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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Functional interfaces / polymer brushes and their response to temperature and hydrostatic pressure

Reinhardt, Matthias 28 March 2014 (has links)
Verankerte Polymere können die Funktionalität einer Oberfläche beeinflussen. Der Schwerpunkt dieser Arbeit liegt auf der Untersuchung von Polymerbürsten aus Polyacrylsäure (PAA) und Poly(N,N-dimethylaminoethyl methacrylat) (PDMAEMA). Auf Oberflächen, die mit PAA Bürsten beschichtet sind, können Proteine im nativen Zustand immobilisiert werden. Für PDMAEMA ist eine Reaktion auf externe Reize bekannt. So kann dessen untere kritische Lösungstemperatur (LCST) zur Einstellung der Hydrophobizität von Oberflächen verwendet werden. Erstmalig im Rahmen dieser Arbeit wurde untersucht, wie sich hydrostatischer Druck von bis zu 1000 bar auf die Funktionalität der verwendeten Polymerbürsten auswirkt. Aus Diblock-Kopolymeren wurden Langmuir-Filme unterschiedlicher Ankerdichte mit der Langmuir-Schäfer Technik auf feste Substrate übertragen. Die Funktionalität der PAA Bürsten wurde vor und nach der Adsorption von Rinderserumalbumin (BSA) in gepufferter D2O-Lösung mit Hilfe der Neutronenreflektometrie (NR) bei 1 bar und 900 bar an der fest-flüssig Grenzfläche untersucht. Es wurden Volumenfraktionsprofile der PAA Bürste und adsorbierten BSA extrahiert, woraus sich eine lineare Abhängigkeit zwischen Ankerdichte und Menge an adsorbiertem Protein feststellen ließ. Erhöhung des hydrostatischen Druckes auf 900 bar veränderte weder die PAA Volumenprofile noch die Immobilisierung von BSA. Die PDMAEMA Bürsten wurden mittels NR bei Temperaturen von 20-60 °C und Drücken von 1-1000 bar untersucht. Zur Analyse der Daten wurde ein neuartiges Dichteprofil-Modell verwendet. Temperaturerhöhung führt zur stetigen Abnahme der Bürstendicke. Dies lässt sich durch den LCST induzierten Phasenübergang der Polymere vom hydrophilen in einen hydrophoben Zustand erklären. Es wurde gefunden, dass eine Erhöhung des hydrostatischen Druckes diesem Prozess entgegenwirkt. Strukturänderungen der Polymerbürsten bei Erhöhung der Temperatur um 10 K ließen sich durch Erhöhung des Druckes um 1000 bar rückgängig machen. / The functionality of an interface can be modified by polymer brushes. The focus of this work is on brushes of either polyacrylic acid (PAA) or poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). PAA brushes provide a soft interface that prevents the denaturation of adsorbed proteins. PDMAEMA is known to respond to external stimuli. The lower critical solution temperature (LCST) of PDMAEMA can be used to tune the hydrophobicity of the interface with temperature. For the first time, the effect of elevated hydrostatic pressure, up to 1000 bar, on the functionality of these systems is investigated. Planar PAA and PDMAEMA brushes are prepared from precursor diblock copolymer Langmuir layers with varied grafting density utilizing the Langmuir-Schäfer transfer technique. For solvent-swollen PAA brushes, neutron reflectivity (NR) measurements are conducted at the solid-liquid interface after incubation in buffered D2O and after the adsorption of bovine serum albumin (BSA) from the aqueous liquid phase at 1 bar and 900 bar. Detailed volume fraction profiles of the PAA brush and adsorbed BSA proteins are extracted. The amount of adsorbed BSA is found to scale linearly with grafting density. An elevated hydrostatic pressure of 900 bar is found to have no impact on the structure of the PAA brush and its capability to bind BSA proteins. The PDMAEMA brushes are investigated by NR at the solid-liquid interface in a temperature range of 20 to 60 °C for hydrostatic pressures from 1 to 1000 bar. A novel theoretical model of the brush density profile is used to fit the experimental NR data. Increasing the temperature causes a continuous decrease of the polymer brush thickness due to a hydrophobic coil to globule transition of the polymer chains when crossing the LCST. Hydrostatic pressure is found to act antagonistic to temperature. The hydrophobic collapse of the PDMAEMA brush caused by a temperature increase of 10 K is counterbalanced by a pressure increase of 1000 bar.
62

