Turyan I, Matsue T, Mandler D
. Patterning and characterization of surfaces with organic and biological molecules by the scanning electrochemical microscope
. Anal ChemAnalytical chemistry. 2000;72 (15) :3431 - 5.Abstract
A novel approach for micropatterning of surfaces with organic and biological microstructures using the scanning electrochemical microscope (SECM) is described. The approach is based on the introduction of the spatial resolution by local deposition of gold particles followed by monolayer formation and functionalization. Specifically, gold patterns were deposited locally on silicon wafers with the SECM as a result of the controlled anodic dissolution of a gold microelectrode. The gold patterns were further used as microsubstrates for assembling cystamine monolayers to which either fluoresceine isothiocyanate (FIT) or glucose oxidase (GOD) were covalently attached. Characterization of the organic monolayers, as well as the biological activity of the enzyme patterns, was carried out by fluorescence microscopy and the SECM, respectively.[on SciFinder (R)]
Markovich I, Mandler D
. The effect of an alkylsilane monolayer on an indium-tin oxide surface on the electrochemistry of hexacyanoferrate.
J. Electroanal. Chem.Journal of Electroanalytical Chemistry. 2000;484 (2) :194 - 202.Abstract
The presence of a disorganized octadecylsilane, C18, monolayer on an indium-tin oxide (ITO) electrode has a profound effect on the electrochem. of hexacyanoferrate, Fe(CN)63-/4-. The alkylsilane monolayer forms a hydrophobic matrix, which affects the heterogeneous rate of electron transfer of the metallic complex, depending on the nature of the counter cation presence in the soln. A model is suggested which accounts for these effects as well as for the changes in the formal redox potential that are obsd. [on SciFinder(R)]
Batz V, Schneeweiss MA, Kramer D, Hagenstrom H, Kolb DM, Mandler D
. Electrochemistry and structure of the isomers of aminothiophenol adsorbed on gold.
J. Electroanal. Chem.Journal of Electroanalytical Chemistry. 2000;491 (1,2) :55 - 68.Abstract
The self-assembled monolayers (SAMs) of the three isomers of aminothiophenol, ATP, have been studied by means of electrochem., in-situ STM and XPS. We find that the isomers are organized differently. The organization is presumably governed by their intermol. and surface interactions. Moreover, the chem. and phys. characteristics of the interface are significantly and differently affected by the isomers comprising the SAMs. The electrochem. of the modified surface as well as the bare gold surface in contact with the thiol-contg. electrolyte, copper deposition and palladium(II) extn. have been studied for the 2-, 3- and 4-ATP monolayers. The organization of the layers has been investigated by STM. In essence, we find that the different isomers are likely to adopt an orientation that is perpendicular to the surface. While 4-ATP forms the densest monolayer, 2-ATP probably interacts with the gold surface with both the amino and the mercapto groups. Moreover, STM images indicate the partial formation of more than a monolayer. This is supported by XPS measurements and electrochem. and can be attributed to the SAM modification soln., i.e. sulfuric acid, which allows the formation of sulfate-bridged ATP bilayers. The chem. and phys. characteristics of the interfaces are governed by the different organization as well as by the individual chem. properties of each isomer. [on SciFinder(R)]
Yasukawa T, Kanaya N, Mandler D, Matsue T
. Imaging of diaphorase micropatterned at gold arrays with scanning electrochemical microscopy.
Chem. Lett.Chemistry Letters. 2000;(5) :458 - 459.Abstract
Diaphorase was hydrophobically immobilized onto a self-assembled monolayer of alkanethiol at an interdigitated Au microarray. The diaphorase activity at the array substrates was imaged with the scanning electrochem. microscopy (SECM) in the presence of NADH and ferrocenemethanol as a redox mediator. The images demonstrate that diaphorase was immobilized onto the SAM layer to form a line-and-space micropattern which reflected the pattern of the Au microarray. [on SciFinder(R)]
Turyan I, Matsue T, Mandler D
. Patterning and Characterization of Surfaces with Organic and Biological Molecules by the Scanning Electrochemical Microscope.
