TiO2介孔材料合成及应用

TiO2介孔材料因其在光催化、催化剂载体、传感器、电化学器件等方面具有种种潜在的用途而备受关注，已经成为材料科学一个崭新的研究方向。综述了介孔TiO2的合成方法及应用等方面的研究成果。     

New families of mesoporous materials

Abstract

Mesoporous materials have been paid much attention in both scientific researches and practical applications. In this review, we focus on recent developments on preparation and functionalization of new families of mesoporous materials, especially non-siliceous mesoporous materials invented in our research group. Replica synthesis is known as the method to synthesize mesoporous materials composed of various elements using originally prepared mesoporous replica. This strategy has been applied for the syntheses of novel mesoporous materials such as carbon nanocage and mesoporous carbon nitride. Carbon nanocage has a cage-type structure with huge surface area and pore volume, which exhibits superior capabilities for biomolecular adsorption. Mesoporous carbon nitride was synthesized, for first time, by using mixed material source of carbon and nitrogen simultaneously. As a totally new strategy for synthesis of mesoporous materials, the elemental substitution method has been recently proposed by us. Direct substitution of component elements in original mesoporous materials, with maintaining structural regularity, provided novel mesoporous materials. According to this synthetic strategy, mesoporous boron nitride and mesoporous boron carbon nitride have been successfully prepared, for first time. In addition to these material inventions, hybridization of high functional materials, such as biomaterials, to mesoporous structure has been also developed. Especially, immobilization of proteins in mesopores was systematically researched, and preparation of peptidehybridized mesoporous silica was demonstrated. These new families of mesoporous materials introduced in this review would have high potentials in future practical applications in wide ranges from electronics and photonics to environmental and medical uses.     

Mesoporous structures confined in anodic alumina membranes

The synthesis of nanoporous membranes based on different concepts and materials is a field of active research. This review focuses on the synthesis strategies, mesophase evolution mechanisms and potential applications of mesoporous materials confined within anodic alumina membranes (AAM). Following a rapid evolution of synthetic techniques, a significant number of different mesoporous materials (e.g., silica, titania, and carbon) with highly regular structures can now be prepared within these membranes. In recent years, efforts have also been made to understand the formation mechanisms of these hierarchical mesophases. The resulting organized nanoporous membranes open up a wide range of potential applications in fields such as templating oriented nanowires and controlled separation and release of molecules. For example, while various synthesis strategies can be used for the preparation of membrane-embedded nanowires, the latter can also be obtained as isolated objects after dissolution of the alumina host matrix. The review also discusses issues such as control of structural defects or integrity of interfaces that should be addressed in future research in order to fully exploit the potential of these hierarchical mesoporous channel structures.     

New families of mesoporous materials

Mesoporous materials have been paid much attention in both scientific researches and practical applications. In this review, we focus on recent developments on preparation and functionalization of new families of mesoporous materials, especially non-siliceous mesoporous materials invented in our research group. Replica synthesis is known as the method to synthesize mesoporous materials composed of various elements using originally prepared mesoporous replica. This strategy has been applied for the syntheses of novel mesoporous materials such as carbon nanocage and mesoporous carbon nitride. Carbon nanocage has a cage-type structure with huge surface area and pore volume, which exhibits superior capabilities for biomolecular adsorption. Mesoporous carbon nitride was synthesized, for first time, by using mixed material source of carbon and nitrogen simultaneously. As a totally new strategy for synthesis of mesoporous materials, the elemental substitution method has been recently proposed by us. Direct substitution of component elements in original mesoporous materials, with maintaining structural regularity, provided novel mesoporous materials. According to this synthetic strategy, mesoporous boron nitride and mesoporous boron carbon nitride have been successfully prepared, for first time. In addition to these material inventions, hybridization of high functional materials, such as biomaterials, to mesoporous structure has been also developed. Especially, immobilization of proteins in mesopores was systematically researched, and preparation of peptide-hybridized mesoporous silica was demonstrated. These new families of mesoporous materials introduced in this review would have high potentials in future practical applications in wide ranges from electronics and photonics to environmental and medical uses.     

Critical effect of aging condition on mesostructural ordering in mesoporous titania thin film

Here we demonstrate facile synthesis method for formation of highly ordered mesoporous cubic Im-3 m titania thin film. The mesostructural ordering is strongly dependent on the aging condition after the spin-coating. The aging condition under low temperature and low humidity is found as an optimum condition for achieving highly ordered mesostructure in titania thin films. The effects of other important synthetic parameters, such as pH of the precursor solutions and aging periods, on the mesostructural ordering are carefully examined. After the calcination, continuous mesoporous films with partially crystallized frameworks are formed without any cracks. The mesostructure of the calcined films is formed by thermal shrinkage of the original Im-3 m mesostructure. The mesostructural change in the films calcined at various temperatures are studied by using the grazing-incidence small-angle X-ray scattering (GI-SAXS). The GI-SAXS patterns show the strong shrinkage along the perpendicular direction to the substrate by increasing the calcination temperature.     

