Controlling pore morphology and properties of nanoporous silica films using the different architecture PS-b-P2VP as a template

Nanoporous silica films were prepared through the templating of amphiphilic block copolymer, poly(styrene-2-vinyl pyridine) (PS-b-P2VP), and monodispersed colloidal silica nanoparticles. The experimental and theoretical studies suggested that the intermolecular hydrogen bonding existes between the colloidal silica nanoparticles and PS-b-P2VP. The effects of the loading ratio and P2VP chain length on the morphology and properties of the prepared nanoporous silica films were investigated. TEM and AFM studies showed that the uniform pore size could be achieved and the pore size increased with increasing porogen loading. The refractive index and dielectric constant of the prepared nanoporous films decreased with an increase in PS-b-P2VP loading. On the other hand, the porosity increased with an increasing PS-b-P2VP loading. This study demonstrated a methodology to control pore morphology and properties of the nanoporous silica films through the templating of PS-b-P2VP.     

Preparation of nanoporous SiO2 particles and their application in drug release control

Nanoporous SiO2 particles which have different pore size and volume were prepared from a colloidal mixture of nano-sized silica particles by a spray heating method. The prepared nanoporous SiO2 particles were employed as a drug carrier to investigate the release behaviors of methylene blue (MB) as a model drug for a selected period of time. The concentration of released MB from the porous particles was measured by a UV-Vis spectroscopy with respect to time. The release of MB from the porous particles was maintained for 400 hours and the maximum amount of the released MB was 0.8 mg at 1.56 cm3/g of pore volume. As pore volume of the nanoporous particles increased, the release rate of MB increased.     

Nanoporous carbon synthesized from sol–gel template for adsorbing gibberellic acid in aqueous solution

A novel method, based on dynamic carbonization and silica template formed by sol–gel, was developed to prepare nanoporous carbon materials with tailored pore structures. The effects of the sol–gel reaction and carbonization process on the final nanoporous carbon product were investigated by pore features such as specific surface area, the total pore volume, and pore size distribution, which were systemically characterized by iodine index, transmission electron microscopy, and nitrogen adsorption. The experimental results indicate that the pore structures of the prepared nanoporous carbon are tunable on the nano-scale by controlling the preparation process in the proposed method. The nanoporous carbon prepared under the optimal conditions has a high total pore volume of 1.26 cm³/g, a large specific surface area of 1744 m²/g, and a maximal adsorption capacity of 9.2 mg/g to gibberellic acid in aqueous solution, which is nearly 6 times that of commercial activated carbon.     

Fabrication of nanoporous TiO2 hollow capsules using core-shell silica nanoparticle templates

We report on the fabrication of the nanoporous TiO2 hollow capsules using core-shell silica nanoparticle templates. The thickness of the capsules can be simply controlled by varying the amount of the TiO2 precursor. The resulting nanoporous capsules exhibited the high specific surface area and the large pore volume of 103-180 m2/g and 0.40-0.86 cm3/g, respectively. Photocatalytic activity of the TiO2 hollow capsules was also investigated and compared to that of the commercial TiO2 nanoparticles.     

Fabrication and textural characterization of nanoporous carbon electrodes embedded with CuO nanoparticles for supercapacitors

Abstract

We introduce a novel strategy of fabricating nanoporous carbons loaded with different amounts of CuO nanoparticles via a hard templating approach, using copper-containing mesoporous silica as the template and sucrose as the carbon source. The nature and dispersion of the CuO nanoparticles on the surface of the nanoporous carbons were investigated by x-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM) and high-resolution transmission electron microscopy (HRTEM). XRD results reveal that nanoporous carbons with embedded CuO nanoparticles exhibit a well-ordered mesoporous structure, whereas the nitrogen adsorption measurements indicate the presence of excellent textural characteristics such as high surface area, large pore volume and uniform pore size distribution. The amount of CuO nanoparticles in the nanochannels of the nanoporous carbon could be controlled by simply varying the Si/Cu molar ratio of the mesoporous silica template. Morphological characterization by SEM and TEM reveals that high-quality CuO nanoparticles are distributed homogeneously within the nanoporous carbon framework. The supercapacitance behavior of the CuO-loaded nanoporous carbons was investigated. The material with a small amount of CuO in the mesochannels and high surface area affords a maximum specific capacitance of 300 F g^-1 at a 20 mV s^-1 scan rate in an aqueous electrolyte solution. A supercapacitor containing the CuO-loaded nanoporous carbon is highly stable and exhibits a long cycle life with 91% specific capacitance retained after 1000 cycles.     

