (tetra-n-butyl titanate) at the water–oil interface. By such a strategy, hollow capsules structured by UiO-67 and decorated by ultra-small TiO2 nanoparticles were produced. The newly-constructed composite combines the CO2 adsorption properties of UiO-67 and the photocatalytic activity of TiO2, showing high activity for the photocatalytic reduction of CO2 to formic acid. Such a composite with a novel structure provides a promising route for the preparation of new compound materials.

The aggregation behavior of the ionic liquid (IL) 1-alkyl-3-methylimidazolium chloride with different alkyl chain lengths in a deep eutectic solvent (DES, composed of choline chloride and glycerol in a 1 : 2 mole ratio) was studied for the first time. The critical micellar concentration, micellar size and intermolecular interactions in IL/DES solutions were investigated by different techniques including the fluorescence probe technique, small angle X-ray scattering and Fourier transform infrared spectroscopy. The solvophobic effect dominates the micellization of CnmimCl in DES and the intermolecular hydrogen-bond interaction plays a positive role to promote micelle formation. The micellar solutions were utilized for the synthesis of the water-unstable metal-organic framework Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) at room temperature. X-Ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption isotherms confirm the formation of crystalline Cu3(BTC)2 nanocrystals with mesoporous structures. The morphologies and porosity properties of Cu3(BTC)2 nanocrystals can be modulated by varying the concentration of CnmimCl.

To develop facile, rapid and low-energy route for metal-organic framework (MOF) formation is of great importance. Here a water-alkane interface strategy was proposed for the MOF formation at room temperature. The content and molecular structure of alkane phase were found to have remarkable effect on regulating the porosity properties of MOFs. For example, the MOF synthesized in 1:1 (v/v) water/n-hexane mixture has the largest BET surface area (1474.1 m(2)/g) and total pore volume (0.7030 cm(3)/g). The mechanism was discussed from the competitive adsorption of water and alkane in the micropores of MOF building blocks during formation process. (C) 2015 Elsevier Inc. All rights reserved.

The hierarchical porous metal oxide combines the advantages of each class of hierarchical pores and has potential applications in different fields. Here we proposed an emulsion-calcination route for producing porous metal oxide. The porous metal-organic complex was first synthesized in CO2-in-water emulsion, then the metal-organic complex was calcined to remove the organic linker and form porous metal oxide. The hierarchical macro- and mesoporous assemblies of Co3O4 nanoparticles were produced. The hierarchical macro- and mesoporous assemblies of Co3O4 nanoparticles were produced, with the macropores in size of hundreds of nanometers and the mesopores in 9-15 nm. The porosity properties and nanoparticle size of Co3O4 can be modulated by controlling CO2 pressure. The as-synthesized Co3O4 is an excellent candidate catalyst for the methylene blue degradation. By taking advantages of the high porosity and small particle size, the Co3O4 have potential applications in catalysis, gas separation, and controlled drug release. The strategy proposed in this work can be applied to the synthesis of different kinds of porous metal oxides. (C) 2015 Elsevier Inc. All rights reserved.

Conjugated polymer/TiO2 composites are promising visible light photocatalysts for solar chemical conversion processes in the field of environmental chemistry for decomposition of organic compounds in water and air. In consideration of the fact that conjugated polymers are also organic substances, particular attention must be focused on the stability of conjugated polymer/TiO2 composites, which has not been laid enough emphasis upon so far. Poly(3-hexylthiophene)/titanium dioxide (P3HT/TiO2) composites, as a representative of conjugated polymer/TiO2 photocatalysts, were prepared by combining chemical oxidative polymerization method and physical blending technique. The stability of the composites was systematically studied by comparative analysis of the physical and chemical structure of P3HT/TiO2 composites before and after the photocatalytic reaction. As confirmed by the results of high-resolution transmission electron microscopy (HRTEM), scanning electron microscope (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), the P3HT/TiO2 composites were quite stable to 10 h of photodegradation of methyl orange (MO) under visible light, maintaining both their physical and chemical structure.

