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Design, fabrication and testing of graphene biosensors
Tripský, Andrej ; Gablech, Imrich (referee) ; Bartošík, Miroslav (advisor)
Pokrok ve vývoji nanotechnologií nám poskytuje dobrou příležitost k vývoji nových špičkových zařízení. Tato práce si klade za cíl vyrobit, popsat a změřit grafenové pH senzory na dvou různých substrátech - polymeru parylenu C a SiO2. Tento pH senzor je prvním krokem ve vývoji nositelné náplasti monitorující stav kůže a možné infekce. Grafen je 2D materiál na bázi uhlíku se zajímavými vlastnosti a nadějnými aplikacemi. Úspěšně jsme provedli dva různé experimenty sloužící k charakterizaci grafenových senzorů a jejich odezvu na různé hodnoty pH. V prvním experimentu jsme použili horní elektrolytické hradlo k určení bodu neutrality (Diracův bod). Druhý experiment popsal změnu rezistence grafenu jako funkce pH. Dále jsme také funkcionalizovali grafen polyanilinem, abychom zlepšili jeho vlastnosti. Prokázali jsme citlivost grafenových senzorů na pH pro oba substráty a objevili jsme několik výzev jako potřebu kontroly iontové síly, experimentů samotných a destrukce grafenu.
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Microviscosity probes in study of aggregation in a biopolymer-surfactant system.
Vašíčková, Kamila ; Vala, Martin (referee) ; Mravec, Filip (advisor)
The effect of cationic surfactant concentration and ionic strength on anisotropy of fluorescence of probes diphenylhexatrien and fluorescein has been investigated in the system of cationic surfactant and in the system of cationic surfactant and hyaluronan. The investigation has been done by fluorescence emission spectroscopy. Obtained anisotropy gives information about microviscosity of investigated systems. Subsequently the system of cationic surfactant and hyaluronan has been investigated by 9-(2-carboxy-2cyanovinyl)julolidine, 4-(dicyanovinyl)julolidine and 1,3-bispyrenylpropane probes. The information about the microviscosity of the system gives the integral under the emission curve of 9-(2-carboxy2-cyanovinyl)julolidine and 4-(dicyanovinyl)julolidine and the ratio between excimer and monomer of 1,3-bispyrenylpropane. It has been discovered that the ionic strength influences the anisotropy of diphenylhexatrien and fluorescein only in the fist addition of salt (concentration 0,025 mol dm-3) and that addition of hyaluronan influences the anisotropy of diphenylhexatrien and fluorescein only in samples without addition of salt. Results of measurment with 9-(2-carboxy2-cyanovinyl)julolidine and 4(dicyanovinyl)julolidine describe the formation of aggregates of catinoc surfactant with hyaluronan and characterize these aggregates from the point of microviscosity.
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Fluorescence study of hydrophilic domains of associating colloids
Londinová, Monika ; Knotková,, Kateřina (referee) ; Pekař, Miloslav (advisor)
The properties of the hyaluronan were investigated by using different fluorescence probes, because hyaluronan is a hopeful carrier of an active matter in medicine and cosmetics. Selected fluorescence probes were: cationic acridine orange, Nile Blue A, methylene blue, amphiphilic 4-Di-2-ASP and anionic fluorescein. Except from fluorescence and absorption spectra of the probes were observed electrostatic and hydrophobic interactions as well. The probes in solvents with different polarity (MeOH, EtOH, DMSO) showed the bathochromic shift in the emission maximum and quenching of the fluorescence with the increasing polarity of the solvents. The influence of the ionic strength on fluorescence properties of the probe acridine orange and 4-Di-2-ASP was investigated in aqueous solutions of chlorides. The formation of acridine orange dimer is inhibited with increasing ionic strength. CaCl2 increased the ionic strength the most, then prevented repulsion of carboxylate groups, so it means the expansion of hyaluronan cluster into the solution. However, the emission of the probe 4-Di-2-ASP was quenched with the addition of CaCl2 the most. The first additions of COO– groups cause the formation of dimers of AO shown as decreasing in extinction coefficient and fluorescence intensity. Next addition of the hyaluronan caused a depolymerization of formed dimers and the increase of the emission intensity. The repolymerization caused the decrease and then again the increase. In case of 4-Di-2-ASP was the pattern of the fluorescence (the intensity and the position of the emission) firstly the same, but at the concentration of 1 g dm-3 the emission intensity increased. The probes MB and F were used for spectroscopic studies of the interaction between methylene blue-fluorescein complex and anionic and cationic surfactants. The absorbance of separate MB and F changed only with the addition of surfactants with the opposite electric charge. Absorbance of the mixture MB-F changed with the addition of the CTAC surfactant, while the addition of SDS into the mixture caused only the change of MB absorption spectra.
