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Charge Transport through Molecular Towers Based on Tetraphenyhmethane Tripods
Kolivoška, Viliam; Šebera, Jakub; Lindner, M.; Valášek, M.; Mayor, M.; Mészáros, G.; Gasior, Jindřich; Hromadová, Magdaléna
2017 - English
Molecular platforms with multiple anchors were introduced recently to provide robusi coupling between molecular electronic components and metallic electrodes. In this work, charge transport in tower-shaped single molecule conductors based on tetraphenylmethane tripod possessing three thiol anchors is investigated by scanning tunneling microscopy break junction technique. The effect of tripod substitution pattern and number of repeating units in molecule is addressed. The substitution was found to influence conductance value in early stages of molecular junction evolution, where tower lays parallel to surface. In late stages, the charge is transported through principal molecular axis and junction breaks thermally in tilted configuration.
Keywords:
conductance; Chaise Transport Through Single Molecules; Break Junction Technique; Molecalar Electronics
Available at various institutes of the ASCR
Charge Transport through Molecular Towers Based on Tetraphenyhmethane Tripods
Molecular platforms with multiple anchors were introduced recently to provide robusi coupling between molecular electronic components and metallic electrodes. In this work, charge transport in ...
Pilot Experiments With a Micro-Volume Voltammetric Cell for the Determination of Electrochemically Reducible Organic Compounds
Skalová, Štěpánka; Barek, J.; Rodrigues, J. A.; Goncalves, L.M.; Navrátil, Tomáš; Vyskočil, V.
2017 - English
A new micro-volume voltammetric cell for analysis of small volumes\nof electrochemically reducible organic compounds was developed\nand tested. The sample (20-100 mu L) is placed in a narrow glass tube\nwith an agar membrane at the bottom and the working electrode is\nimmersed into the sample. The agar membrane, as anion permeable\nlayer, electrically connects the workin g e lectrode immersed in the\nanalysed sample in the glass tube with a large-volume compartment\n(20 mL) filled with Britton-Robinson buffer, where conventional nonminiaturized\nreference and auxiliary electrodes are placed. The system\nwas tested using a polished silver solid amalgam electrode\n(p-AgSAE) as a working electrode. Sodium anthraquinone-2-sulfonate\nwas used as a model compound because it is intended to use this\nsystem to monitor electrochemically reducible organic compounds.
Keywords:
agar membrane; micro-volume voltammetric cell; voltammetry
Available on request at various institutes of the ASCR
Pilot Experiments With a Micro-Volume Voltammetric Cell for the Determination of Electrochemically Reducible Organic Compounds
A new micro-volume voltammetric cell for analysis of small volumes\nof electrochemically reducible organic compounds was developed\nand tested. The sample (20-100 mu L) is placed in a narrow glass ...
Stereoelectrochemistry of Calixarenes
Liška, Alan; Ludvík, Jiří; Vojtíšek, P.
2017 - English
The relationship between the stereochemical properties (shape or molecular geometry in\ngeneral sense) and electrochemical ones (typically number of separate redox proceses, their\nnature and potentials) is very fundamental, however, not easily answerable. The nitro\nsubstituted calix[4]arenes appeared to be suitable series of compounds enabling correlation of\nelectrochemical data (redox potential, current, reversibility) with actual shape, conformation\nand dynamic behavior of the molecules dissolved in solution due to their well defined\ngeometry and clear polarographic and voltammetric response. Electrochemical methods can\nbe therefore used as a straightforward alternative to e.g. temperature dependent NMR\nspectroscopy. The present contribution is focused on thiacalix[4]arenes, their similarities and\ndistinctions from their methylene bridged analogues.\n
Keywords:
Calixarenes; Thiacalixarenes; Stereoelectrochemistry
Available on request at various institutes of the ASCR
Stereoelectrochemistry of Calixarenes
The relationship between the stereochemical properties (shape or molecular geometry in\ngeneral sense) and electrochemical ones (typically number of separate redox proceses, their\nnature and ...
