A utilização de detectores de radiação é de imensa importância na área de dosimetria, pois permite a quantificação da dose absorvida no meio. Uma técnica interessante para esta finalidade é o uso de detectores por cintilação. Estudos recentes com cintiladores plásticos e líquidos demonstraram a viabilidade do uso de detecção de cintilação por uma câmera digital com sensor CCD ou CMOS. Desse modo, este trabalho tem como objetivo desenvolver um dosímetro cintilador de baixo custo para viabilidade de seu uso e, de um sistema de detecção de cintilação através de uma câmera digital, para que assim pudesse ser realizada sua caracterização dosimétrica. O sistema dosimétrico foi construído a partir de um cintilador líquido a base de antraceno. Dosimetricamente verificou-se uma linearidade de resposta para a dose de 0,1 a 25,53 Gy, para a taxa de dose de 6,66 Gy/min e uma pequena diminuição da sensibilidade do dosímetro quando aumentada a taxa de dose de irradiação. Com relação à dependência energética, foi verificado um aumento na sensibilidade do dosímetro de 10,8% ao se variar a energia de 100 a 160 kVp. Quando comparado a um cintilador comercial, apresentou uma intensidade de sinal reduzida e, em uma análise de reprodutibilidade, obteve-se uma variação máxima de 2% em relação a repetição de uma mesma medida. O cintilador líquido apresentou baixa estabilidade pré e pós-irradiação, com uma variação de cor e redução do sinal ao decorrer dos dias. Para medidas bidimensionais o sistema montado mostrou-se promissor, uma vez que em medidas de deposição de dose com a profundidade para várias energias de feixes, verificou-se o aumento da penetração da radiação com o aumento da energia do feixe e as medidas de penumbra de um feixe parcialmente blindado com 2 mmPb apresentaram um valor de 1,79 cm, considerando o tipo de tubo gerador e blindagem utilizada. Por toda a caracterização realizada o sistema dosimétrico mostrou-se aplicável para dosimetria, desde que operado considerando as características apresentadas. / The utilization of radiation detector is important in the dosimetric area, because it allow the quantification of absortion dose in the medium. An interesting tehnique for this finalitypurpose is the use of scintillation detector. Recent studies with plastic scintillators and liquid scintillators have demonstrated the feasibility of using scintillation detection by a digital camera with CCD or CMOS sensors. Thus, this study is the intent to develop a low-cost scintillation dosimeter for the feasibility of its use and detection scintillation system through by a digital camera, with the finality of dosimetric characterization. The dosimetric system was constructed from using liquid scintilator based anthracene. A linearity dose response between 0.1 to 25.53 Gy was found for the dose rate of 6.66 Gy/min and the dosimeter sensibility was decreased when the dose rate increased. When varied the energy from 100 to 160 kVp, was verified an increased of 10.8% in the dosimeter sensibility, due the energy dependence. When compared to a commercial dosimeter, it shows signal intensity decreased and, the study of reproducibility, a maximum variation of 2% was obtained in relation to the repetition of the same measure. The liquid scintillator presented low stability before and after irradiation, with a color variation and signal reduction over the days. For two-dimensional measurements the assembled system proved to be promising, since in dose deposition measurements with the depth for several beam energies, the penetration of the radiation was increased with the increase of the beam energy and the penumbra measurements of a narrow beam with 2mmPb presented a value of 1.79 cm, considering the type of generator tube and narrow used. Throughout the characterization carried out the dosimetric system proved to be applicable for dosimetry, if operated considering the characteristics presented.