Anal. Chem.Analytical Chemistry. 2000;72 (15) :3431 - 3435.Abstract
A novel approach for micropatterning of surfaces with org. and biol. microstructures using the scanning electrochem. microscope (SECM) is described. The approach is based on the introduction of the spatial resoln. by local deposition of Au particles followed by monolayer formation and functionalization. Specifically, Au patterns were deposited locally on Si wafers with the SECM as a result of the controlled anodic dissoln. of a Au microelectrode. The Au patterns were further used as microsubstrates for assembling cystamine monolayers to which either fluoresceine isothiocyanate (FIT) or glucose oxidase (GOD) were covalently attached. Characterization of the org. monolayers, as well as the biol. activity of the enzyme patterns, was carried out by fluorescence microscopy and the SECM, resp. [on SciFinder(R)]
Selzer Y, Mandler D
. Probing the coupling of charge-transfer processes across liquid/liquid interfaces by the scanning electrochemical microscope.
J. Phys. Chem. BJournal of Physical Chemistry B. 2000;104 (20) :4903 - 4910.Abstract
The feedback mode of the scanning electrochem. microscope (SECM) was used to induce and measure charge-transfer coupling (CTC) between two ion-transfer (IT) processes across liq./liq. interfaces. Results are interpreted using a general model for coupling processes under steady-state conditions that is also applicable to other modes of coupling such as IT-ET and ET-ET (ET = electron transfer). The measured feedback curves demonstrate the effect of mass-transfer limitations in these processes on the potential across the interface, shedding new light on the dynamics of bioenergetics and phase-transfer catalysis systems as well as on previous SECM studies of liq./liq. interfaces. [on SciFinder(R)]
Selzer Y, Mandler D
. Scanning Electrochemical Microscopy. Theory of the Feedback Mode for Hemispherical Ultramicroelectrodes: Steady-State and Transient Behavior.
Anal. Chem.Analytical Chemistry. 2000;72 (11) :2383 - 2390.Abstract
This contribution represents the first comprehensive attempt to treat complex geometry configurations of the scanning electrochem. microscope (SECM) using the alternating direction implicit finite difference method (ADIFDM). Specifically, ADIFDM is used to simulate the steady-state as well as the transient (chronoamperometric) behavior of a hemispherical ultramicroelectrode (UME) tip of the SECM. The feedback effect in this configuration is less pronounced as compared with a disk-shaped UME system. The differences between the two systems are discussed. Anal. approxns. for the steady-state behavior and for characteristic features of the transient behavior are suggested. Finally, exptl. feedback currents measured above a conductor and an insulator are in excellent agreement with the theory. [on SciFinder(R)]
Turyan I, Krasovec UO, Orel B, Saraidorov T, Reisfeld R, Mandler D
. "Writing-reading-erasing" on tungsten oxide films using the scanning electrochemical microscope.
Adv. Mater. (Weinheim, Ger.)Advanced Materials (Weinheim, Germany). 2000;12 (5) :330 - 333.Abstract
The authors described fast electrochem.-spectroscopic "writ- ing-reading-erasing" system based on a scanning probe technique. The fast "reading" and "erasing" processes are due to the fact that there is no phase transition between the two states and that the ingression and egression of ions is very fast. In principle, the resoln. of patterning depends on the size of the microelectrodes, which currently can be reduced to the nanometer range. The uniqueness of this system is that the propagation of the lateral charge inside the thin film can be detected independently of its formation. This allows the study of lateral charge transport and enables the development of better systems in terms of resoln. and information storage capabilities. [on SciFinder(R)]
Muskal N, Mandler D
. The electrochemistry of thiol self-assembled monolayers (SAMs) on a hanging mercury drop electrode (HMDE).
Curr. Sep.Current Separations. 2000;19 (2) :49 - 54.Abstract
The electrochem. of functionalized self-assembled monolayers on Hg is studied by cyclic voltammetry and AC voltammetry. The results suggest that thiols can be adsorbed either chem. or phys. depending on the Hg potential. The transformation between these two states occurs via an oxidn.-redn. process. While a multi-layer of short chemisorbed thiols is formed under pos. potentials than the oxidn.-redn. process, a dense monolayer is self-assembled under more neg. potentials. [on SciFinder(R)]