Publications

2006
Cohen-Atiya M, Mandler D. Studying electron transfer through alkanethiol self-assembled monolayers on a hanging mercury drop electrode using potentiometric measurements. Phys Chem Chem PhysPhysical chemistry chemical physics : PCCP. 2006;8 (38) :4405 - 9.Abstract
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)]
Cohen-Atiya M, Nelson A, Mandler D. Characterization of n-alkanethiol self-assembled monolayers on mercury by impedance spectroscopy and potentiometric measurements. J. Electroanal. Chem.Journal of Electroanalytical Chemistry. 2006;593 (1-2) :227 - 240.Abstract
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)]
Kraus S, Mandler D. Complexation of Ferrous and Cupric Ions by Phenanthroline and Terpyridine Langmuir Films. LangmuirLangmuir. 2006;22 (18) :7462 - 7464.Abstract
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)]
Burshtain D, Mandler D. The effect of surface attachment on ligand binding: studying the association of Mg2+, Ca2+ and Sr2+ by 1-thioglycerol and 1,4-dithiothreitol monolayers. Phys. Chem. Chem. Phys.Physical Chemistry Chemical Physics. 2006;8 (1) :158 - 164.Abstract
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)]
Domb AJ, Mandler D, Danziger I, Orom M, Okner R, Shustak G, Swed A, Tal N.; 2006. Modified conductive surfaces having active substances attached thereto and uses thereof.Abstract
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)]
Shustak G, Domb AJ, Mandler D. n-Alkanoic Acid Monolayers on 316L Stainless Steel Promote the Adhesion of Electropolymerized Polypyrrole Films. LangmuirLangmuir. 2006;22 (12) :5237 - 5240.Abstract
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)]
Cohen-Atiya M, Mandler D. Studying electron transfer through alkanethiol self-assembled monolayers on a hanging mercury drop electrode using potentiometric measurements. Phys. Chem. Chem. Phys.Physical Chemistry Chemical Physics. 2006;8 (38) :4405 - 4409.Abstract
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)]
2005
Fireman-Shoresh S, Turyan I, Mandler D, Avnir D, Marx S. Chiral electrochemical recognition by very thin molecularly imprinted sol-gel films. LangmuirLangmuir : the ACS journal of surfaces and colloids. 2005;21 (17) :7842 - 7.Abstract
Thin films with enantioselective properties for electrochemically active chiral probes were developed. Enantioselectivity was accomplished via molecular imprinting. The films were fabricated through the sol-gel technique and were spin-coated on ITO electrodes. The chiral selectivity recognition was detected using two enantiomer pairs: D- and L-3,4-dihydroxyphenylalanine (D- and L-dopa) and (R)- and (S)-N,N'-dimethylferrocenylethylamine [(R)-Fc and (S)-Fc]. A defined chiral cavity was obtained by selection of functional monomers that interact with the template molecule, followed by its removal. Chiral selection properties were measured by cyclic voltammetry and square wave voltammetry. For both template molecules, very good chiral recognition was revealed by electrochemical measurement. The nonspecific adsorption measured for reference nonimprinted films was negligible (less than 5%). Dopa imprinted films revealed both high sensitivity, by the detection of 1 nM (0.2 ppb) concentration, and excellent selectivity, when challenged with a series of catechol derivatives. Fc-imprinted films were able to detect ca. 2 ppm of the target molecule, with very good enantioselectivity and low nonspecific adsorption. To our knowledge, this is the first report of successful molecular imprinting of a ferrocene derivative.[on SciFinder (R)]
Mandler D. Daniel Mandler, Hebrew University of Jerusalem. AnalystThe Analyst. 2005;130 (2) :131 - 3.
