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Material properties of lithium fluoride for predicting XUV laser ablation rate and threshold fluence
Blejchař, T.; Nevrlý, V.; Vašinek, M.; Dostál, Michal; Pečínka, L.; Dlabka, J.; Stachoň, M.; Juha, Libor; Bitala, P.; Zelinger, Zdeněk; Pira, P.; Wild, J.
2015 - English
This paper deals with prediction of extreme ultraviolet (XUV) laser ablation of lithium fluoride at nanosecond timescales. Material properties of lithium fluoride were determined based on bibliographic survey. These data are necessary for theoretical estimation of surface removal rate in relevance to XUV laser desorption/ablation process. Parameters of XUV radiation pulses generated by the Prague capillary-discharge laser (CDL) desktop system were assumed in this context. Prediction of ablation curve and threshold laser fluence for lithium fluoride was performed employing XUV-ABLATOR code. Quasi-random sampling approach was used for evaluating its predictive capabilities in the means of variance and stability of model outputs in expected range of uncertainties. These results were compared to experimental data observed previously.
Keywords:
ablation curve; threshold fluence; lithium fluoride; thermomechanic model; quasi-random sampling
Available on request at various institutes of the ASCR
Material properties of lithium fluoride for predicting XUV laser ablation rate and threshold fluence
This paper deals with prediction of extreme ultraviolet (XUV) laser ablation of lithium fluoride at nanosecond timescales. Material properties of lithium fluoride were determined based on ...
STRAIN ENGINEERING OF THE ELECTRONIC STRUCTURE OF 2D MATERIALS
del Corro, Elena; Peňa-Alvarez, M.; Morales-García, A.; Bouša, Milan; Řáhová, Jaroslava; Kavan, Ladislav; Kalbáč, Martin; Frank, Otakar
2015 - English
The research on graphene has attracted much attention since its first successful preparation in 2004. It possesses many unique properties, such as an extreme stiffness and strength, high electron mobility, ballistic transport even at room temperature, superior thermal conductivity and many others. The affection for graphene was followed swiftly by a keen interest in other two dimensional materials like transition metal dichalcogenides. As has been predicted and in part proven experimentally, the electronic properties of these materials can be modified by various means. The most common ones include covalent or non-covalent chemistry, electrochemical, gate or atomic doping, or quantum confinement. None of these methods has proven universal enough in terms of the devices' characteristics or scalability. However, another approach is known mechanical strain/stress, but experiments in that direction are scarce, in spite of their high promises.\nThe primary challenge consists in the understanding of the mechanical properties of 2D materials and in the ability to quantify the lattice deformation. Several techniques can be then used to apply strain to the specimens and thus to induce changes in their electronic structure. We will review their basic concepts and some of the examples so far documented experimentally and/or theoretically.
Keywords:
2D materials; graphene; electronic structure
Available at various institutes of the ASCR
STRAIN ENGINEERING OF THE ELECTRONIC STRUCTURE OF 2D MATERIALS
The research on graphene has attracted much attention since its first successful preparation in 2004. It possesses many unique properties, such as an extreme stiffness and strength, high electron ...
The Use of Self-Assembled Monolayer of Thiolated Calix[4]arene on Polycrystaline Gold Electrode Surface
Hrdlička, V.; Navrátil, Tomáš; Šestáková, Ivana; Barek, J.; Ludvík, Jiří
2015 - English
This study deals with the use of thiolated calixarene (C[4]A) as gold electrode modifier, alone or in combination with insulating undecanthiol (C11SH), which is used to fill the gaps between calixes. Desorption potential of thiolated C[4]A and C11SH are both pH dependent, cathodic desorption peaks can be recorded in basic solutions only. The properties of the modified electrode were investigated using hydroquinone - electrochemically active molecule which fits inside the C[4]A cavity. Obtained data suggest that the electrochemical oxidation/reduction ofhydroquinone does not use C[4]A cavities as size-selective channels.
Keywords:
calixarene; thiols; gold electrode
Available at various institutes of the ASCR
The Use of Self-Assembled Monolayer of Thiolated Calix[4]arene on Polycrystaline Gold Electrode Surface
This study deals with the use of thiolated calixarene (C[4]A) as gold electrode modifier, alone or in combination with insulating undecanthiol (C11SH), which is used to fill the gaps between calixes. ...
Spectroelectrochemical Study of Electron Transfer in the Extended 1,1 '-Bipyridinium Cation
Hromadová, Magdaléna; Kolivoška, Viliam; Pospíšil, Lubomír; Valášek, M.; Tarábek, Ján
2015 - English
Electron transfer (ET) in the extended 1, 1 ' -bipyridinium has been investigated by UV Nis/NIR and EPR in-situ spectroelectrochemical techniques. During the in-situ cyclic voltammetric scan no EPR signal was observed at the potential corresponding to the first electron transfer at room temperature, whereas the EPR signal for the subsequent ET steadily increased and was observed even at the potentials corresponding to the fourth electron transfer. The EPR signal was detected for the first electron transfer step only at elevated temperature. The evidence for the presence of comproportionation processes and for the formation of n-dimer is discussed.
Keywords:
extended bipyridinium; electron transfer; UV/Vis/NIR and EPR spectroelectrochemistry
Available at various institutes of the ASCR
Spectroelectrochemical Study of Electron Transfer in the Extended 1,1 '-Bipyridinium Cation
Electron transfer (ET) in the extended 1, 1 ' -bipyridinium has been investigated by UV Nis/NIR and EPR in-situ spectroelectrochemical techniques. During the in-situ cyclic voltammetric scan no EPR ...
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 ...
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