利用线性酚醛树脂制备有序介孔碳

三嵌段共聚物F127为模板剂,线性酚醛树脂为碳前驱体,采用溶剂挥发诱导有机-有机自组装法(EI-SA)制备了具有二维六方结构的有序介孔碳。利用FT-IR、XRD、TEM、N2吸附/脱附等方法对有序介孔碳的结构进行了表征,研究了不同焙烧温度和模板剂用量对有序介孔碳结构的影响。结果表明,当模板剂的用量一定时,有序介孔碳的孔径、孔容和孔壁厚度都随着焙烧温度的升高而降低,但比表面积却随着微孔含量的增加而增大。随着模板剂用量的增加,介孔碳的有序性降低。有序介孔碳PF-2-500的比表面积、孔径、孔容、孔壁厚度和微孔比表面积比分别为583.82m2/g、3.05nm、0.31cm3/g、3.40nm和361.18m2/g,而有序介孔碳PF-1-500的比表面积、孔径和孔容相对于PF-2-500有所提高,分别为647.79m2/g、3.44nm和0.41cm3/g,但微孔比表面积和孔壁厚度分别降低为309.46m2/g和3.35nm。     

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.     

有机模板剂对合成纳米TiO_2结构影响规律的研究

以钛酸四丁酯为前驱体,乙醇为溶剂,采用溶胶-凝胶法制备纳米二氧化钛。选择P123作为模板剂考察了不同n(P123)/n(Ti)对TiO2织构性能以及晶粒尺寸的影响。采用碳化的方法使有机物在氩气气氛中高温焙烧后形成的炭层对孔道起支撑作用,防止孔道的塌陷并得到高度晶化的二氧化钛,同时考察了碳化温度和不同模板剂对二氧化钛织构性能的影响规律。结合X射线衍射(XRD)、N2吸附脱附、热分析(TG/DSC)表征手段得到以下结论:物质的量比在0～0.030范围内,P123含量的增加有利于晶粒尺寸的减小和比表面积的增大;碳化过程提高了TiO2的热稳定性,随着碳化温度的升高TiO2比表面积变化不大;P123、PEG2000、CTAB 3种模板剂中P123得到的样品性能最好。     

Co-continuous monolithic titania prepared by organic polymer monolith as pore template

We achieved preparation of co-continuous titania based monolithic materials using several organic polymer monoliths as pore templates. Firstly, the organic polymer monoliths that had well controlled structures were prepared, and filled the pores of polymer monolith with tetra-n-butyl titanate (titan monomer). The following hydrolysis of the titan monomer resulted in titanium dioxide. The polymer monolith was removed by calcination at elevated temperature. We carefully studied the utility of polymer monolithic template, filling method of the titan monomer, and calcination conditions to realize co-continuous titania monolith. In addition, by the change of domain size (size of a skeleton + size of through a pore) of template, we were able to control domain size of the resulting titania monoliths.     

A two-step sol-gel method for synthesis of nanoporous TiO2

This article reports a study of the effects of synthesis parameters on the preparation and formation of mesoporous titania nanopowders by employing a two-step sol-gel method. These materials displayed crystalline domains characteristic of anatase. The first step of the process involved the hydrolysis of titanium isopropoxide in a basic aqueous solution mediated by neutral surfactant. The solid product obtained from step 1 was then treated in an acidified ethanol solution containing the same titanium precursor to thicken the pore walls. Low pH and higher loading of the Ti precursor in step 2 produced better mesoporosity and crystallinity of titanium dioxide polymorphs. The resultant powder exhibited a high surface area (73.8 m2/g) and large pore volume (0.17 cm3/g) with uniform mesopores. These materials are envisaged to be used as precursors for mesoporous titania films as a wide band gap semiconductor in dye-sensitized nanocrystalline TiO2 solar cells.     

