Synthesis of rod-like mesoporous silica with hexagonal appearance using sodium silicate as precursor

Using sodium silicate as precursor, rod-like mesoporous silica with hexagonal appearance was synthesized by controlling the pH value of a mixed micelles solution of cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) during hydrolysis of ethyl acetate. The resulting mesoporous silica was characterized by small angle X-ray diffraction, nitrogen gas adsorption-desorption measurement and scanning electron microscopy. Results showed that the regular rod-like shapes with hexagonal appearance were obtained at a 9:1 molar ratio of CTAB to CTAC, and that the amounts and lengths of the rod-like mesoporous silica particles decreased with decreasing CTAB to CTAC molar ratio. There existed a type IV adsorption isotherm and an H1 hysteresis loop in N₂ gas adsorption-desorption curves.     

以卵磷脂为手性添加剂制备手性介孔二氧化硅

以十六烷基三甲基溴化铵(CTAB)的自组装体为模板,卵磷脂(PC)为手性添加剂,在n_PC:n_CTAB=1:21时,通过溶胶-凝胶法制备了螺旋介孔二氧化硅纳米棒。利用扫描电镜(FESEM)、透射电镜(TEM)、X-射线衍射以及氮气吸附-脱附等测试手段,对该纳米棒的形貌以及孔结构进行了表征。TEM显示该纳米棒的长度约为50~200nm,直径约为30~50nm。X-射线衍射表明孔道呈二维六方排列,虽然FESEM显示纳米棒左右手比例约为1:1,但通过圆二色谱表征证明该纳米棒在埃尺度下倾向于形成单一手性。结果表明,卵磷脂的手性可以传递到螺旋介孔二氧化硅纳米棒中。     

以卵磷脂为手性添加剂制备手性介孔二氧化硅

以十六烷基三甲基溴化铵(CTAB)的自组装体为模板,卵磷脂(PC)为手性添加剂,在n PC∶nCTAB=1∶21时,通过溶胶-凝胶法制备了螺旋介孔二氧化硅纳米棒。利用扫描电镜(FESEM)、透射电镜(TEM)、X-射线衍射以及氮气吸附-脱附等测试手段,对该纳米棒的形貌以及孔结构进行了表征。TEM显示该纳米棒的长度约为50～200 nm,直径约为30～50 nm。X-射线衍射表明孔道呈二维六方排列,虽然FESEM显示纳米棒左右手比例约为1∶1,但通过圆二色谱表征证明该纳米棒在埃尺度下倾向于形成单一手性。结果表明,卵磷脂的手性可以传递到螺旋介孔二氧化硅纳米棒中。     

多面体倍半硅氧烷制备有序介孔氧化硅材料

Octa(tetramethylammonium)-polyhedral oligomeric silsesquioxane(TMA-POSS) with cage-like structure was synthesized, the structure was characterized by NMR, FTIR and Elemental analyses. The mesoporous silica was prepared under alkaline condition using TMA-POSS as the silicon source and hexadecyltrimethylammonium bromide (CTAB) as the template, the structures of these products were characterized by XRD, TEM and nitrogen adsorption and desorption methods. The results indicate that the synthesized silica exhibites a well-ordered hexagonal pore structure with larger specific surface area. With increasing of CTAB molar ratio, the spacing of the crystal plane d100 is increased. The effects of the pH values on the mesoporous structure in the reaction system with different molar ratio of nPOSS / nCTAB were investigated. The synthesis mechanism of mesoporous silica was also discussed.     

