Dear Colleagues

21(11) (2000), 750-753
Communication: The construction of enzyme multilayer films on colloidal particles for biocatalysis is described. The enzyme multilayers were assembled on submicrometer-sized polystyrene spheres via the alternate adsorption of poly(ethyleneimine) and glucose oxidase using a layer-by-layer approach. Microelectrophoresis and single particle light scattering measurements revealed regular and step-wise assembly of the multilayers on the colloids. The high surface area bio- multilayer coated particles formed were subsequently utilized in enzymatic catalysis.

[143] Synthesis and Electrostatic Multilayer Assembly of an Acridine- Containing Polymer with Properties of an Optical Sensor

T. S. Lee, C. D. Yang and W. H. Park

MACROMOL RAPID COMMUN 21(14) (2000), 951-955

We have synthesized an acridine-containing polymer linked with alkyl amide via simple polycondensation reaction. It was found that the polymer exhibits high selectivity and sensitivity toward ferric ions indicating that this polymeric material would be an efficient fluorescence sensor for ferric ions. The formation of self-assembled multilayers was carried out via layer-by-layer deposition technique between the acridine- containing polymer and poly(sodium-4-styrenesulfonate).

[144] Layer-by-Layer Adsorption of Identically Charged Polyelectrolytes

P. Fischer and A. Laschewsky

Macromolecules 33(3) (2000), 1100-1102

[145] PH-Dependent Thickness Behavior of Sequentially Adsorbed Layers of Weak Polyelectrolytes

S. S. Shiratori and M. F. Rubner

Macromolecules 33(11) (2000), 4213-4219
A detailed study of the role that solution pH plays in the layer-by-layer processing of the weak polyelectrolytes poly(acrylic acid) and poly(allylamine hydrochoride) was carried out. It was found that dramatically different polymer adsorption behavior is observed as one systematically increases (or decreases) the charge density of a weak polyelectrolyte including transitions from very thick adsorbed layers (ca. 80 Angstrom) to very thin adsorbed layers (ca. 4 Angstrom) over a very narrow pH range. By controlling pH, it is possible to vary the thickness of an adsorbed polycation or polyanion layer from 5 to 80 Angstrom. In addition, control over the bulk and surface composition of the resultant multilayer thin films is readily achieved via simple pH adjustments. These studies have provided new insights into the polyelectrolyte sequential adsorption process and have already opened up some interesting technological applications.

[146] Lipid Coating on Polyelectrolyte Surface-Modified Colloidal Particles and Polyelectrolyte Capsules

S. Moya, E. Donath, G. B. Sukhorukov, M. Auch, H. Baumler, H. Lichtenfeld and H. Möhwald

Macromolecules 33(12) (2000), 4538-4544

Dipalmitoyldiphosphatidic acid (DPPA), dipalmitoyldiphosphatidylcholine (DPPC), and sphingosine were adsorbed onto polyelectrolyte coated colloids and capsules forming composite lipid-polyelectrolyte layers. The stepwise coating was performed either by adsorption of preformed vesicles onto the capsule surface or by a solvent exchange protocol. The lipid assembly was monitored by zeta-potential measurements. Single particle light scattering, flow cytometry, and fluorescence studies of Forster energy transfer have been used to quantify the lipid coating. Confocal microscopy images of capsules coated with fluorescent lipids demonstrated a homogeneous coverage of the capsule surface. Differential scanning calorimetry shows a phase transition temperature characteristic for lipid layer structures. It was concluded that the adsorbed DPPA form bilayers while DPPC may form multilayers. It was further shown that on top of the lipid layers further polyelectrolyte layers could be assembled. The permeability of B-carboxyfluorescein (6-CF) through the composite layer structure was studied by means of confocal laser scanning microscopy. The permeation time through the composite layer was of the order of 10(1)-10(2) min, while in the absence of lipids 6-CF equilibrated faster than the time resolution of the technique.

