268 resultados para TEOS-VTES
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采用溶胶-凝胶(Sol-Gel)法在已经预涂了一层过渡层的纯钛基体上制备生物玻璃(BG)涂层。试验以正硅酸乙酯(TEOS)、硝酸钙(Ca(NO3)2·4H2O)、氯化镁(MgCl2·6H2O)等为原料,并采用正交试验设计,所得涂层均通过SEM和EDS进行分析,并利用空间几何模型折算绝对偏差,从而确定出最优的试验参数为:[Si]=1M,水酯比(Rω)=4,pH=4.5,浸涂粘度(η)为3.55mPa·s。
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262 p.
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Gas-phase silver nanoparticles were coated with silicon dioxide (SiO2) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO2 precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO2 coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 degrees C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10(7) particles cm(-3).
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Gold-decorated silica nanoparticles were synthesized in a two-step process in which silica nanoparticles were produced by chemical vapor synthesis using tetraethylorthosilicate (TEOS) and subsequently decorated using two different gas-phase evaporative techniques. Both evaporative processes resulted in gold decoration of the silica particles. This study compares the mechanisms of particle decoration for a production method in which the gas and particles remain cool to a method in which the entire aerosol is heated. Results of transmission electron microscopy and visible spectroscopy studies indicate that both methods produce particles with similar morphologies and nearly identical absorption spectra, with peak absorption at 500-550 nm. A study of the thermal stability of the particles using heated-TEM indicates that the gold decoration on the particle surface remains stable at temperatures below 900 °C, above which the gold decoration begins to both evaporate and coalesce.
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A new amino silica monolithic column was developed for DNA extraction in a miniaturized format. The monolithic column was prepared in situ by polymerization of tetraethoxysilane (TEOS) and N-(beta-aminoethyl)-gamma-aminopropylmethyldimethoxysilane (AEAPMDMS). DNA was loaded in 50 mM tris(hydroxylmethyl)aminomethane-EDTA buffer at pH 7.0 and eluted with 300 mM potassium phosphate solution at pH 10.0. Under optimal condition, a 6.0-cm monolithic column provided a capacity of 56 ng