Dual latex/surfactant templating of hollow spherical silica particles with ordered mesoporous shells

Hollow spherical silica particles with hexagonally ordered mesoporous shells are synthesized with the dual use of cetyltrimethylammonium bromide (CTAB) and unmodified polystyrene latex microspheres as templates in concentrated aqueous ammonia. In most of the hollow mesoporous particles, cylindrical pores run parallel to the hollow core due to interactions of CTAB/silica aggregates with the latices. Effects on the product structure of the CTAB:latex ratio, the amount of aqueous ammonia, and the latex size are studied. Hollow particles with hexagonally patterned mesoporous shells are obtained at moderate CTAB:latex ratios. Too little CTAB causes silica shell growth without surfactant templating, and too much induces nucleation of new mesoporous silica particles without latex cores. The concentration of ammonia must be large to induce co-assembly of CTAB, silica, and latex into dispersed particles. The results are consistent with the formation of particles by addition of CTAB/silica aggregates to the surface of latex microspheres. When the size and number density of the latex microspheres are changed, the size of the hollow core and the shell thickness can be controlled. However, if the microspheres are too small (50 nm in this case), agglomerated particles with many hollow voids are obtained, most likely due to colloidal instability.     

Effect of salts on synthesis of mesoporous materials with mixed cationic and anionic surfactants as templates

Mesoporous silica materials were synthesized using tetraеthoxysilane as precursor and liquid crystals formed in aqueous mixtures of cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) as templates, without and with the addition of NaBr or Na₂SO₄. For this purpose, the formation of liquid crystals as a function of the ratio of CTAB and SDS under different conditions was studied. It was found that liquid crystals formed in the mixed system of CTAB and SDS at certain mixing ratios are well-structured templates for the synthesis of mesoporous silicas. The synthesized silica materials were characterized by transmission electron microscope and nitrogen adsorption/desorption analysis. The pore size of mesoporous silicas could be controlled between 3 to 6 nm by simply changing the concentration of NaBr in solution. The mesoporous silicas exhibited lamellar structure and the order of structural arrangement was promoted with addition of NaBr. However, addition of Na₂SO₄ led to ink-bottle type pores of mesoporous silica with a narrow pore size distribution of around 2 nm and a higher specific surface area of 610 m² g^–1.     

Fabrication of MCM-41 mesoporous silica through the self-assembly supermolecule of β-CD and CTAB

Using the self-assembly β-cyclodextrin (β-CD) and cetyltrimethylammonium bromide (CTAB) as structure-directing agents, high-quality ordered MCM-41 silicas have been prepared. Small-angle X-ray diffraction (SXRD), N₂ adsorption-desorption and scanning electron microscope (SEM) techniques were used to characterize the calcined samples. Results showed that the pore structure of the resulting mesoporous silica belonged to the two-dimensional hexagonal structure (space group p6mm). The high-quality hexagonal structure was formed as n?1 (n denotes molar ratio of β-CD to CTAB). N₂ adsorption-desorption curves revealed type IV isotherms, H4 hysteresis loops, for all samples, and H1 hysteresis loops for samples at n=0, 0.1, 1 and 2, respectively. The pore size and the pore wall thickness of the samples increased with the increase in n values, respectively.     

助表面活性剂对介孔二氧化硅孔径的影响

在十六烷基三甲基溴化铵(CTAB)与硝酸形成的胶束体系中,分别加入正戊醇与正辛胺作助表面活性剂,合成出介孔二氧化硅.经小角XRD和N₂气体吸附与脱附实验证实,随着CTAB与正戊醇摩尔比的增加,介孔二氧化硅的孔径增加;而随CTAB与正辛胺摩尔比的增加,介孔二氧化硅的孔径减小.主要原因是正戊醇增大了CTAB胶束体积,从而导致介孔二氧化硅的孔径增加.而在CTAB与正辛胺的混合胶束中,正辛胺同硅酸盐作用力比CTAB强,导致介孔二氧化硅的孔径减小.     

以混合表面活性剂为模板可控合成MCM-48和MCM-41分子筛

利用阳离子和三嵌段共聚物混合表面活性剂为模板,在水热条件、碱性介质中可控合成出MCM-48和MCM-41分子筛。在固定P123(聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物):TEOS(正硅酸乙酯)(物质的量的比)为0.01875的体系中,调节CTAB(十六烷基三甲基溴化铵)∶TEOS(正硅酸乙酯)物质的量比值m,当m在0.12~0.13范围合成出MCM-48分子筛;当m在0.04~0.08范围合成出MCM-41分子筛。通过XRD,TEM,N2物理吸附,IR等方法进行了表征。结果表明:聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物(P123)的加入可以更大程度地降低合成介孔材料所需阳离子表面活性剂的用量;可控合成的介孔材料具有高比表面积、高度有序的孔道结构、较集中的孔径分布。     

