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1
Ross, Peter, and n/a. "Organisational and Workforce Restructuring in a Deregulated Environment: A Comparative Study of The Telecom Corporation of New Zealand (TCNZ) and Telstra." Griffith University. Graduate School of Management, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030930.155125.
Full textAbstract:
In the late 1980s, governments in New Zealand and Australia began to deregulate their telecommunications markets. This process included the corporatisation and privatisation of former state owned telecommunications monopolies and the introduction of competition. The Telecom Corporation of New Zealand (TCNZ) was corporatised in 1987 and privatised in 1990. Its Australian counterpart, Telstra, was corporatised in 1989 and partially privatised in 1997. This thesis examines and compares TCNZ and Telstra's changing organisational and workforce restructuring strategies, as they responded to these changes. It further examines how these strategies influenced the firms' employment relations (ER) policies. Strategic human resource management (SHRM) and transaction costs economics (TCE) theories assist in this analyse. TCE links organisational restructuring to the make/buy decisions of firms and the asset-specificity of their employees. It suggests that firms will retain workers that have developed a high degree of firm-specific skills, and outsource more generic and semi-skilled work. Firm strategies are also influenced by national, contextual, factors. From a TCE perspective, these external factors alter relative transaction costs. Hence, different ownership structures, ER legislation and union power help to explain differences in TCNZ and Telstra's organisational restructuring and ER strategies. During the decade from 1990 to 2000, TCNZ and Telstra cut labour costs through large-scale downsizing programs. Job cuts were supported by outsourcing, work intensification and the introduction of new technologies. These initial downsizing programs were carried out through voluntary redundancies, across most sections of the firms. In many instances workers simply self-selected themselves for redundancies. TCNZ and Telstra's downsizing strategies then became more strategic, as they targeted generic and semi-skilled work for outsourcing. These strategies accorded with a TCE analysis. But TCNZ and Telstra engaged in other practices that did not accord with a TCE analysis. For example, both firms outsourced higher skilled technical work. TCNZ and Telstra's continued market domination and the emphasis that modern markets place on short term profits, provided possible reasons for these latter strategies. This thesis suggests, therefore, that while TCE may help to predict broad trends in 'rational organisations', it may be less effective in predicting the behaviour of more politically and ideologically driven organisations aiming for short term profit maximisation. Some TCNZ and Telstra workers were shifted to subsidiaries and strategic alliances, which now assumed responsibility for work that had previously been performed in-house. Many of these external firms re-employed these workers under more 'flexible' employment conditions. TCNZ and Telstra shifted to more unitarist ER strategies with their core workers and reduced union influence in the workplace. Unions at Telstra were relatively more successful in retaining members than their counterparts at TCNZ. By 2002, TCNZ and Telstra had changed from stand-alone public sector organisations, into 'leaner' commercially driven firms, linked to subsidiaries, subcontractors and strategic alliances.
2
Ross, Peter. "Organisational and Workforce Restructuring in a Deregulated Environment: A Comparative Study of The Telecom Corporation of New Zealand (TCNZ) and Telstra." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/367438.
