纳米多孔二氧化硅薄膜的制备与表征

以正硅酸乙酯为原料,采用酸/碱两步溶胶 凝胶法、结合匀胶和超临界干燥等工艺在硅片上成功制备了纳米多孔二氧化硅薄膜。适合匀胶的二氧化硅溶胶的粘度范围为 9~15mPa·s;多孔二氧化硅薄膜表面均匀平整,其厚度为400~1000nm;折射率为1.09~1.24;介电常数为1.5~2.5。该多孔二氧化硅薄膜具有三维网络结构,二氧化硅微粒直径为10~20nm。     

碱催化多孔二氧化硅薄膜的制备和性能表征

以水为介质,NH3·H2O为催化剂,丙三醇(C3H5(OH)3和聚乙烯醇(PVA)为添加剂,正硅酸乙脂(TEOS)溶胶 凝胶工艺可制备纳米多孔二氧化硅薄膜。体系的H2O/TEOS>15,TEOS的水解 聚合过程可通过添加剂效应,pH效应等控制。碱催化会使二氧化硅的溶解度增大,也能使二氧化硅胶粒带负电荷,抑制了二氧化硅胶粒之间的聚合长大,而丙三醇与TEOS的水解中间Si(OR)4-x(OH)x结合,抑制其与二氧化硅胶粒的聚合。聚乙烯醇(PVA)能使二氧化硅溶胶具有网状结构,使二氧化硅溶胶易于成膜。该工艺制备的多孔二氧化硅薄膜具有纳米多孔结构。其Vicker硬度在600～800N/mm2,热导率<0.2W·m-1K-1。     

纳米多孔二氧化硅薄膜的制备及性能

以N(C_8H_(15))_4~+OH~-为催化剂,用正硅酸乙脂(TEOS)溶胶-凝胶工艺制备出纳米多孔二氧化硅薄膜。体系的H_2O/TEOS>25,强碱催化使二氧化硅的溶解度增大并使二氧化硅胶粒带负电荷,抑制了二氧化硅的聚合。丙三醇与TEOS的水解中间体Si(OC_2H_5)_4-x(OH)_x及二氧化硅胶粒Si_xO_y(OH)_z~(+n)表面Si-OH形成氢键,抑制了二氧化硅的聚沉。聚乙烯醇(PVA)使粒状二氧化硅溶胶具有网状结构,易于成膜。薄膜由致密结构转化为均匀纳米多孔结构是构成薄膜的二氧化硅胶粒在热处理时聚集和塑性形变的结果。多孔二氧化硅薄膜的折射率为1.27～1.42,介电常数为1.578～2.016,热导率为0.2W/(m·K)。     

纳米多孔氧化硅薄膜的制备和表征

以正硅酸乙酯、异丙醇、去离子水为原料,盐酸、氨水为催化剂,采用溶胶-凝胶、旋转涂胶、老化及超临界流体干燥工艺制备纳米多孔氧化硅薄膜.研究了溶胶-凝胶工艺的影响因素,考察了溶胶粘度和匀胶转速对成膜性能的影响,采用扫描电镜表征了薄膜的表面形貌和截面结构,用椭偏仪表征了薄膜的孔隙率、介电常数以及厚度等性能参数,分析了薄膜的结构和红外特性.     

Synthesis and characterization of nanoporous hydroxyapatite using cationic surfactants as templates

Nanoporous hydroxyapatite was synthesized utilizing cationic surfactants as templates. The effects of cetyltrimethylammonium bromide and reaction temperatures on the phase and morphology of HA were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The thermal stability of nanoporous structures was studied by XRD and thermal analyzers (TGA/DTA), while the pore structure of HA was observed using high resolution TEM. It was found that the pore size was about 1 nm, and the pore structure of HA was thermally stable up to 700 °C and the pore size did not change with reaction temperature and CTAB:PO₄^3? ratio. The possible formation mechanism of nanoporous structure was proposed.     

Tailoring silver nanoparticle construction using dendrimer templated silica networks

We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles.     

新型氨基化磁性树状分子纳米颗粒的制备与表征

采用化学共沉淀法,以FeC13.6H2O和FeSO4·7H2O为原料制备磁性Fe3O4纳米颗粒,采用3-氨丙基三乙氧基硅烷(APTES)、丙烯酸丁酯(BA)和无水乙二胺(EDA)对其进行修饰,制备了三代表面氨基化的磁性Fe3O4树状分子纳米颗粒,并对其进行结构表征与性能测试.结果表明:树状分子逐代修饰在磁性颗粒表面,氨基含量逐代增加,分别为0.41、0.69和0.87mmol/g; Fe3O4纳米颗粒平均尺寸在12nm左右,修饰后的三代磁性纳米颗粒的粒径逐代增加,分别为14、27和40nm左右;三代产品仍具备较高的饱和磁化强度,展现出了典型的超顺磁性.这种氨基功能化的磁性纳米粒子在细胞分选、固定化酶和靶向药物等诸多领域有着巨大应用潜力.     

