Solventless Acid‐Free Synthesis of Mesostructured Titania: Nanovessels for Metal Complexes and Metal Nanoclusters

A new and highly reproducible method to obtain mesostructured titania materials is introduced in this contribution. The mesostructured titania is obtained by employing self‐assembled structures of non‐ionic alkyl‐poly(ethylene oxide) surfactants as templates. The materials are produced without additional solvents such as alcohols, or even water. Only the titanium(IV ) ethoxide and the surfactant (C₁₂EO₁₀) are needed. Water, in the form of that attached to the surfactant and from the atmosphere, induces growth of titania nanoclusters in the synthesis sol. It is indicated that these nanoclusters interact with the surfactant EO‐head groups to form a new titanotropic amphiphile. The new amphiphiles self‐assemble into titanium nanocluster–surfactant hybrid lyotropic phases, which are transformed to the final mesostructured materials by further condensation of the titania network. The titania materials can be obtained also with noble‐metal particles immobilized in the mesostructured framework. It is seen that when different metal salts are used as the metal precursors, different interactions with the titania walls are found. The materials are characterized by X‐ray diffraction (XRD), polarization optical microscopy (POM), transmission electron microscopy (TEM), UV‐vis spectroscopy, and micro‐Raman analysis.     

A Novel Mesoporous CaO‐Loaded In2O3 Material for CO2 Sensing

A mesoporous CaO‐loaded In₂O₃ material (with Ca/In₂O₃ ratios ranging from 2.5 to 8.5 at %) has been synthesized and used as resistive gas sensor for the detection of CO₂. A nanostructured In₂O₃ matrix has been obtained by hard template route from the SBA‐15 silica template. Additive presence does not distort the lattice of In₂O₃, which crystallizes in the Ia3 cubic space group. It has been proved by XRD, HRTEM, Raman and XPS measurements that samples contain not only CaO but also CaCO₃ in calcite phase as a consequence of CaO carbonation. Pure In₂O₃ based sensors are low sensitive to CO₂, whereas those containing the additive show an important response in the 300–5000 ppm range of gas concentrations. As seen by DRIFTS, the electrical response arises from the interaction between CO₃^2– and CO₂, yielding bicarbonates products. The reaction is water‐assisted, so that hydration of the sensing material ensures sensor reliability whilst its dehydration would inhibit sensor response. The use of CaCO₃ instead of CaO does not cause significant differences in electrical and DRIFTS data, which corroborates the important role played by carbonate species in the sensing mechanism.     

Surfactant‐Assisted Synthesis of Alumina with Hierarchical Nanopores

Using surfactant‐assisted synthesis, aluminas with hierarchical nanopores are produced. The hierarchical structures are composed of mesopores of 4 nm diameter, and macropores with diameters of about 300 nm. The structures were found to be stable to the thermal removal of the surfactant. Synthesis factors affecting the appearance of the hierarchically structured alumina material are presented. A potential mechanism for the formation of the uniquely structured aluminas is proposed.     

Template‐Assisted Synthesis of Mesoporous Magnetic Nanocomposite Particles

A new concept is proposed to synthesize mesoporous magnetic nanocomposite particles of great scientific and technological importance. Mesoporous silica coatings were created on micrometer‐sized magnetite (Fe₃O₄) particles using cetyltrimethylammonium chloride micelles as molecular templates. The characterization by transmission electron microscopy (TEM), nitrogen adsorption–desorption, diffuse‐reflectance Fourier‐transform infrared spectroscopy, and zeta‐potential measurements confirmed the deposition of mesoporous silica thin layers on the magnetite particles. The synthesized particles showed a drastic increase in specific surface area with an average pore size of 2.5 nm. The coating material showed a negligible effect on the saturation magnetization of the original particles that were fully protected by silica coatings. The synthesized mesoporous magnetic nanocomposite particles have a wide range of applications in toxin removal, waste remediation, catalysis, reactive sorbents, and biological cell separations.     

