Multilayer Films with Nanocontainers: Redox‐Controlled Reversible Encapsulation of Guest Molecules

Stable multilayer films with cucurbit[8]uril have been fabricated on the basis of the alternating layer‐by‐layer assembly of a novel side‐chain pseudopolyrotaxane and a photoreactive polyanion. The as‐prepared multilayer films exhibit good properties as surface‐imprinted multilayers, because cucurbit[8]uril molecules that are locked inside the multilayers can act as nanocontainers with specific binding to certain guest molecules, and the loading and release of the guest is redox‐controllable and reversible.     

Fabrication of a Stable Polyelectrolyte/Au Nanoparticles Multilayer Film

The fabrication of stable polyelectrolyte/Au nanoparticle multilayer films was achieved by the UV irradiation of layer‐by‐layer self‐assembled multilayers consisting of diazoresins and Au nanoparticles. The method promises to be a simple and efficient strategy to construct covalently attached organic/inorganic multilayer hybrids.     

Control of the water permeability of polyelectrolyte multilayers by deposition of charged paraffin particles

We present a new way to protect polyelectrolyte multilayers from water, consisting in the adsorption and subsequent fusing of charged wax particles atop a multilayer. The formation of the wax layer is demonstrated by different techniques such as ellipsometry, contact angle measurements, and atomic force microscopy. The diffusion of water in protected and unprotected multilayers is studied by in situ neutron reflectometry. Whereas a top layer of wax crystals already allows substantial reduction of the diffusion, the fusion of this top layer leads to the dominating exclusion of water from the multilayers when dipped in water. This method opens up new interesting avenues for polyelectrolyte multilayers in practical applications where permeability of water, ions, or hydrophilic drugs is an issue.     

有序纳米金颗粒的多层组装

采用LB技术组装了一种三维有序的由十八胺修饰的纳米金颗粒多层结构.这是一种新的组装纳米颗粒三维有序聚集体的方法.为了扩大这种方法的适用范围,在组装过程中,将有机小分子1-苯基-5-巯基四氮唑引进结构,形成了新的纳米金颗粒多层聚集体.这两种多层膜经透射电子显微镜和小角X射线衍射测量证明构成多层膜的单层膜上的纳米金颗粒是有序的,并且颗粒在层与层之间的排列也是有序的.     

Construction of Polycation‐Based Non‐Viral DNA Nanoparticles and Polyanion Multilayers via Layer‐by‐Layer Self‐Assembly

Summary: The multilayers of polycation‐based non‐viral DNA nanoparticles and biodegradable poly(L ‐glutamic acid) (PGA) were constructed by a layer‐by‐layer (LbL) technique. Poly(ethyleneimine) (PEI) was used to condense DNA to develop non‐viral DNA nanoparticles. AFM, UV‐visible spectrometry, and TEM measurements revealed that the PEI‐DNA nanoparticles were successfully incorporated into the multilayers. The well‐structured, easily processed multilayers with the non‐viral DNA nanoparticles may provide a novel approach to precisely control the delivery of DNA, which may have great potential for gene therapy applications in tissue engineering, medical implants, etc.

A TEM image of the cross section of a (PGA/PEI‐DNA nanoparticle)₂₀ multilayer.     

Mechanical property and corrosion resistance of zirconia/polydopamine nanocomposite multilayer films fabricated via a novel non‐electrostatic layer‐by‐layer assembly technique

Zirconia/polydopamine (ZrO₂/PDA) nanocomposite multilayer films were constructed on Si substrate via a novel nonelectrostatic layer‐by‐layer (NELBL) assembly technique. The building block of this technique is the newly reported dopamine molecule, which can be attached to almost all material surfaces and undergo oxidation‐polymerization to form PDA layers; more importantly, the outer hydroxyl groups of the PDA layer can chelated with certain inorganic oxide nanoparticles to generate oxide films. Thus, ZrO₂/PDA nanocomposite multilayer films were fabricated by sequential NELBL deposition of PDA and ZrO₂ nanoparticles. The formation of the ZrO₂/PDA nanocomposite multilayer films was monitored by the water contact angle (WCA) and ellipsometric thickness measurements, while the microstructure of the fabricated films was analyzed by means of atomic force microscope (AFM), field emission scanning electron microscope (FESEM), X‐ray photoelectron spectrum (XPS), and X‐ray diffraction (XRD) analysis. The mechanical and anticorrosion behaviors of the annealed ZrO₂/PDA nanocomposite multilayers were found to be greatly enhanced as compared with that of the annealed homogeneous ZrO₂ film. The better mechanical and anticorrosion behaviors of the annealed ZrO₂/PDA nanocomposite multilayers than the annealed homogeneous ZrO₂ film may be closely related to their special microstructure. Namely, the organic–inorganic hybrid microstructure of the annealed ZrO₂/PDA nanocomposite multilayers may largely account for the increased nanohardness and corrosion resistance. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparison of Electrochemical and Surface Plasmon Resonance Immunosensor Responses on Single Thin Film

