Europium‐Doped Mesoporous Titania Thin Films: Rare‐Earth Locations and Emission Fluctuations under Illumination

Herein, Eu^III‐doped 3D mesoscopically ordered arrays of mesoporous and nanocrystalline titania are prepared and studied. The rare‐earth‐doped titania thin films—synthesized via evaporation‐induced self‐assembly (EISA)—are characterized by using environmental ellipsoporosimetry, electronic microscopy (i.e. high‐resolution scanning electron microscopy, HR‐SEM, and transmission electron microscopy, HR‐TEM), X‐ray diffraction, and luminescence spectroscopy. Structural characterizations show that high europium‐ion loadings can be incorporated into the titanium‐dioxide walls without destroying the mesoporous arrangement. The luminescence properties of Eu^III are investigated by using steady‐state and time‐resolved spectroscopy via excitation of the Eu^III ions through the titania host. Using Eu^III luminescence as a probe, the europium‐ion sites can be addressed with at least two different environments within the mesoporous framework, namely, a nanocrystalline environment and a glasslike one. Emission fluctuations (⁵D₀→⁷F₂) are observed upon continuous UV excitation in the host matrix. These fluctuations are attributed to charge trapping and appear to be strongly dependent on the amount of europium and the level of crystallinity.     

Stable Ti3+ Defects in Oriented Mesoporous Titania Frameworks for Efficient Photocatalysis

By introducing a compatible reducing agent (2‐ethylimidazole) into a mono‐micelle assembly process, we present a type of ordered mesoporous TiO₂ microspheres that combines radially aligned mesostructure with Ti³⁺ defects in mesoporous frameworks. Such reductant acts as a building block of mesostructured frameworks and reduces Ti⁴⁺ in situ to generate defects during calcination, giving rise to the coexistence of bulk Ti³⁺ defects and an ordered mesostructure. The mesoporous TiO₂ has both excellent mesoporosity (a high surface area of 106 m² g^?1, a mean pore size of 18.4 nm) and stable defects with an extended photoresponse. Such integration of unique mesoscopic architecture and atomic vacancies provide both effective mass transportation and enhanced light utilization, leading to a remarkable increase in H₂ generation rate. A maximum H₂ evolution rate of 19.8 mmol g^?1 h^?1 can be achieved, along with outstanding stability under solar light.     

Rapid Fabrication of Mesoporous Titania Films with Controlled Macroporosity to Improve Photocatalytic Property

Hierarchically porous titania films were fabricated by dual templating using a triblock copolymer such as Pluronic F127 and polystyrene (PS) beads, affording mesoporous films with controlled macroporosity. The presence of the triblock copolymer in the precursor solutions suppressed a regular accumulation of spherical PS beads, and PS‐derived macropores could be dispersed over the whole mesoporous titania film through rapid fabrication by spin‐coating. Some of the macropores were clustered, but the presence of the large spaces was important for keeping the mesostructure after calcination. Photodegradation of methylene blue (MB) was investigated by using the photoactive anatase films. The photodegradation of MB over the porous anatase films was accelerated by effective diffusion of MB molecules in the PS‐derived macropores, but it was important for improving photocatalytic performance to regulate the balance between the effectiveness of the diffusion in the macropores and the decrease of the surface area from the embedded macropores, as well as the reduction in the transparency of the porous films.     

Gold Nanoparticles Supported on Mesoporous Titania Thin Films with High Loading as a CO Oxidation Catalyst

In the present work, 2.4 nm gold nanoparticles (Au NPs) are uniformly dispersed on mesoporous titania thin films which are structurally tuned by controlling the calcination temperature. The gold content of the catalyst is as high as 27.8 wt %. To our knowledge, such a high loading of Au NPs with good dispersity has not been reported until now. Furthermore, the reaction rate of the gold particles is enhanced by one order of magnitude when supported on mesoporous titania compared to non‐porous titania. This significant improvement can be explained by an increase in the diffusivity of the substrate due to the presence of mesopores, the resistance to agglomeration, and improved oxygen activation.     

