The underlying theory of “Spin” of an electron and its associated inter-actions causing internal fields and spectral shift to bulk-magnetism iswell established now. Our understanding of spin properties is significant andmore useful than ever before. In recent years there seems to be an enormousinterest towards application oriented materials that harness those spin prop-erties. Theoretical simulations remain in a position to “assist or pilot” theexperimental discovery of new materials.In this work, we have outlined available methodologies for spin coupling inmulti-reference and DFT techniques. We have benchmarked multi-referencespin-Hamiltonian computation in isoelectronic diradicals - Trimethylenemethane(TMM) and Oxyallyl. Also with DFT, parameters are predicted with anewly discovered TMM-like stable diradicals, reported to have large positiveexchange interactions. Excellent agreement were obtained and our findingsemphasize that the dipole-dipole interactions alone can predict the splittingof triplet states and that DFT spin procedures hold well in organic species.We have extended our spin-studies to a highly application oriented ma-terial - nanographene. Using our novel spin-parameter arguments we haveexplained the magnetism of graphene. Our studies highlight a few signifi-cant aspects - first there seems to be a size dependency with respect to thespin-Hamiltonian; second, there is a negligible contribution of spin-orbit cou-pling in these systems; third, we give a theoretical account of spin restrictedand unrestricted schemes for the DFT method and their consequences forthe spin and spatial symmetry of the molecules; and, finally, we highlightthe importance of impurities and defects for magnetism in graphene. Wepredict triplet-singlet transitions through linear response TDDFT for thetris(8-hydroxyquinoline) aluminium complex, an organic molecule shown tohave spintronics applications in recent experiments. Our spin studies werein line with those observations and could help to understand the role of thespin-coupling phenomena. / QC 20120531

This thesis focuses on the development of new stationary phases for use in hydrophilic interaction liquid chromatography using TRIS-based and phosphorylcholine typed monomers and porous silica particles as starting substrates. In this thesis, several ways of polymerizing highly hydrophilic mono­mers onto pore surfaces of silica supports are described, based on several “grafting from” schemes. “Controlled/living” radical polymerizations including atom transfer radical polymerization (ATRP) and iniferter-mediated polymerization in conjunction with conventional free radical polymerization are demonstrated to be successful tools for grafting different hydrophilic monomers (polyhydroxyl and phosphorylcholine [meth]acrylamide/acrylates) onto the silica surfaces. Reaction solvents are proven to play an essential role to achieve efficient graft polymerization of activated silica surfaces with these amphiphilic vinylic monomers, which is difficult because of their restricted access to the activated surface in solvents that can be used because of solubility constraints. Two tentacle TRIS-based polymer grafted silica, namely TRIS-WAX – TRIS functionality bonded to silica via a C–N–C imine bond and TRIS-Amide – TRIS bonded to silica via an amide bond, prove to be useful as stationary phases for hydrophilic interaction chromatography (HILIC).The TRIS-WAX exhibits a mixed mode hydrophilic partitioning and weak anion exchange (HILIC/WAX) retention mechanism while retention by hydrophilic partitioning is the dominant mechanism on the neutral TRIS-Amide phase which lacks weak anion exchange (WAX) properties. Interestingly, both these phases have selectivities that are radically different from most commercial HILIC stationary phases. Finally, a method is demonstrated for synthesizing a stratified (graft-copolymerized) silica material based on N,N′-methylenebisacrylamide and 2-methacryloyloxyethyl phosphorylcholine (MPC) using a “controlled/living” photoiniferter-mediated polymerization from the N,N-diethyldithiocarbamate iniferter moiety immobilized silica surfaces. This polymerization method proves to be successful for graft-blockcopolymerization of different highly hydrophilic monomers onto the activated surfaces of porous silica. In this way, silica surfaces are grafted with a cross-linked amide-based hydrogel, on top of which a tentacle zwitterionic phosphorylcholine-typed layer is synthesized. The resulted material proves to be useful for HILIC separations and possesses different selectivity for the tested organic acids compared to that of commercial ZIC-cHILIC stationary phase.