Synthesis and characterization of ordered mesoporous silica using rosin-based Gemini surfactants

As structure-directing agents, the molecular structure of surfactants is critical for determining the properties of prepared mesoporous materials. Using dehydroabietic acid as a starting material, a series of rosin-based Gemini surfactants (abbreviated as R-n-R, n = 3, 6, 8 and 10, indicating the carbon atom number contained in the spacer) were synthesized and applied as templates in the preparation of ordered mesoporous silica. The structures and morphologies of the samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and N₂ adsorption–desorption. The R-n-R surfactants feature rigid tricyclic hydrophobic groups with large volumes, which are beneficial for the formation of a three-dimensional cubic phase. Furthermore, the spacer length was found to have a tremendous effect on the structure of the prepared mesoporous silica materials. The head group of R-3-R, which has a short spacer, is excessively charged, leading to silica nanoparticles with an irregular morphology and a rather low BET surface area. With longer spacer lengths, R-6-R, R-8-R and R-10-R are conducive to generating silica nanoparticles with a novel dumbbell-like morphology and with higher BET surface areas of 1171, 1096 and 1186 m² g^?1, respectively. The results demonstrate the particularities of the Gemini surfactant structure in the preparation of mesoporous silica nanoparticles with novel morphologies, and the details of the molecular interactions that occur in the condensation of silicate anions are also revealed.     

氨丙基功能化二氧化硅的制备及结构表征

分别采用液相法和溶胶-凝胶法制备了氨基功能化的二氧化硅(APS),利用FTIR,BET,元素分析和TG等技术对制备的APS进行了结构表征.在液相法制备APS的过程中,为使SiO2表面有更多的羟基与氨丙基三乙氧基硅烷(APTES)发生反应,采用4种方法对SiO2表面进行了预处理.结果表明,微波辐射效果最好,可使SiO2表面羟基数由1.08(个/nm2)增加到1.29(个/nm2).采用液相法制备的APS中氨丙基负载量为8.59%(质量分数),活性位(氨丙基)浓度为1.49mmol/g.采用溶胶一凝胶法制备的APS中氨丙基负载量为6.88%(质量分数),活性位(氨丙基)浓度为1.19mmol/g,均较液相法制备的APS低.     

Functional characterization of heme proteins encapsulated in wet nanoporous silica gels

Myoglobin and hemoglobin were encapsulated in wet, nanoporous silica gels. A rigorous evaluation of the effect of the encapsulation on protein dynamics and function was carried out by measuring the kinetics of carbon monoxide rebinding after nanosecond laser flash-photolysis with transient absorption detection, and the oxygen affinity with absorption microspectrophotometry. The time course of carbon monoxide binding to myoglobin evidenced a strongly enhanced geminate recombination and a faster bimolecular rebinding with respect to solution, whereas T and R quaternary states of hemoglobin exhibited a geminate phase and a bimolecular binding rate very similar to those observed in solution. Oxygen affinity of T-state hemoglobin was found to be close to that observed for the binding of the first oxygen to T-state hemoglobin in solution. Results indicate that some conformational transitions are kinetically restricted, allowing to isolate distinct tertiary and quaternary states. This opens the way to their detailed functional characterization and application to biodevices.     

Synthesis and characterization of silica microcapsules using a sustainable solvent system template

We report direct encapsulation of a sustainable solvent system in silica microcapsules via a sol-gel reaction of silica precursor for potential application of thermoplastic self healing polymeric system. The silica microcapsules were realized by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) using aqueous glycerol microemulsion as template. The pre-hydrolysis of TEOS was found to be useful to obtain isolated free flowing silica microcapsules. Furthermore, the effects of different parameters viz. temperature, rotor speed, the solvent/TEOS ratio on the synthesis of silica microcapsules are studied. A novel micro compression technique to study mechanical properties of the silica microcapsules is reported. The silica microcapsules reported were found to have better mechanical properties compared to incumbent Urea-Formaldehyde (UF) based organic microcapsules.     

Synthesis and characterization of ordered mesoporous silica by using polystyrene microemulsion as templates

A simple room temperature synthesis of pure mesoporous silica by using a homemade and functional template: polystyrene microemulsion is reported. The process consists of HCl-catalysed sol-gel reactions of tetraethyl orthosilicate (TEOS) in polystyrene microemulsion, followed by removal of the template via solvent extraction or calcining. X-ray diffraction, Transmission Electron Microscope and N₂ adsorption-desorption isotherms are then used to characterize the mesostructure. The results indicate that the synthesized mesoporous silica has a large BET surface area with more than 900 m²/g, large pore volume with more than 0.8 cm³/g and ordered mesopore-structure. This provides a possible way to control the meso-structure and pore size of mesoporous materials via potential functional templates.     