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Dynamic light scattering and electroanalytical investigation of hyaluronan-amino acids systems
Muchová, Johana ; Kalina, Michal (referee) ; Chytil, Martin (advisor)
The bachelor thesis deals with interactions between low-molecular and high-molecular weight hyaluronic acid (HA) and protonized amphiphilic amino acids Lysine and Arginine. The interactions were observed in the area of low aminoacids concentrations with in the range 0–15 mmoldm-3. The interactions occur between the carboxyl groups of HA and the amino group of the protonated amino acids. Proving these interactions would allow us to physically modify HA and further more, use such a system as a carrier of pharmaceuticals. The resistence towards the ionic strength at the concentration of 0,015 and 0,15 moldm-3 NaCl was investigated. Previous results show that the system with unprotonated amino acids at low concetrations of electrolyte in the solution is rather disturbing. Therefore, the interactions were reinforced by the aminoacids protonation using HCl. The amino acids were protonated not only completely, but also partly because of negative influence of chloride anions. To study the interactions pH-metry, conductance and Dynamic Light Scattering were used.
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A novel way of preparing hydrogels
Kratochvílová, Olga ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
This work is focused on testing the effect of ionic strength on the preparation of hydrogels prepared by phase separation hylauronanu polyelectrolyte solution (Hya) with cationic surfactant cetyltrimethylammonium bromide (CTAB) called „dry way“. In this case, there is a mixing of the polymer and the surfactant in the dry form and then added to the dispersion medium. With observation and rheology, the effects of the proportion of the components for the formation of the hydrogel. It was found that the higher the ionic strength causes the hydrogel has a lower viscosity and a more fluid. Tthis fact was confirmed from the results of rheological measurements. The gel with the ionic strength of 1 M is less viscous to gel the ionic strength of 0,5 M. Next, the purity of the hydrogel was observed, and it was found that hydrogels with the ionic strength of 0,15 M are clear without the use of centrifugation. In case of getting gel of the specific ionic forces of 0,15 M and 0,3 M formed by addition of multivalent cations/anions from observations we can say that the ionic strength in the case of the method of preparation of gels does not matter.
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Influence of ionic strength on the properties of ionic amphiphilic pairs
Filipová, Lenka ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
The Bachelor thesis studies catanionic vesicle systems consisting of ion pair amphiphile (IPA) and their properties in the presence of ionic strength. Ion pair amphiphile was prepared from single-chained surfactants: cationic surfactant HTMAB (hexadecyltrimethylammonium bromide) and anionic surfactant SDS (sodium lauryl sulfate). Cationic double-chained surfactant DDAC (dimethyldioctadecylammonium chloride) was added in order to stabilize the vesicle system and make it positively charged. Cholesterol was also added to further stabilize the vesicle system. The system is considered to be relatively stable when consisting of 90 % IPA and 10 % DDAC with 43 mol.% cholesterol in a membrane. The stability of the system can be disrupted by external factors such as ionic strength. The Ionic strength was induced by NaCl solutions of varying concentrations (0.0, 0.5, 1.0, 2.0, 50.0, 100.0, 150.0 and 300.0 mM). The change of properties of a vesicle system, which was induced by ionic strength, was analyzed by electrophoretic and dynamic light scattering, fluorescence anisotropy, and generalized polarization. –potential was obtained by electrophoretic light scattering analysis which determines the stability of the system. Dynamic light scattering measurement resulted in the determination of the size of vesicles. The fluidity of vesicles’ membranes was examined by fluorescence anisotropy with DPH (1,6-diphenyl-1,3,5-hexatriene) as a probe. The hydration shell of vesicles was observed by generalized polarization with Laurdan (2-(dimethylamino)-6-dodecanoylnaphthalene) as a probe. As a result, it was found out that low ionic strength (0.5 to 2.0 mM) causes a decrease in the size of vesicles and high ionic strength (50.0 to 300.0 mM) causes vesicles to grow in size. –potential showed a consistent trend for the whole concentration series – its value rapidly decreasing with increasing ionic strength. The samples with the concentrations of salt 50.0 to 300.0 mM were considered unstable according to the –potential data. Fluorescence anisotropy decreases with increasing temperature and increasing ionic strength. The value of generalized polarization decreases with increasing temperature; hence there is more solvation of a vesicle membrane. The highest value of generalized polarization was measured when the concentration of sodium chloride was relatively high (from 50.0 to 300.0 mM), as a result of which the membrane was less hydrated and therefore, more organized.
