Publications

2005
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)]
Burshtain D, Mandler D. Determination of the heterogeneous association constants of metal ions to omega-mercaptoalkanoic acids by using double-layer capacity measurements. ChemphyschemChemphyschem : a European journal of chemical physics and physical chemistry. 2004;5 (10) :1532 - 9.Abstract
The binding of metal ions to ligands in homogeneous solutions and that to the same ligands anchored to metallic surfaces through self-assembled monolayers (SAMs) are expected to differ primarily due to the difference in the degree of freedom of the ligands and the surface potential. We studied the heterogeneous binding of CdII ions to omega-mercaptoalkanoic-acid SAMs on Au. This was accomplished by adding metal ions at a constant pH and following the changes in the double-layer capacity. A mathematical treatment, which is based on calculating the electrochemical-potential differences at the double layer-solution interface, has been developed. Our approach follows that proposed by White et al. and Kakiuchi, who used the acid-base equilibrium at the monolayer-electrolyte interface as a means of calculating the pK of ionizable SAMs. Experimentally, SAMs of omega-mercaptoalkanoic acids, HS(CH2)nCO2H, with different chain lengths (i.e., n=2, 5, and 10) in 0.1 M sodium perchlorate were assembled on Au surfaces and studied. The capacity was measured first in the absence of CdII at different pH values, and then at a constant pH while increasing the concentration of CdII in the solution. We found that the interfacial capacity decreased as the concentration (of either protons or CdII) increased. The results matched the model fairly well, which allowed the extraction of the thermodynamic equilibrium constant that is established at the monolayer-electrolyte interface. The suggested mathematical treatment of this model system is simple and yet very useful for estimating the heterogeneous association constants of metal ions by SAMs.[on SciFinder (R)]
Shacham R, Mandler D, Avnir D. Electrochemically induced sol-gel deposition of zirconia thin films. ChemistryChemistry (Weinheim an der Bergstrasse, Germany). 2004;10 (8) :1936 - 43.Abstract
A novel electrochemical method for deposition of ZrO(2) thin films is described. The films, 50-600 nm thick, were obtained by applying moderate positive or negative potentials (+2.5 V to -1.5 V versus SHE) on conducting surfaces immersed in a 2-propanol solution of zirconium tetra-n-propoxide [Zr(OPr)(4)] in the presence of minute quantities of water (water/monomer molar ratios in the range of 10(-5) to 10(-1)), which was the limiting reagent. Oxidative electrochemical formation of solvated H(+) and reductive formation of OH(-) catalyze the hydrolysis and condensation of the metal alkoxide precursor. The magnitude of the applied potential and its duration provide a convenient way of controlling the film thickness. The films consist of an amorphous phase, as revealed by XRD measurements. The effects of different parameters, such as the applied potential and its duration, the amount of added water and the current-time characteristics, were studied. A mechanism for the electrodeposition of the zirconia films which is in accordance with our findings is proposed.[on SciFinder (R)]
Avissar YY, Sagiv AE, Mandler D, Almog J. Identification of firearms holders by the [Fe(PDT)3](+2) complex. Quantitative determination of iron transfer to the hand and its dependence on palmar moisture levels. J Forensic SciJournal of forensic sciences. 2004;49 (6) :1215 - 9.Abstract
Quantitative data are reported for the first time on the amounts of iron, which are transferred to the hand upon holding a firearm. Iron levels between 21-315 ng/cm2 were found on volunteers' palms after a single holding of a handgun. Determination of the iron traces was accomplished spectrophotometrically using 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) as a complexing agent. The transfer of iron from firearms to the palm was found to be, by and large a chemical (dissolution) rather than mechanical dislodgement. The prime factor that determines the amount of iron transferred from the firearm to the hand is the moisture level on the palm. These findings are likely to be of importance in courts of law, as well as in the war against terrorism and serious crime.[on SciFinder (R)]
