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| Iss 116 (2000), 77-87
This paper describes several applications of polyion- biomolecule films on electrodes related to future development of in vitro chemical toxicity sensors. In the first example, composite films of DNA and ionomers cast onto pyrolytic graphite (PG) electrodes are shown to be useful for detecting DNA damage during incubation with the carcinogen styrene oxide at pH 5.5. Single electrodes can be used to estimate relative damage rates by derivative square wave voltammetry. Films containing the ionomer Nafion gave better reproducibility than another ionomer, Eastman AQ38. In the second example, films containing redox proteins myoglobin (Mb) and cytochrome (cyt) P450(cam) were constructed in alternate layers with polyions including DNA on rough PG electrodes. Films with reversible protein Fe-III/Fe-II electrochemistry with up to 7 electroactive layers were made. Amounts of electroactive protein on rough PG that were 7 to 17-fold larger than in similar films on smooth gold were achieved because many more layers were electroactive. Films of Mb/DNA also showed oxidation peaks after short incubations with styrene oxide that may be attributable to DNA damage. Results are relevant to the future design of enzyme-DNA films which convert pollutants and drugs to reactive metabolites, followed by electrochemical detection of the resulting DNA damage. [62] Ultrathin, Layered Polyamide and Polyimide Coatings on Aluminum J. H. Dai, D. M. Sullivan and M. L. Bruening IND ENG CHEM RES 39(10) (2000), 3528-3535 Ultrathin, passivating films are attractive for protecting metal surfaces without completely masking substrate properties. Alternating polyelectrolyte deposition of layered poly(acrylic acid)/ poly(allylamine hydrochloride) (PAA/PAH) films on Al produces ultrathin coatings that protect Al from Cl--induced corrosion. Although the resistance of these films is minimal, they form a passivating layer on the surface oxide and increase oxide resistance by 2-3 orders of magnitude. Heating of PAA/PAH yields cross-linked polyamides that have film resistances of about 5 M Omega cm(2), even when the film is only 10-nm thick. Although the resistance of these films is high, reductions in corrosion current due to cross-linked films are still primarily due to passivation of the surface oxide as oxide resistance is larger than film resistance. Layer-by-layer covalent deposition of Gantrez/poly(allylamine) films yields ultrathin amic acid- linked layers that can be imidized by heating. Impedances of Al electrodes coated with Gantrez/poly(allylamine) films depend on the number of deposited bilayers and increase by an order of magnitude after imidization. These results suggest that increases in film resistance play a role in oxide passivation by this system. [63] Layer-by-Layer Deposition of J-Aggregates and Polyelectrolytes for Electroluminescence Applications - A Spectroscopic Study S. Kirstein, S. Bourbon, M. Y. Gao and U. Derossi Isr. J. Chem. 40(2) (2000), 129-138 The self-assembly method of layer-by-layer deposition of oppositely charged polyelectrolytes is used to insert J- aggregates of the dye tetrachloro-diethyl-disulfobutyl- benzimido-carbocyanine (TDBC) into thin polymeric films. The J- aggregates are characterized by a narrow absorption- and fluorescence band with its maximum at 590 nm, which is red- shifted with respect to the monomeric transition at 515 nm. The dyes are either coadsorbed with the polyelectrolytes poly(allylamine hydrochloride (PAH) and poly(styrene sulfonate) (PSS), or alternately deposited with the precursor of poly(phenylene vinylene) (pre-PPV). The optical properties of the aggregates are nor changed significantly by the deposition process. The pre-PPV/TDBC films are heated under vacuum to convert the PPV to its conjugated form. The resulting films can be used fur the fabrication of light-emitting devices. The optical properties such as fluorescence and electroluminescence are dominated by the J-aggregates. The excitation energy of PPV is transferred to the dye aggregates with an efficiency of 100%. The electroluminescence is not