AVS 52nd International Symposium
    Surface Science Wednesday Sessions
       Session SS+EM-WeM

Paper SS+EM-WeM9
Vertically Aligned Chromophoric Molecular Assemblies on a Si Surface

Wednesday, November 2, 2005, 11:00 am, Room 202

Session: Self-Assembled Monolayers
Presenter: G.G. Jernigan, US Naval Research Laboratory
Authors: G.G. Jernigan, US Naval Research Laboratory
M.F. Pepitone, US Naval Research Laboratory
J.S. Melinger, US Naval Research Laboratory
O.-K. Kim, US Naval Research Laboratory
Correspondent: Click to Email
Strong motivation for the development of molecular devices is the ability to synthetically create a molecule with desired optical and electronic properties through the linkage of different chemical moieties. The challenge remains, however, to integrate such a molecule with a physical device. Molecules can take various physical conformations and can interact with nearby molecules or surfaces resulting in a loss of optical and electronic properties. We have developed a method for encapsulating a 4-[4-(Dimethylamino) styryl]-1-docosylpyridinium bromide (DASP) chromophore in a helical amylose sheath to produce a supramolecular assembly as a molecular device. The benefits of the supramolecular assembly formation are attributed to the ability of the amylose to rigidify the conformation of the DASP molecule, to individually isolate DASP molecules, and to prevent the DASP molecules from interacting with other DASP molecules to form aggregates. When DASP forms aggregates, the fluorescence is quenched, but when DASP is encapsulated by amylose, the fluorescence intensity is maximized. We report that when the supramolecular assemblies are self-assembled onto a Si surface that DASP emits a strong fluorescence with a spectrum that is similar to that found in solution. More importantly, AFM images show that the assemblies vertically self align at near monolayer coverage on the Si surface. We have subsequently linked a viologen species (electron acceptor) to the DASP (electron donor) through various hydrocarbon chain spacers resulting in distant-dependent electron transfer. We report this system as the basis for a molecular photodiode.