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Effect of changing ionic strength on the properties of catanionic vesicles from HTMA-DS
Filipová, Lenka ; Klučáková, Martina (referee) ; Mravec, Filip (advisor)
This diploma thesis is focused on evaluating the influence of ionic strength on catanionic vesicules made of ion pair amphiphile (IPA) in the form of HTMA-DS (hexadecyltrimethylammonium-dodecyl sulphate). Catanionic vesicles were stabilized by the addition of cationic surfactant dioctadecyldimethylammonium chloride (DODAC) and cholesterol. The ionic strength was attained by adding CaCl2 and Na2SO4 salts in the concentrations 0–300 mM. The changes influenced by ionic strength were studied by dynamic and electrophoretic light scattering (DLS and ELS), fluorescence anisotropy, generalized polarization (GP), pH measurement, and visual observation. During this experiment, the temperature was set both constant and altering in time. The measurement was performed shortly after adding salts to the catanionic vesicles and in-time measurement was performed as well. This thesis follows a bachelor thesis, where the influence of NaCl on the same type of catanionic vesicles in the same range of ionic strength was studied. The CaCl2 and Na2SO4 influences were then compared to the NaCl according to Hofmeister series. By the DLS and ELS method it was found that the size of vesicles with added CaCl2 and Na2SO4 was decreasing at first and then increasing whereas the -potential was exponentially decreasing with increasing ionic strength. The vesicle size, when the ionic strength was applied, was increasing in time while -potential was almost constant in time. The addition of both salts caused slight dehydration of the external part of the membrane which was examined by the fluorescent probe Laurdan (6-dodecanoyl-2-dimethylamino-naphthalene) and generalized polarization. By fluorescence anisotropy with the probe DPH (1,6-diphenyl-1,3,5-hexatriene), it was detected that both salts caused an increase of the fluidity of an inner part of a membrane. By both of the fluorescent techniques, it was confirmed that the increase in temperature caused a phase transition of the membrane from the solid ordered through the liquid ordered phase to the liquid disordered phase. The pH values also did not show any change with the addition of salts. When comparing the salts’ influence (CaCl2 and Na2SO4 versus NaCl) on catanionic vesicles it was found that in most cases NaCl influenced the observed properties the most. The addition of NaCl caused the largest increase in vesicle size, highest -potential values, initial dehydration of the external part of the membrane, and increased fluidity of the inner part of the membrane at I > 15 mM. These results are in agreement with the Hofmeister series. Based on the visual observation, the samples with ionic strength of more than 150 mM for CaCl2 and 75 mM for Na2SO4 were said to be unstable. This fact is in agreement with the result of ELS. The rest of the samples did not show any visual changes in time (28 days). Additionally, the influence of PBS buffer on catanionic vesicles at the same ionic strength values was studied. PBS buffer simulates the ionic environment of living organisms. Its' influence was characterized by the same methods under the same conditions as mentioned above. The effect of PBS on catanionic vesicles displayed almost the same behaviour in the observed properties. During this experiment, it was also found that the PBS influence on the studied properties was more significant than the influence of CaCl2, Na2SO4, and NaCl salts. Influence of PBS was most similar to the effect of NaCl on catanionic vesicles.
