Publications

2004
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)]
Marx S, Zaltsman A, Turyan I, Mandler D. Parathion Sensor Based on Molecularly Imprinted Sol-Gel Films. Anal. Chem.Analytical Chemistry. 2004;76 (1) :120 - 126.Abstract
Thin films of a molecularly imprinted sol-gel polymer with specific binding sites for parathion were developed. The films were cast on glass substrates and on glassy carbon electrodes and were used to detect parathion in aq. solns. Gas-phase binding measurements were performed on coated quartz crystal microbalance resonators. The binding of parathion to the imprinted films in the liq. phase was investigated by steady-state expts. with anal. by GC-FPD and cyclic voltammetry. The imprinted films showed high selectivity toward parathion in comparison to similar organophosphates. The binding was very sensitive to the type of functional monomer used for imprinting, and that rational design of the matrix components is an essential step in mol. imprinting. Specific binding in the gas phase proved to be less sensitive to the imprinting effect and exhibits relatively high nonspecific binding. The difference between mol. recognition in the gas- and liq.-phase imprinted polymer is discussed. [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. 2004;20 (18) :7499 - 7506.Abstract
The electrochem. formation and characterization of decanoic, myristic, palmitic, and stearic acid self-assembled monolayers on a native oxide surface of 316L stainless steel were 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 org. electrolyte soln. While decanoic acid forms a disorganized monolayer of sweeping the potential in an MeCN soln. contg. 0.1 mM of the resp. acid, longer acids, i.e., myristic and palmitic acids, form highly ordered closed-packed monolayers. This electrochem. 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 (a.c. voltammetry), contact angle measurements, XPS, and external reflection-absorption FTIR spectroscopy. The use and implications of this modification technique are discussed. [on SciFinder(R)]
Weiss Z, Mandler D, Shustak G, Domb AJ. Pyrrole derivatives for electrochemical coating of metallic medical devices. J. Polym. Sci., Part A: Polym. Chem.Journal of Polymer Science, Part A: Polymer Chemistry. 2004;42 (7) :1658 - 1667.Abstract
Electropolymn. of medical devices such as cardiovascular stents may possess advantages including a simple and reproducible process with the ability to control the thickness, adherence, and compn. of the coating by the duration and intensity of the applied current, the monomer compn. and concn., the solvent, and the reaction conditions. The properties of the polymer can also be controlled by copolymn. of different monomers, grafting substituents to a functionalized polymer, and by entrapping biomols. This article describes the synthesis of a range of pyrrole-based monomers and their electrocoating onto stainless steel surfaces. N-substituted pyrrole monomers with C1-C18 alkyl chains and polyethylene glycol chains were synthesized in good yields and purity. Electropolymn. of these monomers provided uniform coatings with different hydrophobicities. Studies now focus on the incorporation of drugs in the coated device for release from the surface. [on SciFinder(R)]
Shacham R, Avnir D, Mandler D. Electrodeposition of dye-doped titania thin films. J. Sol-Gel Sci. Technol.Journal of Sol-Gel Science and Technology. 2004;31 (1/2/3) :329 - 334.Abstract
We extend our novel low-voltage electrochem. method for oxide thin film formation from sol-gel monomers to include entrapment of org. mols. within the films. We also describe an extension of the method to titania thin films, which are obtained from titanium tetra-n-propoxide in alc. solns. by applying potentials in the range of +2.0 to -1.4 V to indium tin oxide electrodes. The film thickness (ranging between 20-1000 nm) is controllable by changing either the potential or the duration of its application. We demonstrate that this electrochem. method provides a convenient way for entrapment of org. dopants within the film. Four dyes were used for that purpose: Basic Blue 41, methylene-blue, tris(2,2'-bipyridine)iron(II) and tris(2,2'-bipyridine)ruthenium(II). [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 Sci.Journal of Forensic Sciences. 2004;49 (6) :1215 - 1219.Abstract