The interaction of small molecules with DNA has been extensively studied and has produced a large catalogue of molecules that non-covalently bind to DNA though groove binding, intercalation, electrostatics, or a combination of these binding modes. Anthracene, acridine, and carbocyanine-based chromophores have been examined for their DNA binding properties and photo-reactivities. Their planar aromatic structures make them ideal chromophores that can be used to probe DNA structural interactions and binding patterns. We have studied DNA binding and photocleavgage properties of a bisacridine chromophore joined by a 2,6-bis(aminomethyl)pyridine copper-binding linker (Chapter II), a series of 9-aminomethyl anthracene chromophores (Chapters III and IV), both under conditions of high and low ionic strength, as well as a series of pentamethine linked symmetrical carbocyanine dyes (Chapter V). In Chapter II we present data showing that high ionic strength efficiently increases copper(II)-dependent photocleavage of plasmid DNA by the bisacridine based chromophore (419 nm, pH 7.0). In Chapters III and IV, using an pyridine N-substituted 9-(aminomethyl)anthracene (Chapter III), a bis-9-(aminomethyl)anthracene, and its mono 9-(aminomethyl)anthracene analogue (Chapter IV), pUC19 plasmid DNA was photo-converted to highly diffuse DNA fragments (350 nm, pH 7.0) in the presence of 150 mM NaCl and 260 mM KCl. Spectroscopic analyses suggest that the combination of salts promotes a change in DNA helical structure that initiate a switch in anthracene binding mode from intercalation to an external or groove binding interactions. The alteration in DNA structure and binding mode leads to an increase in the anthracene-sensitized production of DNA damaging reactive oxygen species. Finally, in Chapter V, pUC19 plasmid DNA is converted to its nicked circular and linear forms following irradiation of a series of pentamethine linked symmetrical carbocyanines (red light, pH 7.0). The data suggest that the relative levels of photocleavage arise from the different substituents on the nitrogen alkyl side chain and the pentamethine linker.

Thesis (M.Sc.(Chemistry))--University of Pretoria, 2007. / Includes bibliographical references (leaves 80-85).

Η παρούσα μελέτη διερευνά την ικανότητα των πολυκυκλικών αρωματικών υδρογονανθράκων να (PAHs), όπως είναι το φαινανθρένιο και το ανθρακένιο, να επάγουν συνθήκες stress (stress syndrome) σε ιστούς (π.χ. βράγχια) του είδους Mytilus galloprovincialis. Σύμφωνα με τα αποτελέσματα αυτής της μελέτης, τα μύδια τα οποία εκτέθηκαν για 7 ημέρες σε PH και/ή AN (τελικής συγκέντρωσης 0,1 mg/L σε κάθε περίπτωση) καθώς και σε μίγμα αυτών των οργανικών ρύπων (τελικής συγκέντρωσης 0,2 mg/L), παρουσίασαν αυξημένη συχνότητα εμφάνισης πυρηνικών ανωμαλιών, όπως είναι οι μικροπυρήνων (MN), και επαγωγή νευρολογικών διαταραχών, πράγμα που υποδεικνύεται από την μέτρηση της δραστικότητας της ακετυλχολινεστεράσης (AChE). Επιπλέον, τα αυξημένα επίπεδα της MDA στα βράγχια των εκτιθέμενων ατόμων καθώς και η μείωση του χρόνου ημιζωής (LT50) των μυδιών που εκτέθηκαν στον αέρα (τεχνική Stress on Stress), αντανακλούν στις οξειδωτικές επιπτώσεις που επάγουν οι πολυκυκλικοί αρωματικοί υδρογονανθράκες στους ιστούς των εκτιθέμενων στον αέρα μυδιών, πράγμα που οδηγεί στην επαύξηση των τοξικών επιδράσεων, σε διαφορετικά επίπεδα της λειτουργίας του οργανισμού. / This study investigates the ability of certain polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene (PH) and anthracene (AN), to induce stress conditions (stress syndrome) in tissues (e.g. gills) of mussel Mytilus galloprovincialis. According to the results of this study, mussels exposed for 7 days to PH and/or AN (at a final concentration of 0,1mg/L in each case) as well as to a mixture of these organic pollutants (at a final concentration of 0,2 mg/L) showed increased frequencies of nuclear abnormalities, such as the presence of micronuclei (MN), and induction of neurological disorders, as shown by measuring the activity of acetylcholinesterase (AChE). Furthermore, increased levels of MDA in the gills of exposed individuals, and the reduction of the lethal time (LT50) of challenge mussels superimposed in air (Stress on Stress technique), merely reflect PAHs-induced oxidative effects on tissues of challenge mussels, thus leading to the enhancement of toxic effects to different levels of organism function.

