Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-09-22T18:06:47Z No. of bitstreams: 1 JardelLopes2.pdf: 2675666 bytes, checksum: 0a44c55f63bb5950b0bd1fa2eee9f4c6 (MD5) / Made available in DSpace on 2017-09-22T18:06:47Z (GMT). No. of bitstreams: 1 JardelLopes2.pdf: 2675666 bytes, checksum: 0a44c55f63bb5950b0bd1fa2eee9f4c6 (MD5) Previous issue date: 2017-07-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Most of the research in the crystal growth area is directed in the search for crystals that are used as a reliable frequency converter, And for this it is necessary good NLO coefficient, wide range of transparency in the visible spectrum region, high thermal stability, high Damage threshold, High mechanical strength, ease of growth and low cost of production. The semiorganic crystals aim to combine properties of inorganic materials and purely organic compounds in order to potentiate their properties for optoelectronic applications. Due to its amphoteric behavior, glycine can react with both cations and anions forming numerous complexes with metal ions by means of ionic bonding or even forming semiorganic salts with ions of the series of halogens that stabilize by means of hydrogen bonds. This leads glycine to be the most extensively studied amino acid. This work aims at the synthesis and characterization of crystals of bis-glycine hydrobromide (BGHBr), bis-glycine hydrochloride (BGHCl) and the unpublished bis-glycine chlorobromide crystal (BGHClBr) promoted by the mixture of the growth solutions of the Crystals previously mentioned in the equimolar proportion. The three crystals were grown by the solvent evaporation technique, which were colleted after an average period of 7 to 8 weeks and characterized by X-ray fluorescence, Xray diffraction techniques in conjunction with the refinement of structures by the Rietveld method, FTIR, Raman spectroscopy, differential scanning calorimetry, of XRD as a function of temperature. By means of the XRF analysis it was possible to confirm that ions Cland Brentered the crystal structure of BGHClBr in almost equal concentrations. The XRD analyzes at room temperature in conjunction with the refinement of structures by the Rietveld Method have shown that the synthesized crystals are structural isomorphs having orthorhombic structure (spatial group P212121). The network parameters of the BGHBr and BGHCl samples are in accordance with what has been reported in the literature, presenting a difference of less than 1% and the crystal parameters of BGHClBr have values intermediate to those of the other two crystals, indicating the development of a new crystal. Assignments for the bands presented in the FTIR and Raman spectrum confirmed the existence of two different glycine molecules present in the crystals. One is in the dipole form (NH3 +CH2COO- ) and the other in cationic form (NH3 +CH2COOH). In addition, the similarity between the three spectra can be noted indicating that the three crystals have the same functional groups. The Raman spectra show that the internal modes were practically the same in some regions, indicating the isomorphism between the three samples and that the network modes are different for the three crystals, and in this way these results are in agreement with the XRD analyzes confirming the development of the new material. The DSC curves indicate that the crystal of BGHCl is more stable with melting temperature at approximately 189 °C, the other two, BGHBr and BGHClBr, exhibited the same event at the temperature of approximately 172 °C and 177 °C, respectively. The XRD analyzes in function of temperature indicate the formation and a new phase for BGHBr crystal at about 160 °C. As the crystals of BGHCl and BGHBr already have their efficiency proven in the process of generation of the second harmonic and due to the thermal stability observed for the three crystals, and considering that new crystal developed in this work is structural isomorph of these semiorganic salts, these materials Are promising in the application in non-linear optical devices. / A maioria das pesquisas na área de crescimento de cristais se direciona pela busca por cristais que possam ser utilizados como um conversor de frequência fidedigno, os quais precisam ter um bom coeficiente óptico não-linear (NLO), ampla faixa de transparência na região do espectro visível, elevada estabilidade térmica, alto limiar de dano, alta resistência mecânica, facilidade de crescimento e baixo custo de produção. Os cristais semiorgânicos visam combinar propriedades dos materiais inorgânicos e dos compostos puramente orgânicos com o intuito de potencializar suas propriedades para as aplicações optoeletrônicas. Devido ao seu comportamento anfótero, a glicina pode reagir tanto com cátions como com ânions formando muitos complexos com íons metálicos por meio de ligação iônica ou ainda formando sais semiorgânicos com íons da série dos halogênios que se estabilizam por meio de ligações de hidrogênio e/ou forças de Van der Waals. Isso leva a glicina a ser o aminoácido mais extensivamente estudado. Este trabalho tem por objetivo a síntese e caracterização de cristais de brometo de bis-glicina (BGHBr), cloreto de bis-glicina (BGHCl) e do cristal inédito de clorobrometo de bis-glicina (BGHClBr) promovido pela mistura das soluções de crescimento dos cristais citados anteriormente na proporção equimolar. Os três cristais foram