This diploma thesis deals with preparation of graphene samples for depositions of ultrathin layers of gallium and gallium nitride. Graphene substrates were prepared by chemical vapour deposition in home-build high temperature reactor. After graphene transfer to silicon wafers, a series of chemical and thermal treatments were performed. Obtained samples were suitable for the study of growth of ultrathin layers of Ga and GaN. The growth of Ga and GaN was realized in ultra high vacuum conditions. Molecular beam epitaxy technique was used for gallium depositions together with ion source for nitridation. Obtained ultrathin layers were studied with X-ray photoelectron spectroscopy, atomic force microscopy and with scanning electron microscopy.

Diploma thesis deals with the influence of low energy ions on graphene structures. Graphene structures were modified by nitrogen and argon ions of energies lower than 100 eV. Modified structures were analysed by Raman spectroscopy and x-ray photoelectron spectroscopy. The influence of the dose of ions on quality of graphene were investigated as well. In addition, this diploma thesis includes the literature search which focuses on modification of graphene by charged particles.

The aim of the thesis is to study mechanical properties of nanomaterials (multi-layer graphene, silicon, mica) suitable to be used as novel pressure sensors in laser photoacoustic spectroscopy. Membranes (diameter ~ 4 mm, thickness ~ 100 nm) were prepared by mechanical exfoliation method and then attached to a glass window in several slightly different designs. Movement of these membranes was detected using HeNe laser beam reflected from the membrane's surface onto a position sensitive detector. Methanol was used as a model gas and the signal was collected from studied element and microphone simultaneously. Acoustic wave, induced inside a measuring cell by periodic thermal variations, causes the membranes to move. The movement of a membrane is influenced by its mechanical properties, which is possible to determine by fitting the measured data into a mathematical model. Comparison of the output data of all membranes' measurements shows, that the signal intensity is influenced by the method of attaching membrane to a glass window and by volume of free space on a side of a membrane. Metallization of the membrane's surface (~ 70 nm) decreases its springiness thus decreases the sensitivity. Several membranes reached sensitivity comparable with top class microphone.

CHARLES UNIVERSITY FACULTY OF PHARMACY IN HRADEC KRÁLOVÉ Department of Pharmaceutical Chemistry and Pharmaceutical Analysis Candidate: Aneta Ptáčková Supervisor: PharmDr. Lukáš Lochman, Ph.D. Title of thesis: Modification of capillary wall by graphene for separation applications Capillary electrophoresis (CE) is a highly efficient separation method. Substances are separated due to their different mobility in an electric field. The CE modes of operation can be modified in different ways, e.g. capillary electrochromatography or micellar electrokinetic capillary chromatography. Modification of the inner wall of the capillary is believed to help improve separation efficiency and selectivity. Graphene is carbon with a hexagonal structure in form of two-dimensional sp2 single-atom-thick sheets. Graphene seems to be a suitable material for separation application due to its excellent properties such as large surface area and affinity to aromatic ring through π-π interactions. Our work is focused on the modification of the capillary wall by graphene. One of the methods of capillary wall modification is the Layer-by-Layer method via layering of differently charged substances bounded by electrostatic forces. Another method is chemical coating employing covalent interactions. Different combinations of polymers...

Amphetamine abuse is an enduring problem in many developed nations, including Sweden. It causes lasting damage both to its users and in the form of increased strain on healthcare services. It is therefore critical that police be equipped with the tools necessary to rapidly and accurately identify any samples in order to combat this scourge. Current analysis methods rely on large complex machines such as gas-chromatographs. This causes a significant bottleneck as all samples must be sent to lab for analysis. In this report the potential application of graphene quantum dots(GQDs) as a sensor for amphetamine has been studied. These offer a potentially quick and cheap analysis method that could be integrated into an easily portable detector. It was found that GQDs synthesised by a simple method from citric acid shows increased photo-luminescence in the presence of amphetamine. The response is largely linear with increasing concentrations of amphetamine within an interval of 1mM-200mM. This indicates they may very well serve as a sensing element of an amphetamine detector. / Amfetaminmissbruk har länge varit ett problem i många industrialiserade länder, inklusive Sverige. Det skapar långvariga skador både på dess användare och i form av ökade kostnader för hälsovården. Det är därför kritiskt att polisen ges de verktyg som behövs för att snabbt och precist kunna analysera prov. Nuvarande analysmetoder använder sig av stora avancerade maskiner so som gas-kromatografer. Detta skapar en flaskhals då alla prov som tas måste skickas till labb för analys. I denna rapport har användningen av grafen kvantprickar (GQD) som en sensor för amfetamin studerats. Dessa har potentialen att ge en snabb och enkel analysmetod som skulle kunna integreras i portabel sensor. GQD:er syntetiserade med en simpel metod från citronsyra visas i dessa experiment ha ökad fotoluminiscens när de är lösta tillsammans med amfetamin. Denna respons är linjär relativt till koncentrationen av amfetamin inom intervallet 1mM-200mM. Detta indikerar att dessa GQD:er mycket väl kan användas som ett sensorelement i en amfetamindetektor.