Full textAbstract:
In the late 1980s, governments in New Zealand and Australia began to deregulate their telecommunications markets. This process included the corporatisation and privatisation of former state owned telecommunications monopolies and the introduction of competition. The Telecom Corporation of New Zealand (TCNZ) was corporatised in 1987 and privatised in 1990. Its Australian counterpart, Telstra, was corporatised in 1989 and partially privatised in 1997. This thesis examines and compares TCNZ and Telstra's changing organisational and workforce restructuring strategies, as they responded to these changes. It further examines how these strategies influenced the firms' employment relations (ER) policies. Strategic human resource management (SHRM) and transaction costs economics (TCE) theories assist in this analyse. TCE links organisational restructuring to the make/buy decisions of firms and the asset-specificity of their employees. It suggests that firms will retain workers that have developed a high degree of firm-specific skills, and outsource more generic and semi-skilled work. Firm strategies are also influenced by national, contextual, factors. From a TCE perspective, these external factors alter relative transaction costs. Hence, different ownership structures, ER legislation and union power help to explain differences in TCNZ and Telstra's organisational restructuring and ER strategies. During the decade from 1990 to 2000, TCNZ and Telstra cut labour costs through large-scale downsizing programs. Job cuts were supported by outsourcing, work intensification and the introduction of new technologies. These initial downsizing programs were carried out through voluntary redundancies, across most sections of the firms. In many instances workers simply self-selected themselves for redundancies. TCNZ and Telstra's downsizing strategies then became more strategic, as they targeted generic and semi-skilled work for outsourcing. These strategies accorded with a TCE analysis. But TCNZ and Telstra engaged in other practices that did not accord with a TCE analysis. For example, both firms outsourced higher skilled technical work. TCNZ and Telstra's continued market domination and the emphasis that modern markets place on short term profits, provided possible reasons for these latter strategies. This thesis suggests, therefore, that while TCE may help to predict broad trends in 'rational organisations', it may be less effective in predicting the behaviour of more politically and ideologically driven organisations aiming for short term profit maximisation. Some TCNZ and Telstra workers were shifted to subsidiaries and strategic alliances, which now assumed responsibility for work that had previously been performed in-house. Many of these external firms re-employed these workers under more 'flexible' employment conditions. TCNZ and Telstra shifted to more unitarist ER strategies with their core workers and reduced union influence in the workplace. Unions at Telstra were relatively more successful in retaining members than their counterparts at TCNZ. By 2002, TCNZ and Telstra had changed from stand-alone public sector organisations, into 'leaner' commercially driven firms, linked to subsidiaries, subcontractors and strategic alliances.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Graduate School of Management
Full Text
3
Silva, Maria do Socorro de Paula. "SÃntese e caracterizaÃÃo de complexos bipiridÃnicos de rutÃnio com ligantes polinitrilados." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1453.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoNo presente trabalho, os complexos cis-[Ru(dcbpy)(bpy)(TCNQ)Cl] e cis-[Ru(dcbpy)(bpy)(TCNE)Cl], denominados de Ru-TCNQ e Ru-TCNE, respectivamente, (dcbpy = 4,4â-dicarboxi-2,2â-bipiridina e bpy = 2,2â-bipirina) foram sintetizados e caracterizados por tÃcnicas espectroscÃpicas e eletroquÃmicas. Os espectros de UV-VisÃvel apresentaram para os complexos Ru-TCNQ e Ru-TCNE bandas de absorÃÃo na regiÃo do visÃvel, sendo atribuÃdas Ãs bandas de transferÃncia de carga do tipo MLCT. Os espectros de luminescÃncia apresentaram emissÃo, quando excitados na regiÃo da MLCT (500nm), evidenciando a modificaÃÃo estrutural com a coordenaÃÃo dos ligantes polinitrilados ao RuII. Os decaimentos dos compostos forma biexponenciais, com o complexo Ru-TCNQ apresentou tempos de vida muito mais curtos que o Ru-TCNE. No infravermelho, foi observado que os compostos TCNX encontram-se ligados covalentemente ao Ãtomo de rutÃnio. Essa coordenaÃÃo se dà atravÃs de ligaÃÃo σ entre o Ãtomo de nitrogÃnio de uma das nitrilas, evidenciada pelo surgimento de um maior nÃmero de bandas referentes ao estiramento C≡N, comparativamente aos ligantes livres de coordenaÃÃo. A observaÃÃo do deslocamento dessas bandas para regiÃes de menor energia, quando comparadas aos ligantes livres, permitiram identificar que os ligantes TCNQ e TCNE encontram-se coordenados em sua forma radicalar (TCNX.â). O grau de transferÃncia de carga (Z) baseado nos espectros de infravermelho para os compostos Ru-TCNQ e Ru-TCNE foi de 0,66 e 0,78, respectivamente. Os espectros de RPE confirmaram a coordenaÃÃo dos ligantes ao centro metÃlico na forma reduzida (Ru-TCNQ: g = 2,007 e para Ru-TCNE: g = 2,010). Os potencias redox nos complexos Ru-TCNQ (Ered = 0,70V vs ENH) e Ru-TCNE (Ered = 1,30V vs ENH) foram deslocados para potenciais mais positivos, quando comparados ao precursor cis-[Ru(dcbpy)(bpy)Cl2] (Ered = 0,67V vs ENH), evidenciando o forte carÃter π receptor de elÃtrons dos ligantes TCNX, estabilizando o centro metÃlico na forma reduzida. Esses resultados evidenciam um carÃter retirador de elÃtrons mais pronunciado para o ligante TCNE em relaÃÃo ao TCNQ.
