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Influence of Si surface passivation on growth and ordering of nanostructures
Matvija, Peter ; Kocán, Pavel (advisor) ; Rezek, Bohuslav (referee) ; de la Torre, Bruno (referee)
Silicon is currently the most widely used semiconductor material with applications ranging from solar cells and sensors to electronic devices. Surface functionalization of silicon with molecular monolayers can be used to tune properties of the material toward a desired application. However, site-specific adsorption of molecules or molecular patterning on silicon surfaces is a difficult task due to the high reactivity of silicon. In this work, we use scanning tunneling microscopy, ab-initio calculations and kinetic Monte Carlo simulations to study adsorption of organic molecules on a bare and thallium-passivated Si(111) surface. We show that the polarity of molecules has a large impact on bonding of the molecules with the bare surface. We demonstrate that, in comparison with the bare surface, molecules or single-atom adsorbates deposited on the Tl-passivated surface have significantly higher mobility. The increased mobility induces formation of 2D gases on the surface and enables formation of self-assembled molecular structures. We propose a novel method to directly visualize the 2D surface gases and we show that a phase of surface gases containing molecule-bound dipoles can be controlled by a non-homogeneous electric field. 1
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Nanoparticles formed by complexes of copolymers with low-molar-mass compounds
Vojtová, Jana ; Štěpánek, Miroslav (advisor) ; Filippov, Sergej (referee) ; Hoffmann, Ingo (referee)
This thesis is focused on mixed systems of various copolymers (double hydrophilic block and gradient polyelectrolytes, hydrophobic graft copolymers) and low-molar-mass compounds (sodium dodecyl sulfate as a representative of a ionic surfactant or superparamagnetic iron oxides in the form of nanocrystals). The electrostatic and hydrophobic interactions in the studied systems in aqueous solutions leading to aggregation behavior and to the formation of co-assembled nanoparticles were investigated by combination of scattering and microscopy techniques, including light, X-ray and neutron scattering, electron microscopy and atomic force microscopy. Powered by TCPDF (www.tcpdf.org)
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The D-A and pi-pi interactions and their use in self-assembly
Rejchrtová, Blanka ; Starý, Ivo (advisor) ; Kotora, Martin (referee)
The D-A and π-π Interactions and Their Use in Self-Assembly Due to their well-defined shape, size and properties gold nanoparticles represent an advantageous platform for the study of non-covalent interactions between ligands anchored to their surface both in solution and in monolayers or thin films. The aim of this thesis was the synthesis of ligands for gold nanoparticles bearing an anchoring group at one end and a planar π-electron rich pyrene unit at the other. Six structurally variable ligands were prepared differing in the pyrene substitution pattern and the spacer between the aromatic part and the acetylated thiol function. Furthermore, a synthetic pathway leading to extended π-electron systems (both electron rich and electron poor) such as hexabenzocoronene derivatives and its fragments was explored. The key steps in the synthesis of these compounds are the cyclization reactions of alkynes leading to polycyclic intermediates and their ensuing cyclodehydrogenation (Scholl reaction). All of the prepared ligands and their intermediates were characterized by spectroscopic methods. The structure of the key hexakis(pentafluorosulfanyl-phenyl)benzene was confirmed by single crystal X-ray crystallography. The prepared ligands bearing a pyrene unit were deacetylated and anchored to the surface of...
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Self-Assembly in Mixture of Surfactants and Stimuli-Responsive Polymers with Complex Architecture
Bogomolova, Anna ; Filippov, Sergej (advisor) ; Štěpánek, Miroslav (referee) ; Hanyková, Lenka (referee)
Title: Self-assembly in mixture of surfactants and stimuli-responsive polymers with complex architecture Author: Anna Bogomolova Department: Physical and Macromolecular Chemistry Supervisor: PhD. Sergey K. Filippov, IMC AS CR, v.v.i. Supervisor's e-mail address: filippov@imc.cas.cz Abstract: The issue of construction of complex multi-block copolymers is currently one of the most researched areas. It became a logic consequence of the continuous development in polymer chemistry. Nowadays, a great interest is attracted to multi- responsive block copolymers. As a rule, they consist of hydrophilic, hydrophobic and responsive blocks. That responsive block can be either thermo-sensitive or pH-sensitive as well as sensitive to some other external stimuli. In the present work, we will try to cover topic of stimuli-responsive block copolymers and their interactions with different types of surfactants. Understanding of polymer/surfactant interactions can be a crucial step for future modeling of drug/polymer or protein(DNA)/surfactant interactions. There is a great interest in the investigation of polymer-surfactant interactions. However, while the homopolymer-surfactant interactions are characterized well enough, the same interactions for block copolymers are poorly described. The main development in the latter topic...
