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Use of Silver Solid Amalgam Electrode for Determination of Acaricide Amitraz
Nováková, Kateřina; Harvila, M.; Navrátil, Tomáš; Zima, J.
2015 - English
The electrochemical behavior of amitraz was studied at polished (p-AgSAE) and mercury meniscus modified (m-AgSAE) silver solid amalgam electrodes. The reaction mechanism was investigated using direct current voltammetry (DCV) and elimination voltammetry with linear scan (EVLS). The optimum conditions for differential pulse adsorption stripping voltammetry (DPAdSV) determination of amitraz were found in Britton-Robinson (BR) buffer mixed with ethanol in a volume ration of 1:4. DPAdSV with optimized parameters was applied for determination of amitraz in analyzed solutions. The limits of detection were calculated as 8.9 nmol L-1 (tacc = 20 s) for m-AgSAE and 0.168 mol L-1 (tacc = 20 s) for p-AgSAE. The proposed method was successfully applied for determination of this compound in real sample solutions.
Keywords:
pesticide; amitraz; amalgam
Available at various institutes of the ASCR
Use of Silver Solid Amalgam Electrode for Determination of Acaricide Amitraz
The electrochemical behavior of amitraz was studied at polished (p-AgSAE) and mercury meniscus modified (m-AgSAE) silver solid amalgam electrodes. The reaction mechanism was investigated using direct ...
Reduction and Oxidation of Hydroxyquinolines in Acetonitrile and Dimethylsulfoxide
Sokolová, Romana; Ramešová, Šárka; Fiedler, Jan; Kolivoška, Viliam; Degano, I.; Gál, M.; Szala, M.; Nycz, J. E.
2015 - English
This study is focused on investigation of oxidation and reduction pathways of selected hydroxyquinoline compounds in nonaqueous solutions. The experimentally obtained reduction potentials are reported to well correlate with calculated values of LUMO energies as well as the obtained oxidation potentials are in a good agreement with theoretical HOMO energies. The cyclic voltammetry, in situ UV/Vis spectroelectrochemistry and in situ IR spectroelectrochemistry confirmed that the oxidation mechanism is complicated. Oxidation unexpectedly proceeds together with protonation of the starting compound. This behaviour was found for all studied compounds, hydroxyquinoline carboxylic acids and also for compounds, where a methyl group is present instead of carboxylic group.
Keywords:
quinolines; hydroxyquiolines; reduction
Available at various institutes of the ASCR
Reduction and Oxidation of Hydroxyquinolines in Acetonitrile and Dimethylsulfoxide
This study is focused on investigation of oxidation and reduction pathways of selected hydroxyquinoline compounds in nonaqueous solutions. The experimentally obtained reduction potentials are reported ...
Voltammetry of Metallothioneins on Mercury Meniscus Modified Silver Solid Amalgam Electrode
Šestáková, Ivana; Křivská, D.; Josypčuk, Bohdan; Nováková, Kateřina; Navrátil, Tomáš
2015 - English
Peak of AgMT is formed on m-AgSAE from MT in alkaline media. The height of this peak is proportional to the MT concentration in range 37- to 301 ng /ml and can be increased with accumulation. In ammonia solution with Co(III) salt, apart from usual Brdička response at -1400 mV another, more positive catalytic system is observed, when formation of AgMT is allowed. This phenomenon has been confirmed by elimination voltammetry.
Keywords:
metallothionein; Brdička reaction; silver complex
Available at various institutes of the ASCR
Voltammetry of Metallothioneins on Mercury Meniscus Modified Silver Solid Amalgam Electrode
Peak of AgMT is formed on m-AgSAE from MT in alkaline media. The height of this peak is proportional to the MT concentration in range 37- to 301 ng /ml and can be increased with accumulation. In ...
Experimental and Theoretical Comparative Study of Monolayer and Bulk MoS2 under Compression
del Corro, Elena; Morales-García, A.; Peňa-Alvarez, M.; Kavan, Ladislav; Kalbáč, Martin; Frank, Otakar
2015 - English
Recently, a new family of 2D materials with exceptional optoelectronic properties has stormed into the scene of nanotechnology, the transition metal dichalcogenides (e.g., MoS2). In contrast with graphene, which is a zero band gap semiconductor, many of the single layered materials from this family show a direct band-gap in the visible range. This band-gap can be tuned by several factors, including the thickness of the sample; the transition from a direct to indirect semiconductor state takes place in MoS2 when increasing the number of layers from 1 towards the bulk. Applying strain/stress has been revealed as another tool for promoting changes in the electronic structure of these materials; however, only a few experimental works exist for MoS2. In this work we present a comparative study of single layered and bulk MoS2 subjected to direct out-of-plane compression, using high pressure anvil cells and monitoring with non-resonant Raman spectroscopy; accompanying the results with theoretical DFT studies. In the case of monolayer MoS2 we observe transitions from direct to indirect band-gap semiconductor and to semimetal, analogous to the transitions observed under hydrostatic pressure, but promoted at more accessible pressure ranges (similar to 25 times lower pressure). For bulk MoS2, both regimes, hydrostatic and uniaxial, lead to the semimetallization at similar pressure values, around 30 GPa. Our calculations reveal different driving forces for the metallization in bulk and monolayer samples.
