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| 366(1-2) (2000), 260-264
We demonstrate the fabrication and characterization of an organic light-emitting diode (OLED) device based on self- assembled poly(4-vinyl-pyridine) (P4VPy) with poly(N-vinyl- carbazole) (PVK) and 2-(4-biphenylyl)-5-(4-tert-butyphenyl)- 1,3,4-oxidiazole (PBD) as transport layers. The self-assembly is based on the electrostatic attraction of oppositely-charged polymers. We have shown here that we can use this self- assembled methodology to fabricate alternating multilayers, not only by the poly(phenyl-vinylene) (PPV) and derivatives, but also by partial protonation of P4VPy, by which the charge on P4VPy is generated by the protonation process. The multilayered structures are characterized by specular X-ray reflectivity (XRR), UV absorption, photoluminescence (PL) and electroluminescence (EL). (C) 2000 Published by Elsevier Science S.A. All rights reserved. [168] Nanoengineering of Particle Surfaces F. Caruso Adv. Mater. 13(1) (2001), 11 The creation of core-shell particles is attracting a great deal of interest because of the diverse applicability of these colloidal particles; e.g., as building blocks for photonic crystals, in multienzyme biocatalysis, and in drug delivery. This review presents the state-of-the-art in strategies for engineering particle surfaces, such as the layer-by-layer deposition process (see Figure), which allows fine control over shell thickness and composition. (See also cover). [169] Antireflection Surface with Particle Coating Deposited by Electrostatic Attraction H. Hattori Adv. Mater. 13(1) (2001), 51 Single-layer particulate coatings with special anti-reflection (AR) properties were deposited by an electrostatic attraction between the negatively charged colloidal particles and the positively charged surface of polyelectrolyte multilayers (see Figure). It is shown that the AR properties of the coating depend on the number of sequential depositions as well as on the treatment of the particles after deposition. [170] Hollow Titania Spheres from Layered Precursor Deposition on Sacrificial Colloidal Core Particles F. Caruso, X. Y. Shi, R. A. Caruso and A. Susha Adv. Mater. 13(10) (2001), 740-744 [171] The Sense of Chromophore Orientation in Films Made by Alternating Polyelectrolyte Deposition W. N. Herman and M. J. Roberts Adv. Mater. 13(10) (2001), 744-746 [172] Layer-by-Layer Self-Assembly of Glucose-Oxidase and Os(bpy)(2)Cipych2Nh-Poly(Allylamine) Bioelectrode E. J. Calvo, R. Etchenique, L. Pietrasanta, A. Wolosiuk and C. Danilowicz Anal. Chem. 73(6) (2001), 1161-1168 The uptake of glucose oxidase (GOx) onto a polycationic redox polymer (PAA- Os)-modified surface, by adsorption from dilute aqueous GOx solutions, was followed by the quartz crystal microbalance (QCM) and shows double exponential kinetics. The electrochemistry of the layer-by-layer-deposited redox-active polymer was followed by cyclic voltammetry in glucose-free solutions, and the enzyme, catalysis mediated by the redox polymer was studied in P-D-glucose-containing solutions. AFM studies of the different layers showed the existence of large two dimension enzyme aggregates on the osmium polymer for 1 muM GOx and less aggregation for 50 nM GOx solutions. When the short alkanethiol, 2,2'-diaminoethyldisulfide was preadsorbed onto gold, a monoexponential adsorption law was observed, and single GOx enzyme molecules could be seen on the surface where the enzyme was adsorbed from 50 nM GOx in water. [173] DNA-Mediated Electrostatic Assembly of Gold Nanoparticles into Linear Arrays by a Simple Drop-Coating Procedure M. Sastry, A. Kumar, S. Datar, C. V. Dharmadhikari and K. N. Ganesh Appl. Phys. Lett. 78(19) (2001), 2943-2945 The assembly of nanoparticles in topologically predefined superstructures is an important problem in the area of nanoscale architecture. In this letter, we demonstrate the electrostatic assembly of lysine-capped colloidal gold particles on drop-coated DNA films. Electrostatic interaction between the positive charges on the gold nanoparticles and the negative charges on the phosphate groups of the DNA template molecules leads to the assembly of the gold nanoparticles in linear superstructures. The use of DNA as templates for the assembly of nanoparticles shows promise for extension to more complex geometries through rational design of the DNA base sequences as well as in the realization of nanowires by stringing together metal nanoparticles. (C) 2001 American Institute of Physics. [174] Charge-Dependent Sidedness of Cytochrome-P450 Forms Studied by Quartz-Crystal Microbalance and Atomic-Force Microscopy J. B. Schenkman, I. Jansson, Y. Lvov, J. F. Rusling, S. Boussaad and N. J. Tao Arch. Biochem. Biophys. 