This paper reports results obtained when comparing an electrochemical enzyme immunosensor and a surface plasmon resonance (SPR) based immunosensor on the same gold surface installed in an electrochemical SPR flow cell. Simultaneous electrochemical and SPR measurements were performed on a gold surface modified with multilayers of poly‐L ‐lysine and poly‐styrenesulfonate assembled with the layer‐by‐layer method. First, we obtained the SPR response induced by the formation of an immunocomplex from the shift in the SPR angle by injecting an anti tumor necrosis factor‐α antibody solution labeled with alkaline phosphatase into the flow cell containing the multilayer modified with tumor necrosis factor‐α. Then we compared this SPR result with that obtained for the electrochemical oxidation current of p‐aminophenol catalyzed by alkaline phosphatase from p‐aminophenolphosphate on the same gold film. We compared the two immunosensor responses obtained using the different measurement principles and found that there was a high correlation efficient of 0.973 between them. This was because we were able to immobilize the immunoreagents with good stability and without losing the transport of the enzyme product in the multilayer whose thickness we easily controlled with nanometer scale accuracy. We also report that the detection limit of our electrochemical immunosensor after optimization was around 100 pg/mL (0.4 pM), which is one of the lowest values yet reported for an electrochemical immunosensor.     

Spin Self‐Assembled Clay Nanocomposite Passivation Layers Made from a Photocrosslinkable Poly(vinyl alcohol) and Na+‐Montmorillonite Enhance the Environmental Stability of Organic Thin‐Film Transistors

We investigated the effects of the multilayer polymer‐clay nanohybrid passivation films on the stability of pentacene organic thin‐film transistors (OTFTs) exposed to air and UV irradiation. Well‐ordered multilayer films were deposited by the spin‐assisted layer‐by‐layer assembly method using photocrosslinkable poly(vinyl alcohol) with the N‐methyl‐4(4′‐formylstyryl)pyridinium methosulfate acetal group (SbQ‐PVA) and Na⁺‐montmorillonite in a water‐based solution process. When photocrosslinked, these SbQ‐PVA/clay multilayers were found to serve as excellent barriers to O₂ and UV‐light. Moreover, when used as passivation layers, they enhanced the stability of pentacene OTFT devices exposed to air and UV radiation.     

纳米金属多层膜与多层纳米线的电化学制备及其表征

分别采用单槽法和双槽法电沉积Cu/Co多层膜.研究了两种电沉积方法制备多层膜的工艺条件,利用电化学方法、XRD和SEM对多层膜进行表征,并对Cu/Co多层膜的巨磁阻性能进行了测试. 采用电沉积多层膜的方法，以多孔铝阳极氧化膜（AAO）为模板,在纳米孔内沉积Cu/Co多层线,采用TEM对多层纳米线进行了表征.     

Bioinert solution-cross-linked hydrogen-bonded multilayers on colloidal particles

Bioinert polyelectrolyte multilayers comprised of poly(acrylic acid) and polyacrylamide were deposited on colloidal particles (1.7 microm in diameter) at low pH conditions by layer-by-layer assembly using hydrogen-bonding interactions. The multilayer films were coated uniformly on the colloidal particles without causing any flocculation of the colloids, and the deposited films were subsequently cross-linked by a single treatment of a carbodiimide aqueous solution. The lightly cross-linked multilayer films show excellent stability at physiological conditions (pH 7.4, phosphate-buffered saline), whereas untreated multilayer films dissolved. The multilayer-coated surfaces, both on flat substrates and on colloidal particles, exhibit excellent resistance toward mammalian cell adhesion. With this new solution-based cross-linking method, bioinert H-bonded multilayer coatings offer potential for biomedical applications.     

Stimulation and binding properties of polyelectrolyte multilayers verified by ATR‐FTIR spectroscopy

We report on the deposition and properties of multilayers composed of reactive polymers on planar surfaces. As reactive polymers the poly cations poly(ethylene‐imine), poly(L‐lysine) (PLL), poly(allylamime) (PAA) and the polyanions poly(acrylate) (PAC), poly(vinylsulfate), poly(maleate‐co‐olefines) were used. ATR‐FTIR Spectroscopy was adopted to study deposition, binding and stimulation properties of polymer multilayers. The binding of charged species of different molecular size such as rhodanide anions and sodium oleate from solution was examined, whereby binding was found to be dependent on the charge of the outermost layer. For these two analytes a selectivity parameter Q, defined as the ratio between the adsorbed amount obtained at the negatively charged and that at the positively charged surface, respectively, was determined. Furthermore, swelling experiments on multilayer assemblies of PLL and PAC exposed to mixtures of ethanol/water (10–70% EtOH content) were carried out. Our experiments gave evidence, that the PLL layers showed a more significant increase in density than the PAC layers. The conformation of PLL incorporated into multilayers could be changed by pH variation.     