crescidos pela técnica de evaporação lenta do solvente, os quais foram cultivados após um período médio de 7 a 8 semanas e caraterizados pelas seguintes técnicas: fluorescência de raios X, difração de raios X conjuntamente com o refinamento de estruturas pelo método de Rietveld, espectroscopia no infravermelho com transformada de Fourier, espectroscopia Raman, calorimetria exploratória diferencial, XRD em função da temperatura. Por meio das análises de XRF foi possível confirmar que os íons Cle Brentraram na estrutura do cristal de BGHClBr em concentrações praticamente iguais. As análises de XRD à temperatura ambiente em conjunto com o refinamento de estruturas pelo Método de Rietveld comprovaram que os cristais sintetizados são isomorfos estruturais possuindo estrutura ortorrômbica (grupo espacial P212121). Os parâmetros de rede das amostras de BGHBr e BGHCl estão de acordo com o que foi reportado na literatura, apresentando diferença menor que 1% e os parâmetros do cristal de BGHClBr possui valores intermediários aos dos outros dois cristais, indicando o desenvolvimento de um novo cristal. As atribuições para as bandas apresentadas no espectro de FTIR e Raman confirmaram a existência de duas diferentes moléculas de glicina presente nos cristais. Uma delas está na forma dipolar (NH3 +CH2COO- ) e a outra na forma catiônica (NH3 +CH2COOH). Além disto, pode se notar a semelhança entre os três espectros indicando que os três cristais possuem os mesmo grupos funcionais. Os espectros Raman mostram que os modos internos apresentaram-se praticamente iguais em algumas regiões, indicando o isomorfismo entre as três amostras e que os modos de rede são diferentes para os três cristais. Desta forma, estes resultados estão em concordância com as análises de DRX confirmando o desenvolvimento do novo material. As curvas de DSC indicam que o cristal de BGHCl é mais estável com temperatura de fusão em aproximadamente 189 ºC, os outros dois, BGHBr e BGHClBr, apresentaram o mesmo evento na temperatura de aproximadamente 172 °C e 177 ºC, respectivamente. As análises de DRX em função da temperatura indicam a formação e uma nova fase para o cristal de BGHBr em torno de 160ºC. Como os cristais de BGHCl e de BGHBr já têm sua eficiência no processo de geração do segundo harmônico comprovada e devido a estabilidade térmica observada para os três cristais, e tendo em vista que novo cristal desenvolvido neste trabalho é isomorfo estrutural destes sais semiorgânicos, estes materiais são promissores na aplicação em dispositivos óptico não-lineares.

Over the last decade our understanding of mercury cycling has dramatically changed. Evidence of rapid atmospheric oxidation has been observed in the Arctic, Antarctic, the MBL, coastal environments, saline lakes, and the upper troposphere/lower stratosphere. These results show that, Hg0, can undergo rapid gas-phase oxidation under standard atmospheric conditions. However, the mechanism and importance of this transformation is still unclear. The goal of this work was two-fold: to investigate of the kinetics of potential pathway for the gas phase oxidation of atmospheric mercury and to develop new laser based techniques, which can be employed for both laboratory and field studies of Hg(0) and the products of mercury oxidation. First and foremost, this work determined kinetic rate coefficients for the potentially important mercury reactions. Rate coefficients were determined using a Pulse Laser Photolysis - Laser Induced Fluorescence (PLP-LIF) technique monitoring one or more of the following species, Hg(0), Cl, Br, HgCl, and HgBr. The concentrations of these species were measured by LIF as the reaction occurred and a concentration vs. time profile was generated. From these profiles a rate coefficient for the reaction can be obtained. In the course of this work kinetic rate coefficients for the following mercury reactions were measured. Hg(0) + Cl + M --> HgCl + M Hg(0) + Br + M --> HgBr + M HgBr + M --> Hg(0) + Br + M HgBr + Br --> products HgCl + O2 --> products This work is the first direct measurement of a kinetic rate coefficient for these reactions, and the first work which employed one photon LIF to monitor the HgCl and HgBr products. The second aspect of this work was the development of new laser based techniques to detect atmospheric mercury and its oxidation products for both laboratory and field application. In this work a LIF technique was develop to detect HgCl and HgBr. In addition, a two photon LIF technique initially developed by Bauer et al., 2002 was verified and expanded. The two photon LIF technique was used to directly monitor Hg(0) atoms in-situ, to monitor Hg(0) evolving form a gold tube, and to monitor the Hg(0) evolving from the thermal decomposition of reactive gaseous mercury collected on a KCl coated or uncoated denuder. This work represents a significant advance in the development of a viable method the detect mercury and the mercury oxidation products in the laboratory and in the field and is the first study to observe clear differences in the characteristic desorption profiles of HgO and HgX2. This work has broad implications, it enhanced our current knowledge concerning the biogeochemical cycling of mercury, broadened our understanding of the mercury chemistry in high halogen environment, and provided new techniques which can be applied in future field and laboratory studies.