Mailehen - Erlebnis des "Überlebten" / Ein Brauch als Medium / Mailehen - Experiences of the "survived" / Custom viewed as a medium

Wey, Hans-Willi 13 February 2001 (has links)
No description available.
63

Role of deposition temperature and concentration on the self-assembly and reaction of organic molecules at the solution-graphite interface

Nguyen, Doan Chau Yen 25 April 2017 (has links) (PDF)
Das Hauptthema dieser Dissertation ist die Untersuchung der Selbstorganisation organischer Moleküle an der Flüssig-Fest-Grenzfläche (LSI). Besondere Betonung liegt auf der Kontrolle der Selbstassemblierung durch geeignete Parameter: die Substrattemperatur während der Abscheidung, die Konzentration der gelösten Moleküle, und die chemische Natur der gelösten Stoffe und Lösungsmittel. Die Untersuchungen wurden unter Verwendung der Rastertunnelmikroskopie (STM) durchgeführt. Der erste Schwerpunkt dieser Arbeit ist die systematische Untersuchung der Auswirkung erhöhter Substrattemperatur während der Abscheidung aus der Lösung auf die Selbstorganisation komplexer molekularer Architekturen an der LSI. Diese Untersuchungen wurden mit dem planaren Molekül Trimesinsäure (TMA), sowie dem nicht-planaren Molekül Benzen-1,3,5-triphosphonsäure (BTP) durchgeführt. Es wird gezeigt, dass der Polymorphismus der Adsorbatstrukturen von TMA und BTP durch die Substrattemperatur während der Abscheidung der Moleküle aus der Lösung für verschiedene Lösungsmitteln unterschiedlicher Polarität, wie Phenyloctan, Octansäure und Undecanol, kontrolliert werden kann. Durch die Erhöhung der Temperatur des vorgeheiztem Graphitsubstrates kann die spezifische 2D supramolekulare Struktur and die entsprechende Packungsdichte der Moleküle in der Adsorbatschicht für jedes der untersuchten Lösungsmittel präzise eingestellt werden. Weiterhin wird der Einfluss der Konzentration auf die resultierende Anordnung der TMA Moleküle an der LSI durch ein weiteres Experiment abgeschätzt, bei welchem Rühren (von 0 h bis 40 h) der Lösungen mit verschiedenen Lösungsmitteln eingesetzt wurde. Diese Ergebnisse zeigen, dass die verschiedenen Präparationsmethoden (Erhöhung der Abscheidetemperatur oder Rühren) zu derselben Tendenz der Änderung der geordneten Strukturen sowie der Packungsdichte führt, weswegen man schlussfolgern kann, dass die Erhöhung der Konzentration an der LSI bei erhöhter Abscheidetemperatur ebenso der Hauptgrund für die beobachteten Änderungen ist. Der zweite Schwerpunkt dieser Dissertation ist die Untersuchung von chemischen Reaktionen der selbstassemblierenden Moleküle. Eine Veresterungsreaktion von TMA mit Undecanol wurde gefunden. Weiterhin wurde, als ein erster Schritt zur Untersuchung der Zwillingspolymerisation, die Oligomerisation des Zwillingsmonomers 2,2’-spirobi [4H-1,3,2-benzo-dioxasiline] (SBS) mit STM an der Grenzfläche zwischen der SBS-Undecanol-Lösung und einer Graphitoberfläche untersucht. Erstens wurde durch Ultraschallbehandlung der SBS Lösung in Undecanol für verschieden lange Zeiten die Oligomerisation der SBS Monomere ohne einen Katalysator an der LSI beobachtet. Zweitens konnte die Oligomerisation auch durch Erhöhung der Substrattemperatur während der Abscheidung der Moleküle aus der Lösung initiiert werden. Durch die schrittweise Erhöhung der Temperatur des vorgeheizten Substrates konnten mehrere, verschiedene, periodische Anordnungen von Phenol‒Dimeren, ‒Trimeren, und –Pentameren u.s.w. gefunden werden. Weiterhin wird die Auswirkung der Abscheidetemperatur auf die