Keywords:
MoS2; high pressure; Raman spectroscopy
Available at various institutes of the ASCR
Experimental and Theoretical Comparative Study of Monolayer and Bulk MoS2 under Compression
Recently, a new family of 2D materials with exceptional optoelectronic properties has stormed into the scene of nanotechnology, the transition metal dichalcogenides (e.g., MoS2). In contrast with ...
A COMPARATIVE STUDY OF LIQUID- AND GAS-PHASE CYCLOPENTENE HYDRATION CATALYZED BY THE MCM-22 ZEOLITE
Krupka, J.; Otmar, J.; Pawlesa, Justyna
2015 - English
The study deals with technological aspects of the direct hydration of cyclopentene to cyclopentanol. The catalytic properties of the MCM 22 zeolite were studied in the case of cyclopentene hydration both in liquid and gas phases. MCM-22, unlike other solid acid catalysts, is highly selective for the formation of cyclopentanol in the liquid-phase hydration in the slurry arrangement. It suppresses completely the undesirable etherification of cyclopentanol and allows obtaining cyclopentanol with almost 99% selectivity. But the liquid-phase hydration was found to lead to rapid deactivation of the zeolite. The deactivation is caused mainly by a formation of carbon deposits in the pores of the zeolite. When hydrating in the gas phase on the fixed bed of granular catalyst, it could be easy to periodically reactivate the catalyst in situ. However, it has been found that the exceptional selectivity of MCM-22 to the cyclopentanol formation is characteristic only for the liquid-phase hydration. The reaction in the gas phase is unselective. Furthermore, the equilibrium conversion of cyclopentene to cyclopentanol in the gas-phase hydration has been found to be industrially unusable below 1 % (e.g. under atm. pressure, at 120 degrees C and with a molar ratio of cyclopentene to water 1: 5, it is as low as 0.3 %).
Keywords:
MCM-22 zeolite; cyclopentene; catalysis
Available at various institutes of the ASCR
A COMPARATIVE STUDY OF LIQUID- AND GAS-PHASE CYCLOPENTENE HYDRATION CATALYZED BY THE MCM-22 ZEOLITE
The study deals with technological aspects of the direct hydration of cyclopentene to cyclopentanol. The catalytic properties of the MCM 22 zeolite were studied in the case of cyclopentene hydration ...
Electrochemical Biosensors Based on Silver Solid Amalgam for Analysis in Flow Systems
Josypčuk, Oksana; Barek, J.; Josypčuk, Bohdan
2015 - English
In this contribution, the construction and preparation of 3 types of flow amperometric enzymatic biosensors based on silver solid amalgam (AgSA) were presented. Two of them consist of the tubular detector and enzymatic reactor of porous or powdered AgSA. The third biosensor was constructed using polished AgSA electrode. Reactors and polished AgSA electrodes were modified with thiols or chitosan and different enzymes were covalently immobilized by suitable techniques. Prepared biosensors were used for determination of ascorbic acid, glucose, hydrogen peroxide, catechol, pyrogallol, dopamine and sarcosine in model samples and in same cases in the real samples.
Keywords:
biosensor; silver solid amalgam; electrochemical detection
Available at various institutes of the ASCR
Electrochemical Biosensors Based on Silver Solid Amalgam for Analysis in Flow Systems
In this contribution, the construction and preparation of 3 types of flow amperometric enzymatic biosensors based on silver solid amalgam (AgSA) were presented. Two of them consist of the tubular ...
Information on Several Interesting Case Reports of Liquid Mercury Intoxication
Navrátil, Tomáš; Vlčková, Š.; Mrázová, K.; Nováková, Kateřina; Zakharov, S.; Honsová, Š.; Pelclová, D.
2015 - English
This contribution reports on several mercury non-professional intoxications. It can be summarized that it is very important to differentiate among forms of mercury which can (acute or chronic) endanger human health. Contrarily to the wide spread fears, liquid mercury represents low danger for men and for environment. Solid amalgams are probably the less toxic forms of mercury compounds. On the other hand, widely spread daily consumer goods can be very dangerous and toxic (saving balls, fluorescent tubes, etc.). Moreover, these goods are not marked as “toxic mercury containing”. The article discusses the instruction for removing mercury from our environment. Most of the reported data are based on database of the Czech Toxicological Information Centre (TIC) (from the years 1995 – 2015).