Single Molecule Conductance and Junction Formation in Solution. Solvent Effect
Lachmanová, Štěpánka; Šebera, Jakub; Gasior, Jindřich; Dupeyre, G.; Lainé, P. P.; Mészáros, G.; Hromadová, Magdaléna
2017 - English
The single molecule conductance of expanded pyridinium derivative terminated by pyridyl\nnitrogen as an anchoring group at both ends of the molecule in two different environments\nwas measured by scanning tunneling microscopy break junction technique (STM-BJ). The\nvalues obtained in commonly used 1,3,5-trimethylbenzene (TMB) significantly differ from\nthe values acquired in a mixture of TMB and ethanol. Markedly lower junction length and\nhigher conductance indicate strong influence of adsorption of the molecule to the substrate\nsurface in pure TMB compared to the TMB and ethanol mixture.
Keywords:
Single molecule conductance; Expanded pyridinium derivatives; Solvent effect
Available at various institutes of the ASCR
Single Molecule Conductance and Junction Formation in Solution. Solvent Effect
The single molecule conductance of expanded pyridinium derivative terminated by pyridyl\nnitrogen as an anchoring group at both ends of the molecule in two different environments\nwas measured by ...
Electrochemical biosensors with flow-through enzymatic reactors
Josypčuk, Oksana; Josypčuk, Bohdan
2017 - English
Twelve enzymatic biosensors with various silica powder reactors were fabricated and tested.\nExperiments with six silica materials showed that mesoporous silica SBA-15 was the best one\nin terms of covering by enzymes, sensitivity and lifetime of biosensors. The current response\nof the SBA15-glucose oxidase (GOx) sensor started to decrease only after 200-day testing.\nThe used amalgam tubular detector in a flow system allowed working at highly negative\npotentials. Statistical results of parallel measurements of model solutions with the fabricated\nbiosensors show their high accuracy and sensitivity. The proposed SBA15-GOx biosensor\nwas used for determination of glucose in commercial honey.
Keywords:
Biosensor; Amperometry; Enzymatic reactor
Available on request at various institutes of the ASCR
Electrochemical biosensors with flow-through enzymatic reactors
Twelve enzymatic biosensors with various silica powder reactors were fabricated and tested.\nExperiments with six silica materials showed that mesoporous silica SBA-15 was the best one\nin terms of ...
Voltammetric Determination of Tumor Biomarkers using Flow Injection Analysis with Amperometric Detection
Makrlíková, Anna; Matysik, F.-M.; Barek, J.; Vyskočil, V.
2017 - English
Three tumor biomarkers (homovanillic acid, vanillylmandelic acid,\nand 5-hydroxyindole-3-acetic acid) have been determined by flow\ninjection analysis with amperometric detection at screen-printed\ncarbon electrodes in optimum medium of Britton-Robinson buffer\n(0.04 mol l-1, pH = 2.0). Dependences of the peaks current on the\nconcentration of biomarkers were linear in the tested concentration\nregion from 0.05 to 100 mu mol l-1, with the limits of detection of\n0.065 mu mol l-1 for homovanillic acid, 0.053 mu mol l-1 for vanillylmandelic\nacid, and 0.033 mu mol l-1 for 5-hydroxyindole-3-acetic acid (calculated\nfrom heights), and 0.024 mu mol 1-1 for homovanillic acid,\n0.020 mu mol l-1 forvanillylmandelic acid, and 0.012 mu mol l-1 for 5-hydroxyindole-3-acetic acid (calculated from areas), respectively.
Keywords:
flow injection analysis; 5-hydroxyindole-3-acetic acid; homovanillic acid
Available on request at various institutes of the ASCR
Voltammetric Determination of Tumor Biomarkers using Flow Injection Analysis with Amperometric Detection
Three tumor biomarkers (homovanillic acid, vanillylmandelic acid,\nand 5-hydroxyindole-3-acetic acid) have been determined by flow\ninjection analysis with amperometric detection at ...
Hollow-fibre Based Microextraction and Voltammetric Determination of Vanillylmandelic Acid
Hrdlička, Vojtěch; Barek, J.; Navrátil, Tomáš
2017 - English
New method of liquid/liquid/liquid hollow fibre based microextraction of vanillylmandelic acid coupled with voltammetric determination is being developed. Selected liquid membranes based on alcohols, aliphatic hydrocarbons and esters were tested. Highest enrichment factor of 2.52 after 30 minutes of extraction was obtained using propyl benzoate, RSD = 18.2 % (n=5). Mechanically and cathodically pretreated (-1000 mV vs. Ag/AgCl/3M KCl, 15 s) boron doped diamond electrode in a miniaturized arrangement was used for DPV determination. LOD = 1.2 micromol/l, RSD = 5.9% (n=10) for a 10 microl extract.
