Title

Preparation, characterization and exploitation of novel self-assembled nanostructured thin films

Date of Award

1999

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Janos H. Fendler

Keywords

Self-assembled, Nanostructured, Thin films, Microcrystallization, Langmuir-Blodgett

Subject Categories

Chemistry | Materials Chemistry | Physical Sciences and Mathematics

Abstract

Novel nanostructured thin multilayer films composed of surfactants (DHP, DODAB), polyelectrolytes (PSS, PVS, PDDA, PEI), dyes (ruthenium complexes), J-aggregates (cyanine dye) and metallic or semiconducting nanoparticles (Au, TiO 2 ) were prepared by the techniques of Langmuir-Blodgett and self-assembly. The structure of the self-assembled films, their interactions at interfaces and surfaces, their modification and the role they play were investigated by surface plasmon spectroscopy (SPS), quartz crystal microbalance (QCM), atomic force microscopy (AFM), absorption and emission spectroscopies, near-field scanning optical microscopy (NSOM) and electron microscopies (TEK, SEM).

Microcrystallization, photoluminescence, charge transport, and electron transfer were examined in the layer-by-layer self-assembled films using a variety of characterization techniques. QCM was developed and used in conjunction with simultaneous SPS to assess the nature of the self-assembly process and measure the thickness of multilayered thin films. NSOM was assembled as a complementary technique for the rapid, sensitive and non-destructive optical imaging and local spectroscopy of the supramolecular architecture work at surfaces and interfaces composed of submicron sized structures.

High resolution near-field optical imaging and spectroscopy have been used to provide a valuable insight into the microcrystallization of cationic [Ru(bby) 3 ] 2+ complexes under anionic dihexadecyl phosphate (DHP) monolayers as functions of the surface pressure and the conditioning of the monolayer. It was possible to spatially and spectrally resolve, at a submicron resolution, the presence of isolated seed crystals and their growth into differently shaped [Ru(bpy) 3 ] 2+ microcrystallites in the various phases of the monolayer.

Surface pressure (II) vs . surface area (A) isotherms, Brewster angle microscopy and AFM images provided evidence for a controllable two-dimensional crystal growth of an amphiphile [Ru(bpy) 3 ] 2+ -C 60 dyad molecule at the air-water interface and the existence of a truly monolayered structure. It suggested that the dyad fibers were composed of close-packed clusters with diameters of 100 ± 20 nm.

Finally NSOM was extended to allow single nanoparticle imaging and to probe the enhanced excitonic fluorescence of J-aggregates, attached to a monolayer of gold nanoparticles in a layer-by-layer self-assembled ultra thin film.

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