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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
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.
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Construction and Application of Flow Amperometric Biosensor Based on Enzymatic Reactor for Determination of Choline
Tvorynska, Sofiia ; Barek, J. ; Josypčuk, Bohdan
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.
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Electrochemical Enzymatic Biosensors for Determination of Catecholamines in Flow Systems
Josypčuk, Bohdan ; Barek, J. ; Josypčuk, Oksana
Several biosensors (BS) based on flow enzymatic mini-reactors containing a mesoporous silica powder covered by enzyme laccase or tyrosinase were used for determination of L-DOPA, dopamine, noradrenaline, and adrenaline. The silica powder of MCM-41 with covalently bonded laccase was found to be the best reactor filling for the detection of catecholamines. Relative current response of such BS was 100 % for dopamine, 32.1 % for L-DOPA, 26.2 % for noradrenaline, and 0.71 % for adrenaline. The practical applicability of Lac-MCM41 biosensor was successfully verified by the determination of dopamine and noradrenaline in medical solutions for infusions.
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Voltametrie na uhlíkové pastové elektrodě modifikované silikagelem
Šestáková, Ivana ; Navrátil, Tomáš
Kompositní uhlíkové elektrody s obsahem silikagelu 1,2 se začaly používat již v 90. letech minulého století, a to ve variantě pevné (s obsahem ceresinu) nebo pastové (s parafinovým olejem). Přítomnost silikagelu v uhlíkové pastě vede ke zlepšené amperometrické detekce látek, které lze na povrchu modifikovaném silikagelem nahromadit, a to jak látek organických, tak iontů kovů 3. Reprodukovatelnost povrchu a tím i vlastního stanovení je nejlépe zabezpečena použitím pastové elektrody se speciálně vyvinutým teflonovým držákem s pohyblivým pístem 4. Možnosti charakterizace uhlíkových pastových elektrod byly dále popsány v přehledném článku 5.\nVlastnosti uhlíkové pasty modifikované silikagelem byly dokumentovány při oxidaci flavonoidů a oxidaci kadmia v přítomnosti cysteinu a fytochelatinu PC2.
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