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Determination of stability constants of charged cyclodextrine complexes by capillary electrophoresis
Beneš, Martin ; Zusková, Iva (advisor) ; Dubský, Pavel (referee)
Martin Beneš Determination of stability constants of charged cyclodextrin comlexes by capillary electrophoresis Abstract Stability constant characterizes binding interaction between an analyte and complexation agent. These interactions play very important role in separation processes of, in other way undistinguishable, compounds, e.g. enantiomers. The most widely used complexation agents are cyclodextrins. Affinity capillary electrophoresis (ACE) belongs to methods suitable for the determination of stability constants. The stability constant is determined from the dependence of the effective mobility of analyte on the increasing concentration of complexation agent in background electrolyte (BGE). If charged CDs are used, the attention must be paid not only to viscosity of the BGE and to the influence of Joule heating on the temperature in the capillary but also to the increasing ionic strength. The thermodynamic stability constants of R,R- and S,S-hydrobenzoin and R- and S-(3-brom- 2-methyl-1-propanol) with cationic modified β-cyclodextrin: 6-monodeoxy-6-mono(3- hydroxy)propylamino-β-cyclodextrin hydrochlorid (PABCD) were determined by affinity capillary electrophoresis. The average temperature (25řC) of the BGE in the capillary was kept constant. This was achieved by decreasing of the cassette temperature...
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Characterisation and elimination of compounds difficult to remove during water treatment
Čermáková, Lenka
The Ph.D. thesis deals with the characterization of algal organic matter (AOM), which is difficult to remove in water treatment, and on the basis of AOM character, various methods for its elimination, e.g. coagulation, oxidation with subsequent coagulation and adsorption onto activated carbon are assesed. Special emphasis is placed on identifying the optimal conditions of the processes and on describing the mechanisms and interactions involved. In terms of anthropogenic micropollutants, the thesis deals with the highly topical issue of the occurrence of microplastics in water. It was found that the removal efficiency of the individual AOM components varies substantially depending on the elimination method used. The identified optimum conditions of individual methods and especially the mechanisms that apply to the removal of target substances varied widely. The non-proteinaceous fraction of AOM was removed with very low efficiency (max. 25%) by conventional coagulation even under optimized conditions (pH 6.6- 7.5 for aluminium sulfate as the coagulating agent and pH 7.5-9.0 for polyaluminium chloride) and it was given by the high content of low molecular weight (LMW) substances that are difficult to coagulate. The dominant coagulation mechanism was adsorption onto aluminium hydroxide precipitates....
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Influence of ionic strength on the properties of ionic amphiphilic pairs
Filipová, Lenka ; Smilek, Jiří (referee) ; Mravec, Filip (advisor)
The Bachelor thesis studies catanionic vesicle systems consisting of ion pair amphiphile (IPA) and their properties in the presence of ionic strength. Ion pair amphiphile was prepared from single-chained surfactants: cationic surfactant HTMAB (hexadecyltrimethylammonium bromide) and anionic surfactant SDS (sodium lauryl sulfate). Cationic double-chained surfactant DDAC (dimethyldioctadecylammonium chloride) was added in order to stabilize the vesicle system and make it positively charged. Cholesterol was also added to further stabilize the vesicle system. The system is considered to be relatively stable when consisting of 90 % IPA and 10 % DDAC with 43 mol.% cholesterol in a membrane. The stability of the system can be disrupted by external factors such as ionic strength. The Ionic strength was induced by NaCl solutions of varying concentrations (0.0, 0.5, 1.0, 2.0, 50.0, 100.0, 150.0 and 300.0 mM). The change of properties of a vesicle system, which was induced by ionic strength, was analyzed by electrophoretic and dynamic light scattering, fluorescence anisotropy, and generalized polarization. –potential was obtained by electrophoretic light scattering analysis which determines the stability of the system. Dynamic light scattering measurement resulted in the determination of the size of vesicles. The fluidity of vesicles’ membranes was examined by fluorescence anisotropy with DPH (1,6-diphenyl-1,3,5-hexatriene) as a probe. The hydration shell of vesicles was observed by generalized polarization with Laurdan (2-(dimethylamino)-6-dodecanoylnaphthalene) as a probe. As a result, it was found out that low ionic strength (0.5 to 2.0 mM) causes a decrease in the size of vesicles and high ionic strength (50.0 to 300.0 mM) causes vesicles to grow in size. –potential showed a consistent trend for the whole concentration series – its value rapidly decreasing with increasing ionic strength. The samples with the concentrations of salt 50.0 to 300.0 mM were considered unstable according to the –potential data. Fluorescence anisotropy decreases with increasing temperature and increasing ionic strength. The value of generalized polarization decreases with increasing temperature; hence there is more solvation of a vesicle membrane. The highest value of generalized polarization was measured when the concentration of sodium chloride was relatively high (from 50.0 to 300.0 mM), as a result of which the membrane was less hydrated and therefore, more organized.
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