A dosimetria na radioterapia é realizada periodicamente como parte do controle de qualidade tanto dos equipamentos como dos tratamentos dos pacientes. O dosímetro convencional utilizado para essa finalidade é a câmara de ionização, no entanto, ela pode apresentar limitações quando se necessita de um dosímetro que possua resoluções espacial e temporal altas. Este trabalho tem como objetivo a caracterização do dosímetro de antraceno para radiação de fótons radioterápicos. O antraceno é um cristal orgânico cintilador com vantagens de ser praticamente equivalente à água e tecido mole em feixes radioterápicos e com possibilidade de possuir volume de detecção e tamanho pequenos, para utilizar em radiocirurgia e dosimetria in vivo. Neste trabalho, a caracterização do dosímetro de antraceno foi realizada obtendo-se o sinal de cintilação em função da sua granulosidade média, diâmetro da sua cápsula interna, dose absorvida, taxa de dose absorvida, energia do feixe de radiação e sua resolução espacial, sendo essa última realizada por três métodos diferentes relacionados e equivalentes: (função de espalhamento de borda (FEB), função de espalhamento linear (FEL) e função de transferência de modulação (MTF)). Os feixes de fótons utilizados para as irradiações do cintilador foram os de 60 Co (1,25 MeV), 137 Cs (0,661 MeV) e raios X (energias efetivas de 28,4; 46,5; 48,5; 94,0 e 106,0 keV). A instrumentação utilizada para a detecção do sinal do cintilador foi composta por uma fibra óptica, fotomultiplicadora, fonte de alta tensão, eletrômetro e multímetro. Dos dados obtidos, a contribuição da radiação Cerenkov, produzida na fibra óptica, foi subtraída, e as seguintes características dos sinais resultantes puderam ser inferidas: quanto maior a granulosidade maior o sinal de cintilação detectado; a dependência do sinal com o diâmetro interno da sua cápsula aumenta proporcionalmente com o cubo do diâmetro; dependência linear do sinal com a dose absorvida; independência com a taxa de dose absorvida; dependência linear para baixas energias e independência para altas energia do feixe. Além disso, das resoluções espaciais encontradas pelos três métodos diferentes, aquela calculada pelo método MTF é a que mais se aproximou das dimensões do detector (1,6 mm), tendo sido obtido um valor igual a 1,43+/-0,07 mm. Dos resultados foi possível caracterizar o dosímetro de antraceno de modo que sua utilização em trabalhos futuros seja mais adequada. / New radiotherapy techniques such as intensity-modulated radiation therapy and stereotactic radiosurgery have increased the need for dosimeters that can provide measurements in real time with high spatial resolution. Organic scintillation dosimeters are able to measure with accuracy small radiation fields and fields with high gradients, besides having advantages such as water and soft tissue equivalence and the possibility to be used in vivo. Anthracene is an organic scintillator crystal with the highest known scintillation efficiency among organic scintillation materials. The objective of this work is to characterize the antracene as a dosimeter under radiotherapic photons energies, analysing its signal against average granulosity, intern capsule diameter, absorbed dose, absorbed dose rate, photon energy and its spatial resolution; with the last one analysed under three methods (edge spread function, line spread function and modulation transfer function). The photons energies used were 1.25 MeV ( 60 Co), 0.661 MeV ( 137 Cs) and X-rays (effective energies of 28.4; 46.5; 48.5; 94.0 e 106.0 keV). The scintillation detection system consisted of an optical fiber with one end attached to the anthracene capsule and the other to a photomultiplier tube mantained by power supply followed by an electrometer. Once Cerenkov radiation occurs in the optical fiber, it was removed from the total scintillation signal trough the subtraction of the signal, taken irradiating the optical fiber without the anthracene attached to one of its extremity. From results obtained, one can infer that the dosimeter signal increases proportionally with average granulosity and intern capsule diameter. The signal is linearly dependent of absorbed dose, linearly dependent of low photons energies and independent for high photons energies, as well as independent of the absorbed dose rate. From the spatial resolution values obtained it was possible to infer that the one obtained through modulation transfer function, 1.43+/-0.07 mm, was the one that approximated the most to the actual dosimeter physical size (1.6 mm). From the characteristics obtained with this work, we think that future projects involving the anthracene will be carried out more properly.