In this work, the [Ru(bpy)(dcbpy)(TCNQ)Cl] and [Ru(bpy)(dcbpy)(TCNE)Cl] complexes, called Ru-TCNQ and Ru-TCNE, respectively, where bpy = 2,2â- bipyridine and dcbpy = 4,4â-dicarboxy-2,2â-bipyridine, were synthesized and characterized by spectroscopy and electrochemical techniques. The absorption spectra of the Ru-TCNQ and Ru-TCNE complexes showed bands assigned to metalto-ligand charge transfer transitions (MLCT). The luminescence spectra, with excitation at the MLCT, exhibited emission with maximum of intensity at 570 and 605 nm for the Ru-TCNQ and Ru-TCNE complexes, respectively. The luminescence decay of the complexes follows a biexponential law, with the Ru-TCNQ complex showing shorter lifetime than the Ru-TCNE complex. The infrared vibrational spectra of the complexes show a larger number of nitrile stretching bands, comparatively to the free ligands of coordination. These suggesting that the TCNX compounds are coordinated to the ruthenium atom. Upon coordenation, the shifts of these bands for lower energy values are indicative of the TCNX reduced form (TCNX⋅â). These results are confirmed by EPR spectra with g = 2.007 and 2.010 for Ru-TCNQ and Ru-TCNE complexes, respectively. The degree of charge transfer (Z) for the Ru-TCNQ and Ru-TCNE compounds was evaluated as 0.66 and 0.78, respectively. The RuIII/II redox potentials of the Ru-TCNQ (0.70V) and Ru-TCNE (1.30V) compounds, shifted for more positive potentials, when compared to the starting complex, cis- [Ru(dcbpy)(bpy)Cl2] (0,67V). These results inducate that the ligands acts as π-acceptor allowing a π-back-bonding interaction which imply in a thermodynamic stability of the metal in the reduced state (RuII). The data, all together, suggest that the TCNE compound presents a higher πback-bonding interaction capability than TCNQ compound.
4
Pontes, Daniel de Lima. "Estudo de complexos de ferro-cyclam com ligantes carboxilados e polinitrilados." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2934.
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CoordenaÃÃo de AperfeiÃoamento de NÃvel SuperiorO objetivo deste trabalho à contribuir com o desenvolvimento da quÃmica do sistema Fe-cyclam, atravÃs da sÃntese e caracterizaÃÃo de novos complexos metÃlicos deste sistema com duas classes de ligantes: carboxilados (oxalato e acetato) e ligantes polinitrilados (7,7,8,8 âtetracianoquinodimetano e tetracianoetileno ). AtravÃs da caracterizaÃÃo do complexo cis-[Fe(cyclam)ox]PF6 por infravermelho foi possÃvel identificar que o ligante oxalato encontra-se coordenado ao centro metÃlico de forma bidentada, bem como garantir que o ligante macrocÃclico cyclam continua na esfera de coordenaÃÃo do metal. O potencial formal de meia onda do processo redox Fe3+/2+ do complexo foi observado em â39mV vs Ag/AgCl. O potencial observado encontra-se deslocado 240mV para menores valores em relaÃÃo ao complexo precursor, favorecendo ao estado de oxidaÃÃo Fe3+ do metal, devido ao maior efeito σ doador do ligante oxalato frente aos cloretos. O espectro UV-Vis do complexo cisâ[Fe(cyclam)ox]PF6, em meio aquoso, apresentou trÃs bandas: 229nm, atribuÃda a uma transiÃÃo intraligante do cyclam, 293nm e 357nm, atribuÃdas à transferÃncia de carga de orbitais π do ligante para o orbitais dπ* do metal. Os experimentos fotoquÃmicos demonstraram a grande sensibilidade do complexo à luz, sendo observado a labilizaÃÃo do ligante oxalato da esfera de coordenaÃÃo do metal, e a reatividade da espÃcie formada atravÃs da obtenÃÃo do complexo trans-[Fe(cyclam)acet2]PF6, AtravÃs do estudo de Raio-X, obtido a partir do cristal do complexo trans-[Fe(cyclam)acet2]PF6, foi possÃvel comprovar o modo de coordenaÃÃo das duas molÃculas de acetato na posiÃÃo trans, bem como a identificaÃÃo da disposiÃÃo do cyclam no plano da molÃcula atravÃs de um arranjo conformacional trans-III. Os espectros no infravermelho dos complexos cis - [Fe(cyclam)(TCNX)Cl]Cl, onde TCNX representa os ligantes TCNQ ou TCNE, apresentaram um maior nÃmero de bandas referentes aos estiramentos CN, comparativamente aos ligantes livres, confirmando a alteraÃÃo da simetria do ligante causada pela coordenaÃÃo do metal. Com base nos deslocamentos destas freqÃÃncias para menores valores, comparativamente ao ligante livre, foi possÃvel identificar que os ligantes TCNQ e TCNE estÃo coordenados em sua forma radicalar, estado de oxidaÃÃo â1, sugerindo assim a ocorrÃncia de um processo de transferÃncia de elÃtrons do centro metÃlico, previamente reduzido (Fe2+), para os