Self-Assembled Monolayers of Molecular Conductors with Terpyridine-Metal Redox Switching Elements: A Combined AFM, STM and Electrochemical Study

Self-assembled monolayers (SAMs) of terpyridine-based transition metal (ruthenium and osmium) complexes, anchored to gold substrate via tripodal anchoring groups, have been investigated as possible redox switching elements for molecular electronics. An electrochemical study was complemented by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) methods. STM was used for determination of the SAM conductance values, and computation of the attenuation factor β from tunneling current–distance curves. We have shown that SAMs of Os-tripod molecules contain larger adlayer structures compared with SAMs of Ru-tripod molecules, which are characterized by a large number of almost evenly distributed small islands. Furthermore, upon cyclic voltammetric experimentation, Os-tripod films rearrange to form a smaller number of even larger islands, reminiscent of the Ostwald ripening process. Os-tripod SAMs displayed a higher surface concentration of molecules and lower conductance compared with Ru-tripod SAMs. The attenuation factor of Os-tripod films changed dramatically, upon electrochemical cycling, to a higher value. These observations are in accordance with previously reported electron transfer kinetics studies

Determination of phytohormones in genetically modified Nicotiana plants by differential pulse voltammetry

The differential pulse voltammetry was used for the determination of the phytohormone indole-3-acetic acid (IAA) in plant samples using a glassy-carbon electrode. The limit of detection of the proposed method is 0,45 microg.ml-1. The electrochemical determination of IAA is selective and the concentration of IAA in sample of genetically modified plant Nicotiana langsdorfii was determined in the presence of other phytohormones as abscisic acid and some cytokinins

Adsorption of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine on Au(111) and HOPG

Atomic force microscopy (AFM) was used to study the formation of layers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) on Au(111) and highly oriented pyrolytic graphite (HOPG) in microscopic level. Both substrates were found to support the DPPC layers. The nanoshaving technique was applied to determine the layer thickness. In addition, the influence of deionized water on the DPPC ordering at the substrates was studied by ex-situ and in-situ AFM intermittent contact mode measurements

Electrochemical characterization of water soluble fullerenes

Fullere (C60) is a highly hydrophobic compound and it is considered to be insoluble in water. Different approaches were described for preparing aqueous solutions of C60. One of the possibilities is to create an inclusion complex of the C60 inside a cavity of gamma-cyclodextrin. Recently, we have shown that such complexes are capable of the electrochemical conversion of N2 to ammonium ions

Electrochemical Properties of Mixed Self-Assembled Monolayers Based on Terpyridine Transition Metal Complexes

This work presents the electrochemical characterization of mixed self-assembled monolayers\n(SAMs) of [Os(terpy)2]2+ and terpyridine connected by tripodal anchoring groups to the\npolycrystalline gold bead electrode and provides a comparison with SAM based on\n[Os(terpy)2]2+ tripodal molecules without diluting terpyridine tripodal molecules. It is shown\nthat both arrangements enable reproducible preparation of well-defined compact films. The\nelectron transfer rate constant for mixed SAM was determined from cyclic voltammograms\naccording to Laviron’s analysis and compared with the rate constant obtained previously for\nSAM containing only [Os(terpy)2]2+ tripod

Fullerene C60 in Aqueous Medium

The aqueous solution of C60 was investigated by electrochemical and spectroscopis methods such as UV-Vis, Raman, FTIR and AFM techniques. The association constants of fullerene-gamma-cyclodextrin complex and ,ethanofullerene conjugates with beta-cyclodextrins in aqueous solution were evaluated from the shifts of the formal redox potential of complexed and uncomplexed fullerene. The most suitable techniques for electrochemical characterization of fullerene derivatives proved to be the low-frequency phase-sensitive AC polarography and the steady-state voltammetry

Electrochemical nitrogen fixation in the presence of fullerene -.gamma.-cyclodextrin complex

We report on the electrochemical conversion of dinitrogen to ammonia at ambient pressure and 60oC mediated by reduced fullerene (C60) inside a molecular cavity of .gamma.-cyclodextrin (.gamma.-CD) in aqueous solution

Self-Assembled Monolayers of Molecular Conductors with Terpyridine-Metal Redox Switching Elements: A Combined AFM, STM and Electrochemical Study

Self-assembled monolayers (SAMs) of terpyridine-based transition metal (ruthenium and osmium) complexes, anchored to gold substrate via tripodal anchoring groups, have been investigated as possible redox switching elements for molecular electronics. An electrochemical study was complemented by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) methods. STM was used for determination of the SAM conductance values, and computation of the attenuation factor β from tunneling current–distance curves. We have shown that SAMs of Os-tripod molecules contain larger adlayer structures compared with SAMs of Ru-tripod molecules, which are characterized by a large number of almost evenly distributed small islands. Furthermore, upon cyclic voltammetric experimentation, Os-tripod films rearrange to form a smaller number of even larger islands, reminiscent of the Ostwald ripening process. Os-tripod SAMs displayed a higher surface concentration of molecules and lower conductance compared with Ru-tripod SAMs. The attenuation factor of Os-tripod films changed dramatically, upon electrochemical cycling, to a higher value. These observations are in accordance with previously reported electron transfer kinetics studies

Formation and investigation of 6-cysteinyl amino methylated β-cyclodextrin self-assembled monolayers

International audienceCysteinyl amino methylated β-cyclodextrin was adsorbed on Au(111) as well as on mercury electrode. Scanning probe microscopy and electrochemical techniques confirmed that a chemisorbed self-assembled monolayer (SAM) of the β-cyclodextrin is formed, proving that a single –SH moiety located in the cysteinyl group is sufficient to anchor the entire methylated β-cyclodextrin molecule to the electrode surface. Thus, formed SAM can potentially serve as sensor layer for various organic molecules such as pesticides, antibiotics, and optically active compounds