Graphene, as a recently discovered carbon allotrope, possesses with it many outstanding properties ranging from high electrical conductivity to great mechanical strength. Single layer graphene can be prepared by mechanical cleavage of graphite or by a more sophisticated method, CVD. However, the scale-up process for these preparation techniques is still unconvincing. Solution-processed graphene from exfoliation of graphite oxide on the other hand provides an alternative prospect resulting in the formation of graphene nanoplatelets (GNPs), which can be readily manipulated to tailor-suit various application demands. The main aim of the thesis is to explore the possibility and availability of this versatile method to produce graphene nanoplatelet and its composites with good all-round performance in energy and bioanalytical applications. A range of physical and chemical characterisation techniques were utilised including SEM, TEM, AFM, XPS, XRD, DLS, FTIR, Raman and UV-Vis spectroscopy in order to investigate the structural and chemical information of the graphene-based materials prepared. Functionalisation of graphene oxide with polyelectrolyte polymer could facilitate deposition of platinum nanoparticles in the formation of Pt-GNPs composites. The resultant composite was employed for bioanalytical application in the detection of an important neurotransmitter, glutamate, based on glutamate oxidase enzyme. The performance of Pt-GNPs based glutamate sensor exhibited enhanced sensitivity and prolonged stability compared to the sensors based on Pt decorated diamond or glassy carbon electrodes. The significant interfering effect from concomitant electrochemically active biological compounds associated with Pt-GNPs electrode however could be alleviated via opting for Prussian blue deposited GNPs electrode instead. The oppositely charged Pt-GNPs due to different functionalising polymers were also subject to self-assembly, which was enabled by the electrostatic interaction of the opposite charges of Pt-GNPs. The self-assembled film showed enhanced mechanical stability than the conventional drop-casted film and provided reasonably good activity towards oxidation of hydrogen peroxide. Three-component composite of graphene, nanodiamond and polyaniline was prepared via in-situ polymerisation for usage as an electrode material in electrochemical capacitors ("supercapacitors"). The addition of graphene was shown to significantly enhance specific capacitance while nanodiamond could improve the stability of the electrode by strengthening the polymer core. Another approach to produce a supercapacitor was via electrodeposition of nickel and cobalt hydroxides on graphene oxide film corporated with bicarbonate salt. The film was then subject to thermal reduction of GO and expansion of graphene layers within the film was observed. This leavening process enhanced the surface area of graphene film and thus the higher specific capacitance was obtained. The decoration of nickel and cobalt hydroxides onto the film also boosted the specific capacitance further however the poor cycling stability of the heated film still remained an issue. Graphene nanoplatelets were also used as a support for electrodeposition of Pt nanoparticles for methanol oxidation in acidic media. The preferential phase of the Pt deposited and large surface area of graphene in comparison to other carbon supports studied led to good catalytic activity being observed.

Single-molecule detection has provided insights into how molecules behave. Without the averaging effect of ensemble measurements, the stochastic behaviour of single molecules can be observed and intermediate steps in multistep transformations can be clearly detected. The single-molecule reactants range from small molecules (e.g. propene) to proteins of several tens of kDa (e.g. myosin). One single-molecule detection technique is single-channel electrical recording. This approach is based on the measurement of the transmembrane ionic current flowing through a nanoscale transmembrane pore under an applied potential. In this thesis, the protein α-hemolysin was employed as a nanoreactor. α-Hemolysin is a toxin secreted by Staphylococcus aureus. Its transmembrane pore (~100 Å in length and ≥14 Å in diameter) allows ions, water and small molecules to pass through its lumen. Under an applied potential, chemical changes in reactants attached to the internal wall of the pore modulate the flow of ions, leading to changes in the transmembrane ionic current. Analysis of this current provides information about the reaction kinetics and mechanisms. Chapter 1 – Single-Molecule Chemistry and α-Hemolysin is an introductory chapter that is divided into two parts. Section 1.1 provides an overview of the different techniques for the detection of chemical reactions at the single-molecule level. Section 1.2 gives a brief review of the protein pore α-hemolysin, including its structure, properties and various applications. Chapter 2 – S-Nitrosothiol Chemistry applies cysteine-containing α-hemolysins to study the biologically relevant chemistry of S-nitrosothiols (RSNO). RSNO are important molecules involved in cell signalling, which control physiological processes such as vasodilation and bronchodilation. Three reactions, namely transnitrosation (the transfer of the ‘NO’ group from RSNO to a thiol), S-thiolation (the formation of a disulfide from RSNO and thiol) and S-sulfonation (the generation of an S-sulfonate (RSSO₃⁻) from RSNO and sulfite ion), were investigated at the single-molecule level. The pH-dependency of the two competing reactions (transnitrosation and S-thiolation), the lifetime of the proposed transnitrosation intermediate, and nature of the chemical reaction between RSNO and sulfite (a bronchoconstrictor) were determined. Chapter 3 – Silver(I)-thiolate and cadmium(II)-thiolate complexes describes the kinetics of the formation and breakdown of these two metal-thiolate complexes. Ag⁺ and Cd²⁺ are commonly used in probing the membrane topology and gating properties of ion channels using the scanning cysteine accessibility method (SCAM). The binding of two Ag⁺ ions per thiol group and the stepwise build-up and dissociation of Cd²⁺-glutathione complexes were unambiguously characterized. Chapter 4 – Copper(II)-Catalyzed Diels-Alder Reactions reports the attempt to carry out copper(II)-catalyzed Diels-Alder reactions inside an engineered α-hemolysin. An iminodiacetate ligand was covalently attached within the lumen of the α-hemolysin pore. This ligand chelates Cu²⁺ ion, which can bind bidentate dienophiles and activate them towards Diels-Alder reaction with dienes. However, due to the ‘slow’ reaction rate of the Diels-Alder reaction (rate constant ~10⁻¹ M⁻¹s⁻) relative to the time-scale of the single-molecule experiment, we failed to observed chemical conversion at the single-molecule level. Nevertheless, the engineered metal-binding α-hemolysin may be useful for sensing molecules bearing metal-coordinating groups.