ligantes TCNX. Os potenciais redox dos Ãtomos de ferro, nos complexos com os ligantes polinitrialados TCNQ (693mV vs ENH) e TCNE (854mV vs ENH), foram deslocados para potenciais mais positivos, comparativamente ao observado no complexo precursor cis-[Fe(cyclam)Cl2]Cl (405mV vs ENH), indicando assim um forte deslocamento de densidade eletrÃnica dπ para os orbitais de simetria π dos ligantes TCNX. Os processos centrados nos ligantes coordenados ficaram mais prÃximos do que nos ligantes livres, indicando uma diminuiÃÃo na barreira de transferÃncia de elÃtrons, que segundos dados da literatura leva a uma melhor conduÃÃo elÃtrica. Os espectros eletrÃnicos dos complexos, em meio aquoso, apresentaram uma banda localizada em baixa energia, atribuÃda a transferÃncias de carga do tipo LMCT dos orbitais pπ das molÃculas de TCNX, para os orbitais dπ* do Ãon Fe3+. No complexo com o ligante TCNQ, esta banda aparece em 764nm e no complexo com o ligante TCNE, em 861nm. Observa-se ainda nos dois complexos a presenÃa das bandas referentes Ãs transiÃÃes LMCT dos cloretos para o Ãon Fe3+ em regiÃes muito prÃximas, em 557 no complexo com TCNE e em 568nm no complexo com TCNQ. A presenÃa desta banda novamente sugere a presenÃa do Ferro no estado oxidado (Fe+3).
The main objective of this work is to contribute with the chemistry of the system Fe-Cyclam through the synthesis and characterization of complexes with carboxylate ligants, acetate and oxalate, and polinitrilate ligands, 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE). The infrared spectra of the cis-[Fe(cyclam)ox]PF6 complex allowed to identify the coordination of the oxalate ligand to the iron metal in a bidentate mode as well as to suggest the presence of the macrocycle in the coordination sphere of the metal. The redox potential of the complex was observed at â39mV vs Ag/AgCl. The potential is dislocated 240mV for more positive potential when compared to that observed for the precursor complex cis-[Fe(cyclamCl2]Cl. This effect can be attributed to the stronger σ effect of the oxalate ligand when compared to the chlorine. The UV-Vis spectra of the complex, presented three bands: 229nm, attributed to a cyclam intraligand transition and the bands 293nm and 357nm, referring to ligand to metal electronic transfer from π orbitals of the oxalate to dπ* of the metal. The photochemical experiments proved the great sensibility of the complex to the light presence, being observed the reactivity effect of the complex formed after the light exposition by the formation of the trans-[Fe(cyclam)acet2]PF6 complex. Through the Ray-X obtained of the crystal of the trans-[Fe(cyclam)acet2]PF6 complex was possible to identify the coordination of two molecules of acetate at the trans position, as well as to identify the disposition of the cyclam ligand on the plane in a trans-III arrange. The infrared spectrum of the complexes cis - [Fe(cyclam)(TCNX)Cl]Cl, where the TCNX represent the ligands TCNQ and TCNE, present a great number of bands referring to the νCN, when compared with the ligands not coordinated, confirming the symetry changed induced by the metal coordination. Through the wavenumber variation of these bands was possible to identify that the TCNQ and TCNE ligands are coordinated in your radical way, oxidation state â1, suggestion this way the occurrence of a electron transfer from the iron, previously reduced (Fe+2), to the TCNX ligands. The redox potentials of the iron metals in the complexes with the polinitrilate ligands TCNQ (693mV vs ENH) and TCNE (854mV vs ENH) were dislocated for more positive potentials, when compared to the cis-[Fe(cyclam)Cl2]Cl precursor complex (405mV vs ENH), indicating the occurrence of an electronic density transfer to the TCNX molecules. The two potentials of the ligands on the complexes were closer than the ligands not coordinated, this approximation of the potential indicate a decrease of the inner electron transfer. The electronic spectra of the complexes, showed bands in the low energy region, attributed to a charge transfer LMCT, from the TCNX pπ orbital to the metal dπ* orbital. In the cis-[Fe(cyclam)(TCNQ)Cl]Cl complex, the band was observed at 764nm while in the complex with the TCNE ligand this band was observed at 861nm. Also, the complexes presented bands at 557nm (TCNE complex) and 568nm (TCNQ complex)referring to the LMCT transitions from the chlorine atoms to the iron metal reinforcing the assignment of the (Fe+3) oxidation state for the metal center.
