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Charge Transport in Single Oligophenylene Molecular Wires with Different Anchoring Groups
Hromadová, Magdaléna; Kolivoška, Viliam; Šebera, Jakub; Sebechlebská, Táňa; Gasior, Jindřich; Nováková Lachmanová, Štěpánka; Mészáros, G.; Lindner, M.; Mayor, M.; Valášek, M.
2019 - English
This work compares single molecule conductance measurements of selected organic systems containing identical oligophenylene molecular wires and different tripodal anchoring groups. Single molecule conductance G was obtained by a scanning tunneling microscopy break junction technique complemented by theoretical calculations based on the density functional theory and non-equilibrium Green’s function formalism. Two molecules were compared where the same oligophenylene wire is connected to one of the electrodes via a tripod substituted on each leg by a thiol group either in the meta or para position. By combined experimental and theoretical analysis it was possible to confirm that single molecule conductance in the metal-molecule-metal junction of both molecules corresponds to a fully extended molecular wire, which is attached to one of the electrodes by all three thiolate bonds of the tripod. Experimental results confirmed that G value of meta-connected molecules is lower than that of para, whereas junction formation probability was higher for meta functionalization.
Keywords:
STM break junction; Tetraphenylmethane Tripodal anchor; Single molecule conductance
Available at various institutes of the ASCR
Charge Transport in Single Oligophenylene Molecular Wires with Different Anchoring Groups
This work compares single molecule conductance measurements of selected organic systems containing identical oligophenylene molecular wires and different tripodal anchoring groups. Single molecule ...
Electrochemical Investigation of Polylactic Acid/Carbon Black Composite Filament for the Manufacture of 3D Printed Electrodes
Sebechlebská, Táňa; Vaněčková, Eva; Shestivska, Violetta; Kolivoška, Viliam
2019 - English
Fused deposition modeling 3D printing has recently attracted increasing attention as an inexpensive, fast, reliable, adaptable and environmentally friendly tool to fabricate electrodes and electrochemical cells from composites of thermoplastics and carbon nanostructures. In this work, we use electric conductance measurements and cyclic voltammetry employing Ru(acac)30/1- as an electroactive probe to demonstrate that commercial polylactic acid(PLA)/carbon black composite filaments may be readily used as functional working electrodes in aqueous electrolytes. We further devise a procedure that leads to an improvement of their electrochemical performance. Characteristics of composite filaments treated by the optimized procedure approach those of classical metallic electrodes.
Keywords:
3D printed electrodes; Fused deposition modeling; Polylactic acid; Carbon black
Available on request at various institutes of the ASCR
Electrochemical Investigation of Polylactic Acid/Carbon Black Composite Filament for the Manufacture of 3D Printed Electrodes
Fused deposition modeling 3D printing has recently attracted increasing attention as an inexpensive, fast, reliable, adaptable and environmentally friendly tool to fabricate electrodes and ...
Mechanism of the Water Clusters Formation in the Organic Phase in the Presence of Hydrated Ions
Holub, Karel; Samec, Zdeněk; Mareček, Vladimír
2019 - English
A two-electrode cell comprising a liquid/liquid interface is used to study the water clusters formation in the organic solvent phase following the extraction of tetraalkylammonium chloride (TAACl) from the aqueous phase. The change in the concentration of the common TAA+ ion on the aqueous side of the interface is monitored by the open circuit potential measurements. It is shown that the amount of TAACl extracted into the organic phase exceeds considerably the limit determined by the concentration of Cl- in the organic phase at a given interfacial potential difference and the electroneutrality condition. A mechanism is proposed including an accumulation of the excess TAACl in the water clusters formed from the hydration shell of the Cl- ions, water already dissolved in the organic phase, and additional water extracted from the aqueous phase. At higher concentration of TAACl in the aqueous phase this process leads to the formation of emulsion in the organic phase.
Keywords:
liquid/liquid interface; water co-extraction dynemics; emulsification
Available on request at various institutes of the ASCR
Mechanism of the Water Clusters Formation in the Organic Phase in the Presence of Hydrated Ions
A two-electrode cell comprising a liquid/liquid interface is used to study the water clusters formation in the organic solvent phase following the extraction of tetraalkylammonium chloride (TAACl) ...