385(1) (2001), 78-87 Quartz crystal microbalance (QCM) resonance measurements were used to examine the surface charge characteristics of cytochrome P450 forms and the influence of charge on the docking of redox partners like cytochrome b(5). The distal surface of cytochrome P450 (CYP)101 (pI = 4.5), relative to the heme, is fairly anionic, as is the proximal surface. The latter, however, also has two cationic clusters. A considerably greater extent of CYP101 binding was seen to the cationic, polyethylene-surfaced resonators. CYP2B4 (pI = 8.5) preferentially bound to the polyanionic, polystyrene sulfonate- surfaced resonators. Cytochrome b(5) is an acidic protein that had a preferential binding to the poly(ethyleneimine (PEI)- surfaced resonators. When binding to CYP2B4-surfaced films, cytochrome b(5) preferentially bound to those cytochrome P450 molecules that were adsorbed to cationic (PEI) films. It is suggested that adsorption of CYP2B4 to an anionic poly(styrenesulfonate) (PSS) surface is with cationic clusters that include the cytochrome b(5) docking domain. This diminishes the extent of docking of the cytochrome b(5). In contrast, when CYP2B4 is adsorbed to a cationic film the proximal surface with the cytochrome b(5)-docking site is available for cytochrome b(5) binding. A film of the polycation PEI was adsorbed to the silver QCM surface. It formed polymer islands when viewed with atomic force microscopy. Polyanionic PSS was adsorbed intermittently with the PEI. By the third and fourth layer of polyions the polymer islands were essentially merged and protein adsorption as a fourth or fifth layer formed a nearly continuous film. CYP101 was seen to adsorb as globules with a molecular diameter of about 10 nm. CYP2B4 adsorbed to the polyionic films had a slightly elliptical globular shape, also with a molecular diameter of about 10 nm. (C) 2001 Academic Press. [175] Direct Electrochemistry of Hemoglobin in Layer-by-Layer Films with Poly(Vinyl Sulfonate) Grown on Pyrolytic-Graphite Electrodes L. W. Wang and N. F. Hu Bioelectrochem. 53(2) (2001), 205-212 Stable layer-by-layer electroactive films were grown on pyrolytic graphite (PG) electrodes by alternate adsorption of layers of polyanionic poly(vinyl sulfonate) (PVS) and positively charged hemoglobin (Hb) from their aqueous solutions. Cyclic voltammetry (CV) of {PVS/Hb}(n) films showed a pair of well-defined and nearly reversible peaks at about - 0.28 V vs. SCE at pH 5.5, characteristic of Hb heme Fe(III)/ Fe(II) redox couple. The process of {PVS/Hb} bilayer growth was monitored and confirmed by CV, X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. While the amount of Hb adsorbed in each bilayer was the same, the amount of electroactive Hb in each bilayer decreased dramatically with increase of the number of bilayer, and electroactivity was just extended to 8 {PVS/Hb} bilayers. CVs of {PVS/Hb}(8) films maintained stable in buffers containing no Hb. Positions of Soret band of Hb in {PVS/Hb}(n) films grown on transparent glass slides suggest that Hb in the films keeps its secondary structure similar to its native state in a wide pH range. Trichloroacetic acid and nitrite were catalytically reduced by (PVS/Hb), films with significant lowering of the electrode potential required. (C) 2001 Elsevier Science B.V. All rights reserved. [176] Multilayer Capsules - A Promising Microencapsulation System for Transplantation of Pancreatic-Islets S. Schneider, P. J. Feilen, V. Slotty, D. Kampfner, S. Preuss, S. Berger, J. Beyer and R. Pommersheim Biomaterials 22(14) (2001), 1961-1970 In 1980, Lim and Sun introduced a microcapsule coated with an alginate/polylysine complex for encapsulation of pancreatic islets. Characteristic to this type of capsule is, that it consists of a plain membrane which is formed during a single procedural step. With such a simple process it is difficult to obtain instantly a membrane optimized with