Monodispersed microgels composed of poly-acrylic acid (PAAc) and poly(N-isopropylacrylamide) (PNIPAM) interpenetrating networks were synthesized by 2-step method with first preparing PNIPAM microgel and then polymerizing acrylic acid that interpenetrates into the PNIPAM network. The semi-dilute aqueous solutions of the PNIPAM-PAAc IPN microgels exhibit an inverse thermo-reversible gelation. Furthermore, IPN microgels undergo the reversible volume phase transitions in response to both pH and temperature changes associated to PAAc and PNIPAM, respectively. Three applications based on this novel hydrogel system are presented: a rich phase diagram that opens a door for fundamental study of phase behavior of colloidal systems, a thermally induced viscosity change, and in situ hydrogel formation for controlled drug release. Clay-polymer hydrogel composites have been synthesized based on PNIPAM gels containing 0.25 to 4 wt% of the expandable smectic clay Na-montmorillonite layered silicates (Na-MLS). For Na-MLS concentrations ranging from 2.0 to 3.2 wt%, the composite gels have larger swelling ratio and stronger mechanical strength than those for a pure PNIPAM. The presence of Na-MLS does not affect the value of the lower critical solution temperature (LCST) of the PNIPAM. Surfactant-free hydroxypropyl cellulose (HPC) microgels have been synthesized in salt solution. In a narrow sodium chloride concentration range from 1.3 to 1.4 M, HPC chains can self-associate into colloidal particles at room temperature. The microgel particles were then obtained in situ by bonding self-associated HPC chains at 23 0C using divinyl sulfone as a cross-linker. The volume phase transition of the resultant HPC microgels has been studied as a function of temperature at various salt concentrations. A theoretical model based on Flory-Huggins free energy consideration has been used to explain the experimental results. Self-association behavior and conformation variation of long chain branched (LCB) poly (2-ethyloxazoline) (PEOx) with a CH3-(CH2)17 (C18) modified surface are investigated using light scattering techniques in various solvents. The polymer critical aggregation concentration (cac) strongly depends on solvent polarity, decreasing as the solvent becomes more hydrophobic.

This thesis studies quaternary chalcogenide nanocrystals and their photovoltaic applications. A temperature-dependent phase change between two distinct crystallographic phases of stoichiometric Cu₂ZnSnS₄ is investigated through the development of a one pot synthesis method. Characterisation of the Cu₂ZnSnS₄ nanocrystals was performed using absorption spectroscopy, transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). An investigation was conducted into the effects of using hexamethyldisilathiane (a volatile sulphur precursor) in the nucleation of small (<7nm), mono-dispersed and solution-stable quaternary Cu₂ZnSnS₄ nanocrystals. A strategy to synthesize high quality thermodynamically stable kesterite Cu₂ZnSnS₄ nanocrystals is established, which subsequently enabled the systematic study of Cu₂ZnSnS₄ nanocrystal formation mechanisms, using optical characterization, XRD, TEM and Raman spectroscopy. Further studies employed scanning transmission electron microscopy (STEM) energy dispersive x-ray (EDX) mapping to examine the elemental spatial distributions of Cu₂ZnSnS₄ nanocrystals, in order to analyse their compositional uniformity. In addition, the stability of nanocrystals synthesised using alternative ligands is investigated using Fourier transform infrared spectroscopy, without solution based ligand substitution protocol is used to replace aliphatic reaction ligands with short, aromatic pyridine ligands in order to further improve Cu₂ZnSnS₄ colloid stability. A layer-by-layer spin coating method is developed to fabricate a semiconductor heterojunction, using CdS as an n-type window, which is utilised to investigate the photovoltaic properties of Cu₂ZnSnS₄ nanocrystals. Finally, three novel passivation techniques are investigated, in order to optimise the optoelectronic properties of the solar cells to the point where a power conversion efficiency (PCE) of 1.00±0.04% is achieved. Although seemingly modest when compared to the performance of leading devices (PCE>12%) this represents one of the highest obtained for a Cu₂ZnSnS₄ nanocrystal solar cell, fabricated completely under ambient conditions at low temperatures.