Polypyrrole/polyvinyl alcohol–titanium dioxide (PPy/PVA–TiO 2 ) composite films used as photo-catalysts were fabricated by combining TiO 2 sol with PPy/PVA solution in which PPy was synthesized by in situ polymerization of pyrrole (Py) in polyvinyl alcohol (PVA) matrix and loaded on glass. The prepared photo-catalysts were investigated by X-ray diffraction (XRD), ultraviolet–visible diffuse reflection spectroscopy (UV–vis DRS), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectra and photoluminescence (PL). The results indicate that the composites have same crystal structure as the TiO 2 and extend the optic absorption from UV region to visible light region. By detecting the variation ratio, detected by ultraviolet–vis spectroscopy, of model pollutant rhodamine B (RhB) solution in the presence of the composite films under both UV and visible light irradiation, the photo-catalytic performance of the composite films was investigated. The results show that the PPy/PVA–TiO 2 composite films show better photo-catalytic properties than TiO 2 film both under UV and visible light irradiation, and the photo-catalytic degradation of RhB follows the first-order kinetics. The effects of the composition of composite films and the concentration of RhB on the photo-catalytic performance, as well as the possible photo-catalytic mechanism, were also discussed. By photo-catalytic recycle experiments, the structure stability of the PPy/PVA–TiO 2 composite film was investigated and the results show that the photo-catalytic activity under both UV and visible light irradiation have no significant decrease after four times of recycle experiments, suggesting that the photo-catalyst film is stable during the photo-catalytic process, which was also confirmed by the XRD pattern and FT-IR spectra of the composite film before and after photo-catalytic.

In this article, a novel visible light (VL) active photo-catalyst, calcinated-poly (vinyl alcohol) (C-PVA)/TiO 2 composites, was prepared by calcinating the films on glass substrates obtained from TiO 2 sol and initially thermally treated PVA solution. The results showed that the C-PVA with conjugated C=C bonds was doped onto the surface of TiO 2 and expanded the photo-response from ultraviolet spectrum of the TiO 2 to VL spectrum of the composites; meanwhile, the photo-luminescence of C-PVA was quenched by TiO 2 , indicating charge transfer between C-PVA and TiO 2 . The C-PVA/TiO 2 composites showed improved adsorption and photo-catalytic performances toward rhodamine B (RhB) compared to TiO 2 . When the mass feed ratio (P/T) of polymer (P) to TiO 2 (T) increased from 1:10 to 1:2, the equilibrium adsorption ratio of C-PVA/TiO 2 composites toward RhB continuously increased from 8.2 to 21.6%; while the VL photo-degradation ratio of RhB increased at first, achieving maximum value (92.2%) at P/T = 1:6, and then decreased consecutively. SEM images showed that there were lots of aggregates of TiO 2 and C-PVA on the surface of the composites. Moreover, the morphologies of those aggregates were related to the value of P/T, and the dispersion of TiO 2 in the C-PVA matrix was best while P/T = 1:6. The photo-catalytic activity of C-PVA/TiO 2 composites was closely correlated to aggregate states of C-PVA and TiO 2 , while the adsorption performance was contributed to the exposed C-PVA on the surface of C-PVA/TiO 2 composites.

Here, we propose to modify the hydrophilicity of metal–organic framework (MOF) particles by an interfacial assembling route, which is based on the surface-active nature of MOF particles. It was found that hydrophilic UiO-66-NH2 particles can be converted to hydrophobic particles through an oil–water interfacial assembling route. The underlying mechanism for the conversion of UiO-66-NH2 was investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was revealed that the close assembly of UiO-66-NH2 particles at the oil–water interface strengthens the coordination between organic ligands and metal ions, which results in a decrease in the proportion of hydrophilic groups on UiO-66-NH2 particle surfaces. Hydrophobic UiO-66-NH2 particles show improved adsorption capacity for dyes in organic solvents compared with pristine UiO-66-NH2 particles. It is expected that the interfacial assembling route can be applied to the synthesis of different kinds of MOF materials with tunab...

The thermal decomposition behavior of poly(vinyl alcohol) (PVA) with NaHSO4 at 280∼290°C as well as the optical characteristics and the thermal stability of the resulting thermally decomposed PVA were investigated by means of UV-Vis spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The results suggest that (1) the elimination reactions of side groups in PVA with NaHSO4 can occur under our conditions resulting in formation of carbon–carbon double and triple bonds; (2) most of the carbon–carbon double bonds were conjugated; (3) the PVA thermally treated with NaHSO4 could absorb light in the region of 190∼600 nm; (4) the thermal stability of the resulting PVA was better than that of PVA without thermal treatment; and (5) compared with the thermal reaction of PVA without NaHSO4, the addition of NaHSO4 can promote the thermal elimination of side groups of PVA.

