|
|
Preparation of low-dimensional inorganic perovskites
Nedvěd, Matěj ; Dvořák, Petr (referee) ; Musálek, Tomáš (advisor)
This bachelor thesis deals with the perovskite CsPbBr3. The thesis presents properties and different ways of preparing nanostructures of this inorganic perovskite. The emphasis is placed on physical vapor deposition using effusion cells. The experiments carried out to prepare nanocrystals and nanowires and the subsequent analysis of their morphology, composition and optical properties are described. The effect of the electron beam and long-term exposure to air on the optical properties is studied. Also, the concept of an experiment that should result in the replacement of lead in the perovskite structure by tin is presented.
|
|
|
The deposition of Ga and GaN nanostructures on silicon and graphene substrate
Novák, Jakub ; Jarý, Vítězslav (referee) ; Mach, Jindřich (advisor)
The thesis is focused on the study of properties of GaN nanocrystals and Ga structures on the surface of silicon and graphene substrate. In the theoretical part of this thesis, the basic properties of Ga/GaN and graphene are described, as well as their applications or connection of both structures together in different devices. The ability of metal nanoparticles to enhance not only photoluminescence, due to the interaction of the material with surface plasmons, is also shown in several examples. The experimental part of the work first deals with the production and characterization of graphene sheets prepared by Chemical Vapor Deposition. Ga/GaN growth on both types of substrates was performed in a UHV chamber using an effusion cell for Ga deposition and an atomic ion source for nitridation. Prepared structures were characterized using various methods (XPS, SEM, AFM, Raman spectroscopy or photoluminescence). In the last step, GaN nanocrystals were coated with Ga islands to study the photoluminescence enhancement.
|
|
|
Deposition of GaN nanocrystals with Ga droplets
Novák, Jakub ; Voborný, Stanislav (referee) ; Mach, Jindřich (advisor)
This bachelor thesis deals with preparation and characterization of Ga structures and GaN nanocrystals. In the theoretical part, properties and applications of GaN are introduced. Further, some substrates for the growth and some techniques used for manufacturing of these structures are stated. Further, is also mentioned the photoluminiscence of GaN. The experimental part deals with preparation of Ga and GaN structures and combination of both. These structures were further analyzed by various methods such as XPS, SEM or photoluminiscence.
|
|
|
Preparation and characterization of nanostructured III-V semiconductor materials
Maniš, Jaroslav ; Kostelník,, Petr (referee) ; Hospodková,, Alice (referee) ; Šikola, Tomáš (advisor)
Předkládaná dizertační práce se zabývá výrobou a analýzou gallium nitridových (GaN) nanostruktur ve třech odlišných formách. V prvním případě byl zkoumám trojdimenzionální GaN ve formě nanokrystalů rostených na grafenu. Nanokrystaly byly připraveny s využitím techniky droplet epitaxy, která mimo jiné umožňuje růst nanostruktur za nízké teploty substrátu (T = 200°C). Studium se zaměřovalo jak na charakterizaci kvality připravených nanokrystalů, tak na statistický popis růstu. V dalším kroku byly připravené struktury využity pro výrobu fotodektoru citlivého na ultrafialové světlo. Výroba fotodektoru a jeho úspěšné použití slouží jako základ pro navazující výzkum. Ve druhém případě byly studovány dvoudimenzionální GaN nanostruktury, které byly rovněž připraveny za nízké teploty křemíkového substrátu. Následná analýza se soustředila na popis krystalové struktury a prvkovou analýzu, neboť byly takovéto struktury pozorovány vůbec poprvé. Další rozvoj možností přípravy těchto nanostruktur je předmětem navazujícího výzkumu. Ve třetím případě byly zkoumány jednodimenzionální GaN nanodráty připravené na safírovém substrátu. Účelem tohoto projektu bylo získání datasetu pro ověření teoretického modelu, který popisuje růst horizontálních nanodrátů. Na základě sběru a analýzy dat se podařilo modelovat růstovou dynamiku GaN nanodrátů, která byly v souladu s teoretickým modelem.