respect to all the properties requested for islet transplantation. To overcome these difficulties, it is recommended to build up the membrane in several consecutive steps, each optimized for a certain property. In this study, we have analysed such a multilayer microcapsule for the encapsulation of pancreatic islets. Therefore, empty and islet containing alginate beads were coated with alternating layers of polyethyleneimine, polyacrylacid or caboxymethylcellulose and alginate. By scanning electron microscopy the thickness of the covering multilayer-membrane was estimated to be less than 800 nm by comparison with an apparatus scale. Ellipsometric measurements showed that the membrane thickness is in the range of 145 nm. Neither the encapsulation procedure, nor the membrane-forming step did impede the stimulatory response of the islets. The encapsulation even lead to a significantly better stimulatory response of the encapsulated islets during week three and five of cell culture. Furthermore, the multilayer-membrane did not deteriorate the biocompatibility of the transplanted microcapsules. allowing an easy tuning of the molecular cut-off and the mechanical stability depending on the polycation- polyanion combination used. The multilayer membrane capsule has obvious advantages compared to a one-step encapsulation procedure. These beads guarantee a high biocompatibility, a precisely adjusted cut-off, an optimal insulin-response and high mechanical stability although the membrane is only 145 nm thick. (C) 2001 Elsevier Science Ltd. All rights reserved. [177] Microgravimetric DNA Sensor-Based on Quartz-Crystal Microbalance - Comparison of Oligonucleotide Immobilization Methods and the Application in Genetic Diagnosis X. C. Zhou, L. Q. Huang and S. F. Y. Li Biosensors and Bioelectronics 16(1-2) (2001), 85-95 We report on the study of immobilization DNA probes onto quartz crystal oscillators by self-assembly technique to form variety types of mono- and multi-layered sensing films towards the realization of DNA diagnostic devices. A 18-mer DNA probe complementary to the site of genetic beta -thalassaemia mutations was immobilized on the electrodes of QCM by covalent bonding or electrostatic adsorption on polyelectrolyte films to form mono- or multi-layered sensing films by self-assembled process. Hybridization was induced by exposure of the QCMs immobilized with DNA probe to a test solution containing the target nucleic acid sequences. The kinetics of DNA probe immobilization and hybridization with the fabricated DNA sensors were studied via in-situ frequency changes. The characteristics of QCM sensors containing mono- or multi- layered DNA probe constructed by direct chemical bonding, avidin-biotin interaction or electrostatic adsorption on polyelectrolyte films were compared. Results indicated that the DNA sensing films fabricated by immobilization of biotinylated DNA probe to avidin provide fast sensor response and high hybridization efficiencies. The effects of ionic strength of the buffer solution and the concentration of target nucleic acid used in hybridization were also studied. The fabricated DNA biosensor was used to detect a set of real samples. We conclude that the microgravimetric DNA sensor with its direct detection of amplified products provide a rapid, low cost and convenient diagnostic method for genetic disease. (C) 2001 Elsevier Science B.V. All rights reserved. [178] Fabrication of Heterogeneous Macroporous Materials Based on a Sequential Electrostatic Deposition Process D. Y. Wang and F. Caruso J. Chem. Soc., Chem. Commun. Iss 5 (2001), 489-490 Heterogeneous macroporous materials are prepared by the sequential electrostatic deposition of fluorescein isothiocyanate-labeled poly(allylamine hydrochloride) and cadmium telluride nanocrystals onto macroporous titania structures. [179] Self-Assembly of Photo-Responsive Azo Polyelectrolytes X. L. Tuo, Z. Chen, L. F. Wu, X. G. Wang and D. S. Liu CHEM J CHINESE UNIV CHINESE 22(2) (2001), 329-333 Three azo polyelectrolytes were successfully fabricated into self-assembled multilayers through a layer-by-layer dipping technique, The surface morphology and its variation with the bilayer growth were investigated with atomic force microscopy(AFM). The cis-trans isomerization of the self- assembled thin films was studied with UV-Vis spectroscopy and compared with the spin-coated films, PEAPE/PDAC and PPAPE/PDAC multilayers show significant photochromic effect upon UV light irradiation. In dark condition, the rates of cis-to-trans isomerization depend on the chromophore structure. For polyelectrolytes containing the same chromophores, the azo dyes in self-assembled multilayer recover much faster from cis to trans isomer than those in spin-coated films. [180] Multiple Adsorption of Polythiophene Layers on Ito/Glass Electrodes and Their Optical, Electrochemical, and Conductive Properties G. Zotti, S. Zecchin, A. Berlin, G. Schiavon and G. Giro Chem. Mater. 