Sol–gel method was used to prepare polyvinyl alcohol/titanium dioxide (PVA/TiO 2 ) composite films on glass slide, then the heat-treated polyvinyl alcohol/titanium dioxide (H-PVA/TiO 2 ) composite loaded on glass and used as photo-catalyst was prepared by calcinating the precursor. Scanning electron microscopy (SEM), X-ray diffractionscopy (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RAM) and fluorescence emission spectroscopy (FL) were used to characterize H-PVA/TiO 2 composites. The visible light-induced photo-catalytic activities of the obtained composites prepared by different heat-treated temperature and different composition were examined through investigating the decolouration of rhodamine B (RhB) solution under visible light irradiation in the presence of the composites by means of UV–vis measurement. The results show that under the visible light irradiation, the H-PVA/TiO 2 composite can make rhodamine B be degraded more efficiently than the PVA/TiO 2 composite does, and the visible light photo-catalytic activity obviously depends on the heat-treated temperature and the composite composition. The 180 °C of heat-treated temperature and the 16.7 mass% of polymer content are beneficial for enhancing the efficiency of H-PVA/TiO 2 of degrading RhB.

The ZnO nanocombs were synthesized by chemical vapor deposition method, which the uniform and dense nanotips were along one side of the comb ribbon. The growth mechanism was described as free catalyst self-assembled and vapor-solid model. The optical properties related with the surface states were investigated by Raman and PL spectra. The large redshift of 1LO phonon peak was attributed to the surface and interface states. The normalized PL spectra showed that the deep-level emission decreased for the sample to be annealed in O(2) ambient at 500 degrees C. On the contrary, the deep-level emission increased while for the annealed sample in O(2) ambient at 600 degrees C. The deep-level emission was attributed to the transition from the shallow donor to the deep acceptor. The XPS analysis showed the existence of oxygen rich and Zn deficient in the ZnO nanocombs annealed at 600 degrees C. The abnormal temperature dependence of integrated PL intensity was attributed to the abundant surface states.

The effect of CO(2) on the microstructure of L-alpha-phosphatidylcholine (lecithin) reverse micelles was studied. The small-angle X-ray scattering (SAXS) results show that CO(2) could induce a cylindrical-to-spherical micellar shape transformation. Fourier transform infrared (FT-IR) and UV-vis techniques were also utilized to investigate intermolecular interactions and micropolarity in the reverse micelles at different CO(2) pressures. The reduction of the degree of hydrogen bonding between surfactant headgroups and water with added CO(2) was found to be the main reason for the micellar shape transformation. In the absence of CO(2), the hydrogen bonding between water and P=O of lecithin forms a linking bridge in the interfacial layer. Therefore, the free movement of the polar head of lecithin is limited and the cylindrical reverse micelles are formed. Upon adding CO(2) to the reverse micelles, the hydrogen bonds between lecithin and water in reverse micelles are destroyed, which is favorable to forming spherical micelles. Moreover, the CO(2)-combined reverse micelles were utilized in the synthesis of silica particles. Rodlike silica nanoparticles were obtained in the absence of CO(2), and ellipsoidal and spherical mesoporous silica particles were formed in the presence of CO(2). This method of tuning micellar shape has many advantages compared to traditional methods.

This review describes recent advances in the supercritical (SC) CO 2 -continuous microemulsions, compressed CO 2 -expanded water-in-oil microemulsions, and compressed CO 2 -induced water-in-oil microemulsions, and pays more attention to tuning the aggregation behavior of surfactants in liquid solvents using compressed CO 2 . The applications of these microemulsions in synthesis of nanomaterials and chemical reactions are also discussed briefly.

Lecithin is a very useful biosurfactant. In this work, the effects of compressed CO 2 on the critical micelle concentration (cmc) of lecithin in cyclohexane and solubilization of water, lysozyme, and PdCl 2 in the lecithin reverse micelles were studied. The micropolarity and pH value of the polar cores of the reverse micelles with and without CO 2 were also investigated. It was found that CO 2 could reduce the cmc of the micellar solution and enhance the capacity of the reverse micelles to solubilize water, the biomolecule, and the inorganic salt significantly. Moreover, the water pools could not be formed in the reverse micelles in the absence of CO 2 because of the limited amount of water solubilized. However, the water pools could be formed in the presence of CO 2 because large amounts of water could be solubilized. All of these provide more opportunity for effective utilization of this green surfactant. The possible mechanism for tuning the properties of the reverse micelles by CO 2 is discussed.

