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Interaction of organic molecules with metal passivated semiconductor surfaces studied via STM
Zimmermann, Petr ; Sobotík, Pavel (advisor)
Title Interaction of Organic Molecules with Metal Passivated Silicon Surfaces Studied via STM Author Petr Zimmermann Department Department of Plasma and Surface Science Supervisor Doc. RNDr. Pavel Sobotík, CSc. Department of Plasma and Surface Science Abstract Organic molecules offer a wide range of optical, electronic or chemical properties. Coupling them to silicon could pave way to novel applications and devices, however, a controlled molecular functionalization of silicon remains challenging due to the presence of highly reactive dangling bonds on its surfaces. We attempt to decrease the reactivity of low index silicon surfaces with an ultra-thin layer of a metal adsorbates and study their interaction with organic molecules via scanning tunnelling microscopy. In the first part we investigate the interaction of ethylene, a small unsaturated molecule, with tin and indium 1D chains grown on Si(001) - 2 × 1. The chains consist of dimers structurally analogous to the dimers of the underlying Si(001) - 2 × 1 surface. Aided by photoelectron spectroscopy we find that the Sn chains are less reactive than the Si(001) surface and that the absence of a π dimer bond renders indium chains inert. In the second part we study the interaction of copper phthalocyanine, a small macrocyclic heteroaromatic compound, with the...
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Time-resolved potentiometry on liquid-liquid interface
Mansfeldová, Věra
MSc. Věra Mansfeldová Dissertation thesis: Time-resolved potentiometry on liquid-liquid interface Abstract The aim of this work is to explore the method of temporal resolution in potentiometry as a new prospective electrochemical analytical technique. In connection with interface of two immiscible electrolyte solutions (ITIES) it may find utilization in analytical chemistry. This technique up to my knowledge has not been published yet. Potential response of analyte on liquid/liquid interface includes both distribution processes, their temporal resolution and redox processes, which specificity can modified by changing the composition of individual phases. Unlike "classic" potentiometric techniques, limited just to potential determination, this method, which I have given the working name "time resolved potentiometry at liquid-liquid interface" utilizes time development of potential response, which was found to be an analyte-specific function. The time resolved potentiometry presented in this work includes time course of potential response to analytical parameters specific for particular analyte. It brings series of data characterizing the analyte in given environment in a similar manner as spectra and may allow creating analyte-specific data package - fingerprint. Combination with ITIES allows, unlike...
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Study of the photodynamic inactivation of prions by phthalocyanines.
Kostelanská, Marie ; Holada, Karel (advisor) ; Zimčík, Petr (referee) ; Kolářová, Hana (referee)
Transmissive spongiform encephalopathies, also called prion disorders, are fatal neurodegenerative diseases affecting mammals. In patients, the pathological prion protein (PrPTSE ) accumulates in CNS and causes death. Prions possess high binding affinity to surfaces. Moreover, they are highly resistant to conventional sterilization procedures which rise the risk of nosocomial transmission from patients in subclinical stage of prion disease through medical tools. In the thesis, we evaluate the efficiency of photodynamic inactivation (PDI) for prion decontamination. The PDI is induced by photoactivation of phthalocyanine (Pc) derivates AlPcOH(SO3)2, SiPc(OH)2(SO3)1-3 or ZnPc(SO3)1-3. Pc exposed to light generate reactive oxygen species, mainly singlet oxygen (O2(1 ∆g)). Production of O2(1 ∆g) in aqueous solution was confirmed by iodide method, quenching by NaN3 and oxidative degradation of uric acid. The photoactivation of Pc in infectious brain homogenate led to elimination of PrPres signal (= proteinase K-resistant PrPTSE fragment) below the detection limit of western blot by using nanomolar AlPcOH(SO3)2 concentration. The complete elimination of PrPres signal was accompanied with total protein concentration decrease by a maximum of 20% in brain homogenate No signs of protein fragmentation or...
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Interaction of organic molecules with metal passivated semiconductor surfaces studied via STM
Zimmermann, Petr ; Sobotík, Pavel (advisor)
Title Interaction of Organic Molecules with Metal Passivated Silicon Surfaces Studied via STM Author Petr Zimmermann Department Department of Plasma and Surface Science Supervisor Doc. RNDr. Pavel Sobotík, CSc. Department of Plasma and Surface Science Abstract Organic molecules offer a wide range of optical, electronic or chemical properties. Coupling them to silicon could pave way to novel applications and devices, however, a controlled molecular functionalization of silicon remains challenging due to the presence of highly reactive dangling bonds on its surfaces. We attempt to decrease the reactivity of low index silicon surfaces with an ultra-thin layer of a metal adsorbates and study their interaction with organic molecules via scanning tunnelling microscopy. In the first part we investigate the interaction of ethylene, a small unsaturated molecule, with tin and indium 1D chains grown on Si(001) - 2 × 1. The chains consist of dimers structurally analogous to the dimers of the underlying Si(001) - 2 × 1 surface. Aided by photoelectron spectroscopy we find that the Sn chains are less reactive than the Si(001) surface and that the absence of a π dimer bond renders indium chains inert. In the second part we study the interaction of copper phthalocyanine, a small macrocyclic heteroaromatic compound, with the...
