Dear Colleagues

121(1-3) (2001), 1367-1368
We report the synthesis and characterization of multilayer self- assembled polymer films made from a water-soluble conjugated polymer, poly(2,5-methoxy-propyloxy sulfonate phenylene vinylene) (MPS-PPV). We observe a red shift, of both the absorption and fluorescence spectra with increasing numbers of active MPS-PPV layers. We attribute this red shift to changing polymer conformation and efficient energy transfer. Upon adding a water-soluble C-60 Or C-60-VBA copolymer top layer, the luminescence spectrum is strongly quenched due to charge transfer. The estimated charge transfer quantum efficiency from PL quenching is similar to 95%. We discuss in detail the unidirectional energy transfer followed by charge transfer in the self-assembled multilayered films.

[251] Multilayers Prepared from Electronically Conducting Conjugated Polyelectrolytes

J. Lukkari, A. Viinikanoja, M. Salomaki, T. Aaritalo and J. Kankare

Synthet. Metal 121(1-3) (2001), 1403-1404

Electroactive polyelectrolyte multilayers have been prepared using a water-soluble poly-3-(3'thienyloxy)propanesulfonate CP3TOPS). In aqueous solutions the properties of the multilayers were typical to polythiophene films. Charge transfer rate measurements indicate that P3TOPS can penetrate through ca. 4 polyelectrolyte bilayers.

[252] Photovoltaic Interface Modification via Electrostatic Self- Assembly

J. W. Baur, M. F. Durstock, B. E. Taylor, R. J. Spry, S. Reulbach and L. Y. Chiang

Synthet. Metal 121(1-3) (2001), 1547-1548

The device efficiency of PPV-C-60 based photovoltaic devices has been substantially increased by increasing the interfacial area between the electron donor and acceptor layers. Electrostatic Self-Assembly (ESA) provides a means to deposit thin films of electroactive materials with a very controlled thickness and has shown usefulness in modifying physical and electrical interfaces. in this study, we attempt to control the effective interfacial area by modifying the interface between the PPV electron donor and C-60-based electron acceptor with molecularly blended ESA bilayers of PPV and derivatized C-60 If is observed that with only 2 bilayers of (PPV/C-60(-)) a 3-fold increase in device efficiency is obtained. Thus, ESA films offer promise for the nanoscaled modification of interfaces in organic-based photocells.

[253] Photocarrier Generation Quantum Yield for Ionically Self- Assembled Monolayers

T. Piok, R. Schroeder, C. Brands, J. R. Heflin, G. Leising and W. Graupner

Synthet. Metal 121(1-3) (2001), 1589-1590

We have fabricated photovoltaic cells from organic donor/ acceptor couples arranged as ionically self assembled monolayers, Making use of the morphological control on the nanometer level we were able to study the influence of the device structure and layer composition on the quantum yield of charge carrier photogeneration, The photoluminescence quenching and the photocurrent spectra reveal sample composition, charge carrier photogeneration and transport properties independently.

[254] Microring Light-Emitting Devices with Self-Assembled Multilayer Structures Based on Poly(P-Phenylene Vinylene)S

T. Fujisawa, T. Sonoda, R. Ootake, A. Fujii and K. Yoshino

Synthet. Metal 121(1-3) (2001), 1739-1740

Periodic multilayer structures of poly(p-phenylene vinylene)s have been fabricated by a self-assembly method on flat surfaces and round surfaces of optical fibers. Alternating multilayers consisting of poly(1,4-(2-(5-carboxypentyloxy)-5- methoxyphenylene)vinylene) and poly(p-phenylene vinylene) have been adsorbed onto the positively charged substrates and the optical properties have been studied. The periodic multilayers with microring geometry have also been fabricated around the quartz fibers, and the optical properties and yellow electroluminescence from a light-emitting device with microring geometry have been investigated.

[255] Alternate Deposition of Horseradish-Peroxidase and Bipolar Pyridine Salt on the Solid-Surface to Prepare Electrocatalytically Active Enzyme Thin-Film

W. J. Li, M. Xian, Z. C. Wang, C. Q. Sun and M. Y. Zhao

Thin Solid Films 386(1) (2001), 121-126

Horseradish peroxidase (HRP)-containing multilayer films have been fabricated by alternate deposition with bipolar pyridine salt (PyC6BPC6Py) on the surface of gold electrode derivatized by 3-mercapto-1-proponesulfonate monolayer. The driving force of forming the multilayer structures is the electrostatic interaction between the negatively charged HRP and the positively charged PyC6BPC6Py. The assembly process was monitored by ultraviolet-visible spectroscopy on quartz slides. The electrochemical behavior of the enzyme electrode showed that the multilayer film was stable and electroactive. The diffusing mediator, methylene green in solution as an electron shuttle, was able to Transfer electrons successfully between the active center of the immobilized HRP and the electrode surface. Its potential application as amperometric sensor for hydrogen peroxide is anticipated. (C) 2001 Elsevier Science B.V. All rights reserved.

[256] Self-Assembled Inorganic/Organic Composite Superlattice Thin- Films with Photochromic Properties

Z. H. Chen, Y. Ma and J. N. Yao

Thin Solid Films 384(2) (2001), 160-165

A multicomposite WO3/4,4'-BPPOBp self-assembled multilayer (SAM) film was fabricated by the consecutive self-assembly of WO, and 4,4'-BPPOBp on 3-aminopropyl-triethyoxysilane (APS) modified quartz or silicon substrate by a polyelectrolyte (PE) approach. A well-ordered superlattice structure, d-spacing 0.694 nm, was identified by X-ray diffraction and X-ray reflection techniques. The SAM film shows fine photochromic properties. (C) 2001 Elsevier Science B.V. All rights reserved.

[257] 2-Step Assembly Technique for Preparation of Polymer-Particle Composite Films

H. Hattori

Thin Solid Films 385(1-2) (2001), 302-306

Two-step assembly (TSA) technique for preparation of polymer- particle composite films is presented. The TSA process consists of coating a polyelectrolyte onto a substrate and dipping the coated substrate in a particle suspension. The previously coated polyelectrolyte acts as a particle aggregation promoter, in other words, as an adhesive for particles. Diffusion and adsorption of the polyelectrolyte are important behaviors for this process. Preparation of composite films consisting of commercially available polyelectrolytes such as poly(diallyldimethylammonium chloride) (PDDA) and colloidal silica (SiO2) or titania (TiO2) particles were demonstrated. The composite films were porous and their thickness depended on the thickness and the molecular mass of previously coated polyelectrolyte, treatment time, and the concentration of suspension. Some PDDA-SiO2 composite films with 190 nm SiO2 particles had colloidal crystal domains and reflected visible light. (C) 2001 Elsevier Science B.V. All rights reserved.