very stable and shows a very slow turn-on time. However, the combination of self- assembled PPV/TDBC layers with a spin-coated film of PPV results in stable electroluminescence emission under ambient conditions. In this case, light is emitted from both species, the PPV and the J-aggregates, whereas the ratio of the two intensities strongly depends on temperature. [64] Stepwise Stereocomplex Assembly of Stereoregular Poly(Methyl Methacrylate)S on a Substrate T. Serizawa, K. Hamada, T. Kitayama, N. Fujimoto, K. Hatada and M. Akashi J. Am. Chem. Soc. 122(9) (2000), 1891-1899 Isotactic (it-) and syndiotactic (st-) poly(methyl methacrylate)s (PMMAs) were synthesized by anionic polymerization in toluene at -78 degrees C with t-C4H9MgBr and t-C4H9Li/(C2H5)3Al, respectively, as initiators. Polymers were assembled by the stepwise immersion of a 9-MHz quartz-crystal microbalance (QCM) as a substrate into organic solutions at ambient temperature. Quantitative QCM analysis revealed that acetonitrile was the best solvent for assembly on the substrate compared to acetone and N,N-dimethylformamide (DMF). The analysis also showed linear growth of the assembly except during the initial two steps (possibly due to direct influence of the gold QCM substrate), indicating that the amount of assembly can be easily regulated at each step. A 5 min immersion of the QCM into each PMMA solution was enough to obtain stepwise assembly. The ratios of st-/it-PMMA assembled, the static contact angle of the assembly at each step, and its reflection absorption spectrum (RAS) strongly implied the stepwise formation of a stereocomplex between it- and st-PMMAs in the assembly. The amount of stereocomplex assembled was significantly affected by the addition of water to the organic solutions, the PMMA concentration, and its molecular weight, as well as the solvent species. Atomic force microscopic (AFM) examination of the assembly revealed a smooth surface. The assembly was formed at the step from the physically adsorbed it- PMMA to st-PMMA. A possible assembling mechanism was also proposed. [65] Adsorption and Desorption Behavior of an Anionic Pyrene Chromophore in Sequentially Deposited Polyelectrolyte-Dye Thin- Films C. Tedeschi, F. Caruso, H. Möhwald and S. Kirstein J. Am. Chem. Soc. 122(24) (2000), 5841-5848 Alternating thin films of the anionic dye pyrenetetrasulfonic acid (4-PSA) and poly(allylamine hydrochloride) (PAH) were formed by the sequential deposition of 4-PSA and PAH from aqueous solution onto solid substrates. Film growth was followed by absorption spectroscopy, and the resulting polyelectrolyte dye multilayer assemblies were characterized by using fluorescence spectroscopy, X-ray reflectivity, and atomic force microscopy (AFM) measurements. 4-PSA was successfully deposited in alternation with PAH when the ionic strength of the BAH solution was greater than 0.1 M. At each PAH adsorption step a given amount of previously adsorbed 4-PSA was extracted. The amount of dye released depended on the film thickness and the salt concentration in the PAH solution from which PAH was subsequently adsorbed. However, the total amount of dye remaining in the film after PAH deposition was essentially independent of the salt content in the PAH solution. Both X-ray reflectivity and AFM measurements revealed a high roughness of the 4-PSA/PAH multilayer films (ca. 20 Angstrom). To gain a better understanding of the parameters that control dye adsorption and extraction, dye adsorption was also investigated by immersion of preformed PAH and poly(styrene sulfonate) (PSS) multilayer films of various thickness into 4-PSA solutions. The amount of 4-PSA absorbed by the films increased with film thickness, and saturated at a thickness above about 20 nm. For these films, subsequent adsorption of a PAH layer extracted most of the dye, except for a small amount approximately equal to that present in one 4-PSA/PAH bilayer prepared by the alternate adsorption process. These observations indicate that the dye molecules are adsorbed to a finite depth of about 20 nm, and after deposition of the oppositely charged PAH, a small amount that is independent of film