Kurzbeschreibung
(Englisch)
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This project addresses molecular electronic function of noble metal nanocrystals and nanocrystal–redox molecule hybrids and networks thereof at electrified solid–liquid interfaces in an electrochemical in situ scanning tunnelling microscope configuration, while taking advantage of the superior spatial control provided by oligodeoxyribonucleotide (ODN) scaffolds. Integrated in COST D35 'From Molecules to Devices', we combine nanocrystal and in situ scanning tunnelling probe microscopy expertise in the Bern group with essential oligonucleotide and synthetic redox chemistry know-how from our networking partners.
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, CH, CZ, DE, DK, EE, ES, FI, FR, GR, HU, IE, IT, LT, NL, PL, PT, RO, SE, SK, UK
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Abstract
(Englisch)
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The Project C08.0116 'In-situ Scanning Tunneling Microscopy of Nanocrystal-Redox Moiety-Oligonucleotide Networks' is part of the activities within the Working Group 'Networks of Metal Complexes and Nanoparticles with Electronic, Magnetic and Opto-electronic Properties' of the COST Action D35 entitled 'From Molecules to Molecular Devices: Control of Electronic, Photonic, Magnetic and Spintronic Behavior'. The core objective of the project is to demonstrate and explore active electronic functions of quantum-confinement metal nanocrystals, redox-active moleculs and nanocrystal-redox hybrids through in-situ scanning probe techniques (SPM). The research activities of the Bern group were particularely focused on (i) nanoparticle preparation and characterization and (ii) the construction of functional molecular adlayers at metal and semiconducting substrates and their addressing at electrified solid/liquid interfaces. In particular, the Bern group synthesized monodisperse hexanethiolate-protected gold clusters, Au147-C6C, and a wide range of citrate-stabilized gold and silver nanoparticles (Me(5nm) to Me(60nm)). The electrical, optical and structure properties of these gold nanocrystals as well as their alloys with mercury (Au@Hg) were characterized by electrochemical techniques, UV/VIS spectroscopy and transmission electron microscopy (TEM). Drop-cast films of narrowly dispersed Au147-C6C clusters on Pt demonstrated quantized double layer charging in various organic solvents and ionic liquids. Au@Hg nanoalloy formation was achieved by direct amalgamation. Slow nanoscale diffusion was demonstrated based on structural, spectroscopic and computational approaches. Structural aspects of redox-mediated electron tunneling have been investigated for ferrocene derivatives covalently immobilized in nanoscale STM-type tunneling junctions created in Au/molecule/Au as well as n-type Si(111)/molecule/Au configurations. In particular, situ scanning tunnelling spectroscopy (STS) revealed for the first time with ferrocene-modified Si(111) substrates ambipolar field effect transistor (FET) behaviour upon electrolyte gating. Publications [1] S. F. L.Mertens, G. Meszarosz, Th. Wandlowski: 'Dynamics of Ionic Liquid Mediated Quantized Charging of Monolayer-Protected Clusters'; Phys. Chem. Chem. Phys. 12 (2010) 5417. [2] S. F. L. Mertens, A. Büttikofer, L. Siffert, Th. Wandlowski: 'Covalent vs. electrostatic strategies for nanoparticle immobilization'; Electroanalysis 22 (2010) 2940 - 2946. [3] A. V. Rudnev, I. V. Pobelov, Th. Wandlowski: 'Structural Aspects of redox-mediated electron tunneling'; J. Electroanal. Chem., doi:10.1016/j.jelechem.2010.11.014. [4] S. F. L. Mertens, M. Gara, A. S. Sologubenko, J. Mayer, S. Szidat, K. Krämer, T. Jacob, D. J. Schiffrin, Th. Wandlowski: 'Metal diffusion at the nanoscale for Au@Hg nanoparticles'; Adv. Funct. Mat., doi:10.1002/adfm201100409, in press. [5] A. Mishchenko, M. Abduall, Y. Fu, A. Rudnev, A. R. Pike, Th. Wandlowski: 'Electrochemical Scanning Tunnelling Spectroscopy of a Ferrocene-modified n-Si(111) - Surface: Electrolyte Gating and Ambipolar FET Behaviour'; Chem. Commun., DOI:10.1039, submitted 05/2011.
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