Self-assembled multilayers of alpha,o-aromatic dithiols formed by transition metals.

摘要

Self-assembled multilayers were prepared by alternate deposition of 4,4 ′-dimercaptobiphenyl (DMBP) and copper (II) ions onto planar Au(111) substrates. The multilayers were characterized by ellipsometry, external reflectance Fourier transform infrared spectroscopy (ER-FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Ellipsometry and ER-FTIR results show a linear relationship between the number of layers and the integral area of absorption characteristic of vibrational modes assigned to the biphenyl moieties. XPS data suggest that the copper is present in the +1 and +2 oxidation states in bulk material made by the reaction of DMBP and Cu(II) ions in solution, and only in the +1 state in multilayer films. XPS results also indicate a linear relationship between the number of DMBP-Cu layers and thickness. AFM studies provided details about the surface morphology and confirmed thickness via nanoshaving and nanografting techniques. Based on the combination of these techniques, it is proposed that interlayer disulfide linkages form the DMBP multilayer system. Self-assembled multilayers on of DMBP on Au(111) by alternate deposition of one of each of the metals in-group IIB of the periodic table with DMBP. The multilayers were characterized by ellipsometry, external reflectance Fourier transform infrared spectroscopy (ER-FTIR), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Ellipsometric and ER-FTIR results supported the formation of a multilayer using Mercury (II) and Cadmium(II). XPS results showed both mercury (0) and mercury(II) and no cadmium in the respective multilayer. Models were proposed for both systems. Angle resolved XPS was employed to further explore the similarities and differences between multilayers formed by Cu(II) and Hg(II). The results of CV sweeps of Cu, Hg, Cd, and Zn show similar reduction behavior at similar potential. Their redox behavior remains under investigation. Multilayers of aromatic and aliphatic dithiols were also prepared and characterized. Oligo(phenylene ethynylene) (OPE) protected thiol was synthesized and its multilayer formation was studied by XPS. STM is being used to explore the possibility of using these systems as molecular wires and molecular capacitors and resistors.