SILVA, José Júnior Alves da. Adsorção de átomos alcalinos e halogênios em uma superfície de Grafeno: um estudo de primeiros princípios. 2008. 85 f. Dissertação (mestrado) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2008. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-05-13T22:42:26Z No. of bitstreams: 1 2008_dis_jjasilva.pdf: 4132276 bytes, checksum: 961eed37504f3bed4fe8ed917e245554 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2014-05-14T18:27:16Z (GMT) No. of bitstreams: 1 2008_dis_jjasilva.pdf: 4132276 bytes, checksum: 961eed37504f3bed4fe8ed917e245554 (MD5) / Made available in DSpace on 2014-05-14T18:27:16Z (GMT). No. of bitstreams: 1 2008_dis_jjasilva.pdf: 4132276 bytes, checksum: 961eed37504f3bed4fe8ed917e245554 (MD5) Previous issue date: 2008 / Graphene is currently the hottest topic in condensed-matter physics and materials science and was isolated less than four years ago. Graphene layers have been proposed as alternative materials for replacing carbon nanotubes in some applications, due to its easy synthesis and low costs. In order to explore potential applications of those nanostructures in electronic devices, through first principles based on the density functional theory, we studied the interaction between graphene surface and alkaline (Li, Na and K) and halogens (Cl, I and I$_2$ ) atoms. We verified that the adsorption of these atoms on the graphene surface cause significant modifications in the graphene electronic structure. We observed a large charge transfer between the alkaline (halogens) atoms and graphene surface. These charge transfers were found to be 0,65 - 0,85 e- from the alkaline atoms to graphene and 0,37 (0,27) e- from the graphene to chlorine (iodine) atoms. The alkaline atoms presented a larger stability on the center of one of the graphene hexagons, presenting binding energy in the range -1, 47 and -1, 03 eV, where the order of intensity is given by Li > K > Na. This predisposition for a specific site was not observed for the twostudied halogens. The chlorine atom present the larger stability when adsorbed on a top atom of the graphene surface with binding energy about 0, 98 eV, however this behavior was not be seen in the iodine atom case where equivalent binding energies for all the studied sites were found to be about 0,42 eV. The I2 molecule also does not present predilection for a specific site on the graphene surface, however it showed more stable when adsorbed with its axis perpendicular to the graphene surface plane. / O grafeno é atualmente o tópico mais corrente em física da materia condensada e ciência dos materiais e foi isolado pela primeira vez a menos de quatro anos. O grafeno tem sido proposto como um material alternativo aos nanotubos de carbono em diversas aplicações, devido a sua fácil sintetização e seu baixo custo. A fim de explorar uma potencial aplicação dessas nanoestruturas em dispositivos eletrônicos, através de cálculos de primeiros princípios baseados na teoria do funcional da densidade, estudamos a interação entre uma superfície de grafeno e átomos alcalinos (Li, Na e K) e halogênios (Cl, I e I2). Verificamos que a adsorção desses átomos na superfície do grafeno provoca significativas modificações na estrutura eletrônica do grafeno. Observamos uma grande transferência de carga entre os átomos alcalinos (halogênios) e a superfície do grafeno. Essas transferências foram da ordem de 0,65-0,85 e- dos átomos alcalinos para o grafeno e 0,37 (0,27) e- do grafeno para o átomo de cloro (iodo). Os metais alcalinos apresentaram uma maior estabilidade sobre o centro de um hexágono do grafeno, tendo energias de ligação entre -1,47 e -1,03 eV, onde a ordem de intensidade é dada por Li > K > Na. Essa predisposição por um sítio específico não foi observada para os dois halogênios estudados. O átomo de cloro apresentou uma maior estabilidade quando adsorvido sobre um átomo da superfície do grafeno, com energia de ligação da ordem de 0,98 eV, no entanto, isso não foi visto no caso do átomo de iodo onde energias de ligação equivalentes para todos os sítios estudados foram encontradas da ordem de 0,42 eV. A molécula I2 também não apresentou uma predileção por uma sitio específico da superfície do grafeno, mas mostrou-se mais estável quando adsorvida com seu eixo perpendicular ao plano do grafeno.