Selbstorganisation an der LSI nur der Lösungsmittelmoleküle aus dem reinen Lösungsmittel beschrieben. Dies ist wichtig, da die Undecanol‒Moleküle stets mit den gelösten, in dieser Arbeit verwendeten Stoffen (TMA, BTP, SBS) koadsorbieren und lineare Muster bilden. / The main aim of this thesis is to study the self-assembly of organic molecules at the liquid-solid interface (LSI). Special emphasis is given to controlling the process of self-assembly via suitable parameters such as: the substrate temperature during the initial deposition, the concentration of dissolved molecules, or the chemical nature of solutes and solvents. The investigations are performed using scanning tunneling microscopy (STM). The first focus of this work is the systematic investigation of the effect of the substrate temperature during the deposition out of the solution on the self-assembly of complex molecular architectures at the LSI. These investigations have been done with the planar molecule trimesic acid (TMA), and the non-planar molecule benzene 1,3,5-triphosphonic acid (BTP). We show that the polymorphism of the adsorbate structures of TMA (also with BTP) can be controlled by the substrate temperature during the deposition of the molecules out of the solution for various solvents of different polarity such as phenyloctane, octanoic acid, and undecanol. By increasing the temperature of the pre-heated graphite substrate, the specific 2D supramolecular structure and the corresponding packing density in the adsorbate layer can be precisely tuned for each kind of the solvents studied. Furthermore, the influence of the concentration on the resulting self-assembly of TMA molecules at the LSI is estimated by another experiment using stirring (from 0 h to 40 h) of the solutions of different kinds of solvents. These results demonstrate that choosing different preparation methods (increasing deposition temperatures or stirring) lead to the same tendency in the change of the self-assembled structures as well as the tuning of the packing density from which it can also be concluded that the increase of the concentration at increased deposition temperatures is also the main reason for the observed changes. The second focus of this work is the investigation of chemical reactions of self-assembling molecules. The esterification of TMA with undecanol was observed. Moreover as a first step to study twin polymerization, the oligomerization of the twin monomer 2,2’-spirobi [4H-1,3,2-benzo-dioxasiline] (SBS) was investigated by STM at the SBS-undecanol solution/graphite interface. Firstly, by ultrasonicating the solution of SBS in undecanol for different times the oligomerization of SBS monomer without any catalyst has been observed at the LSI. Secondly, the oligomerization of SBS monomer can also be initiated by the substrate temperature during the deposition of the molecules out of the solution. By stepwise increasing the temperature of the pre-heated substrate, various periodic assemblies of phenolic dimer, trimer, pentamer resin, and so on were observed. Furthermore, the effect of deposition temperature on the self-assembly of solely solvent molecules from the pure liquid at the LSI is described, which is important because the undecanol solvent molecules are always co-adsorbed with the solutes used in this work (TMA, BTP, SBS) to form linear patterns.
64

Role of deposition temperature and concentration on the self-assembly and reaction of organic molecules at the solution-graphite interface