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Silva, Maria. "Síntese e caracterização de complexos bipiridínicos de rutênio com ligantes polinitrilados." reponame:Repositório Institucional da UFC, 2007. http://www.repositorio.ufc.br/handle/riufc/2079.
Full textAbstract:
SILVA, M. S. P. Síntese e caracterização de complexos bipiridínicos de rutênio com ligantes polinitrilados. 2007. 69 f. Dissertação (Mestrado em Química Inorgânica) – Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2007.Submitted by irlana araujo (irlanaaraujo@gmail.com) on 2011-12-29T16:06:49Z No. of bitstreams: 1 2007_dis_Mar Silva.pdf: 4361976 bytes, checksum: 5d026e36da8e46a99cf7b943340c149b (MD5)
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In this work, the [Ru(bpy)(dcbpy)(TCNQ)Cl] and [Ru(bpy)(dcbpy)(TCNE)Cl] complexes, called Ru-TCNQ and Ru-TCNE, respectively, where bpy = 2,2’- bipyridine and dcbpy = 4,4’-dicarboxy-2,2’-bipyridine, were synthesized and characterized by spectroscopy and electrochemical techniques. The absorption spectra of the Ru-TCNQ and Ru-TCNE complexes showed bands assigned to metalto-ligand charge transfer transitions (MLCT). The luminescence spectra, with excitation at the MLCT, exhibited emission with maximum of intensity at 570 and 605 nm for the Ru-TCNQ and Ru-TCNE complexes, respectively. The luminescence decay of the complexes follows a biexponential law, with the Ru-TCNQ complex showing shorter lifetime than the Ru-TCNE complex. The infrared vibrational spectra of the complexes show a larger number of nitrile stretching bands, comparatively to the free ligands of coordination. These suggesting that the TCNX compounds are coordinated to the ruthenium atom. Upon coordenation, the shifts of these bands for lower energy values are indicative of the TCNX reduced form (TCNX⋅–). These results are confirmed by EPR spectra with g = 2.007 and 2.010 for Ru-TCNQ and Ru-TCNE complexes, respectively. The degree of charge transfer (Z) for the Ru-TCNQ and Ru-TCNE compounds was evaluated as 0.66 and 0.78, respectively. The RuIII/II redox potentials of the Ru-TCNQ (0.70V) and Ru-TCNE (1.30V) compounds, shifted for more positive potentials, when compared to the starting complex, cis- [Ru(dcbpy)(bpy)Cl2] (0,67V). These results inducate that the ligands acts as π-acceptor allowing a π-back-bonding interaction which imply in a thermodynamic stability of the metal in the reduced state (RuII). The data, all together, suggest that the TCNE compound presents a higher πback-bonding interaction capability than TCNQ compound.
