Publications by Year: 2013

2013
Vadgama P, Mandler D. Characterization of thin films and membranes. Anal Bioanal ChemAnalytical and bioanalytical chemistry. 2013;405 (5) :1433 - 4.
Raveh M, Liu L, Mandler D. Electrochemical co-deposition of conductive polymer-silica hybrid thin films. Phys Chem Chem PhysPhysical chemistry chemical physics : PCCP. 2013;15 (26) :10876 - 84.Abstract
Conductive polymers, such as polypyrrole (ppy), have been the subject of numerous studies due to their promising applications in organic solar cells, flexible electronics, electrochromic devices, super capacitors, etc. Yet, their application is still limited as a result of poor processability. Silica has been reported to improve the mechanical strength and adhesion of conductive polymer films. In this work, we propose a controllable electrochemical approach for preparing ppy-silica hybrid thin films from a solution containing both pyrrole and silane monomers. It is known that pyrrole can be electropolymerised using anodic potentials, while silica can be electrodeposited under cathodic potentials. Thus, we studied the formation of ppy-silica hybrid thin films on a stainless steel surface by applying alternating potentials, i.e. cathodic followed by anodic pulses (denoted C + A) or anodic followed by cathodic pulses (denoted A + C). We show that by controlling the deposition potential and time for the cathodic and anodic pulses, the film thickness and composition can be manipulated well as analysed using profilometry and EDX. The element depth profile of the films was characterized using secondary ion mass spectroscopy (SIMS). In essence, for the C + A process, pyrrole diffuses through the cathodically electrodeposited wet silica gel layer and undergoes anodic polymerisation on the substrate, while for the A + C process, silane can be electrodeposited both on top of the anodically electrodeposited conductive ppy films as well as on the stainless steel through the pinholes in the ppy film. This offers a simple approach for tuning the structure of conductive polymer-sol-gel composite films.[on SciFinder (R)]
Fedorov RG, Mandler D. Local deposition of anisotropic nanoparticles using scanning electrochemical microscopy (SECM). Phys Chem Chem PhysPhysical chemistry chemical physics : PCCP. 2013;15 (8) :2725 - 32.Abstract
We demonstrate localized electrodeposition of anisotropic metal nanoobjects, namely Au nanorods (GNR), on indium tin oxide (ITO) using scanning electrochemical microscopy (SECM). A gold microelectrode was the source of the gold ions whereby double pulse chronoamperometry was employed to generate initially Au seeds which were further grown under controlled conditions. The distance between the microelectrode and the ITO surface as well as the different experimental parameters (electrodeposition regime, solution composition and temperature) were optimized to produce faceted gold seeds with the required characteristics (size and distribution). Colloidal chemical synthesis was successfully exploited for better understanding the role of the surfactant and different additives in breaking the crystallographic symmetry and anisotropic growth of GNR. Experiments performed in a conventional three-electrode cell revealed the most appropriate electrochemical conditions allowing high yield synthesis of nanorods with well-defined shape as well as nanocubes and bipyramids.[on SciFinder (R)]
Shenawi S, Jaber N, Almog J, Mandler D. A novel approach to fingerprint visualization on paper using nanotechnology: reversing the appearance by tailoring the gold nanoparticles' capping ligands. Chem Commun (Camb)Chemical communications (Cambridge, England). 2013;49 (35) :3688 - 90.Abstract
Gold nanoparticles, AuNPs, capped with mercaptocarboxylic acids followed by silver precipitation develop latent fingermarks on paper as high quality "negative" impressions. This effect stems from hydrogen bonding between the carboxylic group and the paper cellulose and may improve the yield of latent fingermarks since the results are less dependent on sweat composition.[on SciFinder (R)]
Gdor E, Katz E, Mandler D. Biomolecular AND logic gate based on immobilized enzymes with precise spatial separation controlled by scanning electrochemical microscopy. J Phys Chem BThe journal of physical chemistry. B. 2013;117 (50) :16058 - 65.Abstract
A surface-localized enzymatic AND gate based on scanning electrochemical microscopy was designed and studied. The gate is composed of an insulating glass surface modified with the enzyme glucose oxidase (GOx) and another surface opposing it made of a microelectrode. The latter was modified with a second enzyme, invertase (INV). The distance separating the modified microelectrode and surface controlled the output of the AND gate produced upon the biocatalytic reaction of the confined enzymes. Specifically, as the GOx-modified glass substrate entered the diffusion layer of the microelectrode, it catalyzed the regeneration of an electron-transfer mediator, ferroceniummethanol, generated electrochemically at the tip by oxidizing glucose, also generated at the tip, by catalytic cleaving of sucrose by INV. To enhance the activity of the GOx, mutarotase was added to convert α- to β-glucose to be further consumed by GOx. Hence, an increase of the current at the microelectrode was obtained by approaching the glass surface only in the presence of all the components. This is the first micrometer-sized biomolecular logic gate, of which we are aware, that is surface-confined and shows the promise held by the localization of biomolecular information-processing species.[on SciFinder (R)]
