The difference in the heterogeneous binding of Mg(2+), Ca(2+) and Sr(2+) ions by 1-thioglycerol (TG) and 1,4-dithiothreitol (DTT) spontaneously adsorbed monolayers on Au has been studied following the changes in the double layer capacity. A mathematical treatment, based on calculating the electrochemical potential difference at the monolayer-electrolyte interface, has followed our recent work which dealt with the acid-base equilibrium at the interface as a means of calculating the pK of ionizable SAMs and their binding with Cd(2+). Experimentally, spontaneously adsorbed monolayers of TG and DTT were assembled on Au surfaces and studied by impedance spectroscopy and alternating current voltammetry (ACV). The capacity was measured for each of the modified surfaces at increasing concentrations of the divalent metal ions separately. The goal of this study has been to examine the effect of metal ion binding by similar ligands that are differently attached onto the surface. TG and DTT monolayers differ in their flexibility, which is a result of their attachment to the surface through one and two arms, respectively. The general trend of the apparent heterogeneous association constants of the divalent metal ions, which were calculated from the capacity measurements, was substantially different from the classical Irving-Williams series that is applicable to homogeneous systems. This difference could be nicely explained by the reduction of the degree of freedom and flexibility of the attached ligands.[on SciFinder (R)]

The complexation of Fe(II) and Cu(II) ions by phenanthroline and terpyridine-based Langmuir films was studied by the effect the added ions in the subphase on the isotherms. We found that Cu(II) had a pronounced effect on the isotherm consisting of phenanthroline moieties forming a square-planar 1:2 (Cu(II)/phenanthroline) complex. However, Fe(II) affected the isotherm made of 1:1 phenanthroline/terpyridine amphiphiles as a result of forming a pentacoordinate complex.[on SciFinder (R)]

The formation of a self-assembled monolayer significantly promotes the adhesion of electrodeposited polypyrrole on stainless steel. The monolayer affects the nucleation and growth mechanism of polypyrrole as a result of its hydrophobic nature. This was confirmed by analyzing current-time transients of the initial stages of electropolymerization and was in agreement with AFM images.[on SciFinder (R)]

A new approach based on measuring the change of the open-circuit potential (OCP) of a hanging mercury drop electrode (HMDE), modified with alkanethiols of different chain length conducted in a solution containing a mixture of Ru(NH3)6(2+) and Ru(NH3)6(3+) is used for studying electron transfer across the monolayer. Following the time dependence of the OCP allowed the extraction of the kinetic parameters, such as the charge transfer resistance (R(ct)) and the electron transfer rate constant (k(et)), for different alkanethiol monolayers. An electron tunneling coefficient, beta, of 0.9 A(-1) was calculated for the monolayers on Hg.[on SciFinder (R)]

Long chain n-alkanethiol self-assembled monolayers (SAMs) on a hanging Hg drop electrode were studied in detail for the 1st time by impedance spectroscopy (IS) and potentiometry. IS reveals the detailed behavior of the monolayers in the absence and presence of 2 1-electron redox couple: hexaammineruthenium(III) (Ru(NH3)63+) and tris(2,2'-bipyridine)cobalt(III) (Co(bpy)33+). The pinholes-free layers behave as almost ideal capacitors and are permeable to some extent to redox species, depending on their hydrophobicity. Co(bpy)33+ that exhibits sluggish kinetics on a bare Hg electrode reveals a more facile kinetics than Ru(NH3)63+ on an n-octadecanethiol/Hg interface. Potentiometric measurements recorded upon immersing the bare and SAM modified Hg electrode into a soln. contg. a mixt. of the oxidized and reduced forms of the redox couples provide invaluable information on the charge transfer across the monolayer and its ohmic resistance. While Ru(NH3)63+ cannot freely penetrate into the monolayer and therefore establishes a p.d. across the monolayer; penetration of Co(bpy)32+ into the film causes the Fermi level of the Hg surface to attain the Nernst potential of the soln. Finally, increasing the length of the alkane chain of the thiols increases linearly the ohmic resistance of the layer. [on SciFinder(R)]

The complexation of FeII and CuII ions by phenanthroline and terpyridine-based Langmuir films was studied by the effect the added ions in the subphase on the isotherms. We found that CuII had a pronounced effect on the isotherm consisting of phenanthroline moieties forming a square-planar 1:2 (CuII/phenanthroline) complex. However, FeII affected the isotherm made of 1:1 phenanthroline/terpyridine amphiphiles as a result of forming a pentacoordinate complex. [on SciFinder(R)]

The difference in the heterogeneous binding of Mg2+, Ca2+ and Sr2+ ions by 1-thioglycerol (TG) and 1,4-dithiothreitol (DTT) spontaneously adsorbed monolayers on Au has been studied following the changes in the double layer capacity. A math. treatment, based on calcg. the electrochem. p.d. at the monolayer-electrolyte interface, has followed our recent work1 which dealt with the acid-base equil. at the interface as a means of calcg. the pK of ionizable SAMs and their binding with Cd2+. Exptl., spontaneously adsorbed monolayers of TG and DTT were assembled on Au surfaces and studied by impedance spectroscopy and a.c. voltammetry (ACV). The capacity was measured for each of the modified surfaces at increasing concns. of the divalent metal ions sep. The goal of this study has been to examine the effect of metal ion binding by similar ligands that are differently attached onto the surface. TG and DTT monolayers differ in their flexibility, which is a result of their attachment to the surface through one and two arms, resp. The general trend of the apparent heterogeneous assocn. consts. of the divalent metal ions, which were calcd. from the capacity measurements, was substantially different from the classical Irving-Williams series2-4 that is applicable to homogeneous systems. This difference could be nicely explained by the redn. of the degree of freedom and flexibility of the attached ligands. [on SciFinder(R)]

Novel processes for coating metal surfaces and/or for attaching active substances to metal surfaces, objects having coated metal surfaces and/or active substances attached thereto and uses thereof in the prepn. of implantable devices are disclosed. Thus, cyclic voltammetry of a stainless steel electrode in an acetonitrile soln. contg. 0.1 mM decanoic acid was performed to give a self-assembled monolayer on the electrode, showing advancing contact angle 59° and receding contact angle 45°. [on SciFinder(R)]

The formation of a self-assembled monolayer significantly promotes the adhesion of electrodeposited polypyrrole on stainless steel. The monolayer affects the nucleation and growth mechanism of polypyrrole of its hydrophobic nature. This was confirmed by analyzing current-time transients of the initial stages of electropolymn. and was in agreement with AFM images. [on SciFinder(R)]

A new approach based on measuring the change of the open-circuit potential (OCP) of a hanging Hg drop electrode (HMDE), modified with alkanethiols of different chain length conducted in a soln. contg. a mixt. of Ru(NH3)62+ and Ru(NH3)63+ is used for studying electron transfer across the monolayer. Following the time dependence of the OCP allowed the extn. of the kinetic parameters, such as the charge transfer resistance (Rct) and the electron transfer rate const. (ket), for different alkanethiol monolayers. An electron tunneling coeff., β, of 0.9 Å-1 was calcd. for the monolayers on Hg. [on SciFinder(R)]