No description available.

Halogenated heterocycles are common in pharmaceutical and natural products and there is a need to develop a better understanding of processes used to synthesize them. Although the halogenation of simple aromatic molecules is well understood, the mechanisms behind the halogenation of aromatic heterocycles have been more problematic to elucidate because multiple pathways are possible. Recently, new, radical-based mechanisms have been proposed for heterocycle halogenation. In this study, we examine and test the viability of possible nucleophilic substitution, SN2@X, mechanisms in the halogenation of anions derived from the deprotonation of aromatic heterocycles. All the experiments were done in a modified Thermo LCQ Plus equipped with ESI. The modifications allow a neutral reagent to be added to the helium buffer gas in the 3D ion trap. In this system, it is possible to monitor ion/molecule reactions over time periods up to 10 seconds. A variety of aromatic heterocyclic nucleophiles were chosen based on their inclusion of nitrogen and or sulfur as the heteroatoms. In addition to this, the halogenating molecules chosen included traditional halobenzenes and a new class of perfluorinated alkyl iodides. It was found that, experimentally, the SN2@X path is the likely mechanism in the halogenation of deprotonated heterocycles. With computational modeling, we have additional support for this substitution mechanism. From this original study, two more studies were developed to look at the competing nucleophilic aromatic substitution reaction, SNAr. In the first of these studies, the focus was to look at how electron withdrawing substituents about an aromatic ring affect the ratio of SN2@X verses SNAr. As nucleophiles, 2-thiophenide and 5-thiazolide were used. The neutral reagents focus on trifluorobromobenzene derivatives along with pentafluorobromo- and -iodobenzene, and a two trifluoroiodobenzenes. What was found was that the ratio of the reactions depends on where the fluorines, or electron withdrawing substituents are in relation to the bromine or iodine on the ring. If the fluorines are in a close location to stabilize the resulting ionic product, SN2@X proceeds easily. However, the fluorines directly adjacent to the bromine or iodine also provide steric hinderance in the SNAr reaction. In the final project, arylation and benzylation of bromopyridines was examined. The nucleophiles used were benzyl and phenyl anions as well as 5-thiazolide, and the neutral reagents were bromopyridines, with fluorines used as an electron withdrawing groups to help stabilize the transition state. In these experiments, steric hinderance highly affected the results between the phenyl and benzyl nucleophiles. With benzylic anions, the nucleophile is able to reach the aromatic ring with less steric interference and therefore can proceed with an SNAr reaction. In addition to this, with mono and difluorinated pyridine substrates, the nitrogen in the ring activated the ring yielding nucleophilic aromatic substitution losing fluoride rather than bromide in many cases.

Halogen chemistry plays an important role in spring time ozone and mercury depletion events (ODEs and MDEs) and may efficiently oxidize hydrocarbons such as the important greenhouse gas methane (CH4) in the polar marine boundary layer. This thesis presents a detailed study of bromine and chlorine chemistry in the Arctic boundary layer based on measurements of bromine and chlorine containing species using chemical ionization mass spectrometry (CIMS). The capability of CIMS to accurately measure bromine oxide (BrO) was demonstrated. The first direct measurements of hypobromous acid (HOBr) were achieved. Conditions that likely favor bromine activation (e.g. high wind speeds) was presented. To advance the understanding of bromine recycling, a time dependent model was built to simulate the bromine speciation. Unexpected high levels of molecular chlorine (Cl2) were observed at Barrow, AK, which had a large impact on methane oxidation and could contribute to ozone loss and mercury oxidation at Barrow, AK. Moreover, BrO levels observed at Summit, Greenland did not explain the under prediction of hydroxyl radical (OH). However, the enhanced OH was found to be coincident with elevated reactive gaseous mercury (RGM). In addition, airborne BrO measurements were found to be generally consistent with airborne observations of soluble bromide based on the response factors of mist chamber to the bromine species and bromine chemical mechanisms.