含 TiO2(B) 介孔氧化钛材料的制备、特性和应用

 综述了近年来本课题组依据材料化学工程研究思想, 对含 TiO2(B)(一种比金红石和锐钛矿相结构更松散的氧化钛晶型) 介孔氧化钛材料在制备、结构和性能方面所取得的研究进展. 该介孔材料由二钛酸钾经水合、离子交换和热处理得到, 具有良好原子尺度晶格匹配界面特征的锐钛矿和 TiO2(B) 核壳结构. 研究表明, 该介孔材料在兼备高比表面积、高晶化孔壁和高热稳定性的同时, 还表现出良好的纳米颗粒担载稳定性, 在光催化、油品加氢精制、药物载体、固体酸催化和电化学电容器等方面已凸显出良好的应用潜力和推广价值. 目前该新型含 TiO2(B) 介孔氧化钛材料已经实现低成本、规模化制备.     

Aqueous‐Phase Synthesis of Mesoporous Zr‐Based MOFs Templated by Amphoteric Surfactants

Zr‐based mesoporous metal–organic frameworks (mesoMOFs) with uniform mesochannels and crystallized microporous framework were constructed in a water‐based system using amphoteric surfactants as templates. Aqueous‐phase synthesis guaranteed the formation of rod‐shaped surfactant micelles. Meanwhile, the carboxylate groups of amphoteric surfactants provided the anchoring to bridge Zr‐oxo clusters and surfactant assemblies. As a result, the directed crystallization of MOFs proceeded around cylindrical micelles and the hierarchical micro‐ and mesostructure was produced. The dimensions of mesopores were easily tailored by changing the alkyl chain length of the applied surfactants. The included surfactant was effectively extracted thanks to the exceptional stability of the obtained Zr‐based mesoMOFs. The almost complete occupation of the mesopore by cytochrome c exemplifies the accessibility of the mesochannels, suggesting the potential applications of the obtained mesoMOFs with bulky molecules.     

Mesoporous Titania Thin Film with Highly Ordered and Fully Accessible Vertical Pores and Crystalline Walls

We report the preparation of mesoporous titania thin films with the R m pore structure derived from the Im m self‐assembled ordering of the titania species and an EO₁₀₆PO₇₀EO₁₀₆ triblock copolymer. The films were spin‐cast and then aged at 18 °C at a relative humidity of 70 %, which led to the orientation of the Im m structure with the [111] direction perpendicular to the substrates. The [111] body‐diagonal channels became vertical channels upon calcination at 400 °C, thus leading to thin films with vertical channels. The pores are ordered over a large area of up to 1 μm². The titania films can be formed on various types of substrates. By using a titania film formed on a Pt‐coated Si wafer as a template, we produced by an electrochemical‐deposition technique arrays of gold nanowires, whose morphology suggests that most of the pores of the titania thin films are accessible. The pore structure of vertical channels is stable up to 600 °C, at which temperature the wall materials crystallize into anatase.     

Synthesis of Mesoporous Transition‐Metal Phosphates by Polymeric Micelle Assembly

Mesoporous iron phosphate (FePO₄) was synthesized through assembly of polymeric micelles made of asymmetric triblock co‐polymer (polystyrene‐b‐poly‐2‐vinylpyridine‐b‐ethylene oxide; PS‐PVP‐PEO). The phosphoric acid solution stimulates the formation of micelles with core–shell‐corona architecture. The negatively charged PO₄^3? ions dissolved in the solution strongly interact with the positively charged PVP⁺ units through an electrostatic attraction. Also, the presence of PO₄^3? ions realizes a bridge between the micelle surface and the metal ions. The removal of polymeric template forms the robust framework of iron phosphate with 30 nm pore diameter and 15 nm wall thickness. Our method is applicable to other mesoporous metal phosphates by changing metal sources. The obtained materials were fully characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), N₂ adsorption–desorption, Raman spectroscope, and other techniques.     

Structural Study of Mesoporous Titania Prepared from Titanium Alkoxide and Carboxylic Acids

Mesoporous titania with regulated pore size as well as high specific surface area was prepared from titanium alkoxide and various carboxylic acids with different alkyl-chain length [CH₃(CH₂) _n COOH : n = 0–20]. Although the pore size and pore volume of titania changed slightly at n < 10, they increased with increasing the alkyl-chain length of carboxylic acid at n 10. Each carboxylic acid forms a complex with titanium alkoxide in an organic-inorganic precursor, while the precursor prepared by using carboxylic acid with n 10 consists of a lamella-type mesophase. The interplanar distance of the lamella structure increases with increasing the alkyl-chain length of carboxylic acid. During calcination, the lamella structure collapses together with the combustion of organic moieties and titania particles crystallized to anatase aggregate to provide pores. Although carboxylic acid does not act as a true template, the formation of the lamella-type mesophase in the precursor plays an important role in controlling the pore size of titania.     