Sono‐ and Photochemical Routes for the Formation of Highly Dispersed Gold Nanoclusters in Mesoporous Titania Films

A sono‐ and photochemical approach has been developed to incorporate highly dispersed gold nanoclusters into mesoporous TiO₂ films. The first step involves the sonication of a TiO₂ film immersed in a gold chloride solution. This effectively removes the air trapped in the porous film matrix and drives the gold chloride into the pore channels, leading to a homogeneous adsorption of ionic Au in the TiO₂ mesoporous matrix. The second step takes advantage of the photocatalytic property of TiO₂ to reduce the adsorbed Au ions to Au⁰. As the gold nanoclusters thus produced are stabilized by the TiO₂ mesonetwork, no organic capping molecules are required. Highly dispersed Au/TiO₂ nanoheterojunction arrays can be obtained using this interesting approach.     

Thermally Stable Two‐Dimensional Hexagonal Mesoporous Nanocrystalline Anatase,Meso‐nc‐TiO2: Bulk and Crack‐Free Thin Film Morphologies

Herein a novel synthetic route is described for the production of thermally stable, structurally well‐defined two‐dimensional (2D) hexagonal mesoporous nanocrystalline anatase (meso‐nc‐TiO₂), with a large pore diameter, narrow pore‐size distribution, high surface area, and robust inorganic walls comprised of nanocrystalline anatase. The synthetic approach involves the evaporation‐induced co‐assembly of a non‐ionic amphiphilic triblock‐copolymer template and titanium tetraethoxide, but with a pivotal change in the main solvent of the system, where the commonly used ethanol is replaced with 1‐butanol. This seemingly minor modification in solvent type from ethanol to 1‐butanol turns out to be the key synthetic strategy for achieving a robust, structurally well‐ordered meso‐nc‐TiO₂ material in the form of either thick or thin films. The beneficial “solvent” effect originates from the higher hydrophobicity of 1‐butanol than ethanol, enhancing microphase separation and templating, lower critical micelle concentration of the template in 1‐butanol, and the ability to increase the relative concentration of the inorganic precursor to template in the co‐assembly synthesis. Moreover, thin films with dimensions of several centimeters that are devoid of cracks down to the length scale of the mesostructure itself, having high porosity, well‐defined mesostructural features, and semi‐crystalline pore walls were straightforwardly and reproducibly obtained as a result of the physicochemical property advantages of 1‐butanol over ethanol within our synthesis scheme.     

Battery Performance and Photocatalytic Activity of Mesoporous Anatase TiO2 Nanospheres/Graphene Composites by Template‐Free Self‐Assembly

Nanosized mesoporous anatase TiO₂ particles have important applications in high‐performance lithium ion batteries and efficient photocatalysis. In contrast to the conventional synthesis routes where various soft or hard templates are usually employed, the direct growth of uniform mesoporous anatase TiO₂ nanospheres on graphene sheets by a template‐free self‐assembly process is presented. Compared to the conventional mesoporous anatase particles consisting of polycrystalline TiO₂, the microstructure of obtained mesoporous anatase nanospheres on graphene sheets is single‐crystal‐like. The growth mechanism, lithium ion battery performance, and photocatalytic activity of the resultant mesoporous anatase TiO₂ nanospheres/graphene composites are thoroughly investigated. In comparison to the reference TiO₂, the composite shows substantial improvement in lithium specific capacity from 1 C to 50 C, and photocatalytic removing organic pollutant and hydrogen evolution. More strikingly, the specific capacity of the composite at the rate of 50 C is as high as 97 mA h g^?1, 6 times higher than that of the reference TiO₂.     

Highly Organized Mesoporous TiO2 Films with Controlled Crystallinity: A Li‐Insertion Study

A study of electrochemical Li insertion combined with structural and textural analysis enabled the identification and quantification of individual crystalline and amorphous phases in mesoporous TiO₂ films prepared by the evaporation‐induced self‐assembly procedure. It was found that the properties of the amphiphilic block copolymers used as templates, namely those of a novel poly(ethylene‐co‐butylene)‐b‐poly(ethylene oxide) polymer (KLE) and commercial Pluronic P123 (HO(CH₂CH₂O)₂₀(CH₂CH(CH₃)O)₇₀(CH₂CH₂O)₂₀H), decisively influence the physicochemical properties of the resulting films. The KLE‐templated films possess a 3D cubic mesoporous structure and are practically amorphous when calcined at temperatures below 450 °C, but treatment at 550–700 °C provides a pure‐phase (anatase), fully crystalline material with intact mesoporous architecture. The electrochemically determined fraction of crystalline anatase increases from 85 to 100 % for films calcined at 550 and 700 °C, respectively. In contrast, the films prepared using Pluronic P123, which also show a 3D cubic pore arrangement, exhibit almost 50 % crystallinity even at a calcination temperature of 400 °C, and their transformation into a fully crystalline material is accompanied by collapse of the mesoporous texture. Therefore, our study revealed the significance of using suitable block‐copolymer templates for the generation of mesoporous metal oxide films. Coupling of both electrochemical and X‐ray diffraction methods has shown to be highly advisable for the correct interpretation of structure properties, in particular the crystallinity, of such sol–gel derived films.     