A utilização de detectores de radiação é de imensa importância na área de dosimetria, pois permite a quantificação da dose absorvida no meio. Uma técnica interessante para esta finalidade é o uso de detectores por cintilação. Estudos recentes com cintiladores plásticos e líquidos demonstraram a viabilidade do uso de detecção de cintilação por uma câmera digital com sensor CCD ou CMOS. Desse modo, este trabalho tem como objetivo desenvolver um dosímetro cintilador de baixo custo para viabilidade de seu uso e, de um sistema de detecção de cintilação através de uma câmera digital, para que assim pudesse ser realizada sua caracterização dosimétrica. O sistema dosimétrico foi construído a partir de um cintilador líquido a base de antraceno. Dosimetricamente verificou-se uma linearidade de resposta para a dose de 0,1 a 25,53 Gy, para a taxa de dose de 6,66 Gy/min e uma pequena diminuição da sensibilidade do dosímetro quando aumentada a taxa de dose de irradiação. Com relação à dependência energética, foi verificado um aumento na sensibilidade do dosímetro de 10,8% ao se variar a energia de 100 a 160 kVp. Quando comparado a um cintilador comercial, apresentou uma intensidade de sinal reduzida e, em uma análise de reprodutibilidade, obteve-se uma variação máxima de 2% em relação a repetição de uma mesma medida. O cintilador líquido apresentou baixa estabilidade pré e pós-irradiação, com uma variação de cor e redução do sinal ao decorrer dos dias. Para medidas bidimensionais o sistema montado mostrou-se promissor, uma vez que em medidas de deposição de dose com a profundidade para várias energias de feixes, verificou-se o aumento da penetração da radiação com o aumento da energia do feixe e as medidas de penumbra de um feixe parcialmente blindado com 2 mmPb apresentaram um valor de 1,79 cm, considerando o tipo de tubo gerador e blindagem utilizada. Por toda a caracterização realizada o sistema dosimétrico mostrou-se aplicável para dosimetria, desde que operado considerando as características apresentadas. / The utilization of radiation detector is important in the dosimetric area, because it allow the quantification of absortion dose in the medium. An interesting tehnique for this finalitypurpose is the use of scintillation detector. Recent studies with plastic scintillators and liquid scintillators have demonstrated the feasibility of using scintillation detection by a digital camera with CCD or CMOS sensors. Thus, this study is the intent to develop a low-cost scintillation dosimeter for the feasibility of its use and detection scintillation system through by a digital camera, with the finality of dosimetric characterization. The dosimetric system was constructed from using liquid scintilator based anthracene. A linearity dose response between 0.1 to 25.53 Gy was found for the dose rate of 6.66 Gy/min and the dosimeter sensibility was decreased when the dose rate increased. When varied the energy from 100 to 160 kVp, was verified an increased of 10.8% in the dosimeter sensibility, due the energy dependence. When compared to a commercial dosimeter, it shows signal intensity decreased and, the study of reproducibility, a maximum variation of 2% was obtained in relation to the repetition of the same measure. The liquid scintillator presented low stability before and after irradiation, with a color variation and signal reduction over the days. For two-dimensional measurements the assembled system proved to be promising, since in dose deposition measurements with the depth for several beam energies, the penetration of the radiation was increased with the increase of the beam energy and the penumbra measurements of a narrow beam with 2mmPb presented a value of 1.79 cm, considering the type of generator tube and narrow used. Throughout the characterization carried out the dosimetric system proved to be applicable for dosimetry, if operated considering the characteristics presented.

Understanding the thermodynamic properties of multicomponent mixtures is of critical importance in many chemical and industrial applications. Experimental measurements become progressively difficult as the number of solution components increases -- producing the need for predictive models. Problems in development of predictive models arise if the mixture has one or more components that interact through molecular complexation or association. Experimental solubilities of anthracene and pyrene dissolved in binary systems containing one or more alcohols were measured in order to address this problem. Alcohols examined in this study were: 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 3-methyl-1-butanol, and 1-octanol. In binary solvent mixtures containing only a single self-associating alcoholic solvent, the alkane cosolvents studied were: n-hexane, n-heptane, n-octane, 2,2,4-trimethylpentane, cyclohexane, methylcyclohexane, tert-butylcyclohexane. Predictive solubility equations were developed using mobile order theory. This approach differs from classical solution models by representing hydrogen bonding with a probability term rather than with expressions derived from stepwise equilibria or expressions to represent hypothetical solution aggregates. Results were compared with the predicted solubilities found from using expressions developed using the Kretschmer-Wiebe and Mecke-Kempter approaches for modeling associated solutions. It was found that the mobile order approach provided reasonably accurate predictions for the solute solubilities in the systems studied. The limitations and applications for mathematical methods of representing experimental isothermal solubility data were also studied for 72 systems. Two possible descriptive forms for this mathematical representation were suggested based on the various nearly ideal binary solvent (NIBS) and modified Wilson models.