Chemistry of Mesoporous Organosilica in Nanotechnology: Molecularly Organic–Inorganic Hybridization into Frameworks

Organic–inorganic hybrid materials aiming to combine the individual advantages of organic and inorganic components while overcoming their intrinsic drawbacks have shown great potential for future applications in broad fields. In particular, the integration of functional organic fragments into the framework of mesoporous silica to fabricate mesoporous organosilica materials has attracted great attention in the scientific community for decades. The development of such mesoporous organosilica materials has shifted from bulk materials to nanosized mesoporous organosilica nanoparticles (designated as MONs, in comparison with traditional mesoporous silica nanoparticles (MSNs)) and corresponding applications in nanoscience and nanotechnology. In this comprehensive review, the state‐of‐art progress of this important hybrid nanomaterial family is summarized, focusing on the structure/composition–performance relationship of MONs of well‐defined morphology, nanostructure, and nanoparticulate dimension. The synthetic strategies and the corresponding mechanisms for the design and construction of MONs with varied morphologies, compositions, nanostructures, and functionalities are overviewed initially. Then, the following part specifically concentrates on their broad spectrum of applications in nanotechnology, mainly in nanomedicine, nanocatalysis, and nanofabrication. Finally, some critical issues, presenting challenges and the future development of MONs regarding the rational synthesis and applications in nanotechnology are summarized and discussed. It is highly expected that such a unique molecularly organic–inorganic nanohybrid family will find practical applications in nanotechnology, and promote the advances of this discipline regarding hybrid chemistry and materials.     

Host–guest chemistry of mesoporous silicas: precise design of location,density and orientation of molecular guests in mesopores

Abstract

Mesoporous solids, which were prepared from inorganic-surfactant mesostructured materials, have been investigated due to their very large surface area and high porosity, pore size uniformity and variation, periodic pore arrangement and possible pore surface modification. Morphosyntheses from macroscopic morphologies such as bulk monolith and films, to nanoscopic ones, nanoparticles and their stable suspension, make mesoporous materials more attractive for applications and detailed characterization. This class of materials has been studied for such applications as adsorbents and catalysts, and later on, for optical, electronic, environmental and bio-related ones. This review summarizes the studies on the chemistry of mesoporous silica and functional guest species (host–guest chemistry) to highlight the present status and future applications of the host–guest hybrids.     

Synthesis and characterization of surface-modified and organic-functionalized MCM-41 type ordered mesoporous materials

A new and efficient method for the preparation of MCM-41 type ordered mesoporous phases using phosphate as promoter under reflux conditions is reported. The various mesoporous materials studied were: silica (Si-MCM-41), alumino-silicate (Al-MCM-41), and titanium-silicate (Ti-MCM-41). Our concept of promoter-assisted synthesis of zeolites and related microporous materials was found to be applicable in the synthesis of ordered mesoporous materials as well. The addition of small catalytic quantity of phosphate ions (PO ₄ ³⁻ ), used as promoters, significantly reduced the synthesis time (by a factor of 3–4) of all these mesoporous materials. The synthesis of new MCM-41 type organic-inorganic composite materials with unique properties is also reported.     

Highly-ordered mesoporous titania thin films prepared via surfactant assembly on conductive indium-tin-oxide/glass substrate and its optical properties

Highly ordered mesoporous titanium dioxide (titania, TiO₂) thin films on indium-tin-oxide (ITO) coated glass were prepared via a Pluronic (P123) block copolymer template and a hydrophilic TiO₂ buffer layer. The contraction of the 3D hexagonal array of P123 micelles upon calcination merges the titania domains on the TiO₂ buffer layer to form mesoporous films with a mesochannel diameter of approximately 10 nm and a pore-to-pore distance of 10 nm. The mesoporous titania films on TiO₂-buffered ITO/glass featured an inverse mesospace with a hexagonally-ordered structure, whereas the films formed without a TiO₂ buffer layer had a disordered microstructure with submicron cracks because of non-uniform water condensation on the hydrophobic ITO/glass surface. The density of the mesoporous film was 83% that of a bulk TiO₂ film. The optical band gap of the mesoporous titania thin film was approximately 3.4 eV, larger than that for nonporous anatase TiO₂ (~ 3.2 eV), suggesting that the nanoscopic grain size leads to an increase in the band gap due to weak quantum confinement effects. The ability to form highly-ordered mesoporous titania films on electrically conductive and transparent substrates offers the potential for facile fabrication of high surface area semiconductive films with small diffusion lengths for optoelectronics applications.     