No presente trabalho, os complexos cis-[Ru(dcbpy)(bpy)(TCNQ)Cl] e cis-[Ru(dcbpy)(bpy)(TCNE)Cl], denominados de Ru-TCNQ e Ru-TCNE, respectivamente, (dcbpy = 4,4’-dicarboxi-2,2’-bipiridina e bpy = 2,2’-bipirina) foram sintetizados e caracterizados por técnicas espectroscópicas e eletroquímicas. Os espectros de UV-Visível apresentaram para os complexos Ru-TCNQ e Ru-TCNE bandas de absorção na região do visível, sendo atribuídas às bandas de transferência de carga do tipo MLCT. Os espectros de luminescência apresentaram emissão, quando excitados na região da MLCT (500nm), evidenciando a modificação estrutural com a coordenação dos ligantes polinitrilados ao RuII. Os decaimentos dos compostos forma biexponenciais, com o complexo Ru-TCNQ apresentou tempos de vida muito mais curtos que o Ru-TCNE. No infravermelho, foi observado que os compostos TCNX encontram-se ligados covalentemente ao átomo de rutênio. Essa coordenação se dá através de ligação σ entre o átomo de nitrogênio de uma das nitrilas, evidenciada pelo surgimento de um maior número de bandas referentes ao estiramento C≡N, comparativamente aos ligantes livres de coordenação. A observação do deslocamento dessas bandas para regiões de menor energia, quando comparadas aos ligantes livres, permitiram identificar que os ligantes TCNQ e TCNE encontram-se coordenados em sua forma radicalar (TCNX.–). O grau de transferência de carga (Z) baseado nos espectros de infravermelho para os compostos Ru-TCNQ e Ru-TCNE foi de 0,66 e 0,78, respectivamente. Os espectros de RPE confirmaram a coordenação dos ligantes ao centro metálico na forma reduzida (Ru-TCNQ: g = 2,007 e para Ru-TCNE: g = 2,010). Os potencias redox nos complexos Ru-TCNQ (Ered = 0,70V vs ENH) e Ru-TCNE (Ered = 1,30V vs ENH) foram deslocados para potenciais mais positivos, quando comparados ao precursor cis-[Ru(dcbpy)(bpy)Cl2] (Ered = 0,67V vs ENH), evidenciando o forte caráter π receptor de elétrons dos ligantes TCNX, estabilizando o centro metálico na forma reduzida. Esses resultados evidenciam um caráter retirador de elétrons mais pronunciado para o ligante TCNE em relação ao TCNQ.
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Monezi, Natália Mariana. "Espectroscopia Raman ressonante e cálculos DFT de sistemas modelo de transferência de carga." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-24082018-095811/.
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Neste trabalho foram estudados os complexos de transferência de carga resultantes da interação entre as espécies aceptoras de elétrons tetracianoetileno (TCNE) e 7,7,8,8-tetracianoquinodimetano (TCNQ), com aminas mono, bi e tri aromáticas, como espécies doadoras de elétrons, em solução. Também foram estudadas as reações de substituição eletrofílica aromática que ocorre entre o TCNE e aminas. Para tal estudo, foram utilizadas as técnicas espectroscópicas de absorção UV-VIS e Raman, o que permitiu a caracterização dos complexos de transferência de carga, assim como das espécies participantes da reação de tricianovinilação que ocorre entre aminas e TCNE. Para dar suporte aos dados experimentais, cálculos DFT (Teoria do Funcional da Densidade) e TDDFT (Teoria do Funcional da Densidade dependente do tempo) foram realizados, o que permitiu a obtenção das geometrias otimizadas, valores de frequência Raman e energias de transição dessas espécies. Os espectros eletrônicos dos complexos formados entre TCNE e aminas monoaromáticas mostraram que suas energias de transição são proporcionais à capacidade de doação de elétrons da amina. De fato, as energias de transição puderam ser correlacionadas com os valores de potencial de ionização das aminas, apresentando uma correlação linear de acordo com a regra Mulliken. Os espectros Raman permitiram verificar que os modos vibracionais do TCNE envolvidos no processo de transferência de carga apresentam deslocamento para menores números de onda com a diminuição do potencial de ionização da amina, e analogamente, pôde-se obter uma correlação linear entre esses dois parâmetros. No caso das aminas bi e tri aromáticas, a tendência linear entre energia de transição e potencial de ionização foi observada, mas não para os deslocamentos Raman das bandas do TCNE. Na reação de tricianovinilação, os espectros eletrônicos possibilitaram a identificação das espécies participantes da reação, assim como sua caracterização vibracional por espectroscopia Raman ressonante. Através da espectroscopia Raman ressonante, pôde-se, pela primeira vez, caracterizar as espécies intermediárias da reação de tricianovinilação entre TCNE e aminas aromáticas. Os complexos