Synthesis of MCM-48 from silatrane via sol–gel process

High-quality cubic MCM-48 is successfully synthesized using a new silica source known as silatrane and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent via sol–gel process. The effects of synthesis parameters, viz. crystallization temperature, crystallization time, surfactant concentration, quantity of NaOH, and silica source, on the product structure are investigated. The synthesized samples are characterized using X-ray diffractometer (XRD), N₂ adsorption–desorption isotherms, and electron microscopy. Optimally, this product is synthesized from samples crystallized at 140°C for 16 h with a CTAB/SiO₂ ratio of 0.3 and NaOH/SiO₂ ratio of 0.5. The XRD result exhibits a well-resolved pattern, corresponding to the Ia3d space group of MCM-48. The BET surface area of this product is as high as 1,300 m²/g with a narrow pore-size distribution of 2.86 nm. The scanning electron microscopic (SEM) images also show the truncated octahedral shape and well-ordered pore system of MCM-48 particles.     

A controlled release of ibuprofen by systematically tailoring the morphology of mesoporous silica materials

A series of mesoporous silica materials with similar pore sizes, different morphologies and variable pore geometries were prepared systematically. In order to control drug release, ibuprofen was employed as a model drug and the influence of morphology and pore geometry of mesoporous silica on drug release profiles was extensively studied. The mesoporous silica and drug-loaded samples were characterized by X-ray diffraction, Fourier transform IR spectroscopy, N₂ adsorption and desorption, scanning electron microscopy, and transmission electron microscopy. It was found that the drug-loading amount was directly correlated to the Brunauer-Emmett-Teller surface area, pore geometry, and pore volume; while the drug release profiles could be controlled by tailoring the morphologies of mesoporous silica carriers.     

Preparation of Helical Mesoporous Ethenylene-silica Nanofibers with Lamellar Mesopores on Their Surface

The morphologies and pore architectures of mesoporous ethenylene‐silica were controlled using cetyltrimethylammonium bromide (CTAB) as template and (S)‐β‐citronellol as a co‐structure‐directing agent under basic conditions. When the (S)‐β‐citronellol/CTAB molar ratios are in the range of 0.75–2.0, helical nanofibers were obtained. With increasing the (S)‐β‐citronellol/CTAB molar ratio, the lengths of the nanofibers increases. Lamellar mesopores were identified on the surfaces of the nanofibers prepared in the (S)‐β‐citronellol/CTAB molar ratio range of 1.5–2.0. At the (S)‐β‐citronellol/CTAB molar ratio of 2.5:1, nanoparticles with nanoflakes on the surfaces were obtained. The field emission scanning electron microscopy images taken after different reaction times indicated that the helical pitches of the nanofibers decreased with increasing the reaction time. Helical 1,4‐phenylene‐silica and methylene‐silica nanofibers were also prepared. The results indicated that the morphologies and pore architectures of the obtained organic‐inorganic hybrid silicas are also sensitive to the hybrid silica precursors. Helical ethenylene‐silica nanofibers with lamellar mesopores on their surfaces can be also prepared using the mixtures of CTAB and racemic citronellol within a narrower citronellol/CTAB molar ratio range.     

Facile fabrication of hollow mesoporous silica nanospheres for superhydrophilic and visible/near-IR antireflection coatings