Organic electronics are devices based on semiconductors derived from carbon based molecules and polymers. These devices can be made flexible, lightweight and potentially inexpensive with the development of economies of scale. Specific examples of organic electronics include organic thin-film transistors (OTFTs), organic light-emitting diodes (OLEDs) and organic photovoltaic (OPVs). Anthracene-based semiconductors are materials that have generated great interest primarily because of their structural planarity, potential for strong intermolecular interactions, air stability and ideal frontier molecular orbital energy levels. In this thesis, we detail two publications that examined functionalized anthracene molecules integrated into OTFTs, along with their thermal, electrochemical and optical properties. We started by examining seven novel 9,10-anthracene-based molecules. It was found that functionalization of the 9,10-positions with different phenyl derivatives resulted in negligible variation in the optical properties with minor (±0.10 eV) changes in electrochemical behaviour, while the choice of phenyl derivative greatly affected the thermal stability whereby the decomposition temperatures (Td) varied by as much as 128 °C between certain functionalized derivatives. The findings suggested that functionalization of the 9,10-position of anthracene leads to an effective handle for tuning of the thermal stability while having little to no effect on the optical properties and the solid-state arrangement. We continued with the synthesis of several novel anthracene derivatives which were di-substituted at the 2,6-positions. It was found that 2,6-functionalization with various fluorinated phenyl derivatives led to negligible changes in the optical behaviour while influencing the electrochemical properties (±0.10 eV). Furthermore, the choice of fluorinated phenyl moiety had noticeable effects on melting point and thermal stability (ΔTm < 55 °C and ΔTd < 65 °C). OTFTs were fabricated and characterized using the 2,6-anthracene derivatives as the semiconducting layer. The addition of fluorine groups on the phenyl groups led to a transition from p-type behaviour to n-type behaviour in BGBC OTFTs. The results indicated that the choice of functional group as well as its functionalization location, at the 9,10- and 2,6-positions, can act as powerful handles to engineer high performance OTFTs.

La synthèse de graphène par approche « bottom-up » fait l’objet de nombreux travaux de recherche ayant pour but de contrôler les propriétés électroniques et optiques de ce matériau par la fabrication de nanostructures avec une précision atomique. D’autre part, le contrôle de dopant dans le graphène permettant d’en moduler les propriétés suscite un grand intérêt et dans ce contexte l’utilisation de porphyrines avec un taux d’azote contrôlé est attrayante. Par leurs ressemblances structurelles, les porphyrines π-étendues peuvent être considérées comme des nanoparticules de graphène dopées à l’azote (GQDs) présentant de fortes propriétés infrarouge tandis que les briques de construction à base de porphyrines peuvent être utilisées pour la synthèse sur surface de deux type de nanoarchitectures de graphene appélées nanorubans (GNRs) et nanomèches (GNMs). Cette thèse a pour objectif de développer la synthèse de porphyrines à base d’anthracenes et de les utiliser comme précurseurs pour la fabrication de nanostructures. La première partie de cette thèse est dédiée à la synthèse organique de différentes anthracenylporphyrines et à l’étude de leurs assemblages sur surface dans la chambre d’un microscope à effet tunnel. La seconde partie est dédiée à l’étude de formation de porphyrines π-étendues via une méthode pyrolyse flash pouvant activer thermiquement des réactions de couplage par déhydrogenation entre des hydrocarbures aromatiques polyycliques (PAHs) et des porphyrines. La dernière partie est dédiée à la modification post synthétique d’une tetrabromoanthracenylporphyrine par addition de PAHs via la réaction de couplage de Suzuki-Miyaura et à la caractérisation des propriétés optiques de ces porphyrines nouvellement formées. / The synthesis of graphene via bottom-up approach is a hot topic of research that aims to control the electronic and optical properties of this material by the fabrication of atomically precised nanostructures. Moreover, the control of dopant in graphene is of great interest to modulate the