thickness remains. The presence of this remaining 4-PSA is necessary to complex and bind the next PAH layer, hence allowing continued multilayer film growth. It was also found that the 4-PSA adsorption/ desorption process depended on the drying process that was employed during the formation of the PSS/PAH multilayer films. The amount of dye as well as the penetration depth was reduced when the film was dried between deposition of each layer, and minor changes in the film structure were observed by X-ray reflectivity measurements. [66] Influence of Polyelectrolyte Multilayer Films on Calcium- Phosphate Nucleation P. A. Ngankam, P. Lavalle, J. C. Voegel, L. Szyk, G. Decher, P. Schaaf and F. J. G. Cuisinier J. Am. Chem. Soc. 122(37) (2000), 8998-9004 The nucleation of calcium phosphate crystals from a weakly supersaturated calcium phosphate solution on the surface of polyelectrolyte multilayers was investigated in dependence on the chemical nature of the outermost layer. Scanning angle reflectometry was used to follow in situ the initial stages of the nucleation kinetics. The multilayers were constructed by alternate adsorption of poly(styrene sulfonate) (PSS) and poly(allylamine) (PAH), leading to oppositely charged surfaces. It was verified that films terminating with either PSS or PAH exhibited a negative or positive 5-potential, respectively. Surprisingly, both types. of surface layers induced a nucleation process for supersaturations smaller than the one observed on the bare silica surface. According to the literature, such an effect should only be expected on a negatively charged surface. Infrared spectroscopy showed that the nucleated crystals are hydroxyapatite (OHAP) or octacalcium phosphate (OCP) but not dicalcium phosphate dihydrate (DCDP) which is found on bare silica surfaces. On both PSS and PAH surfaces, the nucleation processes started only after a given induction time. The evolution of the induction times with different supersaturations was analyzed within the framework of the classical nucleation theory. The effective surface free energies of the formed crystals were estimated to be on the order of 32 mJ.m(-2) on a multilayer terminating with PSS and to be about 37 mJ.m(-2) on a multilayer terminating with PAH. A mechanism for the enhanced nucleating effect of such polyelectrolyte surfaces is proposed. [67] Layered, Erasable, Ultrathin Polymer-Films S. A. Sukhishvili and S. Granick J. Am. Chem. Soc. 122(39) (2000), 9550-9551 [68] Photoelectrochemistry with Integrated Photosensitizer-Electron Acceptor and Au-Nanoparticle Arrays M. Lahav, V. Helegshabtai, J. Wasserman, E. Katz, I. Willner, H. Durr, Y. Z. Hu and S. H. Bossmann J. Am. Chem. Soc. 122(46) (2000), 11480-11487
[69] Electroluminescence of Different Colors from Polycation/CdTe Nanocrystal Self-Assembled Films M. Y. Gao, C. Lesser, S. Kirstein, H. Möhwald, A. L. Rogach and H. Weller J. Appl. Phys. 87(5) (2000), 2297-2302 Water soluble thiol capped CdTe nanocrystals are assembled into ultrathin films in combination with poly(diallyldimethylammonium chloride) (PDDA) by the self- assembly method of layer-by-layer adsorption of oppositely charged polyelectrolytes. Electroluminescent devices, which produce different color emissions, are fabricated by sandwiching CdTe/PDDA films between indium-tin-oxide (ITO) and aluminum electrodes using CdTe nanocrystals of different sizes. It is shown that the electroluminescence (EL) spectra of the CdTe/polymer films are nearly identical to the photoluminescence spectra of the corresponding CdTe nanocrystals in aqueous solutions. The devices produce room- light visible light output with an external quantum efficiency up to 0.1%. Light emission is observed at current densities of 10 mA/cm(2) and at low onset voltages of 2.5-3.5 V, which depends on the thickness of the film indicating field-dependent current injection. A variation of the EL efficiency with the size of the CdTe particles is observed and explained by the size dependent shift of the CdTe energy levels with respect to the work function of the electron injecting Al electrode. This is confirmed by the behavior of two-layer devices prepared