Zhang J, Mandler D, Unwin PR. Interfacial polymerisation of anilinium at Langmuir monolayers. Chem Commun (Camb)Chemical communications (Cambridge, England). 2004;(4) :450 - 1.Abstract
Anilinium is strongly adsorbed at monolayers of the phospholipid L-alpha-dimyristoylphosphatidic acid (DMPA) and hexadecanesulfonic acid (HDSA) at the air-water interface, and undergoes chemical polymerisation under conditions where bulk polymerisation does not occur.[on SciFinder (R)]
Shustak G, Domb AJ, Mandler D. Preparation and characterization of n-alkanoic acid self-assembled monolayers adsorbed on 316L stainless steel. LangmuirLangmuir : the ACS journal of surfaces and colloids. 2004;20 (18) :7499 - 506.Abstract
The electrochemical formation and characterization of decanoic, myristic, palmitic, and stearic acid self-assembled monolayers on a native oxide surface of 316L stainless steel have been studied. This work describes a new approach to surface modification of stainless steel in which the self-assembly of n-alkanoic acids is facilitated by applying a potential to the stainless steel in an organic electrolyte solution. While decanoic acid forms a disorganized monolayer as a result of sweeping the potential in an acetonitrile solution containing 0.1 mM of the respective acid, longer acids, that is, myristic and palmitic acids, form highly ordered closed-packed monolayers. This electrochemical approach results in highly reproducible monolayers that are deposited within a shorter time than the traditional assembly process. The monolayers were characterized by cyclic voltammetry, double-layer capacity (ac voltammetry), contact angle measurements, X-ray photoelectron spectroscopy, and external reflection-absorption Fourier transform infrared spectroscopy. The utilization and implications of this modification technique are discussed.[on SciFinder (R)]
Sheffer M, Groysman A, Starosvetsky D, Savchenko N, Mandler D. Anion embedded sol-gel films on Al for corrosion protection. Corros. Sci.Corrosion Science. 2004;46 (12) :2975 - 2985.Abstract
We report here on the successful incorporation of org. anions into a sol-gel film on Al as a means of enhancing the protection against corrosion. Following our previous study where we showed that hydrophobic sol-gel films provided pronounced corrosion inhibition, we studied the corrosion inhibition that phenylphosphonic acid (PPA) has when embedded inside a thin sol-gel coating on Al. The anion of this org. acid tends to stay inside a phenyltrimethoxysilane (PTMOS) based sol-gel film due to π-interactions. Our findings, which are derived primarily from potentiodynamic polarization measurements, electrochem. noise, SEM measurements and Auger electron spectroscopy (AES), clearly show that the org. phosphonate adds to the protection efficiency of the sol-gel film. [on SciFinder(R)]
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. 2004;20 (11) :4498 - 4502.Abstract
Various aspects of the adsorption of Cd2+ on self-assembled monolayers (SAMs) of 4-heptadecylpyridine (HDpy) and 4'-tridecyl-4-Me-2,2'-bipyridine (TMbipy) supported on an octadecylsilane (ODS)-modified Ge prism were examd. both ex situ (dry) and in situ (in the presence of aq. solns.) using attenuated total reflection FTIR 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. Anal. 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, θ(pyun), and uncoordinated bipy, θ(bipyun), of ∼0.5 and ∼0.1, resp. The features attributed to the pyun groups for spectra collected for HDpy/ODS/Ge in situ and ex situ are virtually identical, making it possible to isolate by graphical means the most prominent band of pyco centered at ∼1615 cm-1 for HDpy/ODS/Ge collected in situ. The resulting bands for pure pyco and pyun in situ were then used to deconvolute spectra recorded in situ for HPpy/ODS/Ge in contact with Cd2+-contg. solns. in the range 10 nM < [Cd2+] < 0.1 mM, from which information regarding the adsorption isotherm was obtained. [on SciFinder(R)]
Burshtain D, Mandler D. Determination of the heterogeneous association constants of metal ions to ω-mercaptoalkanoic acids by using double-layer capacity measurements. ChemPhysChemChemPhysChem. 2004;5 (10) :1532 - 1539.Abstract