Quant. data are reported for the first time on the amts. 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. Detn. 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 chem. (dissoln.) rather than mech. dislodgement. The prime factor that dets. the amt. 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)]
2003
Zhang J, Barker AL, Mandler D, Unwin PR. Effect of surface pressure on the insulator to metal transition of a langmuir polyaniline monolayer. J Am Chem SocJournal of the American Chemical Society. 2003;125 (31) :9312 - 3.Abstract
A remarkable change in the conductivity of a polyaniline (PAN) Langmuir monolayer in the conducting state, as a function of surface pressure, has been observed using scanning electrochemical microscopy (SECM). The film conductivity, as expressed by the SECM current response of a redox mediator, was measured in-situ in a Langmuir film balance. The conductivity of the film increases significantly with surface pressure, above a threshold value of ca. 20 mN m-1.[on SciFinder (R)]
Shustak G, Marx S, Turyan I, Mandler D. Application of sol-gel technology for electroanalytical sensing. ElectroanalysisElectroanalysis. 2003;15 (5-6) :398 - 408.Abstract
The applicability of thin sol-gel films as selective interfaces in electrochem. sensors has been examd. This requires not only to create a selective interface but also to enable facile diffusion of the analytes across the films. Creation of selectivity has been aimed by molecularly imprinting an electroactive species in the course of sol-gel formation. We have focused primarily on imprinting an iron(II) complex, i.e., tris(2,2'-bipyridine)iron(II) (Fe(bpy)2+3), as a means of selectively detg. iron(II) in aq. soln. Hence, the effect of different parameters, such as the compn. of the sol-gel film and the hydrolysis and drying time, on the diffusion of Fe(bpy)2+3, has been studied. We find that diffusion can be remarkably enhanced upon adding polyethylene glycol or a surfactant, such as decanoic acid. Nevertheless, so far we have not been able to develop thin films, which exhibit selectivity towards this inorg. species. The difficulties in designing such selective interfaces for heavy metals as opposed to org. species is demonstrated by successfully applying the same approach for designing a selective interface for diethyl-p-nitrophenyl phosphate (paraoxon). [on SciFinder(R)]
Zhang J, Barker AL, Mandler D, Unwin PR. Effect of Surface Pressure on the Insulator to Metal Transition of a Langmuir Polyaniline Monolayer. J. Am. Chem. Soc.Journal of the American Chemical Society. 2003;125 (31) :9312 - 9313.Abstract
A remarkable change in the cond. of a polyaniline (PANI) Langmuir monolayer in the conducting state, as a function of surface pressure, was obsd. using scanning electrochem. microscopy (SECM). The film cond., as expressed by the SECM current response of a redox mediator, was measured in-situ in a Langmuir film balance. The cond. of the film increases significantly with surface pressure, above a threshold value of ca. 20 mN m-1. [on SciFinder(R)]
Mandler D, Gal-Oz R, Burshtain D, Turyan I. Electrochemical metal speciation using self-assembled monolayers. J. Phys. IVJournal de Physique IV: Proceedings. 2003;107 (XIIth International Conference on Heavy Metals in the Environment, 2003, Volume 2) :801 - 804.Abstract
The application of self-assembled monolayers (SAMs) as a means of achieving speciation in heavy metal electrochem. detn. is demonstrated. SAMs are monomol. org. layers that can be chem. attached onto different electrode materials and used for the selective extn. of heavy metals. The selectivity is achieved by assembling monolayers that have pendant ligands, which interact selectively with the analytes in the soln. For example, the formation of a monolayer comprising a pyridine group was used to selectively ext. Cr(VI) from aq. solns., whereas the selective detn. of Fe(II) was accomplished using a covalently bound terpyridine monolayer. Yet, detg. the heterogeneous binding consts. of the metallic species by the SAMs is of significant importance and allows studying quant. the interactions between the monolayer and the metal ions. The authors have developed a few methods for detg. the binding consts. of heavy metal ions by SAMs of which two of them are briefly discussed here. [on SciFinder(R)]

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