Construction and Application of Flow Amperometric Biosensor Based on Enzymatic Reactor for Determination of Choline
Tvorynska, Sofiia; Barek, J.; Josypčuk, Bohdan
2019 - English
In this contribution, a novel fast, simple and stable biosensor with the enzymatic reactor based on choline oxidase (ChOx) was developed and applied for the determination of choline using flow injection analysis with amperometric detection. The preparation of the reactor is based on the covalent immobilization of ChOx with glutaraldehyde to mesoporous silica powder (SBA-15) previously covered by NH2-groups. The experimental parameters affecting the sensitivity and stability of the biosensor were optimized. The proposed biosensor with the newly developed ChOx-based reactor possesses good repeatability, reproducibility, long-term stability, and reusability. It was successfully applied for the determination of choline in commercial pharmaceuticals.
Keywords:
choline; choline oxidase; Flow analysis; enzymatic reactor
Available on request at various institutes of the ASCR
Construction and Application of Flow Amperometric Biosensor Based on Enzymatic Reactor for Determination of Choline
In this contribution, a novel fast, simple and stable biosensor with the enzymatic reactor based on choline oxidase (ChOx) was developed and applied for the determination of choline using flow ...
Electrochemical Measurements in Flow Systems on Silver Amalgam Tubular Detector Combined with Auxiliary Electrode
Josypčuk, Bohdan; Barek, J.; Josypčuk, Oksana
2018 - English
A new type of tubular detector (TD+AuxE) was proposed, fabricated, tested and compared\nwith a typical silver amalgam tubular detector developed earlier. Non-stop-flow differential\npulse voltammetric anodic stripping method (AS-DPV) and amperometric method in a\nglucose oxidase biosensor arrangement were tested. Both detectors were applied for AS-DPV\nmeasurements in flow systems for the first time. The proposed combination of tubular\ndetector with auxiliary electrode provides a much greater current response than the classic\narrangement with three individual electrodes. All relevant parameters (potentials of\naccumulation or detection, flow rate, analyte concentrations, shielding sleeve length, etc.)\nwere optimized for the developed TD+AuxE.
Keywords:
Flow analysis; Amperometry; Voltammetry
Available on request at various institutes of the ASCR
Electrochemical Measurements in Flow Systems on Silver Amalgam Tubular Detector Combined with Auxiliary Electrode
A new type of tubular detector (TD+AuxE) was proposed, fabricated, tested and compared\nwith a typical silver amalgam tubular detector developed earlier. Non-stop-flow differential\npulse voltammetric ...
Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen Evolution Reaction on the Surface Structure
Novák, M.; Kocábová, Jana; Kolivoška, Viliam; Pospíšil, Lubomír; Macák, J.; Cichoň, Stanislav; Cháb, Vladimír; Hromadová, Magdaléna
2018 - English
Atomic force microscopy (AFM) was used to characterize surface morphology of pristine zirconium, Si modified and FeSi modified zirconium electrodes prior and after hydrogen evolution at potentials negative of the open circuit potential value. Two main characteristic parameters were obtained from the ex situ AFM height images, namely, the roughness factor and fractal dimension of the studied surface. The effect of hydrogen evolution reaction on the electrode surface morphology was discussed. Fractal dimension values were used successfully to explain the non ideality of the interfacial capacitance.
Keywords:
zirconium electrode; atomic force microscopy; fractal dimension
Available on request at various institutes of the ASCR
Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen Evolution Reaction on the Surface Structure
Atomic force microscopy (AFM) was used to characterize surface morphology of pristine zirconium, Si modified and FeSi modified zirconium electrodes prior and after hydrogen evolution at potentials ...
Differences in Oxidation Mechanism of Selected Bioflavonoids, UV-Vis and IR Spectroelectrochemical Study
Sokolová, Romana; Fiedler, Jan; Ramešová, Šárka; Kocábová, Jana; Degano, I.; Quinto, A.; Křen, Vladimír
2018 - English
The oxidation of selected bioflavonoids (quercetin, rhamnazin, fisetin, rhamnetin, taxifolin, luteolin, silybin and 2,3-dehydrosilybin) was studied by electrochemical and spectroscopic methods. The oxidation mechanism and formation of oxidation products depends on the chemical structure. Only small differences in the chemical structure of compounds with flavone, flavanone and flavonol motif result in extremely variable oxidation pathways and products. Products of oxidation and further decomposition were determined by HPLC-ESIMS/MS and HPLC-DAD.