Self‐Organized Nanoporous Anodic Titania Films and Ordered Titania Nanodots/Nanorods on Glass

We report a new method to fabricate self‐organized nanoporous titania films (pore diameter ≈ 30 nm; ≈ 1100 nm thick) and ordered titania nanorod arrays (rod diameter ≈ 30–60 nm; 70–260 nm high) by combined anodizing of superimposed Al/Ti layers sputter‐deposited on glass substrates. The titania nanostructures mimic the ordered nanoporous anodic alumina films via a through‐mask anodization. We propose a new anodizing electrolyte, i.e., a diluted nitric acid solution, for fabricating uniform, self‐organized, ordered nanoporous titania films with parallel cylindrical pores and without any thickness limit. More significantly, the nanoporous titania films contain a small amount of titanium nitride and dissociated nitrogen, and exhibit a moderate transparency and an enhanced absorption throughout the UV and visible light regions of the electromagnetic spectrum. After heating at 600 °C for 2 h, the nanoporous titania films develop a small absorption red‐shift and exhibit high photocatalytic activity under UV illumination.     

Shape Selectivity in Adsorption of n‐ and Iso‐alkanes on a Zeotile‐2 Microporous/Mesoporous Hybrid and Mesoporous MCM‐48

The adsorption of linear and branched C5–C9 alkanes in the temperature range 50–250 °C on mesoporous MCM‐48 material and its microporous/mesoporous variant Zeotile‐2 at low surface coverage is investigated using the pulse chromatographic technique. On MCM‐48, the differences in adsorption between linear and branched alkanes are merely a result of differences in volatility, indicating that the MCM‐48 material does not present shape‐selective adsorption sites. On Zeotile‐2, there is a preferential adsorption of linear over branched alkanes. The difference arises from a difference in adsorption entropy rather than enthalpy. Upon their adsorption on Zeotile‐2 branched alkanes lose relatively more entropy than their linear isomers do. Zeolitic molecular pockets embedded in the walls of the mesoporous Zeotile‐2 impose steric constraints on the bulky isoalkanes. Zeotile‐2 combines adsorption properties from microporous and mesoporous materials. Compared to the nitrogen molecule, linear and branched C5–C9 alkanes are superior probes for investigating micropores and micropockets in hierarchical materials.     

Novel Solid Acid Catalysts: Sulfonic Acid Group‐Functionalized Mesostructured Polymers

Novel solid acid catalysts have been prepared from Fudan University (FDU)‐type mesoporous polymers with the Ia d and P6mm mesostructures through a carefully controlled sulfonation procedure. Various techniques have been adopted to characterize throughout their structures, porosity, acidity as well as the information related to the sulfonic acid groups. The sulfonic acid group‐functionalized mesopolymers prove to be efficient heterogeneous catalysts in the reactions such as liquid‐phase Beckmann rearrangement of cyclohexanone oxime and condensation of ethylene glycol with the aldehydes having different molecular sizes.     

A Unique Disintegration–Reassembly Route to Mesoporous Titania Nanocrystalline Hollow Spheres with Enhanced Photocatalytic Activity

A novel disintegration–reassembly route is reported for the synthesis of mesoporous TiO₂ nanocrystalline hollow spheres with controlled crystallinity and enhanced photocatalytic activity. In this unique synthesis strategy, it is demonstrated that sol–gel‐derived mesoporous TiO₂ colloidal spheres can be disintegrated into discrete small nanoparticles that are uniformly embedded in the polymer (polystyrene, PS) matrix by surface‐induced photocatalytic polymerization. Subsequent reassembly of these TiO₂ nanoparticles can be induced by an annealing process after further coating of a resorcinol–formaldehyde (RF) resin, which forms self‐supported hollow spheres of TiO₂ at the PS/RF interface. The abundant phenolic groups on the RF resin serve as anchoring sites for the TiO₂ nanoparticles, thus enable the reassembly of the TiO₂ nanoparticles and prevent their sintering during the thermal crystallization process. This unique disintegration–reassembly process leads to the formation of self‐supported TiO₂ hollow spheres with relatively large surface area, high crystallinity, and superior photocatalytic activity in dye degradation under UV light irradiation.     