In this work, a green route to prepare TiO 2 nanotube networks using swim bladder (SB) membrane as a bio-template was reported. In this method, the SB membrane was first dried with CO 2 extraction, which resulted in the fibrous structures of SB membrane. With the CO 2 -dried SB membrane as bio-template, TiO 2 were obtained via the surface sol–gel reaction of titanium isopropoxide on the fibers of SB membrane in supercritical CO 2 , followed by the removal of SB membrane calcined at 600 °C. The resulting TiO 2 was characterized with scanning electron microscopy, transmission electron microscopy and X-ray diffraction. It was indicated that ordered anatase nanotube networks were produced. Compared to the conventional sol–gel method, the protocol adopted in this work could produce TiO 2 nanotubes with regular and ordered structures.

We propose a route to fabricate hollow silica and titanium-containing hollow silica spheres at the interface of supercritical (SC) CO 2 /cetyltrimethyl-ammonium bromide (CTAB) aqueous solution. In this method, tetraethyl orthosilicate (TEOS) and tetrabutyl titanate (TBT) were used as the precursors, SC CO 2 was used as both the solvent for the precursors and as the source of Bronsted acid which can catalyze the hydrolysis reactions. The materials prepared were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), X-ray photoelectron spectra (XPS), IR and UV–vis techniques. It was demonstrated that the diameter and wall thickness of the hollow silica spheres could be changed within the range of nano-scale by varying pressure of CO 2 and the concentration of CTAB, and the diameter and wall thickness decreased with increasing pressure and decreasing CTAB concentration. Increasing concentration of the precursors could increase the size of titanium-containing hollow silica from nano-scale to micron scale. It was also shown that Si atoms were substituted atomically by Ti atoms and there was no bulk TiO 2 in the titanium-containing hollow silica spheres.

The optical properties of poly(3-hexylthiophene) (P3HT), in pristine form or with added anatase titanium dioxide (TiO2) nanoparticles have been investigated, and the interfacial charge transfer between P3HT and TiO2 have been studied by steady-state luminescence spectroscopy analysis. The photoluminescence results revealed that incorporation of TiO2 nanoparticles in concentrations up to 0.3 mM significantly enhanced the luminescence intensity of P3HT when exposing to light of energy higher than TiO2 bandgap. The observed variation suggested an energy transfer from TiO2 nanoparticles to P3HT. Meanwhile, when P3HT/TiO2 composites were exposed to light of energy below TiO2 bandgap, TiO2 nanoparticles gradually quench the fluorescence of P3HT, demonstrating the injection of excited electrons from lowest unoccupied molecular orbit of P3HT to the conduction band of TiO2.

The effect of compressed CO2 on the microenvironment of the two proteins (cytochrome c and RNase A) in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles was investigated using high-pressure steady-state fluorescence and time-resolved fluorescence. It is found that RNase A can shift from the water core to the interface of the reverse micellar cores as CO2 is dissolved, while cytochrome c maintains at the interface of the micellar core. As the pressure reaches to a high enough value, the proteins can be precipitated from the reverse micelle, which has been detected by high-pressure UV–vis technique. The results show that cytochrome c was easier to be precipitated from the reverse micellar solution by CO2 than RNase A. The possible reasons for these behaviors were discussed based on the changes of the microenvironment of the two proteins, which could be tuned by the dissolution of compressed CO2.

In this work, a simple, fast and efficient route is presented for the metal (such as Pt, Rh, etc.) nanocrystal synthesis and deposition on carbon nanotubes (CNTs) in ionic liquids (ILs) via microwave heating. In this method, inorganic salts (such as H2PtCl6 · 4H2O, RhCl3 · 2H2O, etc.) dissolved in ILs, 1,1,3,3-tetramethylguanidinium trifluoroacetate or 1,1,3,3-tetramethylguanidinium lactate, were reduced to metal nanoparticles by glycol with the aid of microwave heating, and the produced metal nanoparticles could be decorated on CNTs in the presence of CNTs in ILs. The resulting nanomaterials were characterized by means of transmission electron microscopy and X-ray diffraction. It was demonstrated that the homogeneously dispersed Pt nanocrystals with the size of 2∼3 nm were obtained using H2PtCl6 · 4H2O as precursor, and they deposited on CNTs with the similar size when CNTs was present in ILs. This technique also can be extended to fabricate other noble metal nanocrystals (including Rh, Au, etc.) and corresponding CNT composites.

