氨基硅烷偶联剂对蒙脱石的修饰改性研究

研究了氨基硅烷偶联剂对蒙脱石的修饰改性,并和长链烷基硅烷偶联剂作对比.通过改性前后蒙脱石的傅立叶红外光谱(FT-IR),广角X射线衍射(WAXD),热失重分析(TGA)研究发现,在冰醋酸的处理下,氨基硅烷偶联剂不但能够对蒙脱石进行表面偶联修饰而且能够以插层剂的形式进入蒙脱石的层间.初步的浸润/分散性实验结果表明:氨基硅烷插层/表面修饰改性的蒙脱石在弱极性乙醇溶剂中的分散性能明显提高.     

离子束修饰对电极表面结构和析氢活性的影响

采用了离子束对工业钛电极进行表面改性，用电化学方法研究了改性电极在Ｈ２ＳＯ４溶液中的析氢活性，用表面能谱分析了电极表面的组分和结构。结果表明：通过离子束修饰在电极表面引入微量的活性元素即可明显改善工业纯钛电极的析氢催化活性；离子束修饰改变了电极表面的组分和相结构，从而达到了改性的目的。     

蒙脱石-石墨-聚氯乙烯复合电极的研制

化学修饰电极自1975年正式问世以来^[1],经过多年的不断发展,现已出现了许多修饰方法^[2];如表面吸附法,聚合物薄膜法,共价键合法等。这些方法虽在一定程度上改善了修饰电极的表面结构,提高了电极的灵敏度和选择性,但由于此类修饰都是在电极表面附上一层修饰剂,容易因修饰层不牢而脱落,或修饰厚度不均匀而影响电极的性能,近年来出现了组合法制作碳糊电极^[3]及蒙脱石修饰碳糊电极^[4]的研究,但由于碳糊及其修饰电极存在电极表面柔软的缺点而使其生理性,稳定性欠佳,本文用聚氯乙烯作粘合剂,在其融状态下,将石墨和蒙脱石混合,加压,冷却制成复合电极,该复合电极用于苯酚测定时,表现出良好的稳定性,重现性和催化效果,并克服了蒙脱石修饰碳糊电极稳定性,重现性差的缺点。     

DNA修饰电极的研究Ⅷ.1,10-菲咯啉存在时钴离子在ssDNA修饰金电极上的电化学行为及痕量钴的检测

发现在过量1,10-菲咯啉存在时,Co3+/2+在单链DNA(ssDNA)修饰金电极上的电化学响应显著增强.采用紫外光谱和循环伏安法考察了Co3+/2+/1,10-菲咯啉体系与ssDNA的相互作用,并利用Co3+/2+在1,10-菲咯啉存在时在ssDNA修饰金电极上的高灵敏电化学响应对痕量钴离子进行了测定.     

DNA修饰电极的研究: VIII. 1, 10-菲咯啉存在时钴离子在ssDNA 修饰金电极上 的电化学行为及痕量钴的检测

发现在过量1,10-菲咯啉存在时,Co^3^+^/^2^+在单链DNA(ssDNA)修饰金电极上的电化学响应显著增强。采用紫外光谱和循环伏安法考察了Co^3^+^/^2^+/1,10-菲咯啉体系与sSDNA的相互作用,并利用Co^3^+^/^2^+在1,10-菲咯啉存在时在ssDNA修饰金电极上的高灵敏电化学响应对痕量钴离子进行了测定。     

DNA修饰电极的研究: VIII. 1, 10-菲咯啉存在时钴离子在ssDNA 修饰金电极上 的电化学行为及痕量钴的检测

发现在过量1,10-菲咯啉存在时,Co^3^+^/^2^+在单链DNA(ssDNA)修饰金电极上的电化学响应显著增强。采用紫外光谱和循环伏安法考察了Co^3^+^/^2^+/1,10-菲咯啉体系与sSDNA的相互作用,并利用Co^3^+^/^2^+在1,10-菲咯啉存在时在ssDNA修饰金电极上的高灵敏电化学响应对痕量钴离子进行了测定。     

硫酸双肼屈嗪修饰玻碳电极安培法测定过氧化氢

在1.0 mol/L H2SO4溶液中,在玻碳电极上修饰硫酸双肼屈嗪制得的修饰电极对过氧化氢还原有催化作用.研究了各种实验条件对修饰电极性能的影响.在-0.3 V工作电位下,用安培法测定过氧化氢的响应电流与其浓度在1.94×10-5～1.05×10-s mol·L-1范围内呈线性关系.该修饰电极具有制作简单,使用寿命长...     