Keywords:
oxidation; flavonoids; decomposition
Available on request at various institutes of the ASCR
Differences in Oxidation Mechanism of Selected Bioflavonoids, UV-Vis and IR Spectroelectrochemical Study
The oxidation of selected bioflavonoids (quercetin, rhamnazin, fisetin, rhamnetin, taxifolin, luteolin, silybin and 2,3-dehydrosilybin) was studied by electrochemical and spectroscopic methods. The ...
Redox Properties of Fluorinated Derivativers of 1,3-Diphenylisobenzofuran-Chromophores for Singlet Fission
Šimková, Ludmila; Ludvík, Jiří
2018 - English
Derivatives of 1,3-diphenylisobenzofuran attract interest because they should be efficient as the molecules for singlet fission. The understanding of singlet fission in isolated molecules might be advantageous for use as solar cell sensitizers. This study is focused on fluorinated derivatives of 1,3-diphenylisobenzofuran and the effect of the position of fluorine atoms on their redox properties. For characterization of the redox properties standard electrochemical methods, and in situ UV-vis and EPR spectroscopy techniques were used.
Keywords:
1,3-diphenylisobenzofuran; fluorinated derivatives; spectroelectrochemistry
Available on request at various institutes of the ASCR
Redox Properties of Fluorinated Derivativers of 1,3-Diphenylisobenzofuran-Chromophores for Singlet Fission
Derivatives of 1,3-diphenylisobenzofuran attract interest because they should be efficient as the molecules for singlet fission. The understanding of singlet fission in isolated molecules might be ...
Electrochemical Monitoring of the Water Clusters Formation in an Organic Solvent in the Presence of Hydrated Ions
Mareček, Vladimír
2018 - English
An electrochemical method has been developed that makes it possible to monitor the\ndynamics of the co-extraction of water with hydrated chloride ions at the interface between\ntwo immiscible electrolyte solutions (ITIES). The interfacial potential was controlled by the\ndistribution of a common tetralkylammonium (TAA+) ion. Changes in the TAA+\nconcentration at the interface were monitored by measuring the open circuit potential (OCP).\nTransfer of hydrated chloride ions is accompanied by the transfer of TAA+, decreasing its\nconcentration on the aqueous side of the interface. This process involves the co-extraction of\nwater molecules with the hydrated chloride ions and the formation of water clusters in the\norganic solvent phase. The ability to monitor the process from the very beginning of interface\nformation allowed us to obtain important kinetic data.
Keywords:
Liquid/liquid interface; Water co-extraction dynamics; Emulsification
Available on request at various institutes of the ASCR
Electrochemical Monitoring of the Water Clusters Formation in an Organic Solvent in the Presence of Hydrated Ions
An electrochemical method has been developed that makes it possible to monitor the\ndynamics of the co-extraction of water with hydrated chloride ions at the interface between\ntwo immiscible ...
Silver Solid Amalgam Electrodes as Perspective Tools for Sensitive Voltammetric Determinations of Food Azo Dyes Amaranth and Allura Red AC
Tvorynska, S.; Barek, J.; Josypčuk, Bohdan
2018 - English
In this paper, for the first time, the electrochemical behaviours of the food azo dyes Amaranth (E 123) and Allura Red AC (E 129) were investigated on two modifications of silver solid amalgam electrode, namely mercury meniscus modified, polished and compared with hanging mercury drop electrode using differential pulse voltammetry and direct current voltammetry. The effect of adsorption and the reduction mechanism on tested electrodes were described in detail. Measurements with amalgam electrodes showed good reproducibility, stability and high sensitivity. As a result, they were successfully applied for the determination of investigated azo dyes in different commercial drink samples.
Keywords:
voltammetry; azo dyes; amaranth
Available on request at various institutes of the ASCR
Silver Solid Amalgam Electrodes as Perspective Tools for Sensitive Voltammetric Determinations of Food Azo Dyes Amaranth and Allura Red AC
In this paper, for the first time, the electrochemical behaviours of the food azo dyes Amaranth (E 123) and Allura Red AC (E 129) were investigated on two modifications of silver solid amalgam ...
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