In this work, silica nanospheres were prepared in reverse micelles using compressed CO 2 first as a reactant and then as an antisolvent. The transmission electronic micrographs (TEM) show that the silica nanoparticles in the size range of 3–15 nm were obtained, and their size increased with an increase in molar ratio of water to surfactant ( w ) and the decreased pressure. Furthermore, the TiO 2 –SiO 2 core–shell particles were prepared by the reaction of compressed CO 2 with sodium silicate on the surface of TiO 2 nanoparticles in the reverse micelles. The morphologies, phase structure, interfacial interaction and the optical properties of the TiO 2 –SiO 2 core–shell particles were characterized by transmission electronic micrographs (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and UV–vis spectra, respectively.

Ag/TiO2 core-shell nanowires were synthesized via a one-step solution method without using a template. Interestingly, the shell morphologies can be controlled to be smooth or bristled by altering the reaction temperature. Moreover, the TiO2 shell thickness and bristle length can be tuned by changing the AgNO3 concentration. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), energy-dispersive X-ray analysis (EDS), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the resultant Ag/TiO2 core-shell nanowires. Moreover, the absorption peaks of our samples are significantly red-shifted compared with those of the uncoated pure silver nanowires, indicating that interaction between the core and shell occurred. On the basis of the experimental results, we proposed a template-induced Oswald ripening mechanism to explain the formation of the Ag/TiO2 core-shell nanowires.

In this work, a simple and inexpensive route to synthesize porous silica microflowers has been developed. By adding supercritical CO 2 into the sodium silicate aqueous solutions, the porous silica microflowers were obtained. The results of scanning electron microscopy, transmission electron microscopy and nitrogen adsorption isotherms show that through the easy control of CO 2 pressure, the morphologies and porosity properties of the obtained silica can be tuned. During this process, supercritical CO 2 works not only as a reactant but also as a modifier to the morphology and porosity of silica. Moreover, the growth of silica microflowers was investigated by changing the reaction time. The silica microflowers show optical properties in the wavelength range of 340–480 nm.

We report a new route to prepare polyaniline (PANI) microtubes via supercritical (SC) CO2/aqueous interfacial polymerization. The synthesis is based on the well-known chemical oxidative polymerization of aniline in an acidic environment, with ammonium peroxydisufate (APS) as the oxidant, and sodium dodecyl sulfate (SDS) surfactant was used as the template. The main feature of this route is that the monomer (aniline) which is dissolved in SC CO2 phase, slowly polymerized at the interface of SC CO2 and aqueous solution to form the PANI microtubes. The morphologies, phase structure, composition and some properties of PANI microtubes were characterized by TEM, SEM, XRD, IR, XPS UV–vis and SYSTEM DM digital multimeter, respectively.

In this paper, we first report the macroporous polyaniline (PANI) microspheres and Ag/PANI core-shell structure via one-pot redox reaction in ethanol at 250 °C. Morphology of the obtained products was characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A series of comparative experiments reveal that both the reaction temperature and AgNO 3 concentration play an important role in preparing macroporous PANI microspheres. Based on comparative experimental results, the bubble-induced mechanism can account for the formation of the macroporous PANI microspheres with small cavities with the sizes ranging from 10 nm to 300 nm on the exterior surface. The BET surface area of the macroporous PNI measured by N 2 adsorption is 80.45 m 2 /g. Meanwhile, PANI microspheres present a nitrogen isotherm of Type II, according with a macroporous adsorbent. The optical properties of the macroporous PANI microspheres were investigated by Fourier transform infrared (FTIR) and UV–vis absorption spectroscopy, respectively. Moreover, DFT results indicate that the PANI structure is not a linear structure, but a curved structure. In addition, Ag/PANI core-shell particles with a large core of the size of about 200 nm and relative thin shell of the thickness of about 50 nm were obtained, which were characterized with X-ray diffraction (XRD), SEM, TEM, and selected-area electronic diffraction (SAED).