DNA with an extraction efficiency of 71 +/- 5.2% (X +/- RSD). When the amino silica monolithic column was applied to extract genomic DNA from the whole blood of crucian carp, an extraction efficiency of 52 +/- 5.6% (X +/- SD) was obtained by three extractions. Since the chaotropic-based sample loading and organic solvent wash steps were avoided in this procedure, the purified DNA was suitable for downstream processes such as PCR. This amino silica monolithic column was demonstrated to allow rapid and efficient DNA purification in microscale.
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稀土配合物由于具有优良的窄带发光性能和较长的荧光寿命,因而在光电学领域比如激光材料或者荧光标记上引起了广泛的兴趣和应用。吸附在固体表面的稀土配合物的发光性质得到了广泛的研究。MCM-48中孔材料是M41S家族中的一种,具有直径20-30A三维结构的中孔孔道,比MCM-41的一维结构孔道更有优势,比如它可以最大可能的避免客体分子的堆积现象。因此本论文中我们研究了将稀土(Eu3+)β-二酮(DBM=dibenzoylmethane)配合物掺杂到纯硅MCM-48以及三种有机基团嫁接的有机-无机杂化MCM-48的孔道中去,得到了各种不同的杂化中孔发光材料。首先烧结后的MCM-48被装载稀土Eu(OBM)3'2H2O配合物之后。XRD结果说明稀土配合物被组装到了MCM-48中,其有序结构因为稀土配合物的进入而受到一定的影响,但是样品仍保持了MCM-48的立方相结构。分别通过吸收光谱和热失重的方法计算了掺杂后的发光MCM-48样品进行洗涤后留在MCM一48中配合物的量。固体漫反射光谱在紫外区有一个OBM配体的Sn基态能级(π)到S1激发态能级份*)的电子跃迁形成的吸收宽带。可见区还观察到E护”离子的4f-4畴征吸收线。与稀土配合物中的OBM配体相比,掺杂MCM-48样品的Sn-S1吸收带均发生蓝移,反映了S1能级向高能方向移动。然后采用了室温两步合成法合成MCM-48,模板剂的去除采用了溶剂萃取法。最佳掺杂浓度为6.98×10-3 mol/l;同时最佳掺杂时间为24小时。在同样的掺杂条件下,稀土配合物在基质中的掺杂量MCM-48>MCM-41>>SiO2。萃取之后的MCM-48在外形上近乎于球形,粒子的直径在0.7-1.2μm之间。粒子显现出多孔的海绵状表面形态,并且具有晶体结构外形,呈菱形十二面体被削去顶端立方体的结构。而且在粒子的表面观察到了类似螺旋结构的孔道,我们认为这是MCM一48所特有的双螺旋型三维孔道结构,这是到目前为止首次报道利用扫描电镜观察到中孔分子筛的孔道结构。荧光光谱结果观察到了激发峰的最大值由于纳米粒子效应出现的蓝移现象。不同基质中的发射系数QZ和04比较可知配合物在三种基质SiO2、MCM-41和MCM-48中环境的极性相差不大。掺杂到中孔MCM-48材料中的稀土配合物的热稳定性比在MCM-41中强,这是由于MCM-48的三维孔道对配合物的保护作用。室温条件下合成的MCM-48分子筛利用后合成嫁接的方法[post-synthesis grajng(PSG)]进行表面修饰,修饰剂选用了带有功能性乙烯基的VTES,链长最短的MTES以及带有氨基的长链NTSED。稀土Eu(DBM)3'2H2O配合物被组装到杂化中孔分子筛材料中。红外光谱与2951核磁共振光谱表明MCM-48的表面被成功的接枝上了有机M下任S,盯任s,N丁s任D基团。与MCM-48相比,MCM-48-R的表面积、孔体积和孔径的减少有以下NTSED>VTES>MTES的顺序。这也许是修饰的有机基团不同的链的长度不同的原因。稀土配合物在这三种有机一无机杂化基质环境的极性比纯硅MCM-48要增大。同时配合物在三种基质的中的QZ的值及发光效率的顺序为:MCM-48-MTES<MCM-48-VTES<MCM-48-NTSED,说明MCM-48经过三种有机硅氧烷修饰之后孔道极性也遵循同样的顺序,可以认为这是由于三种有机基团的链长的不同造成的,链长越长则修饰之后孔道极性增大的就越多。最后通过溶胶一凝胶过程利用提拉法(Dip-coating method)制备了具有中孔结构的SiO2-CTAB-Tb(acac)3透明发光薄膜(Mesostructed Iuminescence thin film,略为MLTF),稀土配合物利用原位合成(In-situ)的办法掺入到透明薄膜中。对薄膜进行热处理过程表明薄膜中的稀土配合物在50℃的时候开始形成。XRO结果表明稀土离子及有机配体的掺入对薄膜中孔相的结构没有太大的影响,荧光薄膜仍保持层状结构。红外光谱结果说明制备的中孔薄膜是由CTAB和硅氧烷聚合物组成的复合薄膜。荧光薄膜的发射光谱给出了Th3+离子的特征发射峰,荧光薄膜中有机配体与丁b离子之间发生了能量传递现象。因为在热处理过程中有机配体逐渐代替了开始与Tb离子配位的OH基团,使得二者间的能量传递更加有效,从而导致了荧光的增强。