Template‐Synthesized Protein Macroporous Biofilms: Conformational Related Direct Electron Transfer

We report on the synthesis of three‐dimensionally ordered structure (3D) of macroporous cytochrome c (cyt‐c) biofilms by using the inverted colloidal polystyrene crystal template technique and Triton X‐100 as entrapping matrix. Electrochemical impedance spectroscopic (EIS) measurements reveal that the immobilized cyt‐c molecules exhibit fast interfacial electron‐communication rate. We found that the orientation of the cyt‐c molecules entrapped in the 3D macroporous structure was determined by the interfacial electric field. Higher interfacial electric field limits the reorientational flexibility of the entrapped cyt‐c molecules, resulting in lower intermolecular electron‐communication rate constant (k°). Therefore, the highest intermolecular electron‐communication rate constant can only be obtained at potentials approaching to the potential of zero charge of the gold electrode, since k° is mainly determined by the molecular orientation in the biofilm. In addition, the prepared biofilms with enhanced functional density could find potential application in the bioelectronic sensing system.     

Highly Ordered Mesoporous Crystalline MoSe2 Material with Efficient Visible‐Light‐Driven Photocatalytic Activity and Enhanced Lithium Storage Performance

Highly ordered mesoporous crystalline MoSe₂ is synthesized using mesoporous silica SBA‐15 as a hard template via a nanocasting strategy. Selenium powder and phosphomolybdic acid (H₃PMo₁₂O₄₀) are used as Se and Mo sources, respectively. The obtained products have a highly ordered hexagonal mesostructure and a rod‐like particle morphology, analogous to the mother template SBA‐15. The UV‐vis‐NIR spectrum of the material shows a strong light absorption throughout the entire visible wavelength region. The direct bandgap is estimated to be 1.37 eV. The high surface area MoSe₂ mesostructure shows remarkable photocatalytic activity for the degradation of rhodamine B, a model organic dye, in aqueous solution under visible light irradiation. In addition, the synthesized mesoporous MoSe₂ possess a reversible lithium storage capacity of 630 mAh g^?1 for at least 35 cycles without any notable decrease. The rate performance of mesoporous MoSe₂ is much better than that of analogously synthesized mesoporous MoS₂, making it a promising anode for the lithium ion battery.     

Formation of Oxynitride as the Photocatalytic Enhancing Site in Nitrogen‐Doped Titania Nanocatalysts: Comparison to a Commercial Nanopowder

A nitrogen‐doped TiO₂ nanocolloid has been successfully prepared and its properties compared with the commercially available TiO₂ nanomaterial, Degussa P25. Several characterization techniques, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM), Fourier transform infrared (FT‐IR) spectroscopy, Raman scattering, and UV‐visible reflectance spectra, are combined in order to determine the crystal phase and grain size, shape, degree of nitrogen incorporation, and nature of the resultant oxynitride chemical bonding on the surface and in the bulk. The high relative photocatalytic activity of the nitrogen doped‐TiO₂ nanocolloid is evaluated through a study of the decomposition of methylene blue under visible light excitation. The ease and degree of substitutional‐insertional nitrogen doping is held accountable for the significant increase in photocatalytic activity in the porous nanocolloid versus the nitrided commercial nanopowder. It is suggested that the nitrogen incorporation produces an NO bonding region as evidenced by the resulting XPS spectrum.     

Sulfur‐Functionalized Mesoporous Carbon

A simple synthesis route to mesoporous carbons that contain heteroaromatic functionality is described. The sulfur‐functionalized mesoporous carbon (S‐FMC) materials that have been prepared show excellent thermal stability, as well as excellent hydrothermal stability, and stability over a wide range of pH values. These materials also show excellent mercury sorption performance over a broad range of pH, much broader than is possible with thiol‐based functionality or most silica‐based sorbents. The superior performance of these mesoporous heterocarbons as heavy‐metal sorbent material is demonstrated. These materials are shown to be stable at elevated temperatures and extreme pHs, making them ideally suited as a new class of absorbent material.     