Reactive halogen species (RHS) are responsible for ozone depletion and oxidation of gaseous elemental mercury and dimethyl sulphide in the polar boundary layer, but the sources and mechanisms controlling their catalytic reaction cycles are still not completely understood. To further investigate these processes, ground– based Multi–Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of boundary layer BrO and IO were made from a portable instrument platform in McMurdo Sound during the Antarctic spring of 2006 and 2007. Measurements of surface ozone, temperature, pressure, humidity, and wind speed and direction were also made, along with fourteen tethersonde soundings and the collection of snow samples for mercury analysis. A spherical multiple scattering Monte Carlo radiative transfer model (RTM) was developed for the simulation of box-air-mass-factors (box-AMFs), which are used to determine the weighting functions and forward model differential slant column densities (DSCDs) required for optimal estimation. The RTM employed the backward adjoint simulation technique for the fast calculation of box-AMFs for specific solar zenith angles (SZA) and MAX-DOAS measurement geometries. Rayleigh and Henyey-Greenstein scattering, ground topography and reflection, refraction, and molecular absorption by multiple species were included. Radiance and box-AMF simulations for MAX-DOAS measurements were compared with nine other RTMs and showed good agreement. A maximum a posteriori (MAP) optimal estimation algorithm was developed to retrieve trace gas concentration profiles from the DSCDs derived from the DOAS analysis of the measured absorption spectra. The retrieval algorithm was validated by performing an inversion of artificial DSCDs, simulated from known NO2 profiles. Profiles with a maximum concentration near the ground were generally well reproduced, but the retrieval of elevated layers was less accurate. Retrieved partial vertical column densities (VCDs) were similar to the known values, and investigation of the averaging kernels indicated that these were the most reliable retrieval product. NO₂ profiles were also retrieved from measurements made at an NO₂ measurement and profiling intercomparison campaign in Cabauw, Netherlands in July 2009. Boundary layer BrO was observed on several days throughout both measurement periods in McMurdo Sound, with a maximum retrieved surface mixing ratio of 14.4±0.3 ppt. The median partial VCDs up to 3km were 9.7±0.07 x 10¹² molec cm ⁻ in 2007, with a maximum of 2.3±0.07 x 10¹³ molec cm⁻², and 7.4±0.06 x 10¹² molec cm⁻² in 2006, with a maximum of 1.05 ± 0.07 x 1013 molec cm⁻². The median mixing ratio of 7.5±0.5 ppt for 2007 was significantly higher than the median of 5.2±0.5 ppt observed in 2006, which may be related to the more extensive first year sea ice in 2007. These values are consistent with, though lower than estimated boundary layer BrO concentrations at other polar coastal sites. Four out of five observed partial ozone depletion events (ODEs) occurred during strong winds and blowing snow, while BrO was present in the boundary layer in both stormy and calm conditions, consistent with the activation of RHS in these two weather extremes. Air mass back trajectories, modelled using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, indicated that the events were locally produced rather than transported from other sea ice zones. Boundary layer IO mixing ratios of 0.5–2.5±0.2 ppt were observed on several days. These values are low compared to measurements at Halley and Neumayer Stations, as well as mid-latitudes. Significantly higher total mercury concentrations observed in 2007 may be related to the higher boundary layer BrO concentrations, but further measurements are required to verify this.

This thesis focuses on the analysis of heavy noble gases (argon, krypton and xenon) and halogens (chlorine, bromine and iodine) in Martian meteorites. In the absence of a sample-return mission, Martian meteorite analysis is essential for establishing evidence for an active fluid system, evaluating the potential for life and understanding the formation and evolution of Mars. Noble gas analysis has multiple applications for Martian meteorite study, as described in this thesis. The noble gas isotopic signatures of Earth’s atmosphere, Martian atmosphere and Martian interior are sufficiently different that they can be distinguished through noble gas analysis. Analysis of bulk and mineral separates of shergottites showed that Martian atmospheric Xe was distributed evenly amongst samples, whilst terrestrially weathered samples contained elevated concentrations of terrestrial atmospheric Xe. Both atmospheric components were introduced by weathering. Shock redistribution is responsible for the distribution of Martian atmosphere into more retentive sites. Crustal contamination may be responsible for the presence or absence of detectable 129Xe from the Martian atmosphere. Halogen abundances can be determined as an