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本论文针对目前用于骨固定和骨修复的聚乳酸/无机纳米粒子复合材料的界面强度低、粒子分散不均匀以及所采用生物活性无机填料粒径较大等缺点,对轻基磷灰石及生物活性玻璃无机纳米粒子的制备、界面改性、粒子的分散、以及复合材料的制备进行了较详细的论述。另外,对材料的力学性能、结晶性能和生物相容性进行了较细统的测试和研究。(1)以磷酸和氢氧化钙为原料在40-80℃的反应条件下制备出了米粒状和棒状的HAP粒子,然后在-50℃的冷冻干燥机中干燥48h,得到白色的HAP粉末。用TEM、SEM、WAXD、FTIR等对所得产物进行了表征。研究结果表明,提高反应温度有利于生成高结晶度的长棒状HAP颗粒。此外,锻烧温度对粒子的形貌和结晶度也有很大的影响,锻烧温度越高,粒子的结晶度就越高,并且,当锻烧温度提高到900℃以上时,HAP粒子的形貌会由长棒形逐渐变成球形。(2)在高纯氢气气氛中,以辛酸亚锡为催化剂的反应条件下使左旋丙交酷开环聚合,直接接枝到HAP的表面,使HAP的粒子表面覆盖一层聚乳酸分子,使HAP的亲油性能得到提高。对表面接枝的轻基磷灰石(g-HAP)用31PMAS-NMR、FTIR、TGA、TEM、SEM和GPC进行了表征。结果表明,用此方法可在HAP表面接枝6%的PLLA。(3)用溶剂法制备了PLLA/g-HAP复合材料,并对其机械性能、结晶性能和生物相容性进行了表征。试验结果表明:与纯HAP相比,g-HAP粒子更容易均匀分散到PLLA基体中,当填料含量达到4%时,PLLAg-HAP复合材料的力学性能达到最好。由Dsc和PoM的实验结果表明,g-HAP粒子在聚合物基体中可以起到异相成核剂的作用。细胞实验结果表明,PLL刀g-HAP复合材料的细胞相容性明显优于纯的PLLA和PLLA/HAP复合材料。(4)以正硅酸乙酷(TEOS)、硝酸钙(Ca(NO3)2)和磷酸氢二按((NH4)ZHPO4)为原料,利用在酸性溶液中水解,碱性溶液中缩聚沉淀,然后将反应液离心分离,冷冻干燥,最后在马弗炉中锻烧的方法,得到白色的5102-coo-PZos三元生物活性玻璃粉末。SEM和TEM分析结果表明,所得到生物活性玻璃是粒径在40nln左右的球形颗粒,且粒径分布非常均匀。(5)以正硅酸乙酷(TEoS)和硝酸钙(Ca(NO3)2)为原料,利用在酸性溶液中水解,碱性溶液中缩聚沉淀,然后将反应液离心分离,冷冻干燥,最后在马弗炉中锻烧的方法,得到粒径为200nm左右的球形SiO2-CaO二元生物活性玻璃粉末。
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自从1992年美孚公司成功地研究开发出介孔材料M41S后,由于其具有不同寻常的结构特点-比较均一的孔径(2-50nm)而且连续可调、较高的比表面积、较大的孔体积、孔的长程有序性以及较好的热稳定性等,具有巨大的潜在应用价值,立即引起了全世界的关注。目前,世界各国的研究主要集中在研究介孔材料的特性、形成机理、介孔材料形貌、结构和孔径的控制、新一代介孔材料的研究开发、介孔材料的改性以及介孔材料的应用等方面。本论文主要在介孔材料的合成、性能以及应用方面开展了研究。选用头尾都是憎水的三嵌段共聚物为模板制备出具有三维无序虫状孔道的介孔材料和以有孔氧化铝膜为模板制备了形态可控的介孔材料,即具有介孔结构高有序纳米管。采用一步法合成了介孔Ag/silica和Y2O3:Eu/silica材料,采用基底受限法制备了银和Y2O3:Eu纳米粒子,同时研究了Ag/silic。作为催化剂时催化性能。(1)在酸性条件下,利用头尾都是憎水的三嵌段共聚物SBS为模板、TEOS为硅源,分别选用丁酮和甲苯作选择性溶剂,通过微乳技术制备出具有三维无序虫状孔道的介孔硅材料。我们通过在SBS胶束溶液中加入TEOS/水的油水混合乳液使SBS胶束与TEOS/水混合乳液之间形成一个界面,从而使TEOS这个界面上完全水解而且生成的小分子硅齐聚物包附在SBS胶束的外表面。经过加热则使TEOS凝聚同时形成具有介孔结构的SBS/硅材料。最后,通过锻烧以移除SBS,从而得到介孔硅材料。在选用甲苯作溶剂,研究发现随着SBS用量的增加或形成胶束温度的升高比表面积、孔体积和孔径等都相应减小。因此,这两个参数可以方便地调节介孔材料的孔径、表面积和孔体积等,进而更好地控制介孔材料的性能。所制备介孔材料的壁厚与SBS用量和形成胶束温度无关,且均超过IOnm,因而材料具有较好的热稳定性,这有利于其进一步在催化剂、吸附和分离等领域应用。(2)以有孔的氧化铝膜为模板制备了具有介孔结构高有序纳米管,即在加热条件下将P123一TEOS薄膜通过毛细力引入有孔的氧化铝膜孔内,同时根据优先润湿机理使P123一TEOS组分润湿氧化铝孔的内壁并同时伴随嵌段共聚物胶束的重排、TEOS组分的凝聚收缩,随后通过烧结手段除去嵌段共聚物、通过溶解手段除去氧化铝模板,这样便在硅基底上得到了形态可控的介孔材料即有序排列的具有介孔结构的纳米管。在一定时间范围内,退火时间对纳米管的形成和生长高度有一定的影响。