Noyhouzer T, Valdinger I, Mandler D. Enhanced potentiometry by metallic nanoparticles. Anal ChemAnalytical chemistry. 2013;85 (17) :8347 - 53.Abstract
Measuring the oxidation-reduction potential (Eh) requires an interface that is not selective toward specific species but exchanges electrons with all redox couples in the solution. Sluggish electron transfer (ET) kinetics with the species will not reflect the "true" Eh of the solution. Here, we present a novel approach by which adsorbed metal nanoparticles (NPs) are used for enhancing ET exchange rates between redox species and electrode surface and therefore affect significantly the measurement of the open circuit potential (OCP) and cyclic voltammetry (CV). The OCP and CV of various organic and inorganic species such as l-dopa, dopac, iron(II), and iodide are measured by bare stainless steel and by stainless steel modified by either Pt or Au NPs. We study the effect of the surface coverage of the stainless steel surface by NPs on the electrochemical response. Moreover, the stainless steel electrode was modified simultaneously by Au and Pt nanoparticles. This improved concurrently the stainless steel response (CV and potentiometry) toward two different species; l-dopa, which shows fast electron transfer on Pt, and catechol, which exhibits fast electron transfer on Au. We believe that this approach could be a first step toward developing a superior electrode for measuring the "true" Eh of complex aquatic systems.[on SciFinder (R)]
Vadgama P, Mandler D. Characterization of thin films and membranes. Anal. Bioanal. Chem.Analytical and Bioanalytical Chemistry. 2013;405 (5) :1433 - 1434.
Noyhouzer T, Mandler D. A New Electrochemical Flow Cell for the Remote Sensing of Heavy Metals. ElectroanalysisElectroanalysis. 2013;25 (1) :109 - 115.Abstract
Remote sensing is a fast developing field. The ability to detect various elements in secluded or inaccessible areas holds great opportunities. We present a new electrochem. flow cell which was developed as part of an autonomous flow system for measuring heavy metals in aquatic environments. The system was designed for remote sensing. Our system can utilize different com. available electrodes and apply a range of electrochem. methods. The system was studied through both electrochem. expts. and simulation. The potential of the platform was demonstrated by analyzing seawater spiked with Cd. Good agreement was found between our results and those obtained by ICP-MS anal. [on SciFinder(R)]
Mandler D. Allen J. Bard, Gyoergy Inzelt, Fritz Scholz (Eds.): Electrochemical dictionary, 2nd ed. Anal. Bioanal. Chem.Analytical and Bioanalytical Chemistry. 2013;405 (21) :6607 - 6608.
Liu L, Mandler D. Electro-assist deposition of binary sol-gel films with graded structure. Electrochim. ActaElectrochimica Acta. 2013;102 :212 - 218.Abstract
Graded SiO2-TiO2 binary composite films were prepd. by a unique electro-assist deposition approach from a mixt. of sol-gel precursors contg. tetramethoxysilane (TMOS) and Ti tetraisopropoxide (TTIP). A neg. potential applied to either stainless steel or ITO substrates causes the redn. of the solvent, thus increasing the concn. of hydroxyl ions, which enhances the precursor condensation and film deposition. The Ti:Si ratio in the films depends on the deposition potential, time and compn. of the precursor soln. This ratio decreases as the films grow thicker due to the more facile kinetics of SiO2 deposition. Nevertheless, the Ti:Si ratio in the films is always lower than in the corresponding precursor soln. As the Ti:Si ratio in the deposition soln. increases, the thickness of the electro-assist deposited films at the same conditions gradually decreases. SIMS and cross-section EDX anal. show that the Ti:Si ratio in the films increases from the surface to the substrate, suggesting electro-assist deposition as a potential method for 1-step prepn. of graded sol-gel films. [on SciFinder(R)]
Raveh M, Liu L, Mandler D. Electrochemical co-deposition of conductive polymer-silica hybrid thin films. Phys. Chem. Chem. Phys.Physical Chemistry Chemical Physics. 2013;15 (26) :10876 - 10884.Abstract
Conductive polymers, such as polypyrrole (ppy), were the subject of numerous studies due to their promising applications in org. solar cells, flexible electronics, electrochromic devices, super capacitors, etc. Yet, their application is still limited as a result of poor processability. SiO2 is reported to improve the mech. strength and adhesion of conductive polymer films. The authors propose a controllable electrochem. approach for prepg. ppy-SiO2 hybrid thin films from a soln. contg. both pyrrole and silane monomers. Pyrrole can be electropolymd. using anodic potentials, while SiO2 can be electrodeposited under cathodic potentials. Thus, the authors studied the formation of ppy-SiO2 hybrid thin films on a stainless steel surface by applying alternating potentials, i.e. cathodic followed by anodic pulses (denoted C + A) or anodic followed by cathodic pulses (denoted A + C). By controlling the deposition potential and time for the cathodic and anodic pulses, the film thickness and compn. can be manipulated well as analyzed using profilometry and EDX. The element depth profile of the films was characterized using secondary ion mass spectroscopy (SIMS). In essence, for the C + A process, pyrrole diffuses through the cathodically electrodeposited wet silica gel layer and undergoes anodic polymn. on the substrate, while for the A + C process, silane can be electrodeposited both on top of the anodically electrodeposited conductive ppy films as well as on the stainless steel through the pinholes in the ppy film. This offers a simple approach for tuning the structure of conductive polymer-sol-gel composite films. [on SciFinder(R)]