Mesoporous SrCO3 spheres with diameter ranging from 200 to 400 nm were synthesized via refluxing the solution of SrCl2 · 6H2O and sodium hydroxide in 1,1,3,3-tetramethylguanidinium lactate at 140 °C in the presence of CO2. The morphology and structure of the as-prepared products were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Nitrogen sorption measurements revealed that the obtained products exhibited high BET surface area of 69.4 m2 g−1 and average pore size of 5.7 nm with narrow pore size distribution. For comparison, CaCl2 was used to synthesize CaCO3 at the same experimental conditions, resulting in hollow calcite spheres and peanut-like structure calcite whose shell thickness and core diameter were about 100 nm and 200 nm, respectively. The BET surface area of the hollow calcite spheres calculated from N2 adsorption is 17.03 m2 g−1.

Here we report a facile route to synthesize mesoporous Eu 2 O 3 –TiO 2 composites by simultaneous decomposition of europium nitrate hexahydrate and hydrolysis of tetrabutyl titanate in ethanol solution with Pluronic P123 as a pore-directing agent at a relatively low temperature of 120 °C. The as-prepared products were characterized with different techniques, including X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), nitrogen adsorption/desorption analysis, and photoluminescence spectroscopy. TEM and N 2 adsorption/desorption analysis show that the Eu 2 O 3 –TiO 2 composite possesses mesoporous structures. The XRD results demonstrate that the products are amorphous. Besides the emission band of TiO 2 at about 450 nm, the composite exhibits emission bands at 590 and 615 nm that originate from Eu 3+ .

In this work, a route for the synthesis of inorganic/polymer core/shell composite nanoparticles was proposed, which can be called the antisolvent-ultrasound method. Compressed CO 2 was used as antisolvent to precipitate the polymer from its solution dispersed with inorganic nanoparticles, during which ultrasonic irradiation was used to induce the coating of precipitated polymers on the surfaces of the inorganic nanoparticles. TiO 2 /polystyrene (PS) core/shell nanocomposites have been successfully prepared using this method. The transmission electronic micrographs (TEM) of the obtained nanocomposites show that the TiO 2 nanoparticles are coated by the PS shells, of which the thickness can be tuned by the pressure of CO 2 . The phase structure, absorption properties, and thermal stability of the composite were characterized by X-ray diffraction (XRD), UV-vis spectra, and thermogravimetry, respectively. The results of X-ray photoelectron spectra (XPS) indicate the formation of a strong interaction between PS and TiO 2 nanoparticles in the resultant products. This method has some potential advantages for applications and may be easily applied to the preparation of a range of inorganic/polymer core/shell composite nanoparticles.

Well-defined superstructures of rectangular-shaped BaCrO4 and extensive network of BaCrO4 nanoparticles constructed by self-assembly were prepared in cetyltrimethylammonium bromide (CTAB) reverse microemulsions. The effects of aging time and reactant concentrations on the morphology and the self-assemble pattern of the nanostructured BaCrO4 were investigated. TEM combined with the electron diffraction was used to characterize the morphology and the crystal structure of the prepared nanostructured BaCrO4 at different conditions.

Mesoporous silica molecular sieve SBA-15 has been grafted with monolayer and doublelayer of titanium dioxide via surface sol–gel process in supercritical carbon dioxide (SC CO 2 ). The materials were characterized by nitrogen adsorption, X-ray photoelectron, X-ray diffraction (XRD), and Raman spectroscopy. The results suggest that the incorporated titanium dioxide is present mainly as anatase phase. The pore diameter decreases with the modification cycle number, and the titanium dioxide exists as a 5 A thick film chemically anchored on the mesopores of SBA-15.

We report a route to fabricate micropatterned polymer films with micro- or nanometer-scale surface concavities by spreading polymer solutions on a non-solvent surface. The route is simple, versatile, highly efficient, low-cost, and easily accessible. The concavity density of the patterned films is tuned from 106 to 109 features cm–2, and the concavity size is controlled in the range from several micrometers to less than 100 nm, by changing the film-forming parameters including the polymer concentration, the temperature of the non-solvent and the interactions between polymer, solvent, and non-solvent. We further demonstrate that these concavity-patterned films have significantly enhanced hydrophobicity, owing to the existence of the surface concavities, and their hydrophobicity could be controlled by the concavity density. These films have been used as templates to successfully fabricate convex-patterned polymer films, inorganic TiO2 microparticles, and NaCl nanocrystals. Their other potential applications are also discussed.