13(1) (2001), 43-52 Polyelectrolyte multilayers containing electrochemically active polythiophenes have been constructed on ITO/glass substrates using the layer-by-layer adsorption deposition technique. Electrochemically active layers of poly(cyclopentadithienyl- alkylsulfonate) poly(cyclopentadithienyl-alkylammonium), and alpha,omega -bis(carboxyhexyl)sexithiophene were deposited with non-electroactive layers of polyallylamine and polystyrenesulfonate. The first sequential adsorption of multilayers in which both the polycation and the polyanion are based on the same polythiophene is reported. UV-vis spectroscopy and cyclic voltammetry indicate a linear dependence of the amount of deposited polymer on the number of deposition cycles. The rate of deposition depends on the oxidation state of the polythiophene being 3 times lower for the oxidized polycationic polymer. Atomic force microscopy characterization of the layers has shown that flat monolayers are deposited with a progressive increase of roughness. Interposition of multiple nonelectroactive layers between the electrode and a single external electroactive polythiophene layer has allowed determination by cyclic voltammetry that each polythiophene layer interpenetrates the confining layers up to a three-layer distance. The conductivities of the multilayers along the surface and perpendicular to it are anisotropic depending on the layer alternation. The photoluminescence properties of the alpha,omega -bis(carboxyhexyl)sexithiophene multilayers are the same for vacuum-deposited polycrystalline layers. [181] Magnetic Nanocomposite Particles and Hollow Spheres Constructed by a Sequential Layering Approach F. Caruso, M. Spasova, A. Susha, M. Giersig and R. A. Caruso Chem. Mater. 13(1) (2001), 109-116 The fabrication of magnetic composite core-shell particles and hollow spheres with tailored dimensions and compositions has been accomplished by a multistep (layer-by-layer) strategy. Composite particles were prepared by coating submicrometer- sized anionic polystyrene (PS) latices with magnetite (Fe3O4) nanoparticle layers alternately adsorbed with polyelectrolyte from aqueous solution. The thickness of the deposited multilayers could be finely tuned with nanoscale precision, either by selection of the number of adsorption cycles performed or by the number of polyelectrolyte layers deposited between each nanoparticle layer (i.e., interlayer). As demonstrated by transmission electron microscopy, a marked improvement in the growth, uniformity, and regularity of the composite multilayers was achieved when the number of polyelectrolyte interlayers was increased from one [(poly(diallyldimethylammonium chloride) (PDADMAC)] to three [(PDADMAC/poly(styrenesulfonate) (PSS)/PDADMAC)]. Hollow, intact magnetic spheres were obtained by calcination of the core-shell particles at elevated temperature. Furthermore, composite hollow spheres were prepared by calcination of PS latices coated with multilayers of silica and Fe3O4 nanoparticles. These nanoengineered colloidal particles may potentially find applications as delivery systems, or in diagnostics, where the particles can be directed by application of an external magnetic field. [182] Layered Aluminosilicate/Chromophore Nanocomposites and Their Electrostatic Layer-by-Layer Assembly D. W. Kim, A. Blumstein, J. Kumar and S. K. Tripathy Chem. Mater. 13(2) (2001), 243-246 [183] Synthesis of Macroporous Titania and Inorganic Composite- Materials from Coated Colloidal Spheres - A Novel Route to Tune Pore Morphology D. Y. Wang, R. A. Caruso and F. Caruso Chem. Mater. 13(2) (2001), 364-371