The binding of metal ions to ligands in homogeneous solns. and that to the same ligands anchored to metallic surfaces through self-assembled monolayers (SAMs) are expected to differ primarily due to the difference in the degree of freedom of the ligands and the surface potential. We studied the heterogeneous binding of CdII ions to ω-mercaptoalkanoic-acid SAMs on Au. This was accomplished by adding metal ions at a const. pH and following the changes in the double-layer capacity. A math. treatment, which is based on calcg. the electrochem.-potential differences at the double layer-soln. interface, has been developed. Our approach follows that proposed by Smith, C.P. and others (1992), White, H.S et al. (1998), Kakiuchi, T. and coworkers (200) who used the acid-base equil. at the monolayer-electrolyte interface as a means of calcg. the pK of ionizable SAMs. Exptl., SAMs of ω-mercaptoalkanoic acids, HS(CH2)nCO2H, with different chain lengths (i.e., n = 2, 5, and 10) in 0.1 M sodium perchlorate were assembled on Au surfaces and studied. The capacity was measured first in the absence of CdII at different pH values, and then at a const. pH while increasing the concn. of CdII in the soln. We found that the interfacial capacity decreased as the concn. (of either protons or CdII) increased. The results matched the model fairly well, which allowed the extn. of the thermodn. equil. const. that is established at the monolayer-electrolyte interface. The suggested math. treatment of this model system is system is simple and yet very useful for estg. the heterogeneous assocn. consts. of metal ions by SAMs. [on SciFinder(R)]
Shacham R, Mandler D, Avnir D. Electrochemically induced sol-gel deposition of zirconia thin films. Chem. - Eur. J.Chemistry - A European Journal. 2004;10 (8) :1936 - 1943.Abstract
A novel electrochem. method for deposition of ZrO2 thin films is described. The films, 50-600 nm thick, were obtained by applying moderate pos. or neg. potentials (+ 2.5 V to -1.5 V vs. SHE) on conducting surfaces immersed in a 2-propanol soln. of zirconium tetra-n-propoxide [Zr(OPr)4] in the presence of minute quantities of water (water/monomer molar ratios in the range of 10-5 to 10-1), which was the limiting reagent. Oxidative electrochem. formation of solvated H+ and reductive formation of OH- catalyze the hydrolysis and condensation of the metal alkoxide precursor. The magnitude of the applied potential and its duration provide a convenient way of controlling the film thickness. The films consist of an amorphous phase, as revealed by XRD measurements. The effects of different parameters, such as the applied potential and its duration, the amt. of added water and the current-time characteristics, were studied. A mechanism for the electrodeposition of the zirconia films which is in accordance with our findings is proposed. [on SciFinder(R)]
Zhang J, Mandler D, Unwin PR. Interfacial polymerization of anilinium at Langmuir monolayers. Chem. Commun. (Cambridge, U. K.)Chemical Communications (Cambridge, United Kingdom). 2004;(4) :450 - 451.Abstract
Anilinium is strongly adsorbed at monolayers of the phospholipid L-α-dimyristoylphosphatidic acid (DMPA) and hexadecanesulfonic acid (HDSA) at the air-water interface, and undergoes chem. polymn. under conditions where bulk polymn. does not occur. [on SciFinder(R)]
de Abril O, Mandler D, Unwin PR. Local cobalt electrodeposition using the scanning electrochemical microscope. Electrochem. Solid-State Lett.Electrochemical and Solid-State Letters. 2004;7 (6) :C71-C74.Abstract
A scanning electrochem. microscope (SECM) has been applied to the local deposition of Co microstructures on Au. The method employs a Co microelectrode to generate a potential-controlled flux of the resp. ions in an aq. soln. The microelectrode was positioned at a precisely defined distance above a gold surface using the steady-state current for oxygen redn. The optimum conditions for Co dissoln. and deposition were identified from voltammetry and chronoamperometry. Applying these conditions in the SECM configuration facilitated the successful deposition of Co structures. The dissoln. and uptake of Co on the Au surface was investigated using SECM double potential step chronoamperometry. [on SciFinder(R)]

Pages