Organic Molecular Self-Assembly System For Electron Transport Study

In the past three decades, self-assembly technique has attracted great interest from many scientists. Self-assembly technique is one of the most important "bottom-up" strategies in fabricating nano- or molecular devices. Understanding to the process of electron transfer in molecular self-assembly systems is essential for the future nano- or molecular devices. The motivation of this thesis is to fabricate highly ordered self-assembly nanostructures and investigate the electron transfer in organic self-assembly systems.1,The self-assembly of chiral organic molecules on Si substrate has been studied. Under the irradiation of white light, chiral organic molecules was attached onto Si-H substrate. This process was monitored by XPS and ellipsometry. Experimental data showed that a relative long time (>15 h) was need to obtain a densely packed self-assembly monolayer under this mild condition.2,Well patterned stripes with alternating CH₃ and COOH terminated self-assembled monolayers (SAMs) have been fabricated by using micro-contact printing technology. Au nanoparticles could be selectively adsorbed on the COOH terminated surface. Theoretical calculation shows that the absorption energy of Au nanoparticles on COOH terminated surface is three times higher than that on CH₃ terminated surface.3,"Core-shell" structure molecular wires have been designed and synthesized using OPE as "core", and dendrimer side chain as "shell". UV-vis and fluorescence spectra show that the dendrimer side chains inhibit the aggregation of molecular wires effectively in both solution and solid state. Quantum Yields increase with the increase of the dendrimer side chain generations. Atom force microscopy (AFM) images show that the structure of thin films changes from fiberic to dendritic when increasing the generation of dendrimer side chains.4,The selective electroanalysis of dopamine (DA) using the self-assembled monolayers of an oligo(phenyleneethynylene)s (OPEs) type molecular wire have been studied for the first time. Cyclic voltammetry measurement showed the OPE modified electrodes preferentially inhibit the electrochemical reaction of ascorbic acid (AA). This work reveals that, besides molecular electronics, biosensor could be an attractive new field of application for the OPE type molecular wires.5,A highly efficient electrochemical assistant method has been used to attach ferrocene compound (FcOH) onto gold electrodes. The method gives densely packed Fc monolayer and exhibits good promoting effect to the direct electrochemistry of Cyt c, which shows potential applications in bio-electronics. It is believed similar method may be applicable to other hydroxyl derivatives to form monolayers on metal surface if the oxidation potentials to their hydroxyl group are in a proper potential window.6,A new series of biferrocene compounds with various conjugation biphenyl groups have been designed and synthesized. Theoretical calculation shows that the conjugation biphenyl groups have much effect on the spectroscopy of the compounds. The designed compounds show the ability to selectively bind Zn²⁺ ions. These molecules could also be used as model molecules to study the intra-molecular electron transfer. Further work is undergoing.