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Characterization of Electrochemical Behaviour and Adsorption of Methyl Viologen on Boron Doped Diamond Electrodes Depending on Their Surface Pre-treatment
Fořtová, Lucie ; Fischer, Jan (advisor) ; Vyskočil, Vlastimil (referee)
In this study we focused on the electrochemical and adsorptive behaviour of methyl viologen on electrode of boron doped diamond (BDD) possessing different termination as result of electrochemical or mechanical pretreatment. Namely was performed anodic activation applying +2.4 V in 0.5 mol L-1 sulphuric acid and cathodic pretreatment in the same solution at -2.4 V to obtain predominantly H-terminated surface. While the O- terminated surface is relatively hydrophilic with low surface conductivity, the H-terminated surface is hydrophobic with certain surface conductivity, which results typically in faster heterogenous electron transfer (HET) kinetics. Fast HET kinetics was observed on polished surfaces, that were obtained by polishing with alumina suspension. Methyl viologen (MV), a widely used herbicide, was used as a model compound because its quasireversible redox transformations result in charge changes of the molecule which includes neutral (MV0 ) or positively charged (MV+ , MV2+ ) forms. Adsorption was connected with MV0 form. The pilot experiments were performed in aqueous media using cyclic voltammetry (CV). The results indicate that adsorption of MV occurs not only on H-terminated surface, but also on the polished and O-terminated surface. Adsorption of MV0 was observed on anodic peaks on...
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Surface-enhanced resonance Raman scattering of Zn(II) porphyrins in systems with aggregated and non-aggregated Ag nanoparticles
Spáčil, Dušan ; Vlčková, Blanka (advisor) ; Procházka, Marek (referee)
In this diploma thesis, SERRS(Surface - enhanced resonance Raman Scattering) and SERS (Surface - enhanced Raman Scattering), surface of plasmon extinction spectra and TEM images of systems with tetracationic zinc porphyrin ZnTMPyP and silver nanoparticles (Ag NPs) were studied and interpreted. The systems with isolated nanoparticles and the systems with compact aggregates were investigated. The systems with isolated nanoparticles were prepared by addition of ZnTMPyP to hydrosol of Ag NPs. NaCl was added to this system and so compact aggregates were prepared. SERRS and SERS spectra of ZnTMPyP were studied at excitation wavelengths λexc= 441.6 nm a 532 nm. Firstly, stationary systems and secondly dynamic development of hydrosol Ag NPs → Ag NPs/ ZnTMPyP → Ag NPs/ ZnTMPyP/ NaCl systems for 680 s was investigated. Time evolution of SERRS and SERS spectra were analyzed by factor analysis (FA) and time evolution of spectra extinction plasmon were measured. FA showed a strong increase of the signal of ZnTMPyP after the addition of NaCl, i.e. after conversion of isolated nanoparticles to compact aggregates. In these systems with high concentration of ZnTMPyP the increase of signal was succeeded by its decreased. With help of FA the limit of SERRS spectral detection (λexc= 441,6 nm) and limit of SERS spectral...
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The effect of methylviologen on secondary metabolites production in in vitro culture of Fagopyrum esculentum, variety Bambi
Vlachová, Veronika ; Tůmová, Lenka (advisor) ; Karlíčková, Jana (referee)
10 ABSTRACT The subject of this study was to evaluate the efect of abiotc elicitor on rutn producton in callus and suspension cultures of buckwheat. The cultvar of buckwheat used for this research was Fagopyrum esculentum Moench var. Bambi, cultvated in Murashige and Skoog nutrient medium with the additon of growth regulator 2,4-dichlorfenoxyacetc acid (2,4-D) in concentraton of 1 mg/l. The elicitor used in this study was a soluton of methylviologen, 1 ml of it was added to the cultures in three diferent concentratons: c1 = 100.0 mg/100 ml, c2 = 10.0 mg/100 ml and c3 = 1.0 mg/100 ml. The elicitor was afectng the cultures for 6, 12, 24, 48, 72 or 168 hours. Afer the defned period of tme, cultures were collected, dried out and stored for further analysis of rutn content. To control samples (without elicitor treatment) 1 ml of ethanol 96% was added and they were collected afer 6, 24, 72 or 168 hours. Releasing of rutn into the nutrient medium was also investgated. Rutn content in each sample of cultures and in each sample of nutrient medium was later determined by HPLC. Any signifcant increase in the producton of rutn was not observed in this study. The maximum amount of rutn detected was 0.1 mg/g DW, thus the lowest quantty detectable, and was found in suspension cultures in three cases, afer the additon of...
