Polyalanine derivatives containing cysteamine linker R-(Ala)14NH-(CH2)2-SH, where R is ferrocenecarbonyl or hydrogen, were synthesized and then used to form self-assembled monolayers on gold. The tilt angles and the packing density of the molecules within monolayer assemblies were determined by FTIR spectroscopy and scanning tunneling microscopy, respectively. Electrochemical properties of monolayer-modified electrodes were studied using cyclic voltammetry and impedance spectroscopy. Measurements of electron-transfer rates using electrochemical techniques and scanning tunneling spectroscopy revealed asymmetry dependent on the applied voltage. It is suggested that the observed electron-transfer behavior is connected with the electric field generated by the molecular dipole of the polyalanine helix.

The ability of Keggin-type phosphododecamolybdates (PMo 12 O 40 3-) to undergo chemisorption and to form anionic monolayers on platinum surfaces is explored here to produce stable colloidal solutions of polyoxometalate-protected platinum nanoparticles (size, 5-10 nm, as determined by transmission electron microscopy and scanning tunneling microscopy). By dip-coating in the above solution, the particles can readily be assembled on carbon electrode substrates. The layer-by-layer method, which involves alternate exposures to the solutions of PMo 12 O 40 3--stabilized Pt nanoparticles and anilinium cations, has been utilized to grow in a controlled manner hybrid network films in which the negatively charged layers of polyoxometalate-protected Pt nanoparticles are linked, or electrostatically attracted, by ultrathin positively charged polyaniline layers. The phosphomolybdate-decorated Pt nanoparticles (immobilized within ultrathin polyaniline film) are attractive for electrocatalysis: they show promising reactivity toward the electroreduction of oxygen.

Organothiol molecules with one or two amide moieties replacing the methylene groups in the alkyl chain were synthesized and self-assembled in mixed monolayers on the gold electrode. Structures of the monolayer films were studied by STM and electrochemical methods. Reflectance infrared spectroscopy confirmed the formation of intermolecular hydrogen bonds between the amide groups. In the case of diamides, the extent of hydrogen bonding in the external and internal planes of the monolayer were compared and both the odd and the even-membered molecules were considered. Impedance spectroscopy and chronoamperometry were employed to measure the electron transfer rate across mixed monolayers containing less than 10% of electroactive ferrocene organothiol with one or two amide groups in the chain. In the present paper, we focus on the amide location effects on kinetics of mediated electron transfer. Our results indicate that the distance between the planes where amide moieties are located and the electrode surface is of crucial importance. Deeply “buried” (i.e., located close to the electrode surface) amide groups were found to be responsible for the significant increase of electronic coupling comparing to simple n-alkanethiol monolayers. The effect of external amides was much less pronounced. This observation was explained as due to the different extent of hydrogen bonding in the internal and external plane of amide groups.

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The gold electrode surface has been functionalized by phenyl groups ending with aminoethyl or carboxyethyl entities. The functionalization was achieved by the electrochemical reduction of 4-aminoethylbenzene- or 4-carboxyethylbenzene-diazonium salts. The laccase layers were studied by polarization modulation infrared spectroscopy (PMIRRAS), linear sweep voltammetry, and electrochemical quartz microbalance. The kind of surface groups controlling the orientation of the enzyme on the surface was revealed by PMIRRAS. The orientation influenced the enzyme activity on its turn. The direct, mediatorless electrocatalytic current due to the oxygen reduction was observed starting from +0.60 V versus Ag/AgCl at pH 4.5 for laccase immobilized on the amine-ended layer. The observed potential value is close to the redox potential of the laccase T1 center. The electrocatalytic current values were equal to 4 mA/cm. Immobilization of laccase on the carboxyethyl groups leads to smaller electrocatalytic current values. The onset of the electrocatalytic current was down-shifted to +0.56 V.

Small multilayer fullerenes, also known as carbon nano-onions (CNOs; 5-6 nm in diameter, 6-8 shells), show higher reactivity than other larger carbon nanostructures. Here we report the first example of an in situ polymerization of aniline on phenyleneamine-terminated CNO surfaces. The green, protonated, conducting emeraldine polyaniline (PANI) was directly synthesized on the surface of the CNO. The functionalized and soluble CNO/PANI composites were characterized by TEM, SEM, DSC, Raman, and infrared spectroscopy. The electrochemical properties of the conducting CNO/PANI films were also investigated. In comparison with pristine CNOs, functionalized carbon nanostructures show dramatically improved solubility in protic solvents, thus enabling their easy processing for coatings, nanocomposites, and biomedical applications.