磷钨酸改性蒙脱土-离子液体修饰电极上百草枯的电化学行为及测定

该文制备了磷钨酸改性蒙脱土-离子液体修饰电极(PTA-MMT-[BMIM]PF6/GCE),用红外光谱对PTA-MMT和[BMIM]PF6进行了表征.通过对比改性前后电极的交流阻抗图,发现PQ在PTA-MMT-[BMIM]PF6/GCE上电荷转移的电阻最小.研究了百草枯(PQ)在该修饰电极上的循环伏安行为.结果表明,在...     

苯二酚在聚吡咯膜修饰电极上的催化反应

儿茶酚等有机化合物是人体内的电活性物质，直接参予人体内的各种生理过程．有关这类物质的电化学行为一直是生物化学和化学领域的重要研究课题之一．但这些物质在固体电极上的电极反应迟缓，过电位高，检测比较困难．利用化学修饰电极可以对这类物质的电极反应进行催化，可制成各种电流式传感器[1]，特别是聚合物膜修饰电极传感器有催化效率高、稳定性好等优点问，是目前电化学传感器研究中的一个主要方面．聚毗咯膜（PPy）修饰电极自从出现以来已得到了广泛的应用，在电分析化学领域更具有稳定性好，制备条件简便等优点．一些在固体电极…     

辅酶Ⅰ在β－萘醌磺酸根修饰金带电极上的电化学还原

研制了聚毗咯／ＮＱＳ修饰金带电极，讨论了ＮＱＳ／ＰＰｙ的电聚合过程及实验条件对金电极上吡咯聚合物膜性质的影响；用成核及生长理论解释了阴离子ＮＱＳ对电聚合过程计时电流曲线的影响，优化了ＮＱＳ／ＰＰｙ／Ａｕ电极的制备条件．该修饰电极稳定性好，对辅酶Ⅰ在金电极上的还原有催化作用．在ｐＨ＝７．０时催化电流在４．０×１０￣（－５）～１．５×１０￣（－３）ｍｏｌ／Ｌ范围内与ＮＡＤ￣＋　浓度有线性关系，探讨了电催化作用的机制．     

Transparent acryl–clay nanohybrid films with low thermal expansion coefficient

The aim of this study was to prepare transparent nanohybrid films with low coefficient of thermal expansion (low CTE), which consist of acryl resin and nanosized clay. The hybrid films with different clay contents were prepared by UV curing of tricyclodecane dimethanol diacrylate (TCDDMDA) including nanosized clay. All obtained films were transparent similar to pure poly(TCDDMDA). In addition, the film containing 40 wt.% of clay showed a low CTE of 10 ppm/K in 150–200 °C, which is similar to that of inorganic materials such as glass. The significant property improvement is related to shape effect and orientation of clay in polymer matrix. Wide-angle X-ray diffraction measurement was carried out to investigate orientation of nanosized clay in polymer matrix. From this measurement, it was confirmed that the clay platelets were oriented parallel with film surface with increasing clay content, and orientation coefficient of the clay in polymer matrix reached to f?=?0.65 for the hybrid film containing 40 wt.% of clay. Though, in comparison with the matrix, the flexibility of the hybrid film evaluated by the wind roll test with steel bar was lowered by increase of clay content, the hybrid film containing 40 wt.% of clay could be rewound with steel bar 10 mm across, and its flexibility was retained.     

Influence of clay concentration on the gas barrier of clay-polymer nanobrick wall thin film assemblies

The influence of the clay deposition suspension concentration on gas barrier thin films of sodium montmorillonite (MMT) clay and branched polyethylenimine (PEI), created via layer-by-layer assembly, was investigated. Films grown with MMT suspension concentrations ranging from 0.05 to 2.0 wt % were analyzed for their growth as a function of deposited polymer-clay bilayers (BL) and their thickness, clay concentration, transparency, nanostructure, and oxygen barrier as a function of the suspension concentration. The film thickness doubles and the visible light transmission decreases less than 5% as a function of MMT concentration for 20-BL films. Atomic force and transmission electron microscope images reveal a highly aligned nanobrick wall structure, with quartz crystal microbalance measurements revealing a slight increase in the film clay concentration as the MMT suspension concentration increases. The oxygen transmission rate (OTR) through these 20-BL composites, deposited on a 179 μm poly(ethylene terephthalate) film, decreases exponentially as a function of the MMT clay concentration. A 24-BL film created with 2.0 wt % MMT has an OTR below the detection limit of commercial instrumentation (<0.005 cc/m(2)·day·atm). This study demonstrates an optimal clay suspension concentration to use when creating LbL barrier films, which minimizes deposition steps and the overall processing time.     