Synthesis,Characterization, and Application of Mesoporous Silica Functionalized with Alkyl‐Hydroperoxides

A variety of alkyl hydroperoxides such as tert‐butyl‐, tert‐octyl‐, 1‐cyclopentyl‐, 1‐cyclohexyl‐, 3,4‐disubstituted‐1‐cyclohexyl‐, n‐propyl, and n‐undecyl‐hydroperoxides have been functionalized onto ordered mesoporous silica, SBA‐15, from the corresponding covalently anchored synthons. All the tert‐hydroperoxides are prepared by autoxidation using molecular O₂ and an initiator, whereas other hydroperoxides are obtained by reaction with H₂O₂. For autoxidation, the use of a combination of an azoinitiator (AIBN) and N‐hydroxyphthalimide increased the hydroperoxide yield compared with using the azoinitiator alone. Synthons containing two or more tert‐ and sec‐hydrogens lead to higher peroxide yield compared to synthons with a single reactive site. Oxidation of Si–OH (silanol groups) with acidic H₂O₂ at low temperature produces Si–OOH. Reusability of these alkyl hydroperoxides is carried out by oxidation of alcohols obtained from the corresponding alkyl hydroperoxides using H₂O₂. Both the covalently anchored synthons and the resulting hydroperoxides are thoroughly characterized by powder X‐ray diffraction, ¹³C cross‐polarized magic angle spinning NMR, TG/DTA, Fourier transform IR spectroscopy, sorption, and surface area measurements. The quantification of the amount of alkyl hydroperoxide was carried out by iodometric titration using a thio solution. The hydroperoxides exhibit high activity for the epoxidation of styrene to styrene oxide and exhibit reasonably high efficiency for oxygen transfer.     

Shape‐ and Orientation‐Controlled Gold Nanoparticles Formed within Mesoporous Silica Nanofibers

Mesoporous silica nanofibers with longitudinal pore channels are synthesized in high yields using cetyltrimethylammonium bromide as the structure‐directing agent in hydrobromic acid solutions. These nanofibers are used as templates to prepare gold nanoparticles along the fiber axis. For the gold‐precursor‐loaded nanofibers that are not completely dried, nearly spherical gold nanoparticles are produced by hydrogen reduction. As the reduction temperature is lowered, the size of the gold nanoparticles decreases and the number density greatly increases, resulting in surface plasmon coupling between neighboring gold nanoparticles. For the gold‐precursor‐loaded nanofibers that undergo an additional drying process, ellipsoidal gold nanoparticles are obtained, with their major axes oriented along the direction of the pore channels. The major axes of ellipsoidal gold nanoparticles can be controlled to be oriented either parallel or perpendicular to the fiber axis by use of nanofibers with either longitudinal or circular pore channels, respectively. These gold‐nanoparticle‐embedded nanofibers can be expected to find interesting applications in the area of photonics and optoelectronics.     

Synthesis of Hierarchically Porous Carbon Monoliths with Highly Ordered Microstructure and Their Application in Rechargeable Lithium Batteries with High‐Rate Capability

In this paper, we report on Li storage in hierarchically porous carbon monoliths with a relatively higher graphite‐like ordered carbon structure. Macroscopic carbon monoliths with both mesopores and macropores were successfully prepared by using meso‐/macroporous silica as a template and using mesophase pitch as a precursor. Owing to the high porosity (providing ionic transport channels) and high electronic conductivity (ca. 0.1 S cm^–1), this porous carbon monolith with a mixed conducting 3D network shows a superior high‐rate performance if used as anode material in electrochemical lithium cells. A challenge for future research as to its applicability in batteries is the lowering of the irreversible capacity.     

Polyamidoamine Dendrimers Prepared Inside the Channels of Pore‐Expanded Periodic Mesoporous Silica

Polyamidoamine dendrimers up to the fourth generation have been grown with unprecedentedly high loading within the channels of pore‐expanded (10.6 nm) MCM‐41 silica. In‐depth characterization using nitrogen adsorption, solid‐state NMR, FTIR, thermogravimetry, and elemental analysis showed that the dendrimers grow inside the channels with an average yield better than 99 %. The pore size and structure of the support have been found to be determining factors as to how much dendrimer growth can be achieved.