Keywords:
mercury; poisoning; toxicity of mercury
Available at various institutes of the ASCR
Information on Several Interesting Case Reports of Liquid Mercury Intoxication
This contribution reports on several mercury non-professional intoxications. It can be summarized that it is very important to differentiate among forms of mercury which can (acute or chronic) ...
Electrochemical Reduction of FOX-7 in Aprotic Solvent Accompanied by Formation of a Radical with Alternating Line-width Effect
Šimková, Ludmila; Lušpai, K.; Klíma, Jiří; Ludvík, Jiří
2015 - English
Different structures of FOX-7 in various solutions play a crucial role in the mechanism of its electrochemical reduction. In aprotic solvent the irreversible four-electron, four-proton reduction of one nitro group proceeds according to the autoprotonation mechanism. The zwitterionic form of FOX-7 serves as a source of protons. The two-step reduction is accompanied by an adsorption step in dependence on used solvent and material of electrode. The in situ spectroelectrochemical measurements revealed formation of a dianion radical intermediate with alternating line-width effect. The intramolecular dynamic processes were described by temperature dependent in situ ESR measurement.
Keywords:
FOX-7; 2,2-dinitroethene-1,1-diamine; zwitterionic form
Available at various institutes of the ASCR
Electrochemical Reduction of FOX-7 in Aprotic Solvent Accompanied by Formation of a Radical with Alternating Line-width Effect
Different structures of FOX-7 in various solutions play a crucial role in the mechanism of its electrochemical reduction. In aprotic solvent the irreversible four-electron, four-proton reduction of ...
EXPERIMENTAL STUDY OF PIB-BASED CVD GRAPHENE TRANSFER EFFICIENCY
Bouša, Milan; Kalbáč, Martin; Jirka, Ivan; Kavan, Ladislav; Frank, Otakar
2015 - English
The transfer of graphene prepared by Chemical Vapor Deposition (CVD) from metal catalyst to target substrate is an important step in preparing desirable nanoscale structures in various fields of science, and thus searching for fast, cheap and clean method attracts great interest. Investigation of mechanical properties of graphene, which are crucial for applications in flexible electronics, performed on bendable synthetic materials, requires a transfer technique using polymers soluble in aliphatic solvents harmless for target polymer substrates. In this study we explore a dry technique using polydimethylsiloxane (PDMS) as stamping polymer and polyisobutylene (PIB) layer as graphene-support polymer. After the transfer PDMS is peeled off and PIB is dissolved in hexane, hence this method fulfils the above mentioned prerequisite. The effectiveness of this transfer was examined by scanning electron microscopy, optical microscopy and Raman microspectroscopy including micro-mapping, and finally by X-ray photoelectron spectroscopy. With all methods carried out, it was found that this sort of stamp-technique is suitable for a high precision transfer of small grains of CVD graphene onto polymer substrates with large yields and similar purity compared to poly(methylmethacrylate) (PMMA)based transfer methods. However, it introduces substantial quantity of surface discontinuities, and therefore this is not a proper method for large scale applications.
Keywords:
graphene; Chemical Vapor Deposition; transfer
Available at various institutes of the ASCR
EXPERIMENTAL STUDY OF PIB-BASED CVD GRAPHENE TRANSFER EFFICIENCY
The transfer of graphene prepared by Chemical Vapor Deposition (CVD) from metal catalyst to target substrate is an important step in preparing desirable nanoscale structures in various fields of ...
Development of the poly(methylene blue) modified graphite electrodes for the electrochemical detection of hydrogen sulphide
Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
2015 - English
A comparative study have been undertaken of the electropolymerization and electrochemical properties of deposited electroactive polymer on two different graphite electrode substrates: basal plane highly oriented pyrolytic graphite (HOPG) and pencil-graphite electrode (PGE). Poly(methylene blue) modified electrodes (HOPG/pMB and PGE/pMB) have been prepared by potential cycling in aqueous electrolyte solution containing methylene blue monomer. It has been found that electrochemical properties and electrocatalytic activity of deposited film are greatly influenced by the type of electrode substrate. Developed electrodes have been further investigated as potential sensors for hydrogen sulphide.
Keywords:
methylene-blue; polymerization; polymers; cyclic voltammetry; electropolymerization
Available at various institutes of the ASCR
Development of the poly(methylene blue) modified graphite electrodes for the electrochemical detection of hydrogen sulphide
A comparative study have been undertaken of the electropolymerization and electrochemical properties of deposited electroactive polymer on two different graphite electrode substrates: basal plane ...
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