properties of the material. In this context, the contribution of porphyrins with a controlled content of nitrogen is attractive in this context. Because of structural similarities with graphene quantum dots (GQDs), π-extented porphyrins can be regarded as nitrogen-doped GQD with promising NIR properties. Porphyrins are convenient building blocks for the synthesis on surface of nanoarchitectures of graphene called nitrogen-doped Graphene Nanoribbons (GNRs) and Graphene NanoMeshes (GNMs). This thesis aims to develop the synthesis of symmetrical and robust porphyrins with anthracenes and to use them as precursors for the fabrication of nanostructures. The first part of this thesis is dedicated to the organic synthesis of variety of anthracenylporphyrins and the study of their assemblies on surface in a chamber of a Scanning Tunneling Microscope. The second part is dedicated to the study of formation of π-extended porphyrins via a method of flash pyrolysis able to thermally activate dehydrogenative coupling reactions between Polycyclic Aromatic Hydrocarbons (PAHs) and porphyrins. The last part is dedicated to the post synthetic modification of a tetrabromoanthracenylporphyrin with additional PAHs via Suzuki-Miyaura coupling and the characterization of the optical properties of the resulting porphyrins.

This thesis presents a compilation of recent work on benchmarking, applying, and developing Auxiliary Field Quantum Monte Carlo (AFQMC) for use in ab initio simulations of the electronic structure of molecules. With Chapter 1 I begin with a benchmark of phaseless AFQMC versus experiment in obtaining gas phase ligand dissociation energies of a set of tetrahedral and octahedral transition metal complexes. ph-AFQMC is shown to acquire chemical accuracy through the use of correlated sampling (CS) and CASSCF trial wave functions selected via a black box procedure. This is followed in Chapter 2 with another gas phase benchmark of ph-AFQMC versus experiment, this time calculating the redox potentials for a set of metallocenes, where we find a mix of correlated sampling and large CASSCF trials necessary to reproduce gas phase experimental values to within 1.7 ± 1.0 kcal/mol. Additionally, the inclusion of QZ ph-AFQMC values, either using UHF or CASSCF trials, was found to be necessary for a few systems, as opposed to using a hybrid approach with alternate methods such as coupled cluster to extrapolate to the basis set limit. In Chapter 3, having established protocols to obtain decent results on transition metal complexes with known experimental values, I apply ph-AFQMC to successfully predict the activity of a set of new annihilators for optical upconversion. For a set of functionalized anthracene molecules, I report agreement within statistics between ph-AFQMC and a localized approximation to coupled cluster singles doubles and perturbative triples (DLPNO-CCSD(T0)), and develop intuitive guidelines for tuning the excited state energies of anthracene. For a single molecule in an additional set of functionalized benzothiadiazole (BTD) molecules, Ph-BTD, ph-AFQMC and DLPNO-CCSD(T) disagree significantly; subsequent experimental testing validates the ph-AFQMC result. In Chapter 4 I present an approach based on localized orbitals to reduce the scaling with system size from quartic to cubic for the energy evaluation, the functional bottleneck for the majority of AFQMC calculations. Additionally, I describe the practical implementation of such an algorithm to be run on large GPU clusters. This allows AFQMC to be run for both larger systems and trials at a significantly decreased cost, while still reproducing full AFQMC results within the statistics of the method. With Chapter 5, I conclude with the development and characterization of a novel constraint, linecut (lc-) AFQMC, which exhbits distinct behavior versus the phaseless constraint. We demonstrate benchmarks for a variety of weakly to strongly correlated molecules for which we have the exact total energies, and observe that lc-AFQMC outperforms ph-AFQMC for the majority of systems studied. I conclude with the description of a systematic method to remove the linecut constraint, partially removing the bias and re-introducing the fermionic sign problem while still maintaining a practicable signal to noise ratio. This allows for us to recover the exact energy of FeO with a fraction of the cost of converging the trial wave function within ph-AFQMC.