from two differently sized CdTe particles being spatially separated, i.e., one size CdTe near ITO and the other size CdTe near Al by using the self-assembly method. (C) 2000 American Institute of Physics. [S0021-8979(00)06404-5]. [70] Self-Assembled Multilayer Films Based on Diazoresins Studied by Atomic-Force Microscopy/Friction Force Microscopy L. Huang, G. B. Luo, X. S. Zhao, J. Y. Chen and W. X. Cao J. Appl. Polym. Sci. 78(3) (2000), 631-638 The layer-by-layer self-assembled NDR-PSS (nitro-containing diazoresin-polysodium p-styrenesulfonate) films were fabricated. The crosslinking structure formed from the conversion of ionic bond to covalent bond after UV irradiation, confirmed by small angle X-ray diffraction. The roughness and microtribological properties of NDR-PSS films were investigated by atomic force microscopy/friction force microscopy. The ordered multilayer films after photoreaction are better in microtribological performance than that of the monolayer film. (C) 2000 John Wiley & Sons, Inc. [71] Probing Nanoscale Photooxidation in Organic Films Using Spatial Hole-Burning Near-Field Scanning Optical Microscopy G. M. Credo, G. M. Lowman, J. A. Dearo, P. J. Carson, D. L. Winn and S. K. Buratto J. Chem. Phys. 112(18) (2000), 7864-7872 Spatial hole burning near-field scanning optical microscopy (SHB-NSOM) is used to locally photopattern three species of organic thin films, poly(2-methoxy, 5-(2'-ethyl hexyloxy)-p- phenylene vinylene) (MEH-PPV), tris-8-hydroxyquinoline aluminum (Alq(3)) and dye-functionalized polyelectrolyte self-assembled layers, on a 100 nm length scale. In SHB-NSOM the film is illuminated with light from a stationary NSOM tip to induce photo-oxidation. The reduction in the fluorescence yield resulting from this exposure is then mapped using fluorescence NSOM (FL-NSOM). We have examined the localized photo-oxidation as a function of time, position, and environment free from the limits of far-field spatial averaging. In all of the thin film materials studied we find that the long-time diameter of the dark spot is much larger than the tip diameter and is a signature of energy migration. Characteristic lengths of the energy migration are extracted from this data by a simple diffusion model and are found to be of the order of a few hundred nanometers for each of the films studied. (C) 2000 American Institute of Physics. [S0021-9606(00)71116-0]. [72] Facile Construction of an Ultra-Thin (60)Fullerene Layer from (60)Fullerene-Homooxacalix(3)Arene Complexes on a Gold Surface T. Hatano, A. Ikeda, T. Akiyama, S. Yamada, M. Sano, Y. Kanekiyo and S. Shinkai J. Chem. Soc., Perkin Trans. 2 5(MAY) (2000), 909-912 A hexacationic homooxacalix[3]arene-[60]fullerene 2:1 complex can be deposited on an anion-coated gold surface as a monolayer (or at least as a monolayer-like ultra-thin film); as expected, this membrane efficiently shows a redox response in cyclic voltammetry and a photoelectrochemical response under visible light irradiation. [73] Investigation of Structure and Growth of Self-Assembled Polyelectrolyte Layers by X-Ray and Neutron-Scattering Under Grazing Angles A. Plech, T. Salditt, C. Munster and J. Peisl J. Colloid Interface Sci. 223(1) (2000), 74-82 The structure of self-assembled polyelectrolyte thin films on float glass has been investigated by interface sensitive X-ray and neutron scattering methods. Special emphazis was given to the adsorption process of poly (ethylene imine) and polystyrole sulfonate as an important model system which is often used as a basis for subsequent multilayer buildup. From complementary X- ray and neutron reflectivity data, the vertical film density profile was derived for various growth parameters, including kinetic effects of different adsorption times. In addition to specular reflectivity, we have for the first time employed nonspecular X-ray scattering to study lateral structure parameters in self-assembled polyelectrolyte films. Furthermore, the technique of time-resolved in situ X-ray reflectivity during film growth has been demonstrated and is discussed in view of its future potential. (C) 2000 Academic Press. [74] Phosphatidylserine/Cholesteral