利用表面活性剂量改变孔洞率制备的纳米多孔SiO2膜

采用表面活性剂十六烷基三甲基溴化氨(CTAB)为模板剂,在酸性条件下产生多孔结构,再经热处理去除CTAB。实验中使用溶胶?凝胶技术,正硅酸乙酯(TEOS)为硅源,以及二次去离子水,盐酸为催化剂等原料,利用表面活性剂与硅源水解后形成的聚集体相互作用,在溶液中形成分子自组装体,制备前驱体溶胶。通过简单提拉迅速蒸发溶剂制备纳米多孔或纳米介孔SiO2薄膜,分析和研究了表面活性剂浓度对纳米多孔SiO2薄膜的结构和孔洞率的影响,通过操纵表面活性剂的含量,能控制薄膜的纳米结构、孔洞率、孔大小和孔的形态以及膜的形貌。小角度射线衍射、场发射透射电子显微镜、原子力显微镜显示可以制得具有六方、立方和由三维六方和简单立方组成的新相结构以及比介孔大的纳米多孔结构的薄膜。椭偏仪测量得到所制备薄膜的孔洞率为51.8%-65.6%,借助此孔洞率能计算薄膜的折射率和介电常数。     

Structural design at the polymer surface interface in nanoporous silica polyamine composites

The factors affecting the rate of silica leaching in alkaline aqueous media from surface silanized, nanoporous, amorphous, silica gels and from silanized silica gels that have been modified with polyamines to form the previously reported silica polyamine composites (SPCs), BP-1 and BP-2 have been investigated. Silanization with alkyl trichlorosilanes slows the rate of silica leaching relative to the unmodified silica gels. The use of bulkier aryl silanes somewhat decreases the silica leaching under the same conditions. Interestingly, after modification of the silanized silica with poly(allylamine) (PAA) to make BP-1, the leaching increases, but subsequent modification of the SPC with chloroacetic acid to make BP-2, quenches this increase. A mechanism explaining these results is discussed. Analogous composites have been prepared using sol–gel chemistry. These materials were characterized and their silica leaching properties were compared with the original BP-1. CPMAS ¹³C and ²⁹Si NMR of the various surfaces have been applied to better understand the nature of the modified surfaces. Significant changes in the nature of the surface siloxanes are observed for the different matrices and on their conversion to the polyamine composite. Scanning electron microscopy and pore size distributions for the composites made from commercial silica gel and from sol–gel chemistry are also reported and compared.     

Nanoporous titania-coated alumina membranes: sol-gel synthesis and characterisation

In this work, nanoporous titania top layers were deposited by dip-coating process on microporous alpha-alumina substrates using the sol-gel process. The alumina substrates were synthesized by slip casting method using Taguchi optimising approach. The microporous substrate was then used to coat nanoporous titania layers by the sol-gel method. The thickness, pore size, structure and permeability of the membranes were characterised using SEM, XRD, STA and Hg-Porosimetry. The process conditions to achieve defect-free nanoporous titania layers with the average pore size of about 4 nm coated on the microporous alumina substrates with the average pore size of about 270 nm were determined.     

Pore structure control of mesoporous carbon as supercapacitor material

The pore structure and electrochemical performances of mesoporous carbons prepared by silica sol template method as electrode material for supercapacitor were investigated in this work. The pore size distribution of the mesoporous carbons changes from unimodal to bimodal and the mean pore size increases with the increase of silica sol/glucose ratio. The specific capacitance of the mesoporous carbons also increases with the increase of silica sol/glucose ratio. A novel technique named as template–chemical activation method, combining both template and chemical activation methods, is proposed, which can effectively control the pore structure, improving the electrochemical properties of the mesoporous carbon with improved porosity especially microporosity.     