[147] Azo Polymer Multilayer Films by Electrostatic Self-Assembly and Layer-by-Layer Post Azo Functionalization

S. H. Lee, S. Balasubramanian, D. Y. Kim, N. K. Viswanathan, S. Bian, J. Kumar and S. K. Tripathy

Macromolecules 33(17) (2000), 6534-6540

This work focuses on the development of a novel method for molecular level assembly and processing of multilayer azo polymer films. Poly(acrylic acid)-based precursor anilino- functional polymer was first synthesized and used as a polyanion. This polymer was assembled into mono- and multilayer thin films by an electrostatic layer-by-layer deposition technique in conjunction with a polycation. The aniline group in the assembled polymer layer was subsequently converted to an azobenzene chromophore by post azo coupling reaction with appropriate diazonium salts. This method provides easy control of film thickness and well-ordered chromophore structure in the multilayer. Second harmonic generation was observed in all multilayer films, indicating acentric organization of the chromophores synthesized in the multilayered films. The second harmonic intensity and film thickness are dependent on the assembly conditions (pH, etc.) of the polyions. The post- functionalized azo polymer layers were further modulated by Light-driven mass transport.

[148] Effects of Spacer Chain Lengths on Layered Nanostructures Assembled with Main-Chain Azobenzene Ionenes and Polyelectrolytes

J. D. Hong, B. D. Jung, C. H. Kim and K. Kim

Macromolecules 33(21) (2000), 7905-7911

With the aim of fabricating internally ordered multilayer assemblies using the layer-by-layer electrostatic deposition method, we have prepared polyelectrolytes called ionenes that contain rigid azobenzene chromophores separated by flexible spacer chains, i.e., poly ((4,4'-bis(6- dimethylammonio)hexyl)oxy)azobenzene bromide), PAZ-B, poly ((4,4'-bis(10-dimethylammonio)decyl)oxy)azobenzene bromide), PAZ-10, and poly ((4,4'-bis(12- dimethylammonio)dodececyl)oxy)azobenzene bromide), PAZ-12. UV/ vis spectroscopy of solutions shows that PAZ-10 and PAZ-12 form robust lamellar aggregates that could be successfully transferred onto a solid substrate by forming multilayer assemblies with oppositely charged polyelectrolytes, From FTIR spectra of the resulting multilayer assemblies, the alkyl chains appeared to be highly ordered, especially in the case of longer spacer chain. The thicknesses of the PAZ monolayers measured atomic force microscopy were overall consistent with the theoretical values (2.61 and 3.23 nn) determined by a model calculation, based on the tilt angle measurement of chromophore and the molecular length of the repeat unit of the ionenes.

[149] Orientation of Nonlinear-Optical Active Dyes in Electrostatically Self-Assembled Polymer-Films Containing Cyclodextrins

P. Fischer, M. Koetse, A. Laschewsky, E. Wischerhoff, L. Jullien, A. Persoons and T. Verbiest

Macromolecules 33(26) (2000), 9471-9473

[150] Ultrathin-Film Fabricated from Pddac/DSB and Ndr/DSB

J. Y. Chen, G. B. Luo, R. X. Wang, X. S. Zhao and W. X. Cao

MATER RES BULL 35(12) (2000), 1945-1954
Two kinds of ultrathin films were successfully fabricated by the self-assembly deposition technique from poly(diallyldimethylammonium chloride) (PDDAC) or nitro- containing diazoresin (NDR) as the polycation and 4,4'- di(sodium styryl-2-sulfonate) biphenyl (DSB) as the dianion. This stepwise fabrication process was monitored by UV-vis spectrometry. The regularity of the film and the morphology of the film surface were examined by X-ray diffraction (XRD) and atom force microscopy (AFM), respectively. The results show that these kinds of films are composed of well arranged molecules, and have a very flat surface. Among them, the PDDAC/ DSB film emits fluorescence when excited with UV light at 354 nm. The NDR/DSB film does not emit fluorescence, because the NDR quenches the fluorescence of DSB; however, the NDR/DSB film possesses more stability against solvent etching (such as DMF), compared with the PDDAC/DSB film. (C) 2001 Elsevier Science Ltd. All rights reserved.