[184] Multilayered Titania, Silica, and Laponite Nanoparticle Coatings on Polystyrene Colloidal Templates and Resulting Inorganic Hollow Spheres R. A. Caruso, A. Susha and F. Caruso Chem. Mater. 13(2) (2001), 400-409 The applicability of the layer-by-layer (LbL) technique for the formation of a range of polymer-core inorganic-shell particles and inorganic hollow spheres is demonstrated. Titanium dioxide, silica, and Laponite nanoparticles were used as the inorganic building blocks for multilayer formation on polystyrene (PS) sphere templates. Composite organic-inorganic particles were formed by the controlled assembly of the preformed nanoparticles in alternation with oppositely charged polyelectrolytes onto PS microspheres. The influence of nanoparticle type, shape (spherical to sheetlike), and size (3- 100 nm), and the diameter of the PS sphere templates (210-640 nm) on the formation of multilayer shells was examined by transmission and scanning electron microscopy. In addition, the LbL technique for coating polymer spheres has been shown to be adaptable with small variations in the coating steps used to optimize the nanoparticle coatings of the different materials. For example, the number of polyelectrolyte multilayers separating the nanoparticle layers, and the number of nanoparticle/polyelectrolyte deposition cycles were varied to generate uniformly coated nanocomposite spheres. These hybrid core-shell particles were subsequently calcined to create well- defined hollow spheres with predetermined diameters. Such hollow spheres may find application in diverse areas, ranging from photonics to fillers and pigments to microencapsulation. [185] Nanocomposite Films Derived from Exfoliated Functional Aluminosilicate Through Electrostatic Layer-by-Layer Assembly D. W. Kim, A. Blumstein and S. K. Tripathy Chem. Mater. 13(5) (2001), 1916-1922 Multilayered nanocomposite films were prepared from aluminosilicate platelets with functional chromophores and polyelectrolytes through electrostatic layer-by-layer assembly. Fluorescent dye coumarin was intercalated into the layered aluminosilicate hectorite, and the resulting hectorite/coumarin intercalation complex particles were broken down into individual platelets by means of extensive shaking and sonication of their water suspension. Atomic force microscopy (AFM) and transmission electron microscopy data show that the exfoliated platelets have the form of lathes of approximately 10-40 nm width, 150-400 nm length, and 2-3 nm average thickness. This last value is consistent with the overall thickness of a single aluminosilicate lamella sheathed with coumarin molecules on both sides. Given the strong negative surface charge of the aluminosilicate layers, films of nanocomposites could be formed by electrostatic layer-by-layer assembly using a cat;ionic polyelectrolyte. The AFM topography of such films revealed a homogeneous monolayer coverage of the underlying substrate. Linear buildup of the multilayer films of up to 20 cycles was demonstrated and investigated using UV/vis absorption spectroscopy. The resulting transparent films have exhibited strong characteristic blue-green fluorescence due to coumarin dye molecules adhered to the exfoliated hectorite platelets. [186] Electrostatic Layer-by-Layer Assembly of Polycation and DNA Multilayer Films by Real-Time Surface-Plasmon Resonance Technique R. J. Pei, X. Q. Cui, X. R. Yang and E. K. Wang Chinese J. Chem. 19(4) (2001), 433-435 The assembly of alternating DNA and positively charged poly(dimethyldiallylammonium chloride) (PDDA) multilayer films by electrostatic layer-by-layer adsorption has been studied. Real time surface plasmon resonance (BIAcore) technique was used to characterize and monitor the formation of multilayer films in solution in real time continuously. The results indicate that the uniform multilayer can be obtained on the poly(ethylenimine) (PEI) coated substrate surface. The kinetics of the adsorption of DNA on PDDA surface was also studied by real-time BIAcore technique, and the observed rate constant was calculated using a Langmuir model (k(obs) = (1.28 +/- 0.08) x 10(-2) s(-1)). [187] Polyelectrolyte Multilayer Capsules Templated on Biological Cells - Core Oxidation Influences Layer Chemistry S. Moya, L. Dahne, A. Voigt, S. Leporatti, E. Donath and H. Möhwald Colloid Surf. A Yüklə 0,52 Mb. Dostları ilə paylaş:
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