extension of the Ar-Ar dating technique. As the halogen system on Earth acts as a tracer for important fluid related processes, Martian halogen abundances in meteorites may provide a tracer for the Martian fluid system. Analysis of bulk and mineral separates of nakhlites showed that halogens are distributed amongst minor phases and clear variation of Br/Cl and I/Cl ratios was observed amongst samples. Elevated I concentrations in low temperature releases of finds NWA 998 and MIL 03346 are consistent with terrestrial contamination. Analysis of Nakhla, (a meteorite fall), showed a trend of elevated Br/Cl and I/Cl ratios in crush and low temperature releases, consistent with Br/Cl ratios observed in Martian rocks, soils and weathering products. In contrast, high temperature releases had lower I/Cl and Br/Cl ratios, which are broadly comparable to the terrestrial mantle. This trend may represent mixing of hydrothermal fluids (low Br/Cl and I/Cl) and surface brines (high Br/Cl and I/Cl). An impact-induced hydrothermal system may provide a mechanism for mixing of both fluid types. The crystallisation ages of nakhlite meteorites were determined using the Ar-Ar dating technique. The apparent ages measured were similar to previous Ar-Ar analysis, and older than reported for other chronometers. Previously unrecognised components were observed, including evidence for a trapped hydrous fluid. This Cl-rich component showed strong correlation with 40Ar and had 40Ar/36Ar and 40Ar/129XeXS ratios consistent with Martian atmosphere. As this component was released during crush and low temperature analysis, fluid inclusions formed by percolation of brines from the Martian surface are likely hosts. Both finds showed clear evidence of a trapped component with 40Ar/36Ar ratios similar to either terrestrial atmosphere or the Martian interior. A further component observed in olivine phases had low 40Ar/36Ar ratios, and likely formed by the release of 36Ar formed by cosmic-ray spallation reactions on iron.

Atomically flat colloidal semiconductor CdSe nanoplatelets (NPLs) with precisely controlled thickness possess a range of unique optoelectronic properties. Here, we study the growth of CdSe, CdTe, and CdS NPLs with the aim of synthesizing thicker NPLs in order to extend their optical activity further into the lower energy/larger wavelength range. We employ cadmium halides, which lead to faster reaction kinetics as confirmed by control experiments with cadmium hydroxide as a Cd-precursor. Addition of halides in all cases led to the formation of thicker NPL species, as compared with the corresponding syntheses without these additives. Analysis of a recent theoretical model of the platelet growth mechanism confirms an earlier suggestion that reducing both the reaction enthalpy and the surface energy of CdSe, by replacing acetate ligands with chloride ions, should indeed lead to thicker NPLs as observed. We noticed a formation of Cd0-metal nanoparticles in the first stage of the synthesis by preparing the Cd-precursor, which is another key finding of our work. We assume that these particles can serve as an active cadmium source facilitating the growth of the NPLs. The resulting 6 ML CdSe NPLs exhibited bright photoluminescence with quantum yield of up to 50%, exceptionally narrow spectrum centered at 582 nm with full width at half-maximum of approx. 11 nm, and small Stokes shift of 2 nm. Moreover, we demonstrated the synthesis of heterostructured core/shell CdSe/CdS NPLs based on 6 ML CdSe platelets, which also exhibited bright fluorescence. This work shows the possibility to overcome energetic barrier limiting the size (thickness) control by using appropriate promoters of the growth of CdSe, CdTe, and CdS 2D structures.

CHARLES UNIVERSITY IN PRAGUE, Faculty of Science Department of Teaching and Didactics of Chemistry Hypermedia educational program Halogen chemistry and its application in the education of gifted pupils in chemistry Mgr. Pavel Teplý Summary of Ph.D. Thesis Prague 2010 This Ph.D. thesis was worked out during a regular doctoral study at the Department of Teaching and Didactics of Chemistry, Faculty of Science, Charles University in Prague. Proposer: Mgr. Pavel Teplý Studijní program: Vzdělávání v chemii Katedra učitelství a didaktiky chemie Přírodovědecká fakulta Univerzity Karlovy v Praze Supervisor: Prof. RNDr. Jan Čipera, CSc. Katedra učitelství a didaktiky chemie Přírodovědecká fakulta Univerzity Karlovy v Praze Supervisor­consultant: Doc. RNDr. Zdeněk Mička, CSc. Katedra anorganické chemie Přírodovědecká fakulta Univerzity Karlovy v Praze Doc. PhDr. Jiří Škoda, Ph.D. Katedra pedagogiky Pedagogická fakulta Univerzity Jana Evangelisty Purkyně v Ústí nad Labem KEY WORDS Hypermedia; education software; interactive and flexible program; XHTML; halogen chemistry; videorecording of chemical experiments; education of gifted pupils; distance education; e-learning. Introduction The education of gifted pupils reflects problems dealt by the current...