Synthesis of mesoporous titania nanoparticles with anatase frameworks and investigation of their photocatalytic performance

In this research paper, we synthesize various types of mesoporous titania nanoparticles (MTNs) with suitable surface area and pore size while creating anatase frameworks by applying hydrothermal treatment or calcination at different temperatures. Wide-angle XRD patterns and N2 adsorption-desorption isotherms reveal that the MTNs with crystallized anatase frameworks can be synthesized after an optimized hydrothermal treatment. In contrast, calcination of MTNs at high temperature caused the collapse of mesoporous structure, resulted in drastic reduction of the surface area of the MTNs. In addition, we investigate the photocatalytic activity of the prepared MTNs by measuring the degradation of methylene blue (MB). The results show that the reaction rates of the photocatalytic MB decomposition strongly depend on the degree of crystallinity in the MTNs frameworks and on the surface area of MTNs.     

Template free synthesis of locally-ordered mesoporous titania and its application in dye-sensitized solar cells

A simple template-free synthesis of unique mesoporous titania materials is reported. The synthesis presented is a good, easy and inexpensive method to obtain both ordered and disordered mesoporous titania with tunable and well defined physicochemical properties such us surface area, porosity and crystallinity. The locally-ordered obtained titania was applied as electrode material in dye-sensitized solar cells. The materials prepared were characterized with both wide and small angle XRD, nitrogen adsorption–desorption isotherms, diffuse reflectance UV-Vis, TEM, HRTEM, FT-IR, TGA and DSC measurements. The presented materials showed good activity in photon-to-current conversion process, with overall photoelectric conversion efficiencies reaching up to 5% with fill factors around 60%.     

有序介孔材料的合成及机理

有序介孔材料作为一种新型的纳米结构材料，近年来已成为跨学科的国际研究热点之一。综述了有序介孔材料的合成及其机理，指出有序介孔材料在分离、催化、纳米技术等领域的潜在应用价值。     

Deformation of Mesoporous Titania Nanostructures in Contact with D2O Vapor

For many applications, mesoporous titania nanostructures are exposed to water or need to be backfilled via infiltration with an aqueous solution, which can cause deformations of the nanostructure by capillary forces. In this work, the degree of deformation caused by water infiltration in two types of mesoporous, nanostructured titania films exposed to water vapor is compared. The different types of nanostructured titania films are prepared via a polymer template assisted sol–gel synthesis in conjunction with a polymer‐template removal at high‐temperatures under ambient conditions versus nitrogen atmosphere. Information about surface and inner morphology is extracted by scanning electron microscopy and grazing incidence small‐angle neutron scattering (GISANS) measurements, respectively. Furthermore, complementary information on thin film composition and porosity are probed via X‐ray reflectivity. The backfilling induced deformation of near surface structures and structures inside the mesoporous titania films is determined by GISANS before and after D₂O infiltration. The respective atmosphere used for template removal influences the details of the titania nanostructure and strongly impacts the degree of water induced deformation. Drying of the films shows reversibility of the deformation.     

Ordered Mesoporous Carbons

Ordered mesoporous carbons have recently been synthesized using ordered mesoporous silica templates. The synthesis procedure involves infiltration of the pores of the template with appropriate carbon precursor, its carbonization, and subsequent template removal. The template needs to exhibit three‐dimensional pore structure in order to be suitable for the ordered mesoporous carbon synthesis, otherwise disordered microporous carbon is formed. MCM‐48, SBA‐1, and SBA‐15 silicas were successfully used to synthesize carbons with cubic or hexagonal frameworks, narrow mesopore size distributions, high nitrogen Brunauer–Emmett–Teller (BET) specific surface areas (up to 1800 m² g^–1), and large pore volumes. Ordered mesoporous carbons are promising in many applications, including adsorption of large molecules, chromatography, and manufacturing of electrochemical double‐layer capacitors.     

Oxide-based inorganic/organic and nanoporous spherical particles: synthesis and functional properties

Abstract

This paper reviews the recent progress in the preparation of oxide-based and heteroatom-doped particles. Surfactant-templated oxide particles, e.g. silica and titania, are possible candidates for various potential applications such as adsorbents, photocatalysts, and optoelectronic and biological materials. We highlight nanoporous oxides of one element, such as silicon or titanium, and those containing multiple elements, which exhibit properties that are not achieved with individual components. Although the multicomponent nanoporous oxides possess a number of attractive functions, the origin of their properties is hard to determine due to compositional/structural complexity. Particles with a well-defined size and shape are keys for a quantitative and detailed discussion on the unique complex properties of the particles. From this viewpoint, we review the synthesis techniques of the oxide particles, which are functionalized with organic molecules or doped with heteroatoms, the physicochemical properties of the particles and the possibilities for their photofunctional applications as complex systems.     