New Triblock Copolymer Templates,PEO‐PB‐PEO,for the Synthesis of Titania Films with Controlled Mesopore Size,Wall Thickness,and Bimodal Porosity

The synthesis and properties of a series of new structure‐directing triblock copolymers with PEO‐PB‐PEO structure (PEO = poly(ethylene oxide) and PB = polybutadiene) and their application as superior pore‐templates for the preparation of mesoporous titania coatings are reported. Starting from either TiCl₄ or from preformed TiO₂ nanocrystalline building blocks, mesoporous crystalline titanium oxide films with a significant degree of mesoscopic ordered pores are derived, and the pore size can be controlled by the molecular mass of the template polymer. Moreover, the triblock copolymers form stable micelles already at very low concentration, i.e., prior to solvent evaporation during the evaporation‐induced self‐assembly process (EISA). Consequently, the thickness of pore walls can be controlled independently of pore size by changing the polymer‐to‐precursor ratio. Thus, unprecedented control of wall thickness in the structure of mesoporous oxide coatings is achieved. In addition, the micelle formation of the new template polymers is sufficiently distinct from that of typical commercial PPO‐PEO‐PPO polymers (Pluronics; PPO = poly(propylene oxide)), so that a combination of both polymers facilitates bimodal porosity via dual micelle templating.     

Synthesis and mechanism study of mesoporous SnO2/SiO2 composites

Mesoporous SnO2/SiO2 composite particles (Si/Sn < or = 0.25) sustainable to calcination up to 600 degrees C have been fabricated using a stepwise sol-gel technique on nonionic surfactant template (tetradecylamine, TDA). The newly designed preparation method involved the pre-formation of SnO2 sol solution from SnCl4. Subsequently, SnO2 nanocrystals were covered by the silicate species (from the hydrolysis of tetraethylorthosilicate, TEOS) in a pH controlled colloidal solution. Upon mixing with the surfactant solution, mesophase composite was obtained. After the removal of templates at various temperatures (400 to 600 degrees C), worm-like mesoporous SnO2/SiO2 with large specific surface area and pore volume as high as 362 m2/g and 0.33 cc/g were obtained, respectively. High thermal stability is mainly due to the effective inhibition of SnO2 crystal growth (mean crystallite size <30 A) by the amorphous SiO2 species at the grain boundaries. Formation of mesoporous silicate skeleton such as M41S family material was prevented. The obtained materials maintain the relatively narrow pore size distribution typically in the range of 30 to 70 A. Relations between material properties and key synthesis parameters (i.e. TDA/Si/Sn molar ratio and calcination temperature) were investigated by TGA, wide/small-angle X-ray scattering, (HR)TEM, BET, and FTIR techniques. Mechanisms on the mesostructure formation and crystal growth inhibition were also proposed with detailed discussion.     

Preparation of TiO2/Al-MCM-41 mesoporous materials from coal-series kaolin and photodegradation of methyl orange

TiO₂/Al-MCM-41 mesoporous materials were prepared via sol-gel method by loading titania onto Al-MCM-41 mesoporous molecular sieve by hydrothermal treatment from coal-series kaolin as raw material. The TiO₂/Al-MCM-41 mesoporous materials were characterized by XRD, FT-IR, HRTEM, N₂ adsorption-desorption and the photocatalytic degradation of methyl orange solution under visible light irradiation. The results showed that the TiO₂/Al-MCM-41 mesoporous materials possessed a high surface area of 369.9–751.3 m²/g and a homogeneous pore diameters of 2.3–2.8 nm. The titania crystalline phase was anatase, and the particles size of TiO₂ increased with TiO₂ content. The Al-MCM-41 mesoporous materials exhibited excellent photodegradation activity under visible-light irradiation for methyl orange.     

Photonic Crystals from Emulsion Templates

Macroporous titania, which undergoes transition to the rutile phase by calcination without collapse of the pore structure, is obtained by polymerizing a titania sol suspended around “colloidal crystals” of oil droplets. The deformable template counteracts cracking of the titania phase. The Figure shows a scanning electron micrograph of a rutile sample with 200 nm pores obtained by the method described.     