On the fatigue fracture at adsorption/desorption of water in/from liquid-repellent nanoporous silica

In this work, fatigue fracture tests on liquid-repellent nanoporous silica micro-particles dispersed in water are reported; then, models of the grain cracking and fragmentation are proposed. Such tests can be regarded, from an external standpoint, as conducted under temporally variable but spatially uniform pressure distribution in the liquid surrounding the silica grains, or from an internal standpoint, as surface fatigue that occurs at the cyclical adsorption/desorption of water in/from the nanoporous particles. The test rig represents a compression–decompression cylinder divided into two chambers, one of constant volume and the other of variable volume. Silica is introduced inside the cavity of fixed volume, and a micro-filter is used to separate it from the chamber of variable volume, in which only water is supplied. Experimental results suggest that the fatigue fracture of silica particles occurs from the inside, explosion-like, oppositely to the previously reported implosion-like collapse of silica under wet pressurization. This is accompanied by enhancement of the hydrophilic silanol groups on the silica surface and by redistribution of the size of particles and pores. Critical numbers of cycles to achieve fracture of the silica particles obtained experimentally, and from the models of grain cracking and fragmentation, under cyclical pressurization, are in good agreement.     

Preparation and photocatalytic activity of nanoglued Sn-doped TiO2

In this paper, Sn-doped TiO(2) photocatalyst was prepared and immobilized on a glass substrate using an about-to-gel SiO(2) sol as a nanoglue. The characterization of the Sn-doped TiO(2) by XRD showed that 5% Sn content is formed by anatase and rutile crystallites. Characterization of the nanoglued photocatalyst by the BET measurement, TEM, and SEM showed that the photocatalyst was a nanoporous material with a high-surface area. The Sn-doped TiO(2) was uniformly dispersed within the three-dimensional network of the silica in the form of nanoparticles. The nanoglued photocatalyst showed high photocatalytic activity during the degradation of penicillin under UV light. The effect of different Sn content on the amount of hydroxyl radical was discussed by using salicylic acid as probe molecules. The results show that an appropriate amount of Sn dopant can greatly increase the amount of hydroxyl radicals generated by TiO(2) nanoparticles, which are responsible for the obvious increase of photocatalytic activity.     

A facile method for the production of high-surface-area mesoporous silica gels from geothermal sludge

Mesoporous silica gels were successfully produced from geothermal sludge by alkali extraction followed by acidification. The silica in the geothermal sludge was dissolved by NaOH solution to produce a sodium silicate solution, which was then reacted with HCl or tartaric acid to produce silica gels. The effects of silica concentration and pH on the silica gel properties were investigated. In addition, an improved method was proposed by incorporating two-step aging. The first aging step, which was conducted at pH 10, was used to induce Ostwald ripening to increase the size of the primary particles, and the second step was used to strengthen the gel network. Decreasing the silica concentration by diluting the as-prepared sodium silicate solution tended to increase the surface area and pore volume of the prepared silica gels. The silica gels produced by tartaric acid possessed higher surface area and pore volume than those by HCl. The surface area and pore volume reached approximately 450 m² g⁻¹ and 0.8 cm³ g⁻¹, respectively. When the gelation pH was decreased to 6, the surface area exceeded 600 m² g⁻¹. The first aging process increased the size and uniformity of the primary particles, which in turn increased the surface area of the particles. The pore diameter for all cases was greater than 5 nm, indicating that the silica gels were mesoporous.     

纳米孔硅铝层柱蒙脱石复合材料的制备和性能研究

以蒙脱石为原料、十六烷基三甲基溴化铵和十二烷胺为结构导向剂,直接利用正硅酸乙酯和异丙醇铝混合物为层柱前驱体,合成了新型纳米孔径硅铝层柱蒙脱石复合材料。运用XRD、TG、FT-IR和N₂等温吸附-脱附等技术表征复合材料。结果表明:合成材料具有大通道(层间距为3.45 nm)、孔径较大且分布窄(平均孔径为2.0 nm)、高比表面积(S_BET=502.0 m2/g)和高热稳定性(大于750 ℃)。和硅层柱多孔粘土复合材料相比,铝的掺入对孔结构和热稳定性影响较小,但明显提高了酸性和酸强度。      

Aerosol-assisted synthesis of nanoporous silica/titania nanoparticles composites and investigation of their photocatalytic properties

Nanoporous silica/titania nanoparticles composites with relatively large TiO2 content are successfully synthesized by aerosol-assisted co-assembly. By the hybridization of titania with nanoporous silica having high surface area, both the adsorption capability and the reaction rates for the photocatalytic decomposition of methylene blue (MB) are dramatically improved in comparison with unmodified titania nanoparticles without nanoporous silica. Through the quantitative evaluation of the amount of adsorbed and photo-decomposed organic molecule throughout the reaction process, the role of nanoporous silica layers on titania surface is clarified. Rational design of future hybrid photocatalyst with precisely controlled nanostructure will be possible by optimization of our synthetic procedure and careful study of the adsorption and photocatalytic properties.     