Nguyen, Doan Chau Yen 17 January 2017 (has links)
Das Hauptthema dieser Dissertation ist die Untersuchung der Selbstorganisation organischer Moleküle an der Flüssig-Fest-Grenzfläche (LSI). Besondere Betonung liegt auf der Kontrolle der Selbstassemblierung durch geeignete Parameter: die Substrattemperatur während der Abscheidung, die Konzentration der gelösten Moleküle, und die chemische Natur der gelösten Stoffe und Lösungsmittel. Die Untersuchungen wurden unter Verwendung der Rastertunnelmikroskopie (STM) durchgeführt. Der erste Schwerpunkt dieser Arbeit ist die systematische Untersuchung der Auswirkung erhöhter Substrattemperatur während der Abscheidung aus der Lösung auf die Selbstorganisation komplexer molekularer Architekturen an der LSI. Diese Untersuchungen wurden mit dem planaren Molekül Trimesinsäure (TMA), sowie dem nicht-planaren Molekül Benzen-1,3,5-triphosphonsäure (BTP) durchgeführt. Es wird gezeigt, dass der Polymorphismus der Adsorbatstrukturen von TMA und BTP durch die Substrattemperatur während der Abscheidung der Moleküle aus der Lösung für verschiedene Lösungsmitteln unterschiedlicher Polarität, wie Phenyloctan, Octansäure und Undecanol, kontrolliert werden kann. Durch die Erhöhung der Temperatur des vorgeheiztem Graphitsubstrates kann die spezifische 2D supramolekulare Struktur and die entsprechende Packungsdichte der Moleküle in der Adsorbatschicht für jedes der untersuchten Lösungsmittel präzise eingestellt werden. Weiterhin wird der Einfluss der Konzentration auf die resultierende Anordnung der TMA Moleküle an der LSI durch ein weiteres Experiment abgeschätzt, bei welchem Rühren (von 0 h bis 40 h) der Lösungen mit verschiedenen Lösungsmitteln eingesetzt wurde. Diese Ergebnisse zeigen, dass die verschiedenen Präparationsmethoden (Erhöhung der Abscheidetemperatur oder Rühren) zu derselben Tendenz der Änderung der geordneten Strukturen sowie der Packungsdichte führt, weswegen man schlussfolgern kann, dass die Erhöhung der Konzentration an der LSI bei erhöhter Abscheidetemperatur ebenso der Hauptgrund für die beobachteten Änderungen ist. Der zweite Schwerpunkt dieser Dissertation ist die Untersuchung von chemischen Reaktionen der selbstassemblierenden Moleküle. Eine Veresterungsreaktion von TMA mit Undecanol wurde gefunden. Weiterhin wurde, als ein erster Schritt zur Untersuchung der Zwillingspolymerisation, die Oligomerisation des Zwillingsmonomers 2,2’-spirobi [4H-1,3,2-benzo-dioxasiline] (SBS) mit STM an der Grenzfläche zwischen der SBS-Undecanol-Lösung und einer Graphitoberfläche untersucht. Erstens wurde durch Ultraschallbehandlung der SBS Lösung in Undecanol für verschieden lange Zeiten die Oligomerisation der SBS Monomere ohne einen Katalysator an der LSI beobachtet. Zweitens konnte die Oligomerisation auch durch Erhöhung der Substrattemperatur während der Abscheidung der Moleküle aus der Lösung initiiert werden. Durch die schrittweise Erhöhung der Temperatur des vorgeheizten Substrates konnten mehrere, verschiedene, periodische Anordnungen von Phenol‒Dimeren, ‒Trimeren, und –Pentameren u.s.w. gefunden werden. Weiterhin wird die Auswirkung der Abscheidetemperatur auf die Selbstorganisation an der LSI nur der Lösungsmittelmoleküle aus dem reinen Lösungsmittel beschrieben. Dies ist wichtig, da die Undecanol‒Moleküle stets mit den gelösten, in dieser Arbeit verwendeten Stoffen (TMA, BTP, SBS) koadsorbieren und lineare Muster bilden.:Chapter 1: Introduction Chapter 2: Basic principle 2.1 Principles of scanning tunneling microscopy (STM) 2.1.1 General working principle 2.1.2 Tunneling effect 2.1.3 Theory of STM 2.1.4 Contrast mechanism of molecular adsorbates 2.1.5 Modes of STM operation 2.2 STM at the liquid-solid interface (LSI) 2.3 Thermodynamics and kinetics 2.3.1 Equilibrium of the adsorption/desorption and initial agglomeration at the LSI 2.3.2 Kinetic and thermodynamic control over 2D molecular self-assembly 2.4 Experimental condition 2.4.1 Role of solvent 2.4.2 Role of concentration 2.4.3 Role of temperature References Chapter 3: Experimental section 3.1 Solutes 3.1.1 Trimesic acid (TMA) (1,3,5?C6H3(COOH)3) 3.1.2 Benzene 1.3.5-Triphosphonic acid (BTP) (1,3,5?C6H3(PO3H2)3) 3.1.3 Twin monomer 2,2’-spirobi[4H-1,3,2-benzo-dioxasiline] (SBS) 3.2 Solvents 3.3 