[151] Ultrathin Nanoparticle ZnS and ZnS Mn Films - Surface Sol-Gel Synthesis, Morphology, Photophysical Properties

N. I. Kovtyukhova, E. V. Buzaneva, C. C. Waraksa and T. E. Mallouk

MATER SCI ENG B SOLID STATE M 69(NSI) (2000), 411-417

Ultrathin films of ZnS and Mn-doped ZnS were grown on silicon substrates using surface sol-gel reactions, and the film growth process was characterized by ellipsometry, atomic force microscopy, X-ray photoelectron spectroscopy, UV-visible absorbance and photoluminescence (PL) spectroscopy. The Si substrates were pre-treated by chemical oxidation. On the oxidized Si/SiOx surface, nanoparticulate films of ZnS and Mn- doped ZnS were grown by sequential immersion in aqueous metal acetate and sodium sulfide solutions. During the first four adsorption cycles, there was little film growth, but thereafter the amount of material deposited was linear with the number of adsorption cycles. This behavior is consistent with the formation of ZnS nuclei at low coverage, followed by particle growth in subsequent cycles. PL spectra are consistent with incorporation of Mn2+ into the ZnS nanoparticles. (C) 2000 Elsevier Science S.A. All rights reserved.

[152] Self-Assembly of Nanostructured Composite ZnO/Polyaniline Films

N. I. Kovtyukhova, A. D. Gorchinskiy and C. Waraksa

MATER SCI ENG B SOLID STATE M 69(NSI) (2000), 424-430

Ultrathin composite ZnO/polyaniline (PAN) films were deposited from organic solutions on silicon and ITO substrates using wet layer-by-layer self-assembly technique. The film growth process was characterized by transmission electron microscopy, ellipsometry, atomic force microscopy, IR and UV-visible absorbance and photoluminescence spectroscopy, and electrical measurements. The Si substrates were pre-treated by chemical oxidation. Multilayer films were grown by sequential immersion of the substrate in an ethanolic ZnO sol and PAN solution in dimethyl formamide. The first adsorption cycle resulted in well- packed monoparticulate ZnO layer almost completely covering the substrate, which predetermined the regular growth of densely packed and quite smooth ten-layer ZnO/PAN film. Photoluminescence and IR data assumed chemical interaction between the components in neighbouring layers. The multilayer (ZnO/PAN)(9)ZnO film sandwiched between ITO and Pr electrodes exhibited strong photoelectrical response while both the components were photoelectrically inactive in our experimental conditions. The reversible conversion from insulating to conducting state was observed under irradiation by light with a wavelength below 350 nm. (C) 2000 Elsevier Science S.A. All rights reserved.

[153] Photoinduced Alignments of Liquid-Crystal Molecules on Alternate Self-Assembly Films Evaluated by the Attenuated Total- Reflection Measurement

A. Baba, F. Kaneko, K. Shinbo, K. Kato, S. Kobayashi and R. C. Advincula

MOL CRYST LIQUID CRYST 347 (2000), 259-268

Photo-induced in-plane alignments of nematic liquid crystal (LC) molecules, 5CB, have been investigated in the cell with alternate self-assembly films of polyelectrolyte and low- molecular weight dyes on the gold electrodes using the attenuated total reflection (ATR) measurement method. Reflectivities due to the excitations of the surface plasmon polariton (SPP) were observed in the ATR properties of the LC cell. In-plane switching of LC molecules adjacent to the aligning layer was evaluated from the ATR curves by means of irradiation of the linearly polarized visible light to the LC cell. It was also estimated that the re-orientation of the LC molecules occurred within about 130 nm from the surface of the aligning layer on the prism by the irradiation of the polarized light.

