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Comparison of Techniques for Single-Molecule Conductance Measurements of Expanded Pyridinium Molecules
Lachmanová, Štěpánka; Hromadová, Magdaléna; Sokolová, Romana; Kocábová, Jana; Gasior, Jindřich; Mészáros, G.; Lainé, P. P.
2015 - English
This work is focused on the comparison of two techniques of single-molecule conductance measurements: Scanning Tunneling Microscopy Break Junction technique and Mechanically Controlled Break Junction technique. The structure of studied compound 9-(pyridin-4-yl)benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium allows the formation of the molecular bridge between two gold electrodes, which are connected to a source of the constant voltage in both of the used methods. The differences, advantages and disadvantages of both of the techniques will be discussed. Both techniques provided two values of conductance of studied compound depending on the experimantal conditions.
Keywords:
Single-molecule conductance; Scanning Tunneling Microscopy Break Junction; Mechanically Controled Break Junction
Available at various institutes of the ASCR
Comparison of Techniques for Single-Molecule Conductance Measurements of Expanded Pyridinium Molecules
This work is focused on the comparison of two techniques of single-molecule conductance measurements: Scanning Tunneling Microscopy Break Junction technique and Mechanically Controlled Break Junction ...
Electrochemical Study of Oxazaborine Chromophores
Mikysek, T.; Josefík, F.; Vytřas, K.; Ludvík, Jiří
2015 - English
This contribution describes a basic electrochemical study of a series of newly synthesized chromophores based on the oxazaborine core. The attention was focused on determination of the first oxidation and the first reduction potentials, their difference and the relationship to the calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies. The oxidation is mostly a two-electron irreversible process, the first reduction is also irrevesible, but involving one-electron. For better understanding of the relationship between the structure and redox properties, the approach using sigma (para) constants of Hammett type was applied, the difference between E(ox) and E(red) was correlated with the HOMO-LUMO gap.
Keywords:
oxazaborines; chromophore; cyclic voltammetry
Available at various institutes of the ASCR
Electrochemical Study of Oxazaborine Chromophores
This contribution describes a basic electrochemical study of a series of newly synthesized chromophores based on the oxazaborine core. The attention was focused on determination of the first oxidation ...
Influence of Cadmium on its Metabolism and Changes of Content of Nutritionally Important Compounds in Spring Barley
Paznocht, L.; Vodičková, H.; Phuong, L. M.; Nováková, Kateřina; Zámečníková, B.; Kotíková, Z.; Miholová, D.; Navrátil, Tomáš
2015 - English
Very important agriculture products are cereals, which significantly contributes to securing of human nutrient needs. Cadmium is a toxic heavy metal, which is readily taken up and accumulated by plants in spite of its harmful effects. This metal cause a stress for the plants and results in many morphological, anatomical, physiological and biochemical changes. The effect of cadmium on the plant metabolism and changes in the content of nutritionally important compounds (protein and some metals – Fe, Zn, Cu, Mn content) was investigated. Results shown, that cadmium was effectively retained in the roots and content of studied compounds was influenced by present of cadmium in nutrient medium. In all the parts of cadmium-treated seedlings decrease in the iron content and increase in the zinc content (except of the first leaves) and decrease in the manganese content was found. The copper content in the root tissue increased by 112.1 %, on the other hand a significant decrease (by 44.4 % and 40.9 % respectively) in the first and the second leaves was observed. In the experimental varieties with cadmium in the concentration of 10-5 mol L-1, the content of soluble proteins was determined statistically higher in the root and basal parts than in the controlled varieties.
Keywords:
Barley; cadmium; cereals
Available at various institutes of the ASCR
Influence of Cadmium on its Metabolism and Changes of Content of Nutritionally Important Compounds in Spring Barley
Very important agriculture products are cereals, which significantly contributes to securing of human nutrient needs. Cadmium is a toxic heavy metal, which is readily taken up and accumulated by ...
Electrochemical Characterization of Poly(methylene Blue) Modified Graphite Electrodes
Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
2015 - English
This work deals with electrochemical study of methylene blue (MB) polymerization as well as characterization of deposited conductive film on 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 sulfhydryl-containing compounds.
Keywords:
Poly(methylene blue); Electropolymerization; cyclic voltammetry
Available at various institutes of the ASCR
Electrochemical Characterization of Poly(methylene Blue) Modified Graphite Electrodes
This work deals with electrochemical study of methylene blue (MB) polymerization as well as characterization of deposited conductive film on basal plane highly oriented pyrolytic graphite (HOPG) and ...
Influence of electrode preparation on electrocatalytic activity of water soluble porphyrazine complex to hydrogen
Klusáčková, Monika; Janda, Pavel; Tarábková, Hana
2015 - English
The influence of electrode preparation and used electrode substrate on electrocatalytic activity of N, N`,N``,N```tetramethyl-tetra-3,4-pyridinopor-phyrazinocobalt (CoTmt-3,4-ppa) complex deposited on electrode surface for hydrogen reaction has been studied. Electrochemical deposition, spontaneous adsorption, and spin coating have been used to the modification of two different electrode substrates: annealed gold and highly oriented pyrolytic graphite. Prepared electrodes have been characterized using cyclic voltammetry, backscattering VIS spectroscopy and atomic force microscopy. The detailed comparison of surface morphology, surface coverage, surface roughness parameters, and thickness of deposited layers of CoTmt-3,4-ppa mediatoronhydrogen reaction has been investigated.
Keywords:
reduction; oxidation; atomic force microscopy; backscattering microscopy; cyclic voltammetry; electrocatalysis; water soluble phthalocyanine
Available at various institutes of the ASCR
Influence of electrode preparation on electrocatalytic activity of water soluble porphyrazine complex to hydrogen
The influence of electrode preparation and used electrode substrate on electrocatalytic activity of N, N`,N``,N```tetramethyl-tetra-3,4-pyridinopor-phyrazinocobalt (CoTmt-3,4-ppa) complex deposited on ...
Lab-made Sensors Based on Boron-doped Diamond for Determination of Herbicide Linuron
Štěpánková, M.; Šelešovská, R.; Janíková, L.; Vojs, M.; Marton, M.; Behúl, M.; Nováková, Kateřina; Chýlková, J.
2015 - English
Voltammetric behaviour of substituted urea herbicide linuron (LIN) was investigated using two types of boron-doped diamond electrodes (BDDE): commercial BDDE and lab-made sensors based on boron-doped diamond (LM-BDDE). Various methods like cyclic voltammetry (CV), direct current voltammetry (DCV) and differential pulse voltammetry (DPV) were examined. It was found that LIN provides one oxidation peak using all of the tested working electrodes and the highest current response was recorded in the acidic media. Thus, Britton-Robinson (B-R) buffer of pH 2 was used as a supporting electrolyte. Parameters of DPV were optimized and the low limits of detection (LOD) were reached 1.41×10−7 M for commercial boron-doped diamond electrode and 8.81×10−9 M, respectively, which represents the lowest LOD obtained for lab-made boron-doped diamond electrodes.
Keywords:
Boron doped diamond electrode; sensors; voltammetry
Available at various institutes of the ASCR
Lab-made Sensors Based on Boron-doped Diamond for Determination of Herbicide Linuron
Voltammetric behaviour of substituted urea herbicide linuron (LIN) was investigated using two types of boron-doped diamond electrodes (BDDE): commercial BDDE and lab-made sensors based on boron-doped ...
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 ...
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