Synthesis and Characterization of Mesoporous Titania Particles and Thin Films

Well-organized mesoporous titania particles and thin films were successfully synthesized by using tetrabutyl titanate as the inorganic precursor and triblock copolymer （Pluronic P123） as the template via evaporationinduced self-assembly process. The resulting materials were characterized by high resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）. Fourier-transform infrared spectroscopy （FT-IR）,Brunauer-Emmett-Teller （BET） and atomic force microscopy （AFM）. Macro shape of mesoporous titania would greatly influence the mesostructure of materials, and the probable reasons were also discussed.     

Dispersion and surface functionalization of oxide nanoparticles for transparent photocatalytic and UV-protecting coatings and sunscreens

Abstract

This review describes recent efforts on the synthesis, dispersion and surface functionalization of the three dominating oxide nanoparticles used for photocatalytic, UV-blocking and sunscreen applications: titania, zinc oxide, and ceria. The gas phase and liquid phase synthesis is described briefly and examples are given of how weakly aggregated photocatalytic or UV-absorbing oxide nanoparticles with different composition, morphology and size can be generated. The principles of deagglomeration are reviewed and the specific challenges for nanoparticles highlighted. The stabilization of oxide nanoparticles in both aqueous and non-aqueous media requires a good understanding of the magnitude of the interparticle forces and the surface chemistry of the materials. Quantitative estimates of the Hamaker constants in various media and measurements of the isoelectric points for the different oxide nanoparticles are presented together with an overview of different additives used to prepare stable dispersions. The structural and chemical requirements and the various routes to produce transparent photocatalytic and nanoparticle-based UV-protecting coatings, and UV-blocking sunscreens are described and discussed.     

Bio-inspired synthesis of mesoporous sílicas using large molecular weight poly-l-lysine at neutral pH

Among the various types of amorphous silica-based materials, those that have mesopores (pore widths between 2 and 50 nm) constitute an important group. Silica mesoporous materials have been considered in fields such as catalysis, adsorption, sensing, and electronics or, more recently in drug delivery. The synthesis of silica mesoporous materials usually involves corrosive reaction media and high temperatures. Nevertheless, some living organisms such as diatoms or sponges produce silica in non-corrosive environments and at ambient temperatures. Important progress has been achieved in the synthesis of silica-based materials by biomimetic or bio-inspired methodologies, but the number of studies that use biomolecules and address specifically the preparation of mesoporous materials is reduced. We report in this work, to our knowledge for the first time, a methodology to obtain mesoporous silicas that involves, simultaneously, a biomolecule (poly-l-lysine) and neutral pH. The prepared materials have pores with widths between 2 and 8 nm and specific surface areas between 232 and 616 m² g^?1.     

介孔氧化硅材料的研究进展

介孔氧化硅材料自1992年首次会成以来,已经成为众多研究领域的一个研究热点．本文综述了介孔氧化硅的合成及分类、合成机理、影响孔径尺寸的因素及研究应用进展状况．介孔氧化硅材料可能在催化及纳米材料等领域具有广泛的应用前景．     

Recent Progress in the Synthesis of Porous Carbon Materials

In this review, the progress made in the last ten years concerning the synthesis of porous carbon materials is summarized. Porous carbon materials with various pore sizes and pore structures have been synthesized using several different routes. Microporous activated carbons have been synthesized through the activation process. Ordered microporous carbon materials have been synthesized using zeolites as templates. Mesoporous carbons with a disordered pore structure have been synthesized using various methods, including catalytic activation using metal species, carbonization of polymer/polymer blends, carbonization of organic aerogels, and template synthesis using silica nanoparticles. Ordered mesoporous carbons with various pore structures have been synthesized using mesoporous silica materials such as MCM‐48, HMS, SBA‐15, MCF, and MSU‐X as templates. Ordered mesoporous carbons with graphitic pore walls have been synthesized using soft‐carbon sources that can be converted to highly ordered graphite at high temperature. Hierarchically ordered mesoporous carbon materials have been synthesized using various designed silica templates. Some of these mesoporous carbon materials have successfully been used as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for enzyme immobilization. Ordered macroporous carbon materials have been synthesized using colloidal crystals as templates. One‐dimensional carbon nanostructured materials have been fabricated using anodic aluminum oxide (AAO) as a template.