High-aspect-ratio, single crystal BaMoO 4 nanofibers with diameters of about 30 nm and lengths up to 30 μm were synthesized in cationic cetyltrimethylammonium bromide (CTAB) reverse microemulsions. The effects of different conditions such as the aging time, the molar ratio of water to surfactant ( w ), the reactant and CTAB concentration on the evolution of single crystal BaMoO 4 nanofibers were discussed. Transmission electron microscope (TEM) and electron diffraction were used to characterize the morphology and the crystal structure of the prepared nanostructured BaMoO 4 obtained at different conditions.

In this work, we proposed a facile route to coat europium oxide on the walls of SBA-15. In this method, europium nitrate hexahydrate dissolved in supercritical ethane–ethanol solution was first carried into the channels of SBA-15 at 35 °C at which europium nitrate was thermally stable. Following in situ thermal decomposition of europium nitrate at 120 °C in the supercritical solution, SBA-15/Eu 2 O 3 composites were fabricated. The composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy and energy dispersive analysis of X-ray (EDAX) during the transmission electron spectroscopy (TEM) observation, and N 2 sorption analysis. TEM results indicate Eu 2 O 3 was successfully coated on the walls of SBA-15. From the analyses of XRD and photoluminescence, the as-prepared composites retained the structure of SBA-15, and exhibited the optical properties originated from Eu 2 O 3 .

Nanosized ZnS particles were synthesized in bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles and then recovered by dissolving compressed CO 2 into the micellar solution. The size of the obtained ZnS nanoparticles can be tailored in the range of 1–100 nm by varying the experimental conditions. The particles’ size decreases with increasing pressure of CO 2 . The size of the particles recovered at 308.2 K is smaller than that of the particles recovered at 298.2 K. Stirring of the solution in the recovery process can reduce the particle size effectively. Increase in molar ratio of water to AOT ( w ) results in an increase in the particle size. However, the effect of the concentration of AOT in the micellar solution on the size of the products is very limited.

Fourier transform infrared (FTIR) spectra and hydrogen bonding of acetic acid in CO 2 (1)+ n -pentane (2) mixture were studied at 308.2 K up to 11 MPa. The experiments were conducted in the mixed supercritical (SC) and subcritical fluids near critical region and far from the critical region. The results demonstrated that the frequency of CO stretching vibration of the monomer and dimer, the molar absorptivities of monomer and dimer, and the monomer–dimer equilibrium were very sensitive to pressure in the subcritical fluids and supercritical fluids in the critical region, especially as the pressure approached the phase boundary, while the effect of pressure on these properties outside the critical region was very limited.

A novel method to prepare nanoparticles using reverse micelles of poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) block copolymer surfactant was proposed. The method i...

Synchrotron radiation small-angle X-ray scattering (SAXS) technique was used to quantitatively derive structural information of the Dynol-604 (a surfactant) based water-in-CO2 reverse micelles. By using the Guinier plot (In I(q) vs. q(2)) on the data sets in a defined small q range (0.025 -0.040 Angstrom(-1)), the radii of the reverse micelles at different pressures and loading water were estimated, which were in the range of 73.8 to similar to 78.1 Angstrom. (C) 2002 Elsevier Science B.V. All rights reserved.

A new route to fabricate a ZnS/MCM-41 (a molecular sieve) composite has been proposed. In this method, the ZnS nanoparticles are first synthesized in the reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in isooctane, and then the ZnS nanoparticles are charged into the mesoporous material with the aid of antisolvent CO2. The ZnS/MCM-41 composites obtained are characterized by X-ray diffraction, nitrogen adsorption, transmission electron microscopy, atomic absorption spectrophotometry, UV−vis absorption, thermogravimetry analysis, and photoluminescence. The results confirm the presence of ZnS in the pores of the molecular sieve. This method has some potential advantages in comparison to the conventional methods. We believe that this new method can be used to prepare some other nanoparticle/mesoporous material composites.