Title: Morfology and surface chemical composition of porous silicon prepared at various conditions Author: Bc. Martin KONEČNÝ Author's e-mail: konecmar@seznam.cz Department: Department of Chemical Physics and Optics Supervisor: Doc. RNDr. Juraj Dian, CSc. Supervisor's e-mail: Juraj.Dian@mff.cuni.cz Abstract: Porous silicon is a silicon-based material prepared mainly by anodic etching of crystalline silicon in hydrofluoric acid. Physical and chemical properties of porous silicon are governed by structures with sizes of the order of ones to tens of nanometers. Properties of nanostructure material are affected - as compared to macroscopic counterparts - by quantum confinement effect and enormous internal surface. According to type of silicon substrate (type of dopant, conductivity, crystallographic orientation) and technological conditions a material with different mean size of pores (macro-, meso- and nanoporous silicon) and surface chemical composition (different ratio of Si-O and Si-H bond) can be prepared. Morphology and surface chemical composition predestinated application potential of porous silicon for sensors of chemical species by taking advantage of strong sensitivity of physical properties of silicon nanocrystals - especially of photoluminescence - on the chemical state of a surface. Detection of...

Regulation of genetically modified organisms and nanotechnology (comparison of British, Czech and Slovak legislation in the context of EU) The aim of this thesis is to first compare the british, czech and slovak legislation relating to genetically modified organisms. By the analysis of their respective features, the author points out the difficult bits and tries to look for the ideal solutions to the current problems of the european GM legislation. In spite of the fact, that the european legislation in this field is highly harmonised, there are still some areas that can be regulated by the member states as well as some holes waiting to be fixed. This thesis is composed of six main chapters which correspond to six main topics of present biotechnology legislation that are in the author's opinion the most significant. First chapter deals with the basic issues of releases of genetically modified organisms into the environment, on market, and with their contained use. Secondly, the author dissects the GM labelling and traceability legislation and shows the various thresholds of GM presence that are applicable to different areas. Third chapter then analyses the rules on co-existence between GM plants on one hand and conventional and organic plants on the other. Nextly, the unilateral acts of member...

The objective of this Ph.D. study is to explore an important and fertile research topic on the methods for synthesis of nanomaterials by homogeneous nonaqueous solution phase reaction. Research in this work focuses on synthesizing several kinds of nanomaterials in different environments and structure, including spherical nanoparticles, nanowires and core-shell structure composites We first synthesized metallic nanomaterials in this system, such as ~10 nm Fe nanoparticles, ~6 nm Au nanoparticles, and ~100 nm Bi nanoparticles, this system are the preparation for the following studies. Secondly, we synthesized bimetallic nanomaterials in this system, such as Fe50Co50 alloy and Bi doped with Mn. For FeCo alloy, after annealing at 500 °C, a pure phase of Fe50Co50 was obtained. And we first synthesized the nanowires of bismuth doped with manganese. By studying intermediates at different temperatures during the growth process of nanowires, the evolution of the crystallization of metallic products and the mechanism of the formation of the nanowires are investigated. Thirdly, we synthesized core-shell structure nanocomposites, including either gold as the shell or polymer as the shell. Au-coated magnetic Fe nanoparticles have been successfully synthesized by partial replacement reaction in a polar aprotic solvent with about 11 nm core of Fe and about 2.5 nm shell of Au. HRTEM images show clear core-shell structure with different crystal lattices from Fe and Au. SQUID magnetometry reveals that particle magnetic properties are not significantly affected by the overlayer of a moderately thick Au shell. The Aucoated particles exhibit a surface plasmon resonance peak that red-shifts from 520 to 680 nm. And Poly (Vinyl Pyrolidone) (PVP) coated iron nanoparticles also have been successfully synthesized in a polar aprotic solvent, which shows the welldefined core-shell structures. In this approach, Poly (Vinyl Pyrolidone) (PVP) was employed as the coating polymer directly coated on metallic core (iron) nanoparticles. In this work, a combination of TEM (transmission electron microscopy), EDS (Energy disperse X-ray spectroscopy), XRD (X-ray powder diffractometry), ICP (inductively-coupled plasma spectrometer), TGA (Thermogravimetric analysis), UV-visible absorption spectroscopy, IR (infrared) spectroscopy and SQUID magnetometry (Superconducting Quantum Interference Device) were employed to characterize the morphology, structure, composition and magnetic properties of the products. In summary, this Ph.D. study successfully and systematically synthesized several kinds of nanocomposites in a system. The synthetic procedure is simple, economic and easily scaled-up for further applications. And many techniques were employed to characterize the products.