Synthesis, characterization and photocatalytic reactions of phosphated mesoporous titania

Mesoporous titania nanoparticles with a well-defined mesostructure was prepared by hydrothermal process, using nonionic triblock copolymer P123 as surfactant template, modified with phosphoric acid and followed by calcination at 600°C. The sol–gel titania was modified by in situ phosphorylation using phosphoric acid and thereby incorporating phosphorous directly into the framework of TiO₂. The resulting materials were characterized by XRD, SEM, TEM, nitrogen adsorption, TGA and DRS. It was found that the structural and optical properties of titania samples are strongly influenced by their phosphate modification. In case of calcined samples a positive effect on the specific surface area for the in situ phosphated sample was found. Mesoporous structure of phosphated titania did not collapse even after calcination at 600°C. The enhanced photocatalytic activity of the synthesized phosphate nanomaterials were evaluated through a study of the decomposition of fluorescein under UV light excitation and compared with undoped titania nanomaterial as well as with commercial titania.     

Fabrication of mesoporous titanium oxide nanotubes based on layer-by-layer assembly

Titanium oxide (TiO2)/polyacrylic acid (PAA) composite nanotubes were firstly fabricated through the sol-gel process of titanium alkoxide in the inner pores of alumina template followed layer-by-layer assembly with polyacrylic acid (PAA). Mesoporous TiO2 nanotubes could be obtained after the removal of PAA component by calcination and etching of the template with concentrated sodium hydroxide aqueous solution. The surface area of as-prepared porous TiO2 nanotubes was measured as twice larger than that of the conventional TiO2 nanotubes and the pore diameter in the wall of the tubes is several nanometers. Such assembled mesoporous nanotubes can serve as carriers for catalysis release and biomolecules.     

A facile route to synthesize mesoporous zirconia with ultra high thermal stability

The mesoporous zirconia with ultra high thermal stability was synthesized via a controllable and facile sol-gel approach. It is found that the strong alkaline solution post-treatment exerted a critical influence on improving the thermal stability of the product. Even after calcination at 700 °C for 4 h, the worm-like mesopore system was fairly preserved in the post-treated product and the sample exhibited a high specific area (198 m² g⁻¹). Whereas for those samples without any post-treatment, its pore walls totally collapsed during calcinations above 400 °C, and the specific area drastically decreased.     

模板法制备介孔TiO2及其光催化性能研究

以十六烷基三甲基溴化铵(CTAB)作为模板剂,钛酸正四丁酯(TBOT)为钛源,异丙醇为溶剂,通过溶胶-凝胶过程合成出介孔TiO2前驱体凝胶后,经老化、焙烧得到了TiO2介孔材料.利用XRD、HR-TEM、TGA、N2的吸附-脱附、BET等方法对材料的结构、形貌、比表面积、孔径分布进行表征.以亚甲基蓝的降解为模型反应,对其催化性能进行评价并与商品DegussaP-25进行比较.实验结果表明,比表面积为137.5m2/g、孔径为8.62nm的锐钛型介孔TiO2具有很高的催化活性.     

介孔氧化钛晶须的合成及机理研究

利用二钛酸钾(K₂Ti₂O₅)独特的三角双锥层状晶体结构, 通过水化反应过程, 控制其介相结构转变, 获得介孔氧化钛晶须, 经N₂吸附-脱附测试比表面积为248m²/g. 高温500℃晶化为锐钛矿型, 比表面积仍可达139m²/g, 孔径为8.7nm, 并且晶须形貌不变. 通过XRD、TEM和HREM等手段, 考察了水化反应过程中K₂Ti₂O₅的结构变化, 提出KOH·nH₂O纳米相的形成是介孔结构的来源.     