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STM study of adsorption and mobility of phtalocyanine molecules on passivated silicon surfaces at lower temperatures
Szabo, Michal ; Ošťádal, Ivan (advisor) ; Matvija, Peter (referee)
The thesis deals with an experiment for studying adsorption of phthalocyanin molecules on silicon surface passivated by a tin reconstruction. The main technique used for imaging surface is scanning tunneling microscopy (STM). The work contains a brief introduction to the studied problem. It deals with the STM method and STM construction. The used ultra-vacuum experimental system is characterized together with particular steps at sample preparation for STM measurements. During the sample preparation all necessary operations were tested on the newly modified system and calibration measurements of sample annealing and tin deposition were performed. A structure of the prepared surface Si(111) 7×7 was investigated by STM and conditions for the preparation in the new system were specified. STM images were used for an evaluation of results at optimizing preparation of the passivated surface. Obtained results are important for further experiments in frame of a research focused on growing molecular structures on silicon surfaces.
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Interaction of organic molecules with metal passivated semiconductor surfaces studied via STM
Zimmermann, Petr ; Sobotík, Pavel (advisor) ; Plšek, Jan (referee) ; Šikola, Tomáš (referee)
Title Interaction of Organic Molecules with Metal Passivated Silicon Surfaces Studied via STM Author Petr Zimmermann Department Department of Plasma and Surface Science Supervisor Doc. RNDr. Pavel Sobotík, CSc. Department of Plasma and Surface Science Abstract Organic molecules offer a wide range of optical, electronic or chemical properties. Coupling them to silicon could pave way to novel applications and devices, however, a controlled molecular functionalization of silicon remains challenging due to the presence of highly reactive dangling bonds on its surfaces. We attempt to decrease the reactivity of low index silicon surfaces with an ultra-thin layer of a metal adsorbates and study their interaction with organic molecules via scanning tunnelling microscopy. In the first part we investigate the interaction of ethylene, a small unsaturated molecule, with tin and indium 1D chains grown on Si(001) - 2 × 1. The chains consist of dimers structurally analogous to the dimers of the underlying Si(001) - 2 × 1 surface. Aided by photoelectron spectroscopy we find that the Sn chains are less reactive than the Si(001) surface and that the absence of a π dimer bond renders indium chains inert. In the second part we study the interaction of copper phthalocyanine, a small macrocyclic heteroaromatic compound, with the...
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Modification of silicon surfaces for selective adsorption
Doležal, Jiří ; Ošťádal, Ivan (advisor) ; Matvija, Peter (referee)
This thesis is focused on adsorption of phthalocyanines on tin and indium passivated silicon Si(111) surfaces with the √3 × √3 reconstruction at room temperature. Scanning tunneling microscopy was used for obtaining atomically resolved surface images. Molecules on these surfaces predominantly adsorb on Si-substitutional defects. Local density of states (LDOS) of strongly adsorbed molecules was obtained by scanning tunneling spectroscopy. The origin of fuzzy imaging of molecules sitting on Si-substitutional double defects was probed. Voltage dependence of mean lifetime of two observed states, between which the "fuzzy" molecule is switching, was measured by analysis of tunneling current fluctuations. We discussed the influence of external parameters on the switching between the two states. We attribute the fuzzy behaviour of the molecule and resulting tunneling current fluctuations to the motion of the molecule in a double-well potential and propose two most likely kinds of the motion which most closely agree with the obtained data.
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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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Excitation wavelength-dependent Raman spectra of single-layer graphene-phtalocyanine hybrid systems
Uhlířová, Tereza ; Vlčková, Blanka (advisor) ; Němec, Ivan (referee)
A systematic chemical and spectroscopic approach to evaluation of the effect of single-layer graphene (SLG) on Raman spectra of free-base phthalocyanine (H2Pc) in glass/SLG/H2Pc hybrid systems has been developed. By a combi- nation of electronic absorption spectra, Raman spectra at five excitation wave- lengths (532, 633, 647, 785 and 830 nm) and excitation profiles of H2Pc Raman spectral bands, the constitution of the three prepared hybrid sysems has been es- tablished in the following manner: Hybrid system I comprises probably a bilayer of H2Pc molecules, system VI approximately a monolayer of H2Pc, and system X a slightly reorganized monolayer of H2Pc molecules. Micro-Raman spectral map- ping of all three hybrid systems yielded H2Pc spectral bands (together with the SLG spectral bands) at all five excitation wavelengths. By contrast, for all three HOPG/H2Pc reference systems (HOPG = highly oriented pyrolytic graphite), prepared by the same procedure as the corresponding samples, H2Pc signal was detected only at 633 and 647 nm excitations. A selective increase of normalized Raman intensities of H2Pc spectral bands for the glass/SLG/H2Pc monolayer hybrid systems at 830 nm was revealed on the basis of a mutual comparison of Raman excitation profiles of all three samples of glass/SLG/H2Pc hybrid systems....
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Time-resolved potentiometry on liquid-liquid interface
Mansfeldová, Věra ; Nesměrák, Karel (advisor) ; Opekar, František (referee) ; Gál, Miroslav (referee)
Věra Mansfeldová: Time-resolved potentiometry on liquid-liquid interface (Dissertation thesis) Abstract The aim of this work is to explore the method of temporal resolution in potentiometry as a new prospective electrochemical analytical technique. In connection with interface of two immiscible electrolyte solutions (ITIES) it may find utilization in analytical chemistry. This technique up to my knowledge has not been published yet. Potential response of analyte on liquid/liquid interface includes both distribution processes, their temporal resolution and redox processes, which specificity can modified by changing the composition of individual phases. Unlike "classic" potentiometric techniques, limited just to potential determination, this method, which I have given the working name "time resolved potentiometry at liquid-liquid interface" utilizes time development of potential response, which was found to be an analyte-specific function. The time resolved potentiometry presented in this work includes time course of potential response to analytical parameters specific for particular analyte. It brings series of data characterizing the analyte in given environment in a similar manner as spectra and may allow creating analyte-specific data package - fingerprint. Combination with ITIES allows, unlike...
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