Burt DP, Cervera J, Mandler D, Macpherson JV, Manzanares JA, Unwin PR. Scanning electrochemical microscopy as a probe of Ag+ binding kinetics at Langmuir phospholipid monolayers. Phys Chem Chem PhysPhysical chemistry chemical physics : PCCP. 2005;7 (15) :2955 - 64.Abstract
A new method has been developed for measuring local adsorption rates of metal ions at interfaces based on scanning electrochemical microscopy (SECM). The technique is illustrated with the example of Ag+ binding at Langmuir phospholipid monolayers formed at the water/air interface. Specifically, an inverted 25 microm diameter silver disc ultramicroelectrode (UME) was positioned in the subphase of a Langmuir trough, close to a dipalmitoyl phosphatidic acid (DPPA) monolayer, and used to generate Ag+ via Ag electro-oxidation. The method involved measuring the transient current-time response at the UME when the electrode was switched to a potential to electrogenerate Ag+. Since the Ag+/Ag couple is reversible, the response is highly sensitive to local mass transfer of Ag+ away from the electrode, which, in turn, is governed by the interaction of Ag+ with the monolayer. The methodology has been used to determine the influence of surface pressure on the adsorption of Ag+ ions at a phospholipid (dipalmitoyl phosphatidic acid) Langmuir monolayer. It is shown that the capacity for metal ion adsorption at the monolayer increased as the density of surface adsorption sites increased (by increasing the surface pressure). A model for mass transport and adsorption in this geometry has been developed to explain and characterise the adsorption process.[on SciFinder (R)]
Avissar YY, Sagiv AE, Mandler D, Almog J. Identification of firearms handling by the [Fe(PDT)(3)](2+) complex: Chemical and time-dependent factors. TalantaTalanta. 2005;67 (2) :328 - 33.Abstract
Handling of a gun results in the formation of invisible impressions, caused by transfer of iron traces to the skin surface. Visualization of these impressions is possible by spraying the palms with a solution of 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT), which forms a magenta complex with iron(II) residues. Hence, mark intensity is directly related to the amounts of iron transferred to the palm. Palmar sweat plays a major role in iron transfer from the firearm to the hand. More factors, however, are involved in this process. Three time-dependent factors have been studied with relation to their effect on the developed mark: the gripping duration of the weapon; the time elapsed from the contact; and the rate of iron dissolution in aqueous solutions containing sweat components in physiological concentrations. We found that the amounts of iron transferred to the palm depend on both, the gripping period and the levels of palmar moisture. Thus, only a few seconds of gripping were required for developing good marks (corresponding to 80ngcm(-2) of iron) on highly-moistured hands, much longer gripping periods were necessary for developing marks of similar intensity on relatively dry hands. Experiments that aimed at studying the effect of sweat components on metallic iron dissolution were carried out in aqueous solutions. It was found that chloride ions in physiological concentrations remarkably enhanced the dissolution, while l-serine, the major amino acid in palmar sweat, had a detrimental effect on this process. Urea, another sweat component, had only a minor effect on the dissolution rate.[on SciFinder (R)]
Fireman-Shoresh S, Turyan I, Mandler D, Avnir D, Marx S. Chiral electrochemical recognition by very thin molecularly imprinted sol-gel films. LangmuirLangmuir. 2005;21 (17) :7842 - 7847.Abstract
Thin films with enantioselective properties for electrochem. active chiral probes were developed. Enantioselectivity was accomplished via mol. imprinting. The films were fabricated through the sol-gel technique and were spin-coated on ITO electrodes. The chiral selectivity recognition was detected using two enantiomer pairs: D- and L-3,4-dihydroxyphenylalanine (D- and L-dopa) and (R)- and (S)-N,N'-dimethylferrocenylethylamine [(R)-Fc and (S)-Fc]. A defined chiral cavity was obtained by selection of functional monomers that interact with the template mol., followed by its removal. Chiral selection properties were measured by cyclic voltammetry and square wave voltammetry. For both template mols., very good chiral recognition was revealed by electrochem. measurement. The nonspecific adsorption measured for ref. nonimprinted films was negligible (<5%). Dopa imprinted films revealed both high sensitivity, by the detection of 1 nM (0.2 ppb) concn., and excellent selectivity, when challenged with catechol derivs. Fc-imprinted films were able to detect ∼2 ppm of the target mol., with very good enantioselectivity and low nonspecific adsorption. To the authors' knowledge, this is the 1st report of successful mol. imprinting of a ferrocene deriv. [on SciFinder(R)]
Shacham R, Avnir D, Mandler D.; 2005. Electrochemical deposition process and devices obtained by such process.Abstract