Wang N, Huang Y, Magdassi S, Mandler D, Hai L, Yi L. Formation of VO2 zero-dimensional/nanoporous layers with large supercooling effects and enhanced thermochromic properties. RSC Adv.RSC Advances. 2013;3 (19) :7124 - 7128.Abstract
Vanadium dioxide is an intriguing candidate for use in intelligent devices such as sensors, magnetic refrigeration and particularly as solar modulating smart window materials. A facile sol-gel route is developed to produce pure VO2 with different nanostructures in a CO2 atmosphere. It was found that the nanoporous structures demonstrated a 16% increase in the luminous transmittance (Tlum) (from 20% to 36%) compared with the vacuum results, while large supercooling effects of up to 30 °C have been obsd. in zero-dimensional structures. [on SciFinder(R)]
Fedorov RG, Mandler D. Local deposition of anisotropic nanoparticles using scanning electrochemical microscopy (SECM). Phys. Chem. Chem. Phys.Physical Chemistry Chemical Physics. 2013;15 (8) :2725 - 2732.Abstract
We demonstrate localized electrodeposition of anisotropic metal nanoobjects, namely Au nanorods (GNR), on indium tin oxide (ITO) using scanning electrochem. microscopy (SECM). A gold microelectrode was the source of the gold ions whereby double pulse chronoamperometry was employed to generate initially Au seeds which were further grown under controlled conditions. The distance between the microelectrode and the ITO surface as well as the different exptl. parameters (electrodeposition regime, soln. compn. and temp.) were optimized to produce faceted gold seeds with the required characteristics (size and distribution). Colloidal chem. synthesis was successfully exploited for better understanding the role of the surfactant and different additives in breaking the crystallog. symmetry and anisotropic growth of GNR. Expts. performed in a conventional three-electrode cell revealed the most appropriate electrochem. conditions allowing high yield synthesis of nanorods with well-defined shape as well as nanocubes and bipyramids. [on SciFinder(R)]
Shenawi S, Jaber N, Almog J, Mandler D. A novel approach to fingerprint visualization on paper using nanotechnology: reversing the appearance by tailoring the gold nanoparticles' capping ligands. Chem. Commun. (Cambridge, U. K.)Chemical Communications (Cambridge, United Kingdom). 2013;49 (35) :3688 - 3690.Abstract
Gold nanoparticles, AuNPs, capped with mercaptocarboxylic acids followed by silver pptn. develop latent fingermarks on paper as high quality "neg." impressions. This effect stems from hydrogen bonding between the carboxylic group and the paper cellulose and may improve the yield of latent fingermarks since the results are less dependent on sweat compn. [on SciFinder(R)]
Lu Y, Liu L, Foo WL, Magdassi S, Mandler D, Lee PS. Self-assembled polymer layers of linear polyethylenimine for enhancing electrochromic cycling stability. J. Mater. Chem. CJournal of Materials Chemistry C: Materials for Optical and Electronic Devices. 2013;1 (23) :3651 - 3654.Abstract
A self-assembled polymer of linear polyethylenimine (LPEI) on indium tin oxide (ITO) is found to stabilize the titanium-doped vanadium oxide film. After modification by LPEI, the oxide film shows good cycling stability, and sustains over 1500 cycles in a three-electrode system, a remarkable improvement compared to that without LPEI modification. [on SciFinder(R)]
Wang N, Magdassi S, Mandler D, Long Y. Simple sol-gel process and one-step annealing of vanadium dioxide thin films: Synthesis and thermochromic properties. Thin Solid FilmsThin Solid Films. 2013;534 :594 - 598.Abstract
A simple and cost effective sol-gel process for producing vanadium dioxide thin films was developed via thermolysis of V2O5·nH2O (n ≈ 2) VV precursors prepd. by dissolving vanadium powder or V2O5 powder in 30% hydrogen peroxide solns. After spin-coating on fused silica substrates and annealing at 750° in vacuum, without any intermediate gas reducing step, the major phase VO2(M, monoclinic phase) was found in both of the films based on V-H2O2 and V2O5-H2O2 precursor, exhibiting large transmittance changes (> 40%) in the IR region (> 2000 nm) and small hysteresis loop width (< 5°) which were comparable to reported epitaxial VO2 films. The two films have similar metal-to-insulator transition temp. τC = 62.5°, lower than the classical value of 68° for VO2 thin films. In addn., the method enables simple doping, as found for 0.56 at.% W-doped VO2 films. This intrinsically simple soln. process followed by one-step annealing makes it potentially useful in smart window applications. [on SciFinder(R)]
Mandler D. Special issue dedicated to Anna Brainina. J. Solid State Electrochem.Journal of Solid State Electrochemistry. 2013;17 (6) :1491 - 1492.