A series of hierarchically mesostructured silica nanoparticles (MSNs) less than 100 nm in size were fabricated by means of a one-step synthesis using dodecanethiol (C(12)-SH) and cetyltrimethylammonium bromide (CTAB) as the dual template, and trimethylbenzene (TMB) as the swelling agent. Silica nanoparticles with varied morphologies and structures, including mesoporous silica nanoparticles with tunable pore size, mesoporous silica nanoparticles with a thin solid shell, hollow mesoporous silica nanoparticles with tunable cavity size, and hollow mesoporous silica nanoparticles with a thin solid shell, were obtained by regulating the TMB/CTAB molar ratio and the stirring rate with the assistance of C(12)-SH. Silica particulate coatings were successfully fabricated by using MSNs with varied morphologies and structures as building block through layer-by-layer dip-coating on glass substrates. The thickness and roughness of the silica particulate coatings could be tailored by regulating the deposition cycles of nanoparticles. The silica particulate coatings composed of hollow mesoporous silica nanoparticles with a thin shell (S2) increased the maximum transmittance of slide glass from 90 to 96%, whereas they reduced its minimum reflection from 8 to 2% at the optimized wavelength region that could be adjusted from visible to near-IR with a growing number of deposition cycles. The coatings also exhibited excellent superhydrophilic and antifogging properties. These mesostructured silica nanoparticles are also expected to serve as ideal scaffolds for biological, medical, and catalytic applications.     

Green preparation of hollow mesoporous silica nanosphere inside-loaded gold nanoparticles and the catalytic activity

In this work, an active nano-catalyst with gold nanoparticles loaded in hollow mesoporous silica nanospheres (HMSNs/Au) was prepared by a one-pot sol-gel method, in which gold ions were loaded in hollow mesoporous silica spheres followed by sodium alginate reduction. The characterization of the HMSNs/Au were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption–desorption isotherms (BET). The high catalytic activity of HMSNs/Au, denoted as apparent turn-over frequency (TOF), was detected by UV-Vis spectrophotometer for the catalytic reduction of 4-nitrophenol (74.5 h^?1) and 2-nitrophenol (108.7 h^?1) in the presence of sodium borohydride solution due to the small gold nanoparticles size and overall exposure of active sites. It is expected that this ecofriendly approach to prepare inorganic composited nanoparticles as high active catalysts based on hollow mesoporous materials was a promising platform for loading noble metal nanoparticles.     

以联二萘酚衍生物为手性添加剂制备介孔二氧化硅

通过溶胶-凝胶法以十八烷基三甲基溴化铵(STAB)自组装体为模板和非离子型联二萘酚衍生物(S)作为手性添加剂制备螺旋介孔二氧化硅。样品利用扫描电镜、透射电镜、X-光衍射以及氮气吸附-脱附进行了表征。结果表明:反应混合物中S与STAB的物质的量之比对介孔二氧化硅的形貌及孔结构有很大影响。改变nS∶nSTAB比,从0.1∶1到0.4∶1时,其结构从螺旋纳米棒状变为表面具有环形层状孔的纳米棒,孔道由沿着纳米棒长轴方向转变为同心环状。当nS∶nSTAB=0.5∶1时,得到类似皱缩花瓣的纳米颗粒。该手性添加剂的引入并没有改变左右手螺旋纳米棒的比例。     

以联二萘酚衍生物为手性添加剂制备介孔二氧化硅

通过溶胶-凝胶法以十八烷基三甲基溴化铵（STAB）自组装体为模板和非离子型联二萘酚衍生物（S）作为手性添加剂制备螺旋介孔二氧化硅。样品利用扫描电镜、透射电镜、X-光衍射以及氮气吸附-脱附进行了表征。结果表明：反应混合物中S与STAB的物质的量之比对介孔二氧化硅的形貌及孔结构有很大影响。改变n_S：n_STAB比,从0.1：1到0.4：1时,其结构从螺旋纳米棒状变为表面具有环形层状孔的纳米棒,孔道由沿着纳米棒长轴方向转变为同心环状。当n_S：n_STAB=0.5：1时,得到类似皱缩花瓣的纳米颗粒。该手性添加剂的引入并没有改变左右手螺旋纳米棒的比例。     

Characterization Studies on the Ionic Liquid-Templated Mesoporous Silica with Wormlike Pores