La réévaluation des impacts toxicologique et environnemental des répulsifs synthétiques conduit à reconsidérer les répulsifs d'origine naturelle pour la prévention des maladies transmises par les insectes (dengue, chikungunya, paludisme,...). Cette étude se rapporte aux structures de type bis(oxazolidine) envisagées comme prodrogues de répulsifs naturels par leur conversion avec le tris(hydroxyméthyl)aminométhane (TRIS). Différents protocoles et voies de synthèse ont été étudiés sur une série représentative d'aldéhydes pour définir l'étendue et les limites de l'approche permettant de concentrer deux unités d'un même principe actif au sein de bis(oxazolidines) symétriques et de reproduire un effet synergique avec deux unités différentes formant des bis(oxazolidines) dissymétriques. La fonctionnalisation des bis(oxazolidines) a été également envisagée pour moduler leur balance hydrophile-lipophile. L'étude de la réaction de cyclocondensation met en évidence l'influence des paramètres structuraux sur le procédé de synthèse des bis(oxazolidines), la stabilité des intermédiaires (monooxazolidines) et la stéréosélectivité de la réaction. L'interprétation des résultats est proposée sur la base des effets (stéréo)-électroniques. Cette étude démontre l'intérêt de cette approche chimique pour la production de prodrogues de répulsifs naturels qui peuvent constituer des atouts pour le développement durable.

Orientador: André Sarto Polo. / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós graduação em Ciência e Tecnologia - Química, 2011.

A novel type of precast, prestressed concrete structural element is being implemented in load-bearing systems in buildings. These structural elements combine the use of high-performance, self-consolidating concrete (HPSCC) and non-corroding carbon fibre reinforced polymer (CFRP) prestressing tendons; this produces highly optimized, slender structural elements with excellent serviceability and (presumed) extended service lives. More widely, the use of new construction techniques, innovative materials, and ground-breaking designs is increasingly commonplace in today's rapidly evolving building construction industry. However, the performance of these and other structural elements in fire is in general not well known and must be understood before these can be used with confidence in load-bearing applications where structural fire resistance is a concern. Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this thesis. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. The research presented in this thesis fundamentally seeks to examine and understand the behaviour of CFRP prestressed HPSCC structural elements in fire, with emphasis placed on undesired 'premature' failure mechanisms linked to the occurrence of heat-induced concrete spalling and/or loss of bond between the pretensioned CFRP tendons and the concrete. Results from fire resistance tests presented herein show that, although compliant with testing standards, temperature distributions inside furnaces (5 to 10% deviation) appear to influence the occurrence of heat-induced concrete spalling for specimens tested simultaneously during a single test; fair comparison of test results is therefore questionable if thermal exposure variability is not explicitly considered. In line with the aims of the research presented in this thesis, H-TRIS is used to carry out multiple comprehensive studies on the occurrence of concrete spalling and bond behaviour of CFRP tendons; imposing a quantified, reproducible and rational thermal exposure. Test results led to the conclusion that a "one size fits all" approach for mitigating the risk of heat-induced concrete spalling (e.g. prescribed dose of polypropylene (PP) fibres included in fresh concrete), appears to be ineffective and inappropriate in some of the conditions examined. This work demonstrates that PP fibre cross section and individual fibre length can have an influence on the risk of spalling for the HPSCC mixes tested herein. The testing presented herein has convincingly shown, for the first time using multiple repeated tests under tightly controlled thermal and mechanical conditions, that spalling depends not only on the thermal gradients in concrete during heating but also on the size and restraint conditions of the tested specimen. Furthermore, observations from large scale standard fire resistance tests showed that loss of bond strength of pretensioned CFRP tendons occurred at a 'critical' temperature of the tendons in the heated region, irrespective of the temperature of the tendons at the prestress transfer length, in unheated overhangs. This contradicts conventional wisdom for the structural fire safety design of concrete elements pretensioned with CFRP, in which a minimum unheated overhang is generally prescribed. Overall, the research studies presented in this thesis showed that a rational and practical understanding of the behaviour of CFRP prestressed HPSCC structural elements during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment. Recommendations for further research to achieve the above goal are provided.