|
|
| |
|
|
Ultrafast laser spectroscopy of semiconductor nanostructures
Chlouba, Tomáš ; Trojánek, František (advisor) ; Žídek, Karel (referee)
In this work we investigate changes in dynamics of CdSe nanocrystalline films caused by different annealing temperatures and different conditions during films growth. We use methods of time-resolved laser spectroscopy like time-resolved pump and probe and streak camera to study these dynamics. We also measured linear absorption and luminiscence. Our goal is to match measured dynamics with dynamics of other samples with different annealing temperatures and discuss the microscopic origin of these dynamics. Powered by TCPDF (www.tcpdf.org)
|
|
|
Optical properties of silicon nanostructures for photovoltaics
Salava, Jan ; Trojánek, František (advisor) ; Žídek, Karel (referee)
Název práce: Optické vlastnosti křemíkových nanostruktur pro fotovoltaiku Autor: Bc. Jan Salava Katedra: Katedra chemické fyziky a optiky Vedoucí diplomové práce: doc. RNDr. František Trojánek, Ph.D., katedra chemické fyziky a optiky Abstrakt: V předložené práci jsou studovány křemíkové nanokrystaly umístěné v SiC matrici - jednotlivé vzorky se odlišují přidáním dopantu (boru) do příslušné vrstvy struktury během depozice metodou PECVD a pasivací vodíkem. Křemíkové nanokrystaly jsou významné zejména tím, že oproti své objemové verzi vykazují účinnou fotoluminiscenci a absorpci ve viditelné oblasti spektra. Změnami parametr· při přípravě lze ladit jejich vlastnosti s ohledem na konkrétní aplikaci. Základní myšlenka integrace křemíkových nanostruktur do solárních článk· spočívá ve zvýšení účinnosti konverze slunečního spektra kombinací několika tenkých vrstev s nanokrystaly a objemového Si článku tak, aby každá vrstva sluneční cely absorbo- vala určitou část spektra. Procesy, které se v těchto strukturách dějí krátce po excitaci nosič· náboje, však stále nejsou zcela popsány. Cílem práce je charakterizace těchto jev· metodami ča- sově rozlišené spektroskopie. Dalším úkolem je popsat vliv dopování jednotlivých částí materiálu a jeho pasivace ve vodíkové atmosféře na chování fotoexcitovaných nosič· a intenzitu...
|
|
|
Preparation of magnetic nanoparticles by hydrothermal method
Repko, Anton ; Nižňanský, Daniel (advisor) ; Buršík, Josef (referee) ; del Puerto Morales, Maria (referee)
Hydrothermal method of nanoparticle preparation, involving oleic acid, has received certain attention in the last years. However, the published works lack systematic approach to the subject, and the mechanism was not thoroughly investigated, so as to achieve a predictable outcome of the synthesis. The present work investigated the influence of composition of organic and water phase on the synthesis of cobalt ferrite (cobalt(II)-iron(III) oxide) and magnetite nanoparticles, and the mechanism of nanoparticle formation was proposed. Organic phase was based on pentanol, octanol or toluene, containing the precursor - metal oleate. Besides hydrophobic particles, it was even possible to directly prepare hydrophilic oleate-coated particles by using water phase with sodium oleate. Synthetic procedure was then simplified by a separate preparation of cobalt-iron oleate, which led also to a product of narrower size distribution and better phase purity. Size control in the range of 6-11 nm and a batch yield of ca. 500 mg was achieved. Attention was given also to the surface modification of the particles, thus imparting them hydrophilicity. Small di- or tricarboxylic acids were utilized, as well as carboxylmethyl dextran and titanium dioxide. Titanium dioxide required additional protection with...
|
|
|
Dynamics of modified diamond nanocrystals in living cells
Majer, Jan ; Libusová, Lenka (advisor) ; Fišer, Radovan (referee)
Nanodiamonds (NDs) are an interesting platform in biological applications and disease treatment. Because of their photoluminescence properties and modifiable surface, they have been investigated as potential carriers for drugs and nucleic acids as well as fluorescent probes. In order to design NDs meeting specifically desired parameters, which would succeed in clinical trials and in medicinal therapy, understanding the mechanism of uptake and intracellular fate of NDs is crucial. The diploma thesis is focused on mechanistic investigation of ND-based nanoparticles delivering nucleic acids to human cells. First, NDs coated with a novel cationic co-polymer were prepared. NDs were then complexed with siRNA in order to transfect siRNA inside U-2 OS cells. NDs proved to be biocompatible and effective transfection particles as observed by qPCR and colorimetric cytotoxicity and cell viability tests. To examine ND uptake by cells, we inhibited endocytosis by specific inhibitors. Obtained results implicated that ND uptake was clathrin- and caveolin dependent. Nonetheless, more than half of NDs was internalized by cells in a different fashion. Some NDs colocalized with early endosomes, lysosomes and caveolin-derived endosomes after internalization. Other NDs resided either in unknown cell structures or escaped from...
|
|
|
Preparation of low-dimensional inorganic perovskites
Nedvěd, Matěj ; Dvořák, Petr (referee) ; Musálek, Tomáš (advisor)
This bachelor thesis deals with the perovskite CsPbBr3. The thesis presents properties and different ways of preparing nanostructures of this inorganic perovskite. The emphasis is placed on physical vapor deposition using effusion cells. The experiments carried out to prepare nanocrystals and nanowires and the subsequent analysis of their morphology, composition and optical properties are described. The effect of the electron beam and long-term exposure to air on the optical properties is studied. Also, the concept of an experiment that should result in the replacement of lead in the perovskite structure by tin is presented.
|
guest ::