纳米管垂直于硅基底且纳米管套内的介孔以六方形式排列在整个纳米管套同时介孔孔道相互平行,所制备的纳米管能保持受限在氧化铝模板时的尺寸而且稳定地粘附在硅基底上。(3)在酸性条件下,采用一步法即在模板剂(P123)形成胶束之后,加入硝酸银或氧化铺和氧化忆混合物同P123胶束形成新的复合体,随后加入硅源(TEOS)以包附在复合体的外表面,从而形成具有介孔相的复合物,通过热处理我们分别制备了高有序的具有二维六方结构的介孔Ag/silica和Y203:Eu/silica材料,其中金属银或YZO3:Eu纳米粒子分散在有序的介孔孔道内。二者的比表面积、孔体积和孔径分别为786m2/g、1.22cm3/g、6.Znm和791m2/g、0.95cm3/g、3.snm。另外,我们采用基底受限法,利用旋涂法分别使介孔Ag/silica和YZO3:E记silica材料分散在硅基底上,通过溶解法除去硅墙后便得到了没有聚集的且具有狭窄粒径分布的金属银(2.5-5.snm)和姚03:Eu(1.5-3.onm)纳米粒子。原子力显微镜(AFM)证实所得到的纳米粒子呈现良好的分散状态,具有狭窄的粒径分布而且粒子尺寸都小于其介孔材料孔径。(4)分别用一步法制备的介孔Ag/SBA--15材料和金属银作为甲醇氧化制备甲醛反应的催化剂,利用甲醇转化率表示催化剂活性、甲醛和二氧化碳产率表示催化剂选择性来研究二者催化性能。由于具有高的比表面积(786扩/g)、较大的孔体积(1.22cm3/g)、较大的孔径(6.2nm)、狭窄的孔径分布和有序的介孔孔洞等特性,在反应温度473K-723K范围内,同本体银作催化剂相比尽管银仅占体系总重量的0.94wt%,介孔Ag/silic。材料却显示出极高的催化活性和催化选择性。
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Silica-based functionalized terbium fluorescent nanoparticles were prepared, characterized and developed as a fluorescence probe for antibody labeling and time-resolved fluoroimmunoassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion containing a strongly fluorescent Tb3+ chelate. N,N.N-1,N-1-12,6-bis(3'-aminomethyl-1'-pyrazolyl)phenylpyridine] tetrakis(acetate)-Tb3+ (BPTA-Tb3+), Triton X-100, octanol, and cyclohexane by controlling copolymerization of tetraethyl orthosilicate (TEOS) and 3-[2-(2- aminoethylamino)-ethylamino]propyl-trimethoxysilane (AEPS) with ammonia water. The characterizations by transmission electron microscopy and fluorometric quantum methods show that the nanoparticles are spherical and uniform in size, 45 +/- 3 nm in diameter, strongly fluorescent with fluorescence yield of 10% and a long fluorescence lifetime of 2.0 ms. The amino groups directly introduced to the nanoparticle's surface by using AEPS in the preparation made the surface modification and bioconjugation of the nanoparticles easier. The nanoparticle-labeled anti-human alpha-fetoprotein antibody was prepared and used for time-resolved fluoroimmunoassay of (x-fetoprotein (AFP) in human serum samples. The assay response is linear from 0.10 ng ml(-1) to about 100 ng ml(-1) with the detection limit of 0.10 ng ml(-1). The coefficient variations (CVs) of the method are less than 9.0%. and the recoveries are in the range of 84-98% for human serum sample measurements. (C) 2004 Elsevier B.V. All rights reserved.