单分散球形介孔SiO_2的合成与表征

以十六烷基三甲基氯化铵(CTAC)为模板剂,正硅酸乙酯(TEOS)为硅源,甲醇为共溶剂,氢氧化钠为催化剂,采用水热法制备出不同粒径、单一分散、高度有序的介孔SiO2微球,并利用扫描电子显微镜(SEM)对所制备的微球进行表征。考察了体系中CTAC浓度、TEOS浓度、甲醇的比率和温度等条件对所制备的SiO2微球的粒径及分散性的影响。同时采用XRD、BET、HRTEM等手段对样品进行分析表征。结果表明合成的单分散球形SiO2具有有序的六方相介孔结构,并且具有较高的比表面积。     

Synthesis and characterization of photoswitchable fluorescent silica nanoparticles

We have designed and synthesized a new functional (amino reactive) highly efficient fluorescent molecular switch (FMS) with a photochromic diarylethene and a rhodamine fluorescent dye. The reactive group in this FMS -N-hydroxysuccinimide ester- allows selective labeling of amino containing molecules or other materials. In ethanolic solutions, the compound displays a large fluorescent quantum yield of 52 % and a large fluorescence modulation ratio (94 %) between two states that may be interconverted with red and near-UV light. Silica nanoparticles incorporating the new FMS were prepared and characterized, and their spectroscopic and switching properties were also studied. The dye retained its properties after the incorporation into the silica, thereby allowing light-induced reversible high modulation of the fluorescence signal of a single particle for up to 60 cycles, before undergoing irreversible photobleaching. Some applications of these particles in fluorescence microscopy are also demonstrated. In particular, subdiffraction images of nanoparticles were obtained, in the focal plane of a confocal microscope.     

Synthesis and characterization of mesoporous composite silica monolith

Coumarin4 (Cou4) was loaded into mesoporous silicon SBA-15 monolith channels by a simple postgrafting method at room temperature. The obtained Cou4/SBA-15 composite monolith was compared with the blank SBA-15 monolith. The investigation of X-ray diffraction, transmission electron microscopy (TEM), UV–vis and photoluminescence (PL) reveals the existence of cou4 in the channels of SBA-15 monolith. In addition, a red-shift and strong fluorescence in PL spectrum was observed from the composite monolith compared with that of Cou4 in C₂H₅OH solution. This is good for the new application of optical materials.     

Self-assembly of uniform nanoporous silica fibers

Self-assembly of nanoporous silica shapes is of great interest for modern nanotechnology because of uniform pore size, simplicity, and low cost of production. However, there are two major problems that prevent broad use of the self-assembly process. First, the process brings too broad a variety of the assembled shapes. Secondly, the yield of the desired shapes is far from 100%. Here, we describe a process of acidic self-assembly of silica shapes that is free of both of these problems. The process described results in virtually a 100% of very uniform fibers. Each fiber has a hexagonal cross section of approximately 2 /spl mu/m and a length of approximately 5 /spl mu/m. The highly uniform pores with periodicity of 3.8 nm are unidirectional along the fiber. These new fibers can be used in chromatography, drug delivery, manufacturing nanowires, nanoreactors for "one-dimensional" chemistry, etc.     

Synthesis and size characterization of silica nanospheres using sedimentation field-flow fractionation (SdFFF)

Silica nanoparticles were synthesized by a conventional emulsion polymerization by mixing ethanol, ammonium hydroxide, water and tetra ethyl orthosilicate (TEOS). A new reaction apparatus was assembled for a large scale synthesis of silica nanospheres in the laboratory, which was designed for uniform mixing of the reactants. The apparatus was equipped with a disc type agitator with six rectangular propellers. The new apparatus allowed high reproducibility in terms of the mean size and the size distribution of the silica nanoparticles with the relative standard deviation of less than about 6%. Sedimentation field-flow fractionation (SdFFF) was employed for determination of the size distribution of the silica nanoparticles. SdFFF provided size-based separation of the silica nanoparticles, with the retention time increasing with the size. When SdFFF analysis was repeated three times for the same sample, the standard deviation was less than 4%, showing reliability of SdFFF in size measurement. SdFFF seems to provide more accurate size distribution than DLS, particularly for those having broad and multimodal size distributions. Change in the agitation speed resulted in significant change in the mean diameter of the silica nanoparticles. Agitation speed of 400 rpm in 3 L reaction vessel yielded silica particles of about 100 nm in diameter, while at 200 rpm in 1 L vessel yielded those of about 500 nm.     

Single-step synthesis of nanoporous silica colloids

Nanoporous silica colloids were prepared by a convenient single-step sol-gel process. In this approach, acidic aluminum nitrate (Al(NO₃)₃) solution was added to the ethanol solution of tetraethoxy orthosilicate (TEOS). In the preliminary stage, alumina/silica core-shell particles were formed. Then the Al₂O₃ cores were dissolved subsequently with the decrease of pH value, and the nanoporous silica was formed. The porous silica particles were characterized by transmission electron microscopy (TEM). The formation mechanism of the porous silica was discussed.     

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.