Bilayers Supported on a Polycation/Alkylthiol Layer Pair L. Q. Zhang, C. A. Booth and P. Stroeve J. Colloid Interface Sci. 228(1) (2000), 82-89 1-Stearoyl-2-oleoyl phosphatidylserine (SOPS)/cholesterol bilayers, supported on a polycation/alkylthiol layer pair on a gold surface, were investigated by surface plasmon resonance (SPR) and fluorescence recovery after photobleaching. The substrate was formed by electrostatic adsorbance of a hydrated poly(diallyldimethylammonium chloride) (PDDA) layer on the negatively charged surface of a self-assembled monolayer of 11- mercaptoundecanoic acid (MUA) on gold. Lipid membranes with different SOPS/cholesterol compositions were deposited on the PDDA/MUA layer pair by vesicle fusion. When the cholesterol content was below 20%, single bilayers were deposited. Fluorescence recovery after the bleaching experiments revealed that the SOPS/cholesterol bilayers were mobile at room temperature; lateral diffusion coefficients of a fluorescence probe were approximately 1 x 10(-9) cm(2)/s. The kinetics of the addition of the ion-channel-forming peptide gramicidin to the supported bilayers was detected by SPR. (C) 2000 Academic Press. [75] Electroactive Films of Alternately Layered Polycations and Iron- Sulfur Protein Putidaredoxin on Gold Z. Q. Lu, Y. Lvov, I. Jansson, J. B. Schenkman and J. F. Rusling J. Colloid Interface Sci. 224(1) (2000), 162-168 Layered, electrochemically active films of bacterial iron- sulfur protein putidaredoxin (Pdx) and poly(dimethyldiallyammonium) (PDDA) polycations were constructed on gold electrodes coated with mercaptopropane sulfonate (MPS) and on quartz slides. Second-derivative UV-vis spectra suggested similar structures of Pdx in films and solutions at pH 7. Direct electrochemistry was achieved between Pdx and gold electrodes in these films, with significantly better electrochemical reversibility than in cast Nafion-lipid- Pdx films. A formal potential dispersion model gave a good fit to square wave voltammograms by regression analysis and was used to estimate an average apparent rate constant of 4.5 s(- 1). Reduced Pdx in the polyion films did not react with its natural redox partner cytochrome P450(cam) because of unfavorable thermodynamics in the film environment. (C) 2000 Academic Press. [76] Assembly of Alternated Multivalent Ion/Polyelectrolyte Layers on Colloidal Particles - Stability of the Multilayers and Encapsulation of Macromolecules into Polyelectrolyte Capsules I. L. Radtchenko, G. B. Sukhorukov, S. Leporatti, G. B. Khomutov, E. Donath and H. Möhwald J. Colloid Interface Sci. 230(2) (2000), 272-280 Alternating adsorption of multivalent ions and oppositely charged polyelectrolytes on colloid particles has been investigated. Multilayer films composed of Tb3+/polysterene sulfonate (PSS) and 4-pyrene sulfate/polyallylamine (PAH) were successfully assembled on polysterene sulfonate (PS) and melamine formaldehyde (MF) latex particles. The amount of assembled material was estimated by fluorescence and the linear growth of the film versus the number of layers was demonstrated. These multilayers are not stable and can be decomposed by salt and temperature, Dissolution of MF particles leads to formation of hollow capsules consisting of multivalent ion/polyelectrolyte multilayers. Comparative analysis of the capsules was done by confocal and scanning force microscopy. Complex hollow spheres consisting of Tb3+/PSS or 4-PS/PAH as an inner shell and stable PSS/PAH as an outer shell were produced. Due to selective permeability of the outer shell after degradation of the inner shell the multivalent ions are released out of the capsule while the polyelectrolytes fill the capsule interior. This is indicative of swelling of the capsule by osmotic pressure. The filled capsules were studied by confocal and scanning electron microscopy. Possibilities of encapsulating macromolecules in defined amounts per capsule are discussed. (C) 2000 Academic Press. [77] Comparative-Studies on Electrochemical-Behavior and Electrocatalytic Properties of Heteropolyanion-Containing Multilayer Films Prepared by 2 Methods L. Cheng and S. Dong J. Electroanal. Chem. 