In this study, template-based methods are used for the fabrication of various nanostructures such as nandots, nanorods, nanowires, nanotubes, and core-shell structures. Porous alumina membranes were employed as templates and metal nanostructures were synthesized in the templates by electrodeposition. By using lithography techniques, controlled patterned nanostructures were also fabricated on alumina templates. The magnetic properties of the various metal nanostructures were investigated. The pore size, interpore distance, and pore geometry highly affect magnetic properties of nanostructures grown in the templates. Hexagonally ordered porous alumina templates can be fabricated by two-step anodization. The pore diameters and interpore distances were readily controlled by appropriately changing anodization conditions and pore widening time. Alumina templates with various pore geometries were also successfully synthesized by changing applied voltage, increasing and decreasing, during a third anodization step. To understand magnetic properties of nanostructures with different aspect rations in the form of nanodots, nanorods, or nanowires, Fe nanostructures were fabricated in the templates by controlling of electrodeposition times. The coercivity of nanostructures increased with increasing aspect ratio. The anisotropy of the arrays was governed by the shape anisotropy of the magnetic objects with different aspect ratios. nanowires in mild-hard alumina and conventional alumina templates showed distinct differences in the squareness of hysteresis loops and coercivity both as a function of pore structure and magnetic component. Iron oxide nanotubes with a unique inner-surface were also fabricated by an electrodeposition method. β-FeOOH nanotubes were grown in alumina templates and transformed into hematite and magnetite structures during various heating processes. Hematite nanotubes are composed of small nanoparticles less than 20 nm diameters and the hysteresis loops and FC-ZFC curves show superparamagnetic properties without the Morin transition. In the case of magnetite nanotubes, which consist of slightly larger nanoparticles, hysteresis loops show ferromagnetism with weak coercivity at room temperature while FC-ZFC curves exhibit the Verwey transition at 125 K. For the patterning of nanowires, lithography techniques including nanosphere lithography and e-beam lithography were used. Nanosphere lithography used self-assembled PS spheres as a mask creates holes between spheres and the size of the holes is determined by the size and geometry of ordered PS spheres on the templates. This method can grow patterned nanowires arrays and also produce unique cup-shaped nanostructures with sizes ranging from micrometer down to several nanometers. E-beam lithography was also combined with template-based electrodeposition. Of these two lithographic methods, this one is the most powerful in the fabrication of patterned nanostructures with high aspect ratios. Various features and the sizes of patterned structures can be readily controlled. By the directing the pore diameters and interpore distances of the alumina template, the size and number of patterned nanowires are also adjustable.

<p>In recent decades there has been great interest to produce novel bio-based composites to reduce carbon footprint without sacrificing the necessities that society demands. To achieve a more sustainable future, research in cellulose biopolymers has risen to the forefront. Impressive mechanical, thermal and optical properties along with its abundant biomass has made nanocellulose (NC) the subject of intense research in the area of electronics, drug delivery, sensors, selective filters, and structural materials, to name a few. The practical utility of any cellulose-based materials requires a more complete understanding of how the fundamental structure affects final performance. This thesis examines several avenues to obtain novel materials by considering processing parameters and preparation methods for working with raw nanocellulose materials, and mechanochemical approaches for surface grafting to obtain modified CNs with improved dispersion in organic media. Lastly, the synergy between the two studies and its impact on advanced materials and nanocomposites is discussed.</p> <p>The low cost and wide availability of cellulose nanofibers (CNF), a refined form of cellulose microfibrils, make these an ideal starting material for our studies. However, the aggregated states of freeze-dried CNFs hinder its use as an additive for reinforcing polymer blends or functional films. The use of <i>tert</i>-butyl alcohol (TBA) as a stabilizer in pharmaceutical drugs has been well studied for its effectiveness in facilitating redissolution and extending product shelf life. Lyophilization of aqueous CNF slurries treated with various amounts of TBA produced a more porous material that could be redispersed with superior colloidal stability relative to untreated freeze-dried CNFs. Furthermore, CNFs lyophilized from aqueous TBA mixtures could be subjected to mild mechanochemical reactions (horizontal ball milling) to produce esterified nanofibers with high degrees of substitution (DS) and good dispersibility profiles in organic solvents. This solventless technique allowed for a variety of carboxylic acids to be grafted onto CNF surfaces. Finally, investigations of new materials with technological utility have been explored using networks of CNFs modified with oleic acid. These can be cast into superhydrophobic (SHP) films having a hierarchical structure characteristic of a self-similar material, with a wettability comparable to that of the lotus leaf. The SHP surface can also be regenerated after surface fouling or physical damage. </p>