Substrate: Highly oriented pyrolytic graphite (HOPG (0001)) 3.4 Preparation of the STM tips 3.5 Experimental methods for sample preparation 3.5.1 Preparation of the solution 3.5.2 Heating of the substrate 3.5.3 Ultrasonication 3.5.4 Stirring 3.6 Computational details References Chapter 4: Deposition temperature? and solvent-dependent 2D supramolecular assemblies of trimesic acid at the liquid-graphite interface revealed by STM Results and discussion 4.1 Hydrogen bonding motifs of trimesic acid molecules 4.2 TMA deposited from solution in octanoic acid 4.3 TMA deposited from solution in phenyloctane 4.4 TMA deposited from solution in undecanol 4.6 Discussion of the solute–solvent interactions 4.5 Effect of the deposition substrate temperature on the formation of ester at the LSI of TMA in undecanol Conclusion References Chapter 5: Role of concentration on the self-assembly of TMA at the LSI influenced by stirring time Results and discussion 5.1 TMA in octanoic acid 5.2 TMA in phenyloctane 5.3 TMA in undecanol Conclusion References Chapter 6: Role of deposition temperature on the self-assembly of the non-planar molecule benzene- 1,3,5- triphosphonic acid (BTP) at the LSI Results and discussion 6.1 BTP in undecanol at room temperature 6.2 BTP in undecanol at high substrate temperature during deposition Conclusion References Chapter 7: Role of deposition temperature on the self-assembly of pure undecanol solvent at the LSI Results and discussion 7.1 Adsorption geometry of undecanol on HOPG 7.2 Herringbone structures of undecanol 7.3 Parallel structure of undecanol at high substrate temperature during deposition Conclusion References Chapter 8: A first step to microscopically study twinpolymerization: self-assembly of twin monomer 2,2’-Spirobi[4H-1,3,2-benzo-dioxasiline] (SBS) at the LSI influenced by ultrasonication and deposition substrate temperature 8.1 Coadsorption of SBS and undecanol without ultrasonication and at room temperature 8.2 SBS deposited from solution in undecanol in dependence on the duration of ultrasonication 8.3 SBS deposited from solution in undecanol at varied deposition temperature of the substrate 8.4 Discussion and open questions Appendix References CHAPTER 9: SUMMARY AND OUTLOOK ERKLÄRUNG CURRICULUM VITAE ACKNOWLEDGEMENT / The main aim of this thesis is to study the self-assembly of organic molecules at the liquid-solid interface (LSI). Special emphasis is given to controlling the process of self-assembly via suitable parameters such as: the substrate temperature during the initial deposition, the concentration of dissolved molecules, or the chemical nature of solutes and solvents. The investigations are performed using scanning tunneling microscopy (STM). The first focus of this work is the systematic investigation of the effect of the substrate temperature during the deposition out of the solution on the self-assembly of complex molecular architectures at the LSI. These investigations have been done with the planar molecule trimesic acid (TMA), and the non-planar molecule benzene 1,3,5-triphosphonic acid (BTP). We show that the polymorphism of the adsorbate structures of TMA (also with BTP) can be controlled by the substrate temperature during the deposition of the molecules out of the solution for various solvents of different polarity such as phenyloctane, octanoic acid, and undecanol. By increasing the temperature of the pre-heated graphite substrate, the specific 2D supramolecular structure and the corresponding packing density in the adsorbate layer can be precisely tuned for each kind of the solvents studied. Furthermore, the influence of the concentration on the resulting self-assembly of TMA molecules at the LSI is estimated by another experiment using stirring (from 0 h to 40 h) of the solutions of different kinds of solvents. These results demonstrate that choosing different preparation methods (increasing deposition temperatures or stirring) lead to the same tendency in the change of the self-assembled structures as well as the tuning of the packing density from which it can also be concluded that the increase of the concentration at increased deposition temperatures is also the main reason for the observed changes. The second focus of this work is