<p>Processes where a molecule absorbs visible light and then disposes of the excess energy via electron/energy transfer reactions have an important role both in nature (e.g. in photosynthesis) and in many technical applications (e.g. in photography and photovoltaics). This thesis uses different spectroscopical techniques, mainly ultrafast transient absorption, to study such processes. The thesis can roughly be divided into three parts.</p><p>In the first part, donor-acceptor systems linked by different conjugated bridges are studied. The objective was to see to what extent the conjugated link could enhance excited state energy or electron transfer, via so-called superexchange processes. The studied links do enhance the electron/energy transfer but in the electron transfer study the resulting charge separated state was very short lived.</p><p>The second part explores the possibility of constructing acceptor-donor-acceptor triads where the direction of electron transfer is determined by the electronic state of the donor. Direct evidence of electron transfer in the form of radical absorption was found from both the first and the second excited states of the donor.</p><p>In the last part, two common chromophores were investigated by transient absorption anisotropy. In the case of Ru(bpy)₃²⁺, it was found that the complex lost all memory of the polarization of the exciting light much faster than what was previously thought. This means that electron transfer between ligands is normally not the rate limiting step in electron transfer reactions involving this complex. In the case of zinc porphyrin, it was seen that the measured anisotropy differed depending on which electronic state was excited suggesting differences in the degree of coherence.</p>

Processes where a molecule absorbs visible light and then disposes of the excess energy via electron/energy transfer reactions have an important role both in nature (e.g. in photosynthesis) and in many technical applications (e.g. in photography and photovoltaics). This thesis uses different spectroscopical techniques, mainly ultrafast transient absorption, to study such processes. The thesis can roughly be divided into three parts. In the first part, donor-acceptor systems linked by different conjugated bridges are studied. The objective was to see to what extent the conjugated link could enhance excited state energy or electron transfer, via so-called superexchange processes. The studied links do enhance the electron/energy transfer but in the electron transfer study the resulting charge separated state was very short lived. The second part explores the possibility of constructing acceptor-donor-acceptor triads where the direction of electron transfer is determined by the electronic state of the donor. Direct evidence of electron transfer in the form of radical absorption was found from both the first and the second excited states of the donor. In the last part, two common chromophores were investigated by transient absorption anisotropy. In the case of Ru(bpy)32+, it was found that the complex lost all memory of the polarization of the exciting light much faster than what was previously thought. This means that electron transfer between ligands is normally not the rate limiting step in electron transfer reactions involving this complex. In the case of zinc porphyrin, it was seen that the measured anisotropy differed depending on which electronic state was excited suggesting differences in the degree of coherence.