Keywords:
Hollow-fibres; Liquid phase microextraction; Voltammetry
Available at various institutes of the ASCR
Hollow-fibre Based Microextraction and Voltammetric Determination of Vanillylmandelic Acid
New method of liquid/liquid/liquid hollow fibre based microextraction of vanillylmandelic acid coupled with voltammetric determination is being developed. Selected liquid membranes based on alcohols, ...
Voltammetric Determination of Tumor Biomarkers using Flow Injection Analysis with Amperometric Detection
Němečková-Makrlíková, Anna; Matysik, F.-M.; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
2017 - English
Three tumor biomarkers (homovanillic acid, vanillylmandelic acid, and 5-hydroxyindole-3-acetic acid) have been determined by flow injection analysis with amperometric detection at screen-printed carbon electrodes in optimum medium of Britton-Robinson buffer (0.04 mol l(-1), pH = 2.0). Dependences of the peaks current on the concentration of biomarkers were linear in the tested concentration region from 0.05 to 100 mu mol l(-1), with the limits of detection of 0.065 mu mol l(-1) for homovanillic acid, 0.053 mu mol l(-1) for vanillylmandelic acid, and 0.033 mu mol l(-1) for 5-hydroxyindole-3-acetic acid (calculated from heights), and 0.024 mu mol l(-1) for homovanillic acid, 0.020 mu mol l(-1) for vanillylmandelic acid, and 0.012 mu mol l(-1) for 5-hydroxyindole-3-acetic acid (calculated fromareas), respectively.
Keywords:
vanillylmandelic acid; homovanillic-acid; urine; flow injection analysis; 5-hydroxyindole-3-acetic acid; homovanillic acid; vanillylmandelic acid; tumor biomarkers
Available at various institutes of the ASCR
Voltammetric Determination of Tumor Biomarkers using Flow Injection Analysis with Amperometric Detection
Three tumor biomarkers (homovanillic acid, vanillylmandelic acid, and 5-hydroxyindole-3-acetic acid) have been determined by flow injection analysis with amperometric detection at screen-printed ...
Determination of 5-hydroxyindole-3-acetic acid using Flow Injection Analysis with Electrochemical Detection
Makrlíková, Anna; Matysik, F.-M.; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
2017 - English
Tumour biomarker, 5-hydroxyindole-3-acetic acid, has been determined at screen-printed carbon electrodes using flow injection analysis with amperometric detection. Britton-Robinson buffer (0.04 mol-l-1 , pH 2.0) was used as an optimum carrier solution.\nDependence of the peak current on the analyte concentration was linear in the whole tested\nconcentration range (from 0.5 to 100 mikromol-l-1) with limits of detection 0.033 mikromol-l-1 \n(calculated from peak heighst) and 0.012 mikromol-l-1 (calculated from peak areas).
Keywords:
Amperometric detection; Flow injection analysis; 5-Hydroxyindole-3-acetic acid
Available on request at various institutes of the ASCR
Determination of 5-hydroxyindole-3-acetic acid using Flow Injection Analysis with Electrochemical Detection
Tumour biomarker, 5-hydroxyindole-3-acetic acid, has been determined at screen-printed carbon electrodes using flow injection analysis with amperometric detection. Britton-Robinson buffer (0.04 ...
Effect of pH on the Oxide Film Formation on a Pristine Zr Electrode
Hromadová, Magdaléna; Kocábová, Jana; Kolivoška, Viliam; Pospíšil, Lubomír
2017 - English
Effect of pH on the oxidation of zirconium metal was studied by cyclic voltammetry in\naqueous borate buffer solutions as a function of the potential scan rate and pH from 4.80 to\n9.17. The results show that the oxide growth kinetics depends on pH of the electrolyte\nsolution and the total amount of irreversibly formed oxide under the potentiodynamic\nconditions decreases with decreasing buffer pH in accord with thermodynamic considerations.\nCathodic current corresponding to hydrogen evolution reaction diminishes in the presence of\nanodically modified electrode compared to bare zirconium.
Keywords:
zirconium; oxide film; hydrogen evolution
Available on request at various institutes of the ASCR
Effect of pH on the Oxide Film Formation on a Pristine Zr Electrode
Effect of pH on the oxidation of zirconium metal was studied by cyclic voltammetry in\naqueous borate buffer solutions as a function of the potential scan rate and pH from 4.80 to\n9.17. The results ...
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