Smart Soft‐Templating Synthesis of Hollow Mesoporous Bioactive Glass Spheres

Hollow bioactive glass spheres with mesoporous shells were prepared by using dual soft templates, a diblock co‐polymer poly(styrene‐b‐acrylic acid) (PS‐b‐PAA) and a cationic surfactant cetyltrimethylammonium bromide (CTAB). Hollow mesoporous bioactive glass (HMBG) spheres comprise the large hollow interior with vertical mesochannels in shell, which realize large uptake of drugs and their sustained release. The formation of hydroxyapatite layer on the surface of HMBG particles shows the clear evidence for promising application in bone regeneration.     

A Single‐Step Synthesis of Electroactive Mesoporous ProDOT‐Silica Structures

The single‐step preparation of highly ordered mesoporous silica hybrid nanocomposites with conjugated polymers was explored using a novel cationic 3,4‐propylenedioxythiophene (ProDOT) surfactant (PrS). The method does not require high‐temperature calcination or a washing procedure. The combination of self‐assembly of the silica surfactant and in situ polymerization of the ProDOT tail is responsible for creation of the mesoporosity with ultralarge pores, large pore volume, and electroactivity. As this novel material exhibits excellent textural parameters together with electrical conductivity, we believe that this could find potential applications in various fields. This novel concept of creating mesoporosity without a calcination process is a significant breakthrough in the field of mesoporous materials and the method can be further generalized as a rational preparation of various mesoporous hybrid materials having different structures and pore diameters.     

Spiky Mesoporous Anatase Titania Beads: A Metastable Ammonium Titanate‐Mediated Synthesis

A complex titania nanostructure of monodisperse spiky mesoporous anatase beads composed of anatase nanocrystals with diameters of less than 15 nm in the core and much larger hollow‐cone shaped spikes on the surface was fabricated using a facile solvothermal process in the presence of ammonia. This proceeded through a controllable phase transformation from an amorphous titania to a metastable amorphous titania/ammonium titanate core‐shell structure then finally to anatase titania. The size of the spiky anatase nanostructures can be increased from approximately 55×100 nm to 160×410 nm (square edge×length) by increasing the ammonia concentration used in the solvothermal treatment step from 2.2 to 17.4 wt. %. Such hollow‐cone shaped nanostructures, as revealed by HRTEM characterization, are single crystals elongated along the c axis of the tetragonal anatase titania. The resultant spiky titania beads have high surface areas of up to 112 m²g^?1 and pore diameters and pore volumes that vary depending on the ammonia concentration and solvothermal treatment time. The morphological evolution and crystallization process of the spiky titania beads was investigated using SEM and XRD techniques. A metastable amorphous titania/ammonium titanate core‐shell structure evolved from the smooth amorphous precursor beads producing a “fluffy” titanate intermediate, on further heating the final spiky mesoporous titania beads were clearly observed. This titanate‐phase‐mediated approach allows control over the size of the nanocrystals in the core of the bead, as well as the anatase spikes on the surface, and thereby, tuning of the surface area and porosity of the resultant products. The spiky mesoporous titania beads have been used to prepare working electrodes for dye‐sensitized solar cells achieving a solar to electric power conversion efficiency of 10.30 %, indicating their potential for application in the photovoltaic field. Such complex titania nanostructures would have a number of other possible applications, such as photocatalysis, lithium ion batteries, and catalysis.     

Synthesis of Continuous Mesoporous Alumina Films with Large‐Sized Cage‐Type Mesopores by Using Diblock Copolymers

Mesoporous alumina films with large‐sized cage‐type mesopores were prepared by using commercially available diblock copolymer (PS‐b‐PEO) and economic inorganic salt (AlCl₃) as aluminum source. The obtained mesopore sizes drastically expand from 35 nm to 80 nm when the amount of ethanol in the precursor solutions were controlled. More interestingly, under an optimized amount of ethanol as co‐solvent, there was no significant change of micelle morphology on the substrate, even though the relative amount of PS‐b‐PEO to alumina source was dramatically varied. When the amount of alumina precursor was decreased, the pore walls gradually became thinner, thereby improving pore connectivity. The ordered mesoporous alumina films obtained in this study exhibit high thermal stability up to 1000 °C, and their frameworks are successfully crystallized to γ‐alumina phase. This technique could also be applicable for creating other metal oxide thin films with large mesopores.     