the investigation of chemical reactions of self-assembling molecules. The esterification of TMA with undecanol was observed. Moreover as a first step to study twin polymerization, the oligomerization of the twin monomer 2,2’-spirobi [4H-1,3,2-benzo-dioxasiline] (SBS) was investigated by STM at the SBS-undecanol solution/graphite interface. Firstly, by ultrasonicating the solution of SBS in undecanol for different times the oligomerization of SBS monomer without any catalyst has been observed at the LSI. Secondly, the oligomerization of SBS monomer can also be initiated by the substrate temperature during the deposition of the molecules out of the solution. By stepwise increasing the temperature of the pre-heated substrate, various periodic assemblies of phenolic dimer, trimer, pentamer resin, and so on were observed. Furthermore, the effect of deposition temperature on the self-assembly of solely solvent molecules from the pure liquid at the LSI is described, which is important because the undecanol solvent molecules are always co-adsorbed with the solutes used in this work (TMA, BTP, SBS) to form linear patterns.:Chapter 1: Introduction Chapter 2: Basic principle 2.1 Principles of scanning tunneling microscopy (STM) 2.1.1 General working principle 2.1.2 Tunneling effect 2.1.3 Theory of STM 2.1.4 Contrast mechanism of molecular adsorbates 2.1.5 Modes of STM operation 2.2 STM at the liquid-solid interface (LSI) 2.3 Thermodynamics and kinetics 2.3.1 Equilibrium of the adsorption/desorption and initial agglomeration at the LSI 2.3.2 Kinetic and thermodynamic control over 2D molecular self-assembly 2.4 Experimental condition 2.4.1 Role of solvent 2.4.2 Role of concentration 2.4.3 Role of temperature References Chapter 3: Experimental section 3.1 Solutes 3.1.1 Trimesic acid (TMA) (1,3,5?C6H3(COOH)3) 3.1.2 Benzene 1.3.5-Triphosphonic acid (BTP) (1,3,5?C6H3(PO3H2)3) 3.1.3 Twin monomer 2,2’-spirobi[4H-1,3,2-benzo-dioxasiline] (SBS) 3.2 Solvents 3.3 Substrate: Highly oriented pyrolytic graphite (HOPG (0001)) 3.4 Preparation of the STM tips 3.5 Experimental methods for sample preparation 3.5.1 Preparation of the solution 3.5.2 Heating of the substrate 3.5.3 Ultrasonication 3.5.4 Stirring 3.6 Computational details References Chapter 4: Deposition temperature? and solvent-dependent 2D supramolecular assemblies of trimesic acid at the liquid-graphite interface revealed by STM Results and discussion 4.1 Hydrogen bonding motifs of trimesic acid molecules 4.2 TMA deposited from solution in octanoic acid 4.3 TMA deposited from solution in phenyloctane 4.4 TMA deposited from solution in undecanol 4.6 Discussion of the solute–solvent interactions 4.5 Effect of the deposition substrate temperature on the formation of ester at the LSI of TMA in undecanol Conclusion References Chapter 5: Role of concentration on the self-assembly of TMA at the LSI influenced by stirring time Results and discussion 5.1 TMA in octanoic acid 5.2 TMA in phenyloctane 5.3 TMA in undecanol Conclusion References Chapter 6: Role of deposition temperature on the self-assembly of the non-planar molecule benzene- 1,3,5- triphosphonic acid (BTP) at the LSI Results and discussion 6.1 BTP in undecanol at room temperature 6.2 BTP in undecanol at high substrate temperature during deposition Conclusion References Chapter 7: Role of deposition temperature on the self-assembly of pure undecanol solvent at the LSI Results and discussion 7.1 Adsorption geometry of undecanol on HOPG 7.2 Herringbone structures of undecanol 7.3 Parallel structure of undecanol at high substrate temperature during deposition Conclusion References Chapter 8: A first step to microscopically study twinpolymerization: self-assembly of twin monomer 2,2’-Spirobi[4H-1,3,2-benzo-dioxasiline] (SBS) at the LSI influenced by ultrasonication and deposition substrate temperature 8.1 Coadsorption of SBS and undecanol without ultrasonication and at room temperature 8.2 SBS deposited from solution in undecanol in dependence on the duration of ultrasonication 8.3 SBS deposited from solution in undecanol at varied deposition temperature of the substrate 8.4 Discussion and open questions Appendix References CHAPTER 9: SUMMARY AND OUTLOOK ERKLÄRUNG CURRICULUM VITAE ACKNOWLEDGEMENT
65