Orientation of platelets in multilayered nanocomposite polymer films

The orientation of platelets in micro-meter-thick polymer-clay nanocomposite films was investigated with small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD). The films with various clay contents (15–60% by mass fraction) were prepared by a layer-by-layer approach from polymer-clay solutions that led to the formation of a high degree of orientation in both polymer and clay platelets. Shear-induced orientation of polymer-clay solutions is compared with the orientation of polymer-clay films. SANS, SAXS, and WAXD, with beam configurations in and perpendicular to the spread direction of the film, were used to determine the structure and orientation of platelets. In all films, the clay platelets oriented preferentially in the plane of the film. The observed differences in semidilute solutions, with clay surface normal parallel to the vorticity direction, versus bulk films and with clay surface normal parallel to the shear gradient direction at clay mass fractions of 40 and 60%, were attributed to the collapses of clay platelet during the drying process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3237–3248, 2003     

Formation of Langmuir-Blodgett films of a clay and a water-soluble alkylammonium cation

We have studied the formation of ultrathin hybrid films composed of a water-soluble alkylammonium cation (trimethyloctadecylammonium caiton: TMODAH+) and clay nanosheets at an air-water interface. When a chloroform solution of the ammonium salt of TMODAH+Cl- was spread onto a surface of an aqueous clay suspension in a Langmuir trough, a stable monolayer of the water-soluble ammonium cation was formed by hybridization with the clay nanosheets at the air-water interface. Surface pressure--molecular area (pi-A) isotherm curve of the hybrid monolayer shifted to the smaller molecular area side with the increase in the concentration of the ammonium salt in the solution or with the decrease in that of the clay in the suspension. In some cases, the lift-off areas in the pi-A isotherm curves were less than the cross-sectional area of an alkyl chain (ca. 0.19 nm2). These results indicated that some ammonium cations spread onto the clay suspension were dissolved into the aqueous subphase before the hybridization with the clay nanosheets. The hybrid monolayers were transferred onto a glass plate in a layer-by-layer way by horizontal dipping to form a hybrid multilayerd film. Interestingly, the densities of TMODAH+ determined by the infrared spectral analysis were constant in the hybrid multilayers prepared from the clay suspensions at the same concentration, regardless of the concentrations of the ammonium salt solutions. XRD patterns of the films showed that the cations of TMODAH+ would lie down on the clay layer in the hybrid film.     

Formability and properties of self-standing clay film by montmorillonite with different interlayer cations

Influences of exchangeable interlayer cations were investigated on self-standing film formability, film morphology, and properties of the clay films such as flexibility and gas barrier property. Ion-exchanged montmorillonite samples were prepared by a cation exchange from naturally bearing cation, mostly Na⁺, to Li⁺, Mg²⁺, Ca²⁺, Al³⁺, and Fe^{2+, 3+}. Self-standing films were prepared from aqueous colloidal dispersions of these montmorillonite samples with no additives. The montmorillonite samples with monovalent or divalent cation formed flat self-standing films while the Al-montmorillonite sample produced a distorted film. The Fe-montmorillonite sample formed many separated reddish-brown rod-shaped pieces. Clay film microstructures were different with interlayer cations. The films with monovalent interlayer cations were constructed by the stacking of units with delicately waved thin clay sheets in the whole film, but other films show different morphologies between the upper side and lower side; the upper side is laminated with thin sheets; the lower side is laminated with large thick sheets.The self-standing films’ flexibility and gas barrier property differed according to the interlayer cations. These properties were good in cases of samples with monovalent cations. The innumerable short wave and sheet thinness are considered to foster good flexibility and gas barrier properties. The differences in film formability and properties of the films are attributable to different swellability among samples with different interlayer cations. The montmorillonite samples with monovalent cations swell sufficiently by water, but those with polyvalent cations swell poorly. In the latter case, clay crystals aggregate in water, then the aggregate grows into large particles, creating a film with large particles.     

Nanocomposite-based lignocellulosic fibers 1. Thermal stability of modified fibers with clay-polyelectrolyte multilayers

The layer-by-layer (LbL) assembly process of creating highly structured thin films derived from layers of polyelectrolytes and nanoparticles was adopted in this study to modify the surface of lignocellulosic fibers. Aqueous dispersions of clay nanoplatelets were created with ultrasonication and characterized with dynamic light scattering and atomic force microscopy in which confirmed the presence of individual clay nanoplatelets. Film thickness of never-dried clay and poly(diallyldimethylammonium chloride) (PDDA) multilayers was studied with a quartz crystal microbalance with dissipation monitoring (QCM-D). Using identical LbL deposition parameters, a slurry of steam-exploded wood fibers was modified by alternate adsorption of PDDA and clay with multiple rinsing steps after each adsorption cycle. Zeta potential measurements were used to characterize the fiber surface charges after each adsorption step while SEM images revealed that the LbL film masked the cellulose microfibril structure. Using a thermogravimetric analyzer, LbL modified steam-exploded wood fibers were observed to attain increased thermal stability relative to the unmodified material tested in both air and nitrogen atmospheres. Significant char for the LbL clay coated steam-exploded wood suggests the multilayer film serves as a barrier creating an insulating layer to prevent further decomposition of the material. This nanotechnology may have a positive impact on the processing of lignocellulosic fibers in thermoplastic matrices, designing of paper-based overlays for building products, and modification of cellulosic fibers for textiles.     