The present invention provides an electrochem. method for depositing a thin film comprising metal oxides or silicon oxides on a conductive surface placed on a non-conductive substrate by electrodeposition of sol-gel precursors on the conductive surface selectively. The sol-gel precursors may further comprise various dopants thereby patterning the conductive layer. [on SciFinder(R)]
Walcarius A, Mandler D, Cox JA, Collinson M, Lev O. Exciting new directions in the intersection of functionalized sol-gel materials with electrochemistry. J. Mater. Chem.Journal of Materials Chemistry. 2005;15 (35-36) :3663 - 3689.Abstract
A review. The implications of organically-modified SiO2-based materials in electrochem. science is reviewed along with some selected recent trends in the field of functionalized and sol-gel SiO2 electrochem. These recent trends include the electro-assisted generation of organosilica films on solid electrode surfaces, the prepn. and applications of sol-gel derived composite (C, Au, nanotubes) electrodes, the electrochem. characterization of mass transfer reactions in porous functionalized silicas, solid-state electrochem. and gas sensors involving sol-gel materials, imprinted functionalized SiO2, and the electrochem. characterization and applications of ordered mesoporous organosilicas. [on SciFinder(R)]
Avissar YY, Sagiv AE, Mandler D, Almog J. Identification of firearms handling by the [Fe(PDT)3]2+ complex: Chemical and time-dependent factors. TalantaTalanta. 2005;67 (2) :328 - 333.Abstract
Handling of a gun results in the formation of invisible impressions, caused by transfer of iron traces to the skin surface. Visualization of these impressions is possible by spraying the palms with a soln. of 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT), which forms a magenta complex with iron(II) residues. Hence, mark intensity is directly related to the amts. of iron transferred to the palm. Palmar sweat plays a major role in iron transfer from the firearm to the hand. More factors, however, are involved in this process. Three time-dependent factors have been studied with relation to their effect on the developed mark: the gripping duration of the weapon; the time elapsed from the contact; and the rate of iron dissoln. in aq. solns. contg. sweat components in physiol. concns. We found that the amts. of iron transferred to the palm depend on both, the gripping period and the levels of palmar moisture. Thus, only a few seconds of gripping were required for developing good marks (corresponding to 80 ng cm-2 of iron) on highly-moistured hands, much longer gripping periods were necessary for developing marks of similar intensity on relatively dry hands. Expts. that aimed at studying the effect of sweat components on metallic iron dissoln. were carried out in aq. solns. It was found that chloride ions in physiol. concns. remarkably enhanced the dissoln., while -serine, the major amino acid in palmar sweat, had a detrimental effect on this process. Urea, another sweat component, had only a minor effect on the dissoln. rate. [on SciFinder(R)]
Turyan I, Etienne M, Mandler D, Schuhmann W. Improved resolution of local metal deposition by means of constant distance mode scanning electrochemical microscopy. ElectroanalysisElectroanalysis. 2005;17 (5-6) :538 - 542.Abstract
The potential assisted ion-transfer between two immiscible electrolyte solns. has been implemented in scanning electrochem. microscopy (SECM) for depositing metal microstructures on conducting surfaces. An improved approach for local metal deposition is presented, taking advantage from a recently described non-optical shear-force detection system integrated in the SECM, which provided a current-independent tip-surface distance positioning. This allowed positioning of the micropipette in very close proximity to the surface without applying a potential during the approach, and hence, resulted in an improved resoln. for metal deposition. Moreover, it allowed the use of potential pulses for a discontinuous delivery of metal ions over the liq.-liq. interface. The advantages of this approach and its applicability for creating micro- and nanostructures are discussed. [on SciFinder(R)]
Burt DP, Cervera J, Mandler D, Macpherson JV, Manzanares JA, Unwin PR. Scanning electrochemical microscopy as a probe of Ag+ binding kinetics at Langmuir phospholipid monolayers. Phys. Chem. Chem. Phys.Physical Chemistry Chemical Physics. 2005;7 (15) :2955 - 2964.Abstract