Electrodeposition of biodegradable sol-gel derived silica onto nanoporous TiO2 surface formed on Ti substrate

This paper demonstrates the utility of an electrodeposition technique to deposit a layer of biodegradable sol-gel derived silica on a Ti substrate coated with a nanoporous TiO₂ layer in a controlled manner. The deposition pattern of the silica phase was tailored by controlling the silica sol content in the diluted solution and the deposition time. This allowed the nanopores to be filled with the silica phase, confirmed by energy dispersive spectroscopy and Fourier-transform infrared spectroscopy, whilst preserving the nanoporous surface, particularly when electrodeposition was carried out in a dilute solution with a silica sol content of 30 vol.% for < 30 min at an electric field of 2.5 V/cm.     

Al3+掺杂对硅胶吸附材料性能的影响

将陶瓷纤维纸用水玻璃和铝盐溶液等浸渍制备出新型Al3 掺杂硅胶吸附材料,研究了Al3 掺杂对硅胶吸附材料性能的影响.傅立叶变换红外谱、扫描电子显微镜及X射线能谱(SEM-EDS)揭示吸附材料中掺杂Al3 的存在及其含量;多孔介质孔隙分析显示,一定程度的Al3 掺杂可提高材料的比表面积和孔容,影响其孔径结构及分布,增加活性吸附位,从而提高了材料的吸附性能,在材料表面形成的Al-O-Si键增强了材料表面孔道骨架支撑力,提高了表面导热性,使其耐热性能、耐破指数和裂断长显著提高.     

Fabrication of high-pore volume carbon nanosheets with uniform arrangement of mesopores

Carbon nanosheets with a tunable mesopore size,large pore volume,and good electronic conductivity are synthesized via a solution-chemistry approach.In this synthesis,diaminohexane and graphene oxide (GO) are used as the structural directing agents,and a silica colloid is used as a mesopores template.Diaminohexane plays a crucial role in bridging silica colloid particles and GO,as well as initiating the polymerization of benzoxazine on the surfaces of both the GO and silica,resulting in the formation of a hybrid nanosheet polymer.The carbon nanosheets have graphene embedded in them and have several spherical mesopores with a pore volume up to 3.5 cm3·g-1 on their surfaces.These nuerous accessible mesopores in the carbon layers can act as reservoirs to host a high loading of active charge-storage materials with good dispersion and a uniform particle size.Compared with active materials with wide particle-size distributions,the unique proposed configuration with confined and uniform particles exhibits superior electrochemical performance during lithiation and delithiation,especially during long cycles and at high rates.     

印刻法制备中间相沥青基中孔炭

用中间相沥青作碳源,硅胶水溶液作造孔剂,采用胶体印刻法制得一系列中孔碳。实验发现当适量纳米级硅源添加到中间相沥青中,会在彼此颗粒间形成一定的纳米孔道,从而导致中间相沥青在炭化过程中没有沥青由固相向液相转化的过程。结果表明：碳硅比、印刻温度以及中间相沥青的基本物化性质都将对中孔碳的孔结构发生重要影响。且制得比表面积和孔容分别为482m2/g和1.62cm3/g的中孔碳。     

氯化钙改性硅胶吸湿材料的制备及性能研究

目的 针对水溶液改性硅胶基质易破裂,普通硅胶吸水率不高等问题,采用氯化钙醇溶液浸渍法制备不同浓度的氯化钙改性硅胶吸湿材料。方法 对比采用氯化钙水溶液和醇溶液制备的氯化钙改性硅胶吸湿材料的外观质量;采用气体吸附法测试等温吸附脱附曲线,基于吸附理论和FHH模型获得氯化钙改性硅胶吸湿材料孔隙参数和分形维数;采用静态吸附法获得水蒸气静态吸附曲线,根据准一级和准二级动力学模型建立适用于氯化钙改性硅胶吸湿材料的吸附动力学方程。结果 采用氯化钙醇溶液浸渍制备的氯化钙改性硅胶吸湿材料的破裂程度明显减少;比表面积和孔容随氯化钙含量的增加而减小,孔径变化较小;吸湿量随氯化钙含量的增加而增加。在模拟吸附过程中,准二级动力学模型相关系数更高,因此能更好地模拟吸附动力学过程。结论 采用质量分数为25%的氯化钙醇溶液制备的氯化钙改性硅胶吸湿材料的吸湿率最高、基质破裂率较低、再生能力优异,具有良好的应用前景。