Characterization of heterogeneous diffusion in confined soft matter

Täuber, Daniela 26 October 2011 (has links) (PDF)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
66

Characterization of heterogeneous diffusion in confined soft matter

Täuber, Daniela 20 October 2011 (has links)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
67

Kořeny moravské urbanistické struktury / Roots of Moravian Urban Structure

Mohelník, Ladislav Unknown Date (has links)
The thesis has been written on the basis of main architectural concepts and their application in real life within a historical context investigation. Main architectural concepts are represented in a harmony of architectural composition that deals with relations among form, structure and space in the unique art work. Genius loci play very important role in the architectural creation - it represents a special and extra-ordinary urban locality and its architectural value in the historical, geographical and cultural context. The origin of Ostravice village within the historical frame concept of Moravia domain is the topic of this thesis. Other historical documents gave information about Bruneswerde as the Brno Castle. That means Brno Castle had to be founded not in Brno (as it has been consid-ered for many years) but it was located in Beskydy at Ostravice. The sacred city – Civitas Dei had been located in Bruneswerde region in early ages as the centre of European culture, education and spiritual life. Civitas Dei – divine Jerusalem in the transcription of St. Augustine's book De civitate Dei – is not only glorification of God and religious fantasy. It is also one of significant clues for recognition of historical architecture. The depiction of unknown settlement from the book of unde-fined origin is a superb testimony about extinct architectural works. They are legible from cadastral maps. Brno Castle - residence of nobility and power served shelter to St. Vojtěch, St. Prokop, St. Václav and St. Ludmila as it is obvious for the mentioned picture. Three major temples, three com-position axes symbolized by three towers on coins are in analogical relation to Brno triangle of four saints - the Saint family of Brno temples. Powerful ambitions of Brno City principals and clergy are inscribed into the urban structure in the way of composition relations which are legible to them who devoted themselves to the mystery of harmony. The absence of historical continuity affects personal attitudes and also identity of the whole community. The architecture truly reflects the past state of polis and it is eloquent even after its death. The architectural composition relations influence the natural environment for long time, longer than the architectural work existence. The geometric order of Renaissance Brno existence has not been in attention of architects so far. The features were discovered in characteristic paintings by Albrecht Durer. They are evidently secret works of the genius. A meaningful collaborator and follower in the extensive project was also his friend Jan Čert from Brno and lately from Vienna. His noble genealogy played a significant role in history of Silesia and Moravia for centuries. It is tendency to consider him as Austrian or even German architect. It is because of the fact that the genealogy tree of his noble family had roots in Moravia. It is supposed that Durer with Jan Čert´s support created the extraordinarily monumental architectural and urban works in Brno. A remarkable consensus in the urban composition of two squares and transition of traditional urban structure of Ostravice Civitas Dei into the modern Brno is also confirmed due to the identification of noble creators and owners, who were at the foundation, transformation and extinction of elements of the Moravian urban structure.

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