双网络增强自支撑多层膜的制备

通过石英晶体微天平(QCM)研究不同最外层对单体、交联剂、引发剂扩散入多层膜的结果显示,聚乙烯亚胺( PEI)为最外层的多层膜更有利于负电荷分子扩散.将(聚乙烯亚胺/聚丙烯酸)12-聚乙烯亚胺[( PEI/PAA)12-PEI]多层膜浸入带有单体、引发剂、交联剂的溶液后,经过光聚合交联与热交联后可形成自支撑膜.XPS数...     

Individually Addressable Patterned Multilayer Microchambers for Site‐Specific Release‐On‐Demand

Patterned arrays of light‐responsive microchambers are suggested as candidates for site‐specific release of chemicals in small and precisely defined quantities on demand. A composite film is made of poly(allylammonium)‐poly(styrene sulfonate) multilayers and gold nanoparticles incorporated between subsequent stacks of polyelectrolytes. The film shaped as microchambers is loaded with colloid particles or oil‐soluble molecules. The microchambers are sealed onto a glass slide precoated with an adhesive poly(diallyldimethylammonium)‐poly(styrene sulfonate) multilayer film. A focused laser beam is used for remote addressing the individual microchambers and site‐specific release of the loaded cargo.     

Amperometric glucose enzyme electrode by immobilizing glucose oxidase in multilayers on self-assembled monolayers surface

A novel and robust amperometric enzyme electrode for the determination of glucose was constructed by immobilizing glucose oxidase (GOD) and Os(bpy)(2)Cl-poly(4-vinyl)pyridine (Os-PVP) complex multilayers on thiol self-assembled monolayers surface. The apparent Michaelis-Menton constant K(m)' increased with increasing the number of Os-PVP/GOD multilayers. The concentration range of linear response and detection limit were 0.1-10 and 0.05 mM, the interference of ascorbic acid and uric acid were eliminated by the presence of SAMs and the enzyme electrodes were stable over 3 weeks. The preparation technique may be useful for controlling the performance of multilayer enzyme electrodes by changing the enzyme content.     

Catalytic Polymer Multilayer Shell Motors for Separation of Organics

A catalytic polymer multilayer shell motor has been developed, which effects fast motion‐based separation of charged organics in water. The shell motors are fabricated by sputtering platinum onto the exposed surface of silica templates embedded in Parafilm, followed by layer‐by‐layer assembly of polyelectrolyte multilayers to the templates. The catalytic shell motors display high bubble propulsion with speeds of up to 260 μm s^?1 (13 body lengths per second). Moreover, the polyelectrolyte multilayers assembled at high pH (pH>9.0) adsorb approximately 89 % of dye molecules from water, owing to the electrostatic interaction between the positively charged polymers and the anionic dye molecules, and subsequently release them at neutral pH in a microfluidic device. The efficient propulsion coupled with the effective adsorption behavior of the catalytic shell motors in a microfluidic device results in accelerated separation of organics in water and thus holds considerable promise for water analysis.     

浸泡法和旋涂法对偶氮聚电解质静电吸附自组装膜结构及性能的影响

利用浸泡和旋涂静电吸附自组装技术制备了含有偶氮生色团的聚电解质薄膜,比较了两种方法在自组装膜生长机理、膜结构以及膜光学性能方面的差异.利用紫外光谱和椭偏仪检测自组装膜的生长情况,利用原子力显微镜对膜表面结构进行了表征,并用偏振激光在膜表面进行了写光栅实验.结果表明,采用浸泡法和旋涂法都可以制备出表面光滑均匀的含偶氮生色团的聚电解质自组装膜.但是浸泡法自组装膜的生长速度要比旋涂法快.在自组装膜厚度较小的情况下,旋涂法得到的自组装膜可以写出明显的光栅而浸泡法不可以.随着自组装膜厚度的增加,两种方法得到的自组装膜都可以写出明显的光栅.这些结果说明浸泡法自组装膜内部聚电解质分子的层间穿插比较严重,而旋涂法自组装膜内分子穿插要弱得多.     