481(2) (2000), 168-176 Two modification methods for multilayer formation, i.e. immersion growth and electrochemical growth, were studied comparatively for their influence on the electrochemical behavior and the electrocatalytic properties of the thus- fabricated SiMo11V-containing multilayer films. Electrochemical growth was proven to be a more suitable method than immersion growth in preparing uniform ultrathin multilayer self- assemblies with good functions. We investigated the effects of scan rate and pH on the electrochemical behavior of the monolayer and multilayer films. We also compared the electrocatalytic effects on the reduction of BrO3- and HNO2 by the multilayer films prepared by the two methods. Moreover, the influence of multilayer thickness and the identity of the outermost layer on the electrocatalytic properties were studied. Much higher catalytic currents appeared on the thicker multilayer films than those on the thinner ones. On the other hand, the catalytic currents became smaller when the multilayer films with SiMo11V as the outermost layer were covered with an additional quarternized poly(4-vinylpyridine) layer partially complexed with osmium bis(2,2'-bypyridine) chloride (QPVP-Os layer). These influences were believed to be due to the different quantities of electrocatalyst loaded in the multilayer films and the blocking effect of the QPVP-Os outermost layer. (C) 2000 Elsevier Science S.A. All rights reserved. [78] An Enlarged bis-Bipyridinium Cyclophane-Au Nanoparticle Superstructure for Selective Electrochemical Sensing Applications M. Lahav, A. N. Shipway, I. Willner, M. B. Nielsen and J. F. Stoddart J. Electroanal. Chem. 482(2) (2000), 217-221 Highly stable electrostatically-linked superstructures of 13 nn Au-colloids have been constructed by the use of the tetracationic cyclophanes cyclobis(paraquat-p-phenylene) and cyclobis(paraquat-p-biphenylene). These architectures have been characterized by optical and electrochemical means and exhibit sensing capabilities that are shown to depend on the crosslinking cyclophane. While superstructures linked by cyclobis(paraquat-p-phenylene) sense hydroquinone derivatives and not ferrocene derivatives, those linked by the larger receptor cyclobis(paraquat-p-biphenylene) sense only the ferrocene derivatives. This high degree of selectivity is based on the topological and supramolecular fit of the analyte in the cavity of the receptor. Arrays containing both cyclophanes are shown to exhibit sensing characteristics that are dependent on the position of each cyclophane in the superstructure, possibly as a consequence of the limited porosity of the composite. (C) 2000 Elsevier Science S.A. All rights reserved. [79] Electrochemical-Behavior and Electrocatalytic Properties of Ultrathin Films Containing Silicotungstic Heteropolyanion Siw12O404- L. Cheng and S. J. Dong J. Electrochem. Soc. 147(2) (2000), 606-612 We describe here a controlled fabrication of ultrathin monolayer and multilayer films consisting of silicotungstic heteropolyanion SiW12O404- and a cationic polymer of quaternized poly(4-vinylpyridine) partially complexed with osmium bis(2,2'-bipyridine) on Au electrodes previously self- assembled with cysteamine monolayers based on layer-by-layer electrostatic interaction. The thus-forming monolayer and multilayer chemically modified electrodes are investigated by cyclic voltammetry on their electrochemical behavior and electrocatalytic properties. The composite ultrathin films exhibit remarkable electrocatalytic effects on the reduction of BrO3-, H2O2, and HNO2. The electrocatalytic effects on HNO2 reduction are enhanced with increasing layer number from 1 to 3 but level off with much thicker multilayers. The stability of the monolayer and multilayer films is also examined. (C) 2000 The Electrochemical Society. S0013-4651(99)04-057-4. All rights reserved. [80] Luminescence Properties of the J-Aggregate of Cyanine Dyes in Multilayer Assemblies N. Kometani, H. Nakajima, K. Asami, Y. Yonezawa, I. G. Scheblykin and A. G. Vitukhnovsky J. Luminesc. Yüklə 0,52 Mb. Dostları ilə paylaş:
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