[154] Rectifying Self-Assembled Ultrathin Films

T. P. Cassagneau, B. Swerydakrawiec and J. H. Fendler

MRS BULL 25(9) (2000), 40-46

[155] Nanoassemblies of Sulfonated Polyaniline Multilayers

N. Sarkar, M. K. Ram, A. Sarkar, R. Narizzano, S. Paddeu and C. Nicolini

NANOTECHNOL 11(1) (2000), 30-36
A self-assembly layer-by-layer (LBL) technique was used for the sequential adsorption of polycation, poly(diallyldimethylammonium chloride) (PDDA) and polyanion, sulfonated polyaniline (SPANI) on glass. indium-tin-oxide (ITO) coated grass plates, polystyrene sulfonate (PSS)/glass and PSS/ ITO surfaces, respectively The building up of such multilayers was characterized by the increment of the: adsorbed amount through UV-visible spectroscopy and cyclic voltammetry The atomic force microscopic study showed the granular surface topology of such self-assembled films of sulfonated polyaniline. PDDA/SPANI LBL films were electrically active and detailed electrochemical parameters were investigated.

[156] Nano-Assembly of Glucose-Oxidase on the in-Situ Self-Assembled Films of Polypyrrole and Its Optical, Surface and Electrochemical Characterizations

M. K. Ram, M. Adami, S. Paddeu and C. Nicolini

NANOTECHNOL 11(2) (2000), 112-119

An in situ self-assembly technique with nanometre control over thicknesses and multilayered structures was used to manufacture the ultrathin films of polypyrrole (PPY). The PPY film was deposited on a polyanion, poly(styrene sulfonate) (PSS) modified surface as a Function of time, previously PSS had been deposited on various substrates (glass, mica, indium-tin-oxide coated glass plates). Later, alternate PPY and PSS films were fabricated on such substrates using a layer-by-layer (LBL) technique. The glucose oxidase (GOD) molecules were also deposited on such self-assembled PPY films by the LBL technique. The PSS/PPY/GOD, PPY/PPY/GOD/poly(ethylene imine) (PEI)/GOD etc, film configurations were fabricated. and functionally as well as structurally characterized by UV- visible, electrochemical and scanning probe microscopy techniques, respectively. The results of a scanning probe microscopic study on the films were analysed to understand the molecular orientation of GOD on the PPY surface, and the dependence of the enzyme concentration for the depositing solutions. Moreover, the electrochemical studies performed provided information with respect to the electron transfer processes on the spatial arrangement of GOD molecules on the PPY surfaces. The immobilization of GOD on a conductive PPY represented a crucial and important step, and allowed us to construct the glucose-responsive biosensors.

[157] Molecular-Scale Interface Engineering for Polymer Light- Emitting-Diodes

P. K. H. Ho, J. S. Kim, J. H. Burroughes, H. Becker, S. F. Y. Li, T. M. Brown, F. Cacialli and R. H. Friend

Nature 404(6777) (2000), 481-484

Achieving balanced electron-hole injection and perfect recombination of the charge carriers is central to the design of efficient polymer light-emitting diodes(1,2) (LEDs). A number of approaches have focused on modification of the injection contacts, for example by incorporating an additional conducting-polymer layer at the indium-tin oxide (ITO) anode(3,4). Recently, the layer-by-layer polyelectrolyte deposition route has been developed for the fabrication of ultrathin polymer layers(5,6). Using this route, we previously incorporated ultrathin (<100 Angstrom) charge-injection interfacial layers in polymer LEDs(7). Here we show how molecular-scale engineering of these interlayers to form stepped and graded electronic profiles can lead to remarkably efficient singlelayer polymer LEDs. These devices exhibit nearly balanced injection, near-perfect recombination, and greatly reduced pre-turn-on leakage currents. A green-emitting LED comprising a poly(p-phenylene vinylene) derivative sandwiched between a calcium cathode and the modified ITO anode yields an external forward efficiency of 6.0 per cent (estimated internal efficiency, 15-20 per cent) at a luminance of 1,600 candelas per m(2) at 5 V.