Electroactive planar waveguide studies of Ru(bpy)3(2+) intercalated in a thin clay film: I. Transport and electrochemical phenomena

Electroactive planar waveguide (EAPW) instrumentation was used to perform potential modulated absorbance (PMA) experiments at indium tin oxide (ITO) electrodes coated with 0-, 300-, 800-, and 1200-nm-thick SWy-1 montmorillonite clay. PMA experiments performed at low potential modulation monitor mass transport events within 100 nm of the ITO surface and, thus, when used in conjunction with cyclic voltammetry (CV), can elucidate charge transport mechanisms. The data show that at very thin films electron transfer is controlled by electron hopping (sensitive to the anion species in the electrolyte) in an adsorbed Ru(bpy)(3)(2+) layer. As the thickness of the clay film grows, electron transfer may become controlled by mass transfer of Ru(bpy)(3)(2+) within the clay film to and from the electrode surface, a mechanism that is affected by the swelling of the film. Film swelling is controlled by the cation of the electrolyte. Films loaded with Ru(bpy)(3)(2+) while being subjected to evanescent wave stimulation demonstrate a large hydrophobic layer. The growth of the hydrophobic layer is attributed to the formation of Ru(bpy)(3)(2+*), which has negative charge located at the periphery of the molecule enhancing clay/complex repulsion. The results suggest that the structure of the film and the mechanism of charge transport can be rationally controlled. Simultaneous measurements of the ingress of Ru(bpy)(3)(2+) into the clay film by CV and PMA provide a means to determine the diffusion coefficient of the complex.     

Electrochemically active films of negatively charged molecules,surfactant and synthetic clays

The electrochemical behavior of anionic molecules such as hexacyanoferrate and vitamin B₁₂ hexacarboxilate intercalated into clay–surfactant films is investigated. The results indicate that composites of surfactant cetyltrymethylammonium bromide (CTAB) and synthetic clay facilitate the permeation of the charged molecules through the film. By heating the modified electrode at 120°C for 1 h, the charged molecules, depending on hydrophobic and coulombic forces, are able to accommodate inside the film. Coulombic forces retain the anionic molecules in the clay–CTAB composite. The films are stable with good electroactivity.     

Point of zero potential of single-crystal electrode/inert electrolyte interface

In this work, a method to prepare a thermally stable QDs/clay powder is reported. First, several water soluble CdTe QDs characterised by different size-dependent emission wavelengths were synthesised through wet chemistry. Montmorillonite-Na(+) clay in water was dispersed into a muddy suspension by sonication. Then, the clay-water suspension was used as the host media for CdTe QDs to prepare the QDs/clay powder by freeze drying. The experiments showed that QDs/clay powder could be re-dispersed in water without changing the luminescent property of the QDs; this process was reversible. EDX showed that Cd and Te elements existed in the QDs/clay powder and the XRD tests showed that the clay [001] reflection peaks for raw clay, QDs (λ(em)=514 nm)/clay and QDs (λ(em)=560 nm)/clay were the same, namely 2θ=7.4°. Finally, QDs/clay powder was applied to the HDPE polymer extrusion process at 200 °C to produce thin films; the resultant QDs-polymer nanocomposite film exhibited strong fluorescence.     

Supramolecular structures in nanocomposite multilayered films

We investigate the multilayered structures of poly(ethylene)oxide/montmorillonite nanocomposite films made from solution. The shear orientation of a polymer-clay network in solution combined with simultaneous solvent evaporation leads to supramolecular multilayer formation in the film. The resulting films have highly ordered structures with sheet-like multilayers on the micrometer length scale. The polymer covered clay platelets were found to orient in interconnected blob-like chains and layers on the nanometer length scale. Inside the blobs, scattering experiments indicate the polymer covered and stacked clay platelets oriented in the plane of the film. The polymer is found to be partially crystalline although this is not visible by optical microscopy. Atomic force microscopy suggests that the excess polymer, which is not directly adsorbed to the clay, is wrapped around the stacked platelets building blobs and the polymer also interconnects the polymer-clay layers. Overall our results suggest the re-intercalation of clay platelets in films made from exfoliated polymer-clay solutions as well as the supramolecular order and hierarchical structuring on the nanometer, via micrometer to the centimeter length scale.