Preparation of monodispersed mesoporous silica spheres with tunable pore size and pore-size effects on adsorption of Au nanoparticles and urease

Monodispersed mesoporous silica spheres (MMSS) with controllable porosity and pore size were successfully prepared by calcination method in the presence of complex salts. The effect of calcination temperature on the pore size of MMSS was examined. The results show that the pore size of MMSS samples can be tuned in the range from 3.20 to 46.80 nm by varying the calcination temperature. It is worth mentioning that the pore size of MMSS can be controlled on a much larger scale by this method compared to the templating approach, by which the pore size can only be expanded up to 10 nm. It is very advantageous for the application in loading enzymes. Moreover, it could be found that the method is feasible, effective and simple. In addition, the use of various MMSS samples as adsorbents for Au nanoparticles of different sizes as well as urease has also been demonstrated. It was confirmed that MMSS with adequate surface charge and optimum matching pore size showed excellent adsorption properties for Au nanoparticles and urease.     

氧化硅对二氧化钛纳米晶相变和晶粒生长的抑制作用

通过让正硅酸乙酯先水解，用溶胶－凝胶法制备了织构均匀的二氧化硅／二氧化钛复合粉体。用紫外－可见吸收光谱、傅里叶红外，透射电镜、X射线衍射和比表面仪对复合粉体进行了表征，发现添加少量的二氧化硅有效地抑最二氧化钛晶粒生长和锐钛矿向金红石的相变，选择性溶解能除去复合粉体中90％以上的氧化硅，得到高比表面积，骨架为锐钛矿相的介孔二氧化钛，复合粉体中二氧化硅主要形成了连通的网络结构，这种网络结构在800℃仍有很好的稳定性。     

纳米介孔氧化铝的制备工艺及性能

分别采用碳黑和十六烷基三乙基溴化铵作为模板剂,硝酸铝为前驱体,用溶胶-凝胶法合成介孔氧化铝.通过N2吸附一脱附、TG-DSC等测试手段对样品进行了对比分析表征.考察了两种不同模板剂对其晶体结构、比表面及孔径大小的影响.实验结果表明,相对于十六烷基三甲基溴化铵或碳黑做模板剂,采用十六烷基三甲基溴化铵和碳黑组成的复合模板剂可以合成较大的比表面积、孔径和孔容(分别为370m2/g、6.5nm和1.54cm3/g)的介孔氧化铝,而且具有较窄的孔径分布.     

A dual template method for synthesizing hollow silica spheres with mesoporous shells

PS/silica core/shell composites were synthesized by the modified Stöber method using polystyrene spheres and cetyltrimethylammonium bromide as dual templates under room temperature. The silicate species and the templates were self-assembled to form mesoporous silica shell on the surface of the PS spheres. Hollow silica spheres with mesoporous shell were obtained by removing the polymer core and the templates through calcination. The hollow silica spheres showed high specific surface area of 1099.5 m²/g and narrow pore size distribution centered at 2.31 nm.     

Synthesis and tuning of ordering and crystallinity of mesoporous titanium dioxide film

Synthesis of well-organized and highly crystalline mesoporous titania (TiO₂) film is demonstrated using triblock copolymer (Pluronic P123) as a structure directing template, through the evaporation induced self-assembly (EISA) process. The issue of thermal and structural stability of a mesoporous TiO₂ film was addressed via optimization of annealing temperature and time. An anatase phase, high crystallinity TiO₂ film with ordered pores was obtained at 430 °C after annealing for 15 min. The synthesized film was crack free with TiO₂ nanoparticle size of 10–15 nm, quasi-hexagonal pore diameter in the range of 8–10 nm and film thickness of ~ 150 nm.     

Properties and catalytic activity of NOx reduction of alumina-titania catalysts prepared by sol-gel method

The alumina-titania catalysts were prepared from various alumina and titania sources by sol-gel method, which were metal alkoxide and metal alkoxide modified with organic groups. Specific surface area, pore size distribution, solid acidity and catalytic activity of NO reduction for the alumina-titania catalysts depended on the alumina and titania sources. The alumina-titania catalyst prepared from metal alkoxide for alumina source and metal alkoxide modified with organic groups for titania source exhibited higher activity of NO reduction than the other alumina-titania catalysts. Catalytic activity of NO reduction for the alumina-titania catalysts depended on specific surface area and solid acidity. It was suggested that solid acidity of the alumina-titania catalysts depended on the coordination structure of Al atoms and the homogeneity of alumina and titania components.