Ordered Polyelectrolyte Multilayers: Unidirectional FRET Cascade in Nanocompartmentalized Polyelectrolyte Multilayers

Multifunctional polyelectrolyte (or layer‐by‐layer, LbL) multilayers consisting of a set of nanocompartments separated by impermeable ultrathin barriers, whereby the thickness of the compartments is tuned in the range 1–10 nm, are synthesized. Each compartment contains a different dye, introduced by co‐adsorption during multilayer deposition. Different LbL barriers are tested for impermeability towards dye diffusion while simultaneously allowing energy transfer to occur between the compartmentalized dyes. Cross‐linked LbL multilayers based on poly(acrylic acid) and poly(allyl amine) are shown to provide the desired impermeability for thicknesses as small as about 2.5 nm. A proof‐of‐concept system is then realized involving a cascade of two FRET processes, whereby the light energy is collected in a first nanocompartment containing pyranine, sent to a second nanocompartment loaded with fluorescein, before finally being transferred to a third, Nile blue‐filled compartment located at the external surface of the film. This demonstrates the possibility to fabricate complex light‐harvesting antenna systems by LbL assembly while controlling the architecture of the antenna down to a few nanometers.     

Layer-by-layer electrostatic self-assembly of single-wall carbon nanotube polyelectrolytes

We have used anionic and cationic single-wall carbon nanotube polyelectrolytes (SWNT-PEs), prepared by the noncovalent adsorption of ionic naphthalene or pyrene derivatives on nanotube sidewalls, for the layer-by-layer self-assembly to prepare multilayers from carbon nanotubes with polycations, such as poly(diallyldimethylammonium) or poly(allylamine hydrochloride) (PDADMA or PAH, respectively), and polyanions (poly(styrenesulfonate), PSS). This is a general and powerful technique for the fabrication of thin carbon nanotube films of arbitrary composition and architecture and allows also an easy preparation of all-SWNT (SWNT/SWNT) multilayers. The multilayers were characterized with vis-near-IR spectroscopy, X-ray photoelectron spectroscopy (XPS), surface plasmon resonance (SPR) measurements, atomic force microscopy (AFM), and imaging ellipsometry. The charge compensation in multilayers is mainly intrinsic, which shows the electrostatic nature of the self-assembly process. The multilayer growth is linear after the initial layers, and in SWNT/polyelectrolyte films it can be greatly accelerated by increasing the ionic strength in the SWNT solution. However, SWNT/SWNT multilayers are much more inert to the effect of added electrolyte. In SWNT/SWNT multilayers, the adsorption results in the deposition of 1-3 theoretical nanotube monolayers per adsorbed layer, whereas the nominal SWNT layer thickness is 2-3 times higher in SWNT/polyelectrolyte films prepared with added electrolyte. AFM images show that the multilayers contain a random network of nanotube bundles lying on the surface. Flexible polyelectrolytes (e.g., PDADMA, PSS) probably surround the nanotubes and bind them together. On macroscopic scale, the surface roughness of the multilayers depends on the components and increases with the film thickness.     

Determination of the inhibitory effect of green tea extract on glucose‐6‐phosphate dehydrogenase based on multilayer capillary enzyme microreactor

Natural herbal medicines are an important source of enzyme inhibitors for the discovery of new drugs. A number of natural extracts such as green tea have been used in prevention and treatment of diseases due to their low‐cost, low toxicity and good performance. The present study reports an online assay of the activity and inhibition of the green tea extract of the Glucose 6‐phosphate dehydrogenase (G6PDH) enzyme using multilayer capillary electrophoresis based immobilized enzyme microreactors (CE‐IMERs). The multilayer CE‐IMERs were produced with layer‐by‐layer electrostatic assembly, which can easily enhance the enzyme loading capacity of the microreactor. The activity of the G6PDH enzyme was determined and the enzyme inhibition by the inhibitors from green tea extract was investigated using online assay of the multilayer CE‐IMERs. The Michaelis constant (K_m) of the enzyme, the IC₅₀ and K_i values of the inhibitors were achieved and found to agree with those obtained using offline assays. The results show a competitive inhibition of green tea extract on the G6PDH enzyme. The present study provides an efficient and easy‐to‐operate approach for determining G6PDH enzyme reaction and the inhibition of green tea extract, which may be beneficial in research and the development of natural herbal medicines. Copyright © 2016 John Wiley & Sons, Ltd.     

Kinetic studies of glucose oxidase in polyelectrolyte multilayer films by means of scanning electrochemical microscopy (SECM)

Multilayer films of glucose oxidase (GOx) and poly(dimethyl diallyl ammonium chloride) (PDDA) prepared by layer-by-layer deposition were studied using scanning electrochemical microscopy (SECM). Aminated glass slides were coated with five bilayers of poly(styrene sulfonate) (PSS) and PDDA and used as substrates onto which GOx/PDDA multilayers were deposited. UV-Vis experiments confirmed multilayer growth, scanning force microscopic images provided morphological information about the films. SECM current-distance curves enabled the determination of kinetic information about GOx in GOx/PDDA multilayers as a function of layer number, film termination, inert covering layers, and enzyme substrate concentration after fitting to numerical models. The results indicate that only the topmost layers contributed significantly to the conversion. An odd-even pattern was observed for PDDA-terminated films or GOx-terminated films that correlated with morphological changes.