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Study of light-harvesting antennae based on bacteriochlorophyll aggregates
Alster, Jan ; Pšenčík, Jakub (advisor) ; Fidler, Vlastimil (referee) ; Balaban, Teodor Silviu (referee)
Title: Study of light-harvesting antennae based on bacteriolorophyll aggregates Author: Jan Alster Department: Department of Chemical Physics and Optics Supervisor of the doctoral thesis: doc. RNDr. Jakub Pšenčík, Ph.D. Abstract: Artificial photosynthesis is a potential future source of renewable energy. e light-to-emical energy conversion process starts with capturing light. Chlorosomes of green phototropic bacteria are probably the most efficient light-harvesting antenna found in the Nature. Moreover, their unique structure based on a self-organised ag- gregate of pigment molecules makes them relatively easy to mimic in vitro. is work explores formation and properties of self-assembled aggregates of bacteriolorophyll molecules in aqueous solvents by means of steady state and time resolved optical spec- troscopy with time resolution in the microsecond to femtosecond range. Various ag- gregation inducing agents have been tested. Isoprenoid quinones introduce a redox- dependent excitation energy quening meanism into the bacteriolorophyll aggre- gates. Carotenoids enhance the light-harvesting properties of the aggregates by cap- turing light in the spectral region where bacteriolorophyll does not and transferring the excitation energy to bacteriolorophyll. e results indicate that self-assembled...
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The study of self-assembly governed by the formation of donor-acceptor complexes
Warzecha, Tomáš ; Starý, Ivo (advisor) ; Betík, Robert (referee)
The study of self-assembly governed by the formation of donor-acceptor complexes This work deals with the preparation of 2-[(3-carboxyphenyl)ethynyl]benzoic acid, which a represents simplified model of monodisperse (p-phenylen)ethynylene oligomers, functionalized by carboxylic groups. Such a dicarboxylic acid was synthesized via Sonogashira coupling and then taken over to a series of diesters with corresponding alcohols. The theoretical part contains concise introduction to nanoscience, self assembly and donor - acceptor (D-A) interactions. The most frequently used synthetic reactions - Sonogashira coupling and Steglich esterification are described. The experimental part deals with the preparation of dimeric dicarboxylic acid and corresponding esters with alcohols containing electronacceptor functional groups. The synthetized compounds were characterized by spectroscopic methods (NMR, MS, IR, UV/VIS) and elemental composition established by HR MS. Melting points were measured for crystalline compounds.
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Computer simulations of conformational behavior of block copolymers in selective solvents
Šindelka, Karel ; Limpouchová, Zuzana (advisor) ; Kuldová, Jitka (referee)
The presented bachelor thesis deals with the study of the conformational be- haviour of diblock copolymers in the selective solvent. The polymer solution was modelled using a coarse-grained model and is simulated using dissipative particle dynamics (DPD). An original C-code for DPD simulations together with a new software package for processing of simulation data was developed. Functionality of the code and software were tested for two systems. The first system corre- sponded to a linear homopolymer in a solvent and the scaling laws for homopoly- mer in dilute solution were reproduced. The second system represented diblock copolymers in selective solvents and micellar behaviour simulated with the de- veloped code agreed with simulations by Sheng et al. Then, the self-assembly of long copolymer chains in selective solvents that mimics a block copolymer of poly(methacrylic acid) and poly(ethylene oxide) in aqueous solution at pH 1 was studied for different polymer concentrations. The simulation results provided valuable insight into the studied system and serve as a good starting point for DPD simulations of this system with added surfactants and at different values of pH, where the electrostatic interactions become important.
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Building blocks of hydrogen-bonded supramolecular polymers
Roudná, Štěpánka ; Svoboda, Jan (advisor) ; Zedník, Jiří (referee)
The connection of molecular monomers through non-covalent interaction (e.g. hydrogen bonding, π-π interaction, coordination bonding) enables the formation of supramolecular polymers. The major advantage of these bonds is their reversibility and consequently their ability to self-assembly or to disconnect depending on given conditions. This thesis examines the self-assembly through quadruple hydrogen bonding, which is strong and the resulting structures stable. Ureidopyrimidinon A and aromatic amines were always used as the starting compound for the preparation of monofunctional and bifunctional ureidopyrimidinones.
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Effects of structural and processing parameters on th eproperties of polymer nanocomposites
Zárybnická, Klára ; Žídek, Jan (referee) ; Jančář, Josef (advisor)
The work deals mainly with preparation protocol of nanocomposites. The task of this work is to study structural and procedural parameteres that control the dispersion of nanoparticles in polymer solution to be able to prepare desired spatial organization of nanoparticles. The work resolves the effect of various components such as polymer matrices, nanoparticles and solvent, in which matrices and nanoparticles are blended. Used components control final dispersion state of nanoparticles and it influences also properties of investigated materials such as glass transition temperature, stiffness and rheological properties.
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