Easy and General Synthesis of Large‐Sized Mesoporous Rare‐Earth Oxide Thin Films by ′Micelle Assembly′

Large‐sized (ca. 40 nm) mesoporous Er₂O₃ thin films are synthesized by using a triblock copolymer poly(styrene‐b‐2‐vinyl pyridine‐b‐ethylene oxide) (PS‐b‐P2VP‐b‐PEO) as a pore directing agent. Each block makes different contributions and the molar ratio of PVP/Er³⁺ is crucial to guide the resultant mesoporous structure. An easy and general method is proposed and used to prepare a series of mesoporous rare‐earth oxide (Sm₂O₃, Dy₂O₃, Tb₂O₃, Ho₂O₃, Yb₂O₃, and Lu₂O₃) thin films with potential uses in electronics and optical devices.     

Low‐Temperature Route to Crystalline Titania Network Structures in Thin Films

A low temperature route to crystalline titania nanostructures in thin films is presented. The synthesis is performed by the combination of sol‐gel processes, using a novel precursor for this kind of application, an ethylene glycol‐modified titanate (EGMT), and the structure templating by micro‐phase separation of a di‐block copolymer. Different temperatures around 100 °C are investigated. The nanostructure morphology is examined with scanning electron microscopy, whereas the crystal structure and thin film compositions are examined by scattering methods. Optoelectronic measurements reveal the band‐gap energies and sub‐band states of the titania films. An optimum titania thin film is created at temperatures not higher than 90 °C, regarding sponge‐like morphology with pore sizes of 25–30 nm, porosity of up to 71 % near the sample surface, and crystallinity of titania in the rutile phase. The low temperature during synthesis is of high importance for photovoltaic applications and renders the resulting titania films interesting for future energy solutions.     

Effects of Template Contents on the Physicochemical Sorption Properties of Zr—Incorporated Mesoporous Titania Materials

Zr-Incorporated mesoporous titania materials were prepared via nonsurfactant templated sol-gel process of zirconium(IV) butoxide(ZBT) and titanium(IV) butoxide(TBT) in the presence of urea molecules as template or pore forming agent.The effcets of template contents on the pore parameters of the materials synthesized with fixed Zr incorporation contents were investigated by mitrogen adsorption-desrption measurements,powder X-ray diffraction(XRD) study and transmission electron microscopy(TEM).The changes of template contents play significant roles on the pore parameters at low incorporsation content of Zr.The pore diameters display a clear increase tendency with the increase of template contents.When high Zr incorporation content is used,the template contents have less effect on the pore diameters that almost keep unchanged with the increase of template contents.All the materials possess type IV isotherms with H2 hysteresis loops suggesting the formation of mesophase.The materials with low Zr incorporation content have anatase structures；however,it can not be found in the materials with high Zr incorporation content.TEM images show that some accumulated inter-particulate pores and welldistributed worm-like pores are present in the Zr-incorporated materials.     

Tunable‐Sized Polymeric Micelles and Their Assembly for the Preparation of Large Mesoporous Platinum Nanoparticles

Platinum nanoparticles with continuously tunable mesoporous structures were prepared by a simple, one‐step polymeric approach. By virtue of their large pore size, these structures have a high surface area that is accessible to reagents. In the synthetic method, variation of the solvent composition plays an essential role in the systematic control of pore size and particle shape. The mesoporous Pt catalyst exhibited superior electrocatalytic activity for the methanol oxidation reaction compared to commercially available Pt catalysts. This polymeric‐micelle approach provides an additional design concept for the creation of next generation of metallic catalysts.     

Synthesis of Nitrogen‐Doped Mesoporous Carbon Spheres with Extra‐Large Pores through Assembly of Diblock Copolymer Micelles

The synthesis of highly nitrogen‐doped mesoporous carbon spheres (NMCS) is reported. The large pores of the NMCS were obtained through self‐polymerization of dopamine (DA) and spontaneous co‐assembly of diblock copolymer micelles. The resultant narrowly dispersed NMCS possess large mesopores (ca. 16 nm) and small particle sizes (ca. 200 nm). The large pores and small dimensions of the N‐heteroatom‐doped carbon spheres contribute to the mass transportation by reducing and smoothing the diffusion pathways, leading to high electrocatalytic activity.