[158] Electrooptic Property Measurements of Electrostatically Self- Assembled Ultrathin Films

L. M. Zhang, F. J. Zhang, K. Cooper, Y. Q. Wang, Y. J. Liu and R. Claus

Opt. Commun. 186(1-3) (2000), 135-141

A new class of ultrathin electro-optic films have been developed by the electrostatically self-assembled monolayer process. Using a simple ellipsometric technique, the electro- optic coefficients were measured as a function of the frequency of the applied electric field. The maximum of the coefficients is 600 pm/V. From these measurements, we deduce the orientational and the electronic contributions to the electro- optic modulation. At modulating frequencies lower than 20 Hz, the orientation dominates the electro-optic modulation process. At frequencies higher than 800 Hz, electrons are responsible for electro-optic behavior. (C) 2000 Elsevier Science B.V. All rights reserved.

[159] The Influence of Molecular-Weight over the Ultrathin Films of Biodegradable Polyion Complexes Between Chitosan and Poly(Gamma- Glutamic Acid)

W. Tachaboonyakiat, T. Serizawa, T. Endo and M. Akashi

Polym. J. 32(6) (2000), 481-485

Alternate adsorption is a well-known method for developing the novel. ultrathin films of biodegradable polyion complexes. This study revealed variations in the effect of chitosan and poly(gamma-glutamic acid) [gamma-PGA] molecular weight on the complex formation process. High molecular weight gamma-PGA showed a high adsorption frequency. Tn contrast, no molecular weight effect was observed in the case of chitosan. Addition of certain organic solvents in the chitosan and gamma-PGA aqueous solution also influenced ultrathin film polyion complex formation.

[160] Physical Insight in the in-Situ Self-Assembled Films of Polypyrrole

M. K. Ram, M. Adami, P. Faraci and C. Nicolini

Polymer 41(20) (2000), 7499-7509

The ultrathin films with nanometre control over thickness and multilayered structures of polypyrrole (PPY) were manufactured by in-situ self-assembled technique. A controlled thickness of PPY was deposited on polyanion, poly(styrene sulfonate) (PSS) surfaces as a function of time; previously PSS had been deposited on various substrates (glass, mica, indium-tin-oxide coated glass plates). Later, alternate PPY and PSS films were fabricated on such substrates by the layer-by-layer technique. The films were characterized by using UV-visible, electrochemical and Quartz Crystal Microbalance techniques. The resulting morphology of the manufactured films was investigated by Atomic Force and the Scanning Tunneling Microscopies. The electrochemical surveying of self-assembled PPY films in different electrolytic media highlighted the sensor application. Typical supramolecular films of PPY/PSS were found to have conductivity values in the range of 10(-2)-10(-1) S/cm. (C) 2000 Elsevier Science Ltd. All rights reserved.

[161] Polymeric Nanostructured Composite Films

J. C. Shen, J. Q. Sun and X. Zhang

Pure Appl. Chem. 72(1-2) (2000), 147-155

This research news describes the construction of polymeric nanostructured composite film based on a variety of interactions, such as hydrophobic-hydrophilic effect, electrostatic interaction, hydrogen bonding, etc. The work focused on developing strategies to solve the basic problems in the area of ultrathin film research, such as stability, improving the interface quality, creating patterned interface, and techniques to construct nanolayered structure. With in- depth study of the relationship between the microscopic layered architecture and macroscopic function of supramolecular assemblies, it is anticipated that one could obtain miniature devices or machines of high efficiency through integration of the assembling process and device fabrication.