A new method was developed for measuring local adsorption rates of metal ions at interfaces based on scanning electrochem. microscopy (SECM). The technique is illustrated with the example of Ag+ binding at Langmuir phospholipid monolayers formed at the H2O/air interface. Specifically, an inverted 25 μm diam. Ag disk ultramicroelectrode (UME) was positioned in the subphase of a Langmuir trough, close to a dipalmitoyl phosphatidic acid (DPPA) monolayer, and used to generate Ag+ via Ag electrooxidn. The method involved measuring the transient current-time response at the UME when the electrode was switched to a potential to electrogenerate Ag+. Since the Ag+/Ag couple is reversible, the response is highly sensitive to local mass transfer of Ag+ away from the electrode, which, in turn, is governed by the interaction of Ag+ with the monolayer. The methodol. was used to det. the influence of surface pressure on the adsorption of Ag+ ions at a phospholipid (dipalmitoyl phosphatidic acid) Langmuir monolayer. The capacity for metal ion adsorption at the monolayer increased as the d. of surface adsorption sites increased (by increasing the surface pressure). A model for mass transport and adsorption in this geometry was developed to explain and characterize the adsorption process. [on SciFinder(R)]
Burshtain D, Mandler D. Studying the binding of Cd2+ by ω-mercaptoalkanoic acid self assembled monolayers by cyclic voltammetry and scanning electrochemical microscopy (SECM). J. Electroanal. Chem.Journal of Electroanalytical Chemistry. 2005;581 (2) :310 - 319.Abstract
Cyclic voltammetry (CV) and scanning electrochem. microscopy (SECM) were used for studying the binding of protons and Cd(II) ions by 8-mercaptooctanoic acid monolayer that was assembled on an Au surface. Binding of the cations by the monolayer affected the kinetics of electron transfer to neg. charged species, i.e., IrCl63-, in the soln. Increasing the pH of the soln. causes the CV of IrCl63- to become less reversible and the feedback current of the SECM to decrease as the distance between the microelectrode and the surface decreases. However, addn. of Cd2+ to the soln. at pH 6.8 increases the CV reversibility and the feedback current of the SECM of neutralizing the neg. charge of the monolayer by the metallic ions. A model based on the Frumkin correction was used to account for these findings and for extg. the heterogeneous assocn. const. of Cd2+ by the monolayer. [on SciFinder(R)]
Whitworth AL, Mandler D, Unwin PR. Theory of scanning electrochemical microscopy (SECM) as a probe of surface conductivity. Phys. Chem. Chem. Phys.Physical Chemistry Chemical Physics. 2005;7 (2) :356 - 365.Abstract
Scanning electrochem. microscopy (SECM) can be used in the feedback mode as a 'contactless' method for probing the cond. of ultra-thin films. With this new technique a sample is bathed with one form of a reversible redox (Red/Ox) couple, e.g. Red, and an ultramicroelectrode (UME), located close to the film surface is used to locally convert Red to Ox by diffusion-limited oxidn. Ox diffuses from the UME to the film where it may undergo conversion back to Red. This process is driven by a potential gradient, which depends on the surface cond. A model is developed for the SECM feedback process from which the cond. of the film can be extd. Two routes arising from the model are considered: an approx. method which allows an order of magnitude est. of the film cond. and a more involved approach, which can be used with greater accuracy. The merits of the two approaches are assessed by analyzing exptl. data for the effect of surface pressure on the cond. of a polyaniline monolayer at a water/air interface. [on SciFinder(R)]
2004
Burshtain D, Wu J, Melman A, Mandler D, Scherson DA. Binding of Cd2+ to self-assembled bilayers bearing pyridine terminal groups: attenuated total reflection Fourier transform infrared spectroscopic studies. LangmuirLangmuir : the ACS journal of surfaces and colloids. 2004;20 (11) :4498 - 502.Abstract
Various aspects of the adsorption of Cd2+ on self-assembled monolayers (SAMs) of 4-heptadecylpyridine (HDpy) and 7-tridecyl-4-methyl-1,10-bipyridine (TMbipy) supported on an octadecylsilane (ODS)-modified Ge prism have been examined both ex situ (dry) and in situ (in the presence of aqueous solutions) using attenuated total reflection Fourier transform infrared spectroscopy. In direct analogy with the behavior found for a variety of genuine pyridine (py) and bipyridine (bipy) metal ion complexes, Cd2+ binding to both SAMs led to shifts in the skeletal vibrational modes of the corresponding uncoordinated ligands in the region 1650-1400 cm(-1), toward higher energies. Analysis of spectra acquired ex situ for HDpy/ODS/Ge and TMbipy/ODS/Ge before and after exposure to 0.1 mM [Cd2+] yielded values for the fraction of uncoordinated py, theta(py(un)), and uncoordinated bipy, theta(bipy(un)), of about 0.5 and about 0.1, respectively. The features attributed to the py(un) groups for spectra collected for HDpy/ODS/Ge in situ and ex situ were found to be virtually identical, making it possible to isolate by graphical means the most prominent band of py(co) centered at about 1615 cm(-l) for HDpy/ODS/Ge collected in situ. The resulting bands for pure py(co) and pyun in situ were then used to deconvolute spectra recorded in situ for HPpy/ODS/Ge in contact with Cd2+containing solutions in the range 10 nM < [Cd2+] < 0.1 mM, from which information regarding the adsorption isotherm was obtained.[on SciFinder (R)]

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