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The effect of methylviologen on secondary metabolites production in in vitro culture of Fagopyrum esculentum, variety Spačinski
Vaicová, Nicole ; Tůmová, Lenka (advisor) ; Spilková, Jiřina (referee)
Plants are an important source of secondary metabolites, which are a valuable natural substance used in many fields. One way to increase their production is by the elicitation method. In this paper the effect of abiotic elicitor methylviologene in three different concentrations was studied on the rutin production in callus and suspension culture of Fagopyrum esculentum Moench variety Spačinki. The cultivation was carried out on Murashige and Skoog nutrient medium with the addition of a 1 mg/l 2,4- dichlorophenoxyacetic acid as growth regulator. Samples were taken at regular time intervals after 6, 12, 24, 48, 72 and 168 hours of elicitation. The rutin content was analyzed by HPLC. The maximum rutin production (0.3 mg/g DW) was recorded in the callus culture after 48 hours of methylviologene treatment at a concentration of 2.1929.10-4 mol/l. No increase in rutin content after methylviologene elicitation was observed in the suspension culture. The study also included monitoring of the rutin release into nutrient medium, but this was not demonstrated.
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The effect of methylviologen on secondary metabolites production in in vitro culture of Fagopyrum esculentum, variety Pyra
Zajačíková, Pavla ; Tůmová, Lenka (advisor) ; Kašparová, Marie (referee)
Elicitation is one of the methods used for increasing the production of secondary metabolites in vitro cultures. The aim of this work is to evaluate the effect of abiotic elicitor methylviologen (paraquat) on the production of flavonoids in callus and suspension cultures of Fagopyrum esculentum Moench., variety Pyra. The cultures were cultivated in Murashige and Skoog nutrient medium with addition of 2,4-D in concentration of 1 mg/l as a growth regulator. Elicitor was added as a solution in three different concentrations (c1 = 2.1929 · 10-4 mol/l, c2 = 2.1929 · 10-3 mol/l and c3 = 2.1929 · 10-2 mol/l). The effect of elicitation on rutin production was monitored in six time intervals: 6, 12, 24, 48, 72 and 168 hours. The rutin content was determined by HPLC analysis. No rutin was produced in callus and suspension cultures without the presence of elicitor. Even after the elicitation, there was no statistically significant increase in the production of rutin. The maximum rutin content was detected in the suspension culture after 12 hours of elicitor treatment in c2 concentration, the content was 0.1 mg/g DW. The release of rutin into the nutrient medium was also not observed.
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The effect of methylviologen on secondary metabolites production in in vitro culture of Fagopyrum esculentum, variety Bambi
Vlachová, Veronika ; Tůmová, Lenka (advisor) ; Karlíčková, Jana (referee)
10 ABSTRACT The subject of this study was to evaluate the efect of abiotc elicitor on rutn producton in callus and suspension cultures of buckwheat. The cultvar of buckwheat used for this research was Fagopyrum esculentum Moench var. Bambi, cultvated in Murashige and Skoog nutrient medium with the additon of growth regulator 2,4-dichlorfenoxyacetc acid (2,4-D) in concentraton of 1 mg/l. The elicitor used in this study was a soluton of methylviologen, 1 ml of it was added to the cultures in three diferent concentratons: c1 = 100.0 mg/100 ml, c2 = 10.0 mg/100 ml and c3 = 1.0 mg/100 ml. The elicitor was afectng the cultures for 6, 12, 24, 48, 72 or 168 hours. Afer the defned period of tme, cultures were collected, dried out and stored for further analysis of rutn content. To control samples (without elicitor treatment) 1 ml of ethanol 96% was added and they were collected afer 6, 24, 72 or 168 hours. Releasing of rutn into the nutrient medium was also investgated. Rutn content in each sample of cultures and in each sample of nutrient medium was later determined by HPLC. Any signifcant increase in the producton of rutn was not observed in this study. The maximum amount of rutn detected was 0.1 mg/g DW, thus the lowest quantty detectable, and was found in suspension cultures in three cases, afer the additon of...
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Surface-enhanced resonance Raman scattering of Zn(II) porphyrins in systems with aggregated and non-aggregated Ag nanoparticles
Spáčil, Dušan ; Vlčková, Blanka (advisor) ; Procházka, Marek (referee)
In this diploma thesis, SERRS(Surface - enhanced resonance Raman Scattering) and SERS (Surface - enhanced Raman Scattering), surface of plasmon extinction spectra and TEM images of systems with tetracationic zinc porphyrin ZnTMPyP and silver nanoparticles (Ag NPs) were studied and interpreted. The systems with isolated nanoparticles and the systems with compact aggregates were investigated. The systems with isolated nanoparticles were prepared by addition of ZnTMPyP to hydrosol of Ag NPs. NaCl was added to this system and so compact aggregates were prepared. SERRS and SERS spectra of ZnTMPyP were studied at excitation wavelengths λexc= 441.6 nm a 532 nm. Firstly, stationary systems and secondly dynamic development of hydrosol Ag NPs → Ag NPs/ ZnTMPyP → Ag NPs/ ZnTMPyP/ NaCl systems for 680 s was investigated. Time evolution of SERRS and SERS spectra were analyzed by factor analysis (FA) and time evolution of spectra extinction plasmon were measured. FA showed a strong increase of the signal of ZnTMPyP after the addition of NaCl, i.e. after conversion of isolated nanoparticles to compact aggregates. In these systems with high concentration of ZnTMPyP the increase of signal was succeeded by its decreased. With help of FA the limit of SERRS spectral detection (λexc= 441,6 nm) and limit of SERS spectral...
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