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Aluminum-substituted mesoporous SBA-15 (Al-SBA-15) materials were directly synthesized by a hydrolysis-controlled approach in which the hydrolysis of the silicon precursor (tetraethyl orthosilicate, TEOS) is accelerated by fluoride or by using tetramethyl orthosilicate (TMOS) as silicon precursor rather than TEOS. These materials were characterized by powder X-ray diffraction (XRD), N-2 sorption isotherms, TEM, Al-27 MAS NMR, IR spectra of pyridine adsorption, and NH3-TPD. It is found that the matched hydrolysis and condensation rates of silicon and aluminum precursors are important factors to achieve highly ordered mesoporous materials. Al-27 MAS NMR spectra of Al-SBA-15 show that all aluminum species were incorporated into the silica framework for the samples prepared with the addition of fluoride. A two-step approach (sol-gel reaction at low pH followed by crystallization at high pH) was also employed for the synthesis of Al-SBA-15. Studies show that the two-step approach could efficiently avoid the leaching of aluminum from the framework of the material. The calcined Al-SBA-15 materials show highly ordered hexagonal mesostructure and have both Bronsted and Lewis acid sites with medium acidity.
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Much attention has been paid to carbazole derivatives for their potential applications as optical materials. For the first time, the blue-light-emitting carbazole chromophore has been covalently bonded to the ordered mesoporous SBA-15 (The resultant hybrid mesoporous materials are denoted as carbazole-SBA-15) by co-condensation of tetraethoxysilane (TEOS) and prepared compound 3-[N-3-(triethoxyilyl)propyl]ureyl-9-ethyl-carbazole (denoted as carbazole-Si) in the presence of Pluronic P123 surfactant. The results of H-1 NMR and Fourier transform infrared (FTIR) reveal that carbazole-Si has been successfully synthesized.
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In this study. Nafion (R) 117 membrane is surface-modified with mesoporous silica layers through in situ surfactant-templated sol-gel reaction. The reaction makes use of tetraethyl orthosilicate (TEOS) under acidic condition via dip-coating technique on both sides. Scanning electron microscopy (SEM), Fourier transformation infrared (FTIR), and thermogravimetric analysis (TGA) are employed to characterize the resultant membranes. Proton conductivity and methanol permeability of the membranes are also studied.
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Ternary europium complex Eu(tta)(3)phen was covalently bonded with the general mesoporous. material SBA-15 and SBA-15-type of periodic mesoporous organosilica (PMO) material via impregnation of Eu(tta)(3)center dot 2H(2)O into phen-S15 and phen-PMO, respectively, through a ligand exchange reaction. The parent materials of phen-S15 and phen-PMO were synthesized by co-condensation of tetraethylorthosilicate (TEOS) or 1,2-bis(triethoxysilyl)ethane (BTESE) and the functionalized chelate ligand 5-(N,N-bis(3-triethoxysilyl)propyl)ureyl-1,10-phenanthroline (phen-Si) in the presence of Pluronic P123 surfactant as template, which were confirmed by SEM, XRD, FTIR, Si-29 CP-MAS NMR, and N-2 adsorption measurements.
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Silica-gel nanowire/Na+-montmorillonite (Na+-MMT) nanocomposites were prepared by the in situ sol-gel process of tetraethyl orthosilicate (TEOS) in the presence of Na+-MMT and ammonia as catalyst. Microstructure characterization of the nanocomposites was done by SEM, , EDX, XRD and FTIR. It was found that a lot of silica-gel nanowires grew along the edges of Na+-MMT. The combination between the nanowires and Na+-MMT was accomplished via polycondensation of the hydrolyzed TEOS and the edge-OH groups of Na+-MMT.