This master thesis deals with the topic of alternative production of hydrogen as the energy carrier of the future. The primary focus is on the production of hydrogen based on photocatalytical water splitting in the presence of semiconductor materials (especially modified and unmodified TiO2). The aim of the thesis is a synthesis of nanostructured oxide, graphene/graphene oxide particles and its composites, and a study of its structures and photocatalytical properties regarding photolysis of water. Products of the syntheses are described from the point of view of phase composition, surface area and photocatalytical activity. The main output of the thesis is a discussion of the influence of alkaline complex forming reagents on the hydrothermal low-temperature synthesis of biphasic TiO2, and a study of the influence of graphene/graphene oxide modification on photocatalytical activity of biphasic TiO2.

The near-Fermi-energy energy band structure of carbon nanotubes is given by cross-sections of the graphene Dirac cones near the K and K' points. Using second-order perturbation theory and a nearest-neighbor approximated tight-binding model, curvature-induced corrections to the graphene-based effective model are derived. In addition to the already known Dirac-point shift, the curvature is shown to cause not only a warping of the Dirac cone, tantamount to a slight compression and a correction to the overall Fermi velocity, but also a tilting of the Dirac cone and the associated nanotube energy bands. This tilting results in a velocity asymmetry for left- and right-going waves and two different kinds of excitations, allowing for varying degeneracy in the same sample. Previous experiments have shown irregularities in the level degeneracy and should be reconsidered in this context. / Energibandstrukturen för kolnanorör ges av tvärsnitt av grafens Dirac-koner nära K- och K'-punkterna. Medelst andra ordningens störningsteori och en tight-binding-modell med närmaste-granne-approximationen härleds de kurvaturinducerade korrektionerna till den grafenbaserade effektiva modellen. Utöver det redan kända Dirac-punkt-skiftet så visas kurvaturen orsaka inte bara en förvrängning av Dirac-konen, liktydigt med en mild kompression och en korrektion till den övergripande fermihastigheten, utan också en lutning av Dirac-konen och de associerade nanorörsenergibanden. Denna lutning resulterar i en hastighetsasymmetri för vänster- och högergående vågor och två olika sorters excitationer, vilket tillåter för varierande degeneration i samma prov. Tidigare experiment har visat oregelbundenheter i nivådegenerationen och bör omprövas i denna kontext.

This master’s thesis is focused on preparation and analysis of ultrathin CaF2 (calcium fluoride) films on a graphene substrate. CaF2 was deposited in UHV conditions at substrate temperatures in the range from 20 °C to 400 °C. The material was deposited on Si(111) with a native SiO2 layer and on a substrate with a CVD graphene layer. The deposited films were analyzed by XPS, AFM and SEM. Moreover four different sample holders for deposition purposes were designed in this work.

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.

V této práci byl demonstrován grafenový polem řízený transistor (GFET) jako platforma pro detekci glukózy. Sukcinimidyl ester pyrenbutanové kyseliny (PSE) sloužící jako nosič a enzym glukóza oxidáza (GOx) byly úspěšně použity k funkcionalizaci grafenového kanálu ve FE transistoru. Enzym GOx byl imobilizován na kanálu pro glukózovou detekci, jelikož indukuje selektivní katalytickou reakci glukózy. Proces funkcionalizace byl charakterizován pomocí Ramanovy spektroskopie a Atomární silové mikroskopie (AFM). Vyrobený biosenzor na bázi grafenu umožnil elektrickou detekci glukózy ve dvou různých uspořádáních. V uspořádní FET prostřednictvím posunu Diracova bodu ve voltampérové charakteristice, jakož i v nastavení pro kotinuální monitorování v reálném čase prostřednictvím změny odporu grafenového kanálu. Tato studie naznačuje, že grafen je slibným materiálem pro vývoj nanoelektronických biosenzorů včetně aplikací pro monitorování hladiny glukózy.