¤@¡BRole of 5-thio-(2-nitrobenzoic acid)-capped gold nanoparticles in the sensing of chromium(VI): remover and sensor This study describes a simple, rapid method for sensing Cr(VI) using 5-thio-(2-nitrobenzoic acid) modified gold nanoparticles (TNBA-AuNPs) as a remover for Cr(III) and as a sensor for Cr(VI). We discovered that TNBA-AuNPs were dispersed in the presence of Cr(VI), whereas Cr(III) induced the aggregation of TNBA-AuNPs. Due to this phenomenon, TNBA-AuNPs can be used as a sorbent material for the removal of > 90% Cr(III), without removing Cr(VI). After centrifuging a solution containing Cr(III), Cr(VI), and TNBA-AuNPs, Cr(III) and Cr(VI) were separately present in the precipitate and supernatant. In other words, TNBA-AuNPs are capable of separating a mixture of Cr(III) and Cr(VI). The addition of ascorbic acid to the supernatant resulted in a reduction of Cr(VI) to Cr(III), driving the aggregation of TNBA-AuNPs. The selectivity of this approach is more than 1000-fold for Cr(VI) over other metal ions. The minimum detectable concentration of Cr(VI) was 1 £gM using this approach. Inductively coupled plasma mass spectrometry provided an alternative for the quantification of Cr(III) and Cr(VI) after a mixture of Cr(III) and Cr(VI) had been separated by TNBA-AuNPs. The applicability of this approach was validated through the analysis of Cr(VI) in drinking and tap water. ¤G¡BFluorescent Sensing of Total, Protein-bound, Free, and Oxidized Homocysteine in Plasma through the Combination of Tris(2-carboxyethyl)Phosphine Reduction, Fluorosurfactant-Capped Gold Nanoparticles Extraction, and o-Phthaldialdehyde Derivatization This study reports a simple, selective, and sensitive method for fluorescent detection of total, protein-bound, free, and oxidized homocysteine (HCys) using tris(2-carboxyethyl)phosphine (TCEP) as a reducing agent, fluorosurfactant-capped gold nanoparticles (FSN-AuNP) as a preconcentrating probe, and o-Phthaldialdehyde (OPA) as a derivatizing agent. TCEP was used to reduce the disulfide bonds of protein-bound and oxidized HCys. FSN-AuNPs were capable of extracting HCys from a complicated complex because the FSN capping layer can stabilize the AuNPs in a high-salt solution and inhibit non-specific adsorption. HCys was selectively derivatized with OPA in the absence of a nucleophile. By taking advantage of these features, the selectivity of the proposed system is greater than 100-fold for HCys and homocystine (HCys-HCys disulfide; diHCys) compared to any aminothiols. The limits of detection (LODs) for HCys and diHCys were 4.4 and 4.6 nM, respectively. Compared to other sensors, the proposed system provides an approximately 3-300-fold improvement in the detection of HCys. Different forms of plasma HCys were determined by varying the order of disulfide reduction with TCEP. The proposed system was successfully applied to determine the total, protein-bound, free, and oxidized HCys in plasma. To the best of our knowledge, the proposed system not only provides the first method for detecting various forms of plasma HCys, but also has the lowest LOD value for HCys when compared to other sensors.

Electron transfer, ET, and proton-coupled electron transfer, PCET, reactions are central to biological reactions involving catalysis, energy conversion and energy storage. The movement of electrons and protons in either a sequential or concerted manner are coupled in a series of elementary reaction steps in respiration and photosynthesis to harvest and convert energy consumed in foodstuffs or by absorption of light into high energy chemi-cal bonds in the form of ATP. These electron transfer processes may be modulated by conformational dynamics within the protein matrix or at the protein-protein interface, the energetics of which are still not well understood. Photoacoustic calorimetry is an estab-lished method of obtaining time-resolved reaction enthalpy and volume changes on the nanosecond to microsecond timescale. Photoacoustic calorimetry is used here to probe 1) the energetics and volume changes for ET between the self-assembled anionic uroporphy-rin:cytochrome c complex and the role of the observed volume changes in modulating ET within the complex, 2) the enthalpy and volume change for the excited state PCET reac-tion of a tyramine functionalized ruthenium(II) bis-(2,2'-bipyridine)(4-carboxy-4'-methyl-2,2'-bipyrine) meant to be a model for the tyrosine PCET chemistry carried out by cyto-chrome c oxidase and photosystem II, 3) the enthalpy and volume changes related to car-bon monoxide and tryptophan migration in heme tryptophan catabolic enzyme indoleam-ine 2,3-dioxygenase.

Fossil fuel and advanced industrialization techniques contribute to global warming through emissions of greenhouse gases such as CO2. In order to mitigate climate change, there is a desperate need to reduce CO2 emissions from different sources. CO2 capture and sequestration (CCS) play an important role in these reductions. Naturally occurring enzymes, e.g., carbonic anhydrase (CA), can catalyze these reactions in living systems. Much effort has been focused on complexes of zinc with ligands such as teta, cyclen and tripodal ligands including BIMA and Trispyrazolylborates. These complexes have many interesting CO2 capture properties, but maintain toxic perchlorate ions. We desired to replace them with less hazardous counteranions like BF4- or PF6-. Our research focused mainly on the synthesis and characterization of Zn, Co and Cu cyclen and teta complexes that could mimic CA. We also examined some of these species for catalytic CO2 hydration behavior on wetted-wall column (WWC) at Center for Applied Energy Research (CAER). We successfully synthesized and characterized eight new complexes. These catalysts as CO2 capture systems are more stable have low molecular weights (compared to CA) and more cost effective than enzymes. In terms of catalytic activity significant results were obtained only for few of the catalysts