This article reports a novel preparation of wormlike mesoporous silica with 1-hexadecane-3-methylimidazolium bromide (C₁₆MIM)Br, a kind of room-temperature ionic liquids (RTILs), as a template via a sol-gel nanocasting technique. The characterization studies were carried out in contrast with that of the mesoporous silica with cetyltrimethylammonium bromide (CTAB), a usually used template, which has the same alkyl chain length with (C₁₆MIM)Br. The structures of the silica materials have been characterized by Transmission electron microscopy (TEM), High-resolution TEM (HRTEM) and N₂ adsorption-desorption measurements. The results show that both the mesoporous materials prepared with different templates respectively can form regular wormlike mesopores with ca. 2 nm in pore diameter. They also have large BET surface areas with narrow size distribution. Compared to the CTAB-template mesoporous silica, the material with (C₁₆MIM)Br as a template has highly uniform pore size and larger surface area. In addition, the formation mechanism of the wormlike mesopores with RTIL has been proposed by an electrostatic charge matching assembly-pathway and steric factor.     

Synthesis of mesoporous NiO with crystalline walls by a simple sol–gel route

Mesoporous NiO particles with crystalline walls were prepared by a simple sol-gel technique. X-ray diffraction (XRD), N₂ adsorption–desorption, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) have been used to investigate the mesoporous NiO particles. The as-prepared mesoporous NiO possessed narrow pore in the range of mesopores and was stable up to 700 ^oC. Various characterization results showed that the mesostructure was formed through the aggregation of nanocrystals and stearic acid in the precursor played an important role in formation of the final mesoporous structures. Mesoporous Ni particles have also been successfully synthesized by reduction of the obtained mesoporous NiO at 700 ^oC for 30 min.     

Facile synthesis of monodisperse microspheres and gigantic hollow shells of mesoporous silica in mixed water-ethanol solvents

Mesoporous silica materials with a variety of morphologies, such as monodisperse microspheres, gigantic hollow structures comprising a thin shell with a hole, and gigantic hollow structures consisting of an outer thin shell and an inner layer composed of many small spheres, have been readily synthesized in mixed water-ethanol solvents at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained mesoporous silica generally shows a disordered mesostructure with typical average pore sizes ranging from 3.1 to 3.8 nm. The effects of the water-to-ethanol volume ratio (r), the volume content of tetraethyl orthosilicate TEOS (x), and the CTAB concentration in the solution on the final morphology of the mesoporous silica products have been investigated. The growth process of gigantic hollow shells of mesoporous silica through templating emulsion droplets of TEOS in mixed water-ethanol solution has been monitored directly with optical microscopy. Generally, the morphology of mesoporous silica can be regulated from microspheres through gigantic hollow structures composed of small spheres to gigantic hollow structures with a thin shell by increasing the water-to-ethanol volume ratio, increasing the TEOS volume content, or decreasing the CTAB concentration. A plausible mechanism for the morphological regulation of mesoporous silica by adjusting various experimental parameters has been put forward by considering the existing state of the unhydrolyzed and partially hydrolyzed TEOS in the synthesis system.     

水热合成Co3O4的制备参数调变及其催化分解N2O性能

以十六烷基三甲基溴化胺（CTAB）为模板剂,通过调变CTAB浓度水热合成了氧化钴前驱体,焙烧制得棒状形貌的Co₃O₄,在其表面浸渍K₂CO₃溶液制得K改性的Co₃O₄催化剂,用于N₂O分解。用X射线衍射（XRD）、N₂物理吸附（BET）、扫描电镜（SEM）、X射线光电子能谱（XPS）、H₂程序升温还原（H₂-TPR）和O₂程序升温脱附（O₂-TPD）等技术对催化剂进行了表征,考察了CTAB/钴及尿素/钴物质的量比等制备参数对Co₃O₄催化分解N₂O活性的影响。结果表明,CTAB浓度为0.05 mol/L、CTAB/钴离子物质的量比为1、尿素/钴离子物质的量比为4时,所制备的Co₃O₄催化剂具有较高的N₂O分解活性,而K改性可以进一步提升其催化性能。K改性的Co₃O₄在有氧有水气氛中400℃下进行N₂O分解反应,50 h后N₂O转化率仍保持在91%以上。