Shahar T, Tal N, Mandler D. The synthesis and characterization of thiol-based aryl diazonium modified glassy carbon electrode for the voltammetric determination of low levels of Hg(II). J. Solid State Electrochem.Journal of Solid State Electrochemistry. 2013;17 (6) :1543 - 1552.Abstract
Electrochem. detn. of Hg(II) in aquatic solns. on bare and modified glassy carbon electrode (GCE) is reported. Optimizing the parameters used for a bare GCE, such as the electrolyte soln., the potential and time of deposition, resulted in linear response over a large range of Hg(II) concns. (4-160 ppb) using linear sweep anodic stripping voltammetry. Modification of the electrode with 4,4'-disulfanediyldibenzenediazonium (DSBD) yielded a lowest detection limit of 1 ppb. Two procedures for DSBD synthesis are described for the 1st time, and the product was characterized by microanal., FTIR and 1H-NMR. The electrochem. attachment of DSBD to the electrode was studied and compared with the electrochem. behavior of DSBD analogous mols., i.e. 4-aminophenyl disulfide, p-aminothiophenol and Ph disulfide. [on SciFinder(R)]
Gdor E, Katz E, Mandler D. Biomolecular AND Logic Gate Based on Immobilized Enzymes with Precise Spatial Separation Controlled by Scanning Electrochemical Microscopy. J. Phys. Chem. BJournal of Physical Chemistry B. 2013;117 (50) :16058 - 16065.Abstract
A surface-localized enzymic AND gate based on scanning electrochem. microscopy was designed and studied. The gate is composed of an insulating glass surface modified with the enzyme glucose oxidase (GOx) and another surface opposing it made of a microelectrode. The latter was modified with a second enzyme, invertase (INV). The distance sepg. the modified microelectrode and surface controlled the output of the AND gate produced upon the biocatalytic reaction of the confined enzymes. Specifically, as the GOx-modified glass substrate entered the diffusion layer of the microelectrode, it catalyzed the regeneration of an electron-transfer mediator, ferroceniummethanol, generated electrochem. at the tip by oxidizing glucose, also generated at the tip, by catalytic cleaving of sucrose by INV. To enhance the activity of the GOx, mutarotase was added to convert α- to β-glucose to be further consumed by GOx. Hence, an increase of the current at the microelectrode was obtained by approaching the glass surface only in the presence of all the components. This is the first micrometer-sized biomol. logic gate, of which the authors are aware, that is surface-confined and shows the promise held by the localization of biomol. information-processing species. [on SciFinder(R)]
Noyhouzer T, Valdinger I, Mandler D. Enhanced Potentiometry by Metallic Nanoparticles. Anal. Chem. (Washington, DC, U. S.)Analytical Chemistry (Washington, DC, United States). 2013;85 (17) :8347 - 8353.Abstract
Measuring the oxidn.-redn. potential (Eh) requires an interface that is not selective toward specific species but exchanges electrons with all redox couples in the soln. Sluggish electron transfer (ET) kinetics with the species will not reflect the true Eh of the soln. Here, the authors present a novel approach by which adsorbed metal nanoparticles (NPs) were used for enhancing ET exchange rates between redox species and electrode surface and therefore affect significantly the measurement of the open circuit potential (OCP) and cyclic voltammetry (CV). The OCP and CV of various org. and inorg. species such as l-dopa, dopac, Fe(II), and iodide are measured by bare stainless steel and by stainless steel modified by either Pt or Au NPs. The authors study the effect of the surface coverage of the stainless steel surface by NPs on the electrochem. response. Also, the stainless steel electrode was modified simultaneously by Au and Pt nanoparticles. This improved concurrently the stainless steel response (CV and potentiometry) toward two different species; l-dopa, which shows fast electron transfer on Pt, and catechol, which exhibits fast electron transfer on Au. Probably this approach is a 1st step toward developing a superior electrode for measuring the true Eh of complex aquatic systems. [on SciFinder(R)]

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