[162] Preparation of DNA-Cationic Amphiphile Multilayer Films by Alternate Adsorption and a Study of Their Structure

L. I. Shabarchina, M. M. Montrel, G. B. Sukhorukov, I. V. Savintsev and B. I. Sukhorukov

Russian J. Phys. Chem. 74(11) (2000), 1908-1914

DNA-hexadecylamine and DNA-hexadecyltrimethylammonium bromide multilayer films were produced by alternate adsorption of DNA and a cationic amphiphile on a solid support. The growth of the film was studied by UV spectroscopy The interlayer distances, DNA conformational states, and hydration and stability of the films in aqueous and aqueous-salt solutions were determined by small-angle X-ray scattering and IR and UV spectroscopies. The structures of the films were proposed. It was shown that the DNA double helix is unwound during the formation of the hexadecylamine multilayer film. In the case of hexadecyltrimethylammonium, the DNA double helix retains the B- form, but its lability diminishes; no transition into the A- form occurs with decreasing humidity. As for hexadecylamine, the influence of the polar head of the amphiphile molecule on the DNA conformational state occurs because of the substitution of base-base intramolecular hydrogen bonds by base- hexadecylamine intermolecular hydrogen bonds. Multilayer films containing the same components but prepared under different conditions (Langmuir process or alternate adsorption of the components on the support) were found to differ in structure.

[163] Self-Assembly of Polyaniline Ultrathin Films Based on Doping- Induced Deposition Effect and Applications for Chemical Sensors

D. Li, Y. D. Jiang, Z. M. Wu, X. D. Chen and Y. R. Li

SENSOR ACTUATOR B CHEM 66(1-3) (2000), 125-127

Electroactive nanocomposite ultrathin films of polyaniline (PAN) and isopolymolybdic acid (PMA) were fabricated by a novel molecular self-assembling process based on the alternate deposition of PAN and PMA from their dilute solutions. The process was based on doping-induced deposition effect of emeraldine base. The process was monitored by UV/VIS spectroscopy measurement. It was found that the conductivity of the PAN films is sensitive to humidity, NO2 and NH3. The technique may be used to fabricate chemical sensors and other molecular devices. (C) 2000 Elsevier Science S.A. All rights reserved.

[164] Fabrication of Self-Assembled Polyaniline Films by Doping- Induced Deposition

D. Li, Y. D. Jiang, Z. M. Wu, X. D. Chen and Y. R. Li

Thin Solid Films 360(1-2) (2000), 24-27

The ultrathin films of polyaniline (PAni)/poly (styrenesulfonic acid)(PSSA) were fabricated via a novel self-assembling process by alternately immersing the substrates into dilute PAni solution in N-methylpyrrolidinone (NMP) and the aqueous solution of PSSA. The process was characterized by W-Vis absorption spectroscopy. It was found that the oxidation state of polyaniline in single monolayers was dependent on the thickness of the film. The self-assembling mechanism was based on the acid-base reaction between PAni and PSSA. The thickness of the films can be easily manipulated at nanometer scale by controlling the solution chemistry and recycling times. The resulting films are uniform and adhere strongly to the substrates. (C) 2000 Elsevier Science S.A. All rights reserved.

[165] Electrostatic Self-Assembly of Sulfonated C-60-Porphyrin Complexes on Chitosan Thin-Films

H. Jiang, W. Su, J. Hazel, J. T. Grant, V. V. Tsukruk, T. M. Cooper and T. J. Bunning

Thin Solid Films 372(1-2) (2000), 85-93

Sulfonatcd C-60, 5,10,15,20-tetra kis 4-[meso-tetra-methyl (4- pyridinyl)] porphyrin (C-60(SO3-)(n)-TMePyP4+) complex films have been prepared by electrostatic self-assembly of each chromophore from solution. When these complex films are formed on a thin film of chitosan polymer, the stacked bilayer films exhibit nearly twice the absorption as those prepared on conventional silanized substrates. X-ray photoelectron spectroscopy measurements disclose a strong interaction between the C-60(SO3-)(n) and TMePyP4+. Atomic force microscopy results of the surface morphology, hardness, and the chemical functionality are used to explain the differences between substrate treatments. (C) 2000 Elsevier Science S.A. All rights reserved.

[166] Effect of Added Ionic Salt on the Quantum Efficiency of Self- Assembled Films Prepared with Poly( P-Phenylene Vinylene)

J. Cho, K. Char, S. Y. Kim, J. D. Hong, S. K. Lee and D. Y. Kim

Thin Solid Films