Presentes há mais de dois séculos no cenário acadêmico mundial, as terras taras (TR) figuram há várias décadas entre as mais atuais tecnologias desenvolvidas pelo homem em diversas áreas do conhecimento. Particularmente, no que tange às aplicações de materiais luminescentes, as propriedades espectroscópicas únicas das TR tornaram-nas, nos últimos anos, praticamente insubstituíveis em dispositivos clássicos tricolores (tais como lâmpadas fluorescentes compactas ou tubos de raios catódicos). Contudo, o surgimento de novas tecnologias de visualização (displays compactos de alta resolução) e iluminação (eliminação do mercúrio de lâmpadas fluorescentes) impulsiona cada vez mais o estudo das propriedades e dos métodos de síntese de luminóforos a base de TR. Nesse sentido, o presente trabalho consistiu na avaliação de processos sintéticos para a obtenção de sólidos nanoestruturados a base de fosfatos e vanadatos de TR capazes de atuar como luminóforos sob excitação no ultravioleta de vácuo, além da caracterização estrutural e espectroscópica desses materiais. Desenvolveram-se adaptações de três abordagens sintéticas para o preparo dos sólidos: o método dos precursores poliméricos (Pechini) e os métodos de precipitações em microemulsões reversas e de precipitações coloidais. Tais métodos são adaptáveis de acordo com as necessidades de síntese (controle morfológico, controle composicional, grau de agregação de partículas etc.) e consistem em abordagens consideravelmente eficientes para a obtenção de fosfatos e/ou vanadatos de TR nanoestruturados. Sintetizaram-se ortofosfatos (TRPO4), fosfovanadatos (TRP1-xVxO4) e sistemas core@shell (TRVO4@TRPO4) com diferentes composições, a fim de se obterem luminóforos vermelhos, verdes e azuis, além de sólidos com emissão por conversão ascendente (upconversion). Os compostos obtidos foram caracterizados por difratometria de raios-X, microscopia eletrônica, espalhamento dinâmico de luz, análise térmica, espectroscopia vibracional e espectroscopia de luminescência (emissão/excitação, tempos de vida, eficiências quânticas, cromaticidade, parâmetros de intensidade de Judd-Ofelt). / The rare earth elements (RE) have figured in the academic scenario for over two centuries, being an integral part of most up-to-date developed technologies in several fields of expertise. Regarding the applications of luminescent materials over the last years, the unique spectroscopic properties of RE elements have made them almost irreplaceable in classic tricolor devices, such as compact fluorescent lamps or cathode ray tubes. Nevertheless, the advent of new visualization and lighting technologies, like the high-resolution compact displays and the elimination of mercury from fluorescent lamps, has stimulated scientists to investigate the synthesis and properties of RE-based phosphors. In this work, we have evaluated the processes available for the synthesis of nanostructured RE phosphates and vanadates capable of acting as phosphors under vacuum ultraviolet excitation, and conducted the structural and spectroscopic characterization of these materials. We used three strategies to prepare the solids: the polymeric precursor method (Pechini), precipitation into reverse microemulsions, the colloidal precipitations. These methods can be adapted to the synthesis requirements and enable the control of morphology, composition and particle aggregation, thus constituting highly efficient ways to obtain nanostructured RE phosphates and/or vanadates. We synthesized orthophosphates (REPO4), phosphovanadates (REP1-xVxO4), and core@shell structures (REVO4@REPO4) with different composition, to generate of red, green, and blue phosphors, as well as solids with upconversion emissions. We characterized the prepared compounds by X-ray diffractometry, electron microscopy, dynamic light scattering, thermal analysis, and vibrational and luminescence spectroscopies (emission/excitation, luminescence lifetimes, quantum yields, chromaticity, and Judd-Ofelt intensity parameters).