envolvendo TCNQ e aminas monoaromáticas apresentou tendência semelhante à observada em complexos com o TCNE. As energias de transição desses complexos diminuem linearmente, assim como, os modos vibracionais do TCNQ, que apresentam deslocamentos para menores frequências Raman com a diminuição do potencial de ionização da amina. Por outro lado, complexos formados pelo TCNQ e aminas com mais de um anel aromático em sua estrutura, não apresentam correlação entre potencial de ionização do doador e energia de transição e deslocamentos Raman. Os cálculos dos espectros eletrônicos e vibracionais apresentaram boa concordância com os obtidos experimentalmente, porém algumas limitações ficam evidentes na descrição das interações π nesses sistemas modelo.In this work the charge transfer complexes resulting from the interaction between tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), as electron accepting species and mono, bi and tri aromatic amines, as electron donating species, were studied in solution. Also the electrophilic aromatic substitution that occurs between the TCNE and amines has been studied. For this study, the spectroscopic techniques of UV-VIS absorption and Raman were used, which allowed the characterization of the charge transfer complexes, as well as of the species involved in the reaction of tricianovinylation that occurs between amines and TCNE. In order to support the experimental data, DFT (Density Functional Theory) and TDDFT (Time-dependent Density Functional Theory) calculations were performed, to obtain the optimized geometries, Raman frequency values and theoretical transition energies of such species. The electronic spectra of the complexes formed between TCNE and monoaromatic amines showed that their transition energies are proportional to the amine electron donation capacity. In fact it could be linearly correlated with the ionization potential values of the amines, following the Mullikens rule. The Raman spectra allowed to verify that the vibrational modes of the TCNE involved in the process of charge transfer, were displaced to lower wavenumbers with the reduction of the ionization potential of the amine, and analogously, a linear correlation between these two parameters could be obtained. In the case of bi and tri aromatic amines, the linear trend between transition energy and ionization potential was observed, but not for the Raman shifts of the TCNE bands. In the reaction of tricianovinylation, the electronic spectra enabled the identification of the participating species in the reaction, and their vibrational characterization by resonance Raman. Using resonance Raman spectroscopy, it was possible to characterize the intermediate species of the tricianovinylation reaction between TCNE and aromatic amines for the first time. The complexes involving TCNQ and monoaromatic amines showed a similar trend to that observed in complexes with TCNE. The transition energies of these complexes decrease linearly, as well as the vibrational modes of the TCNQ, which present shifts to lower Raman frequencies with the decrease of the ionization potential of the amine. On the other hand, complexes formed by TCNQ and amines with more than one aromatic ring in their structure do not present correlation between donor ionization potential and transition energy and Raman displacements. The calculations of the electronic and vibrational spectra presented good agreement with those obtained experimentally, however some limitations were evidenced in the description of the π interactions in these model systems.
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Decoster, Marc, and E. Guerchais-Jacques. "Contribution à l'étude de la réactivite de polynitriles neutres et anioniques : comportement de TCNQ et TCNE vis-a-vis de complexes du molybdène ; propriétés électrochimiques et complexantes d'anions polycyanocarbones." Brest, 1994. http://www.theses.fr/1994BRES2017.
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Les travaux presentes dans la these ont pour objectif le comportement d'entites polycyanocarbonees vis-a-vis de derives inorganiques et peuvent etre scindes en deux parties. La premiere partie de ce travail traite de l'action d'oxydant doux du type tcnx (x = q, e) sur des complexes mono et dinucleaires du molybdene possedant des ligands dialkyldithiocarbamates rdtc ; r = me, et comme mo(rdtc)#4, mo#2o#3(rdtc)#4 et mo#2(rdtc)#4. Plusieurs composes ont ete synthetises: mo(rdtc)#4(tcnq)#n (n = 1,2) moo(rdtc)#3(tcnq), mo#2o(rdtc)#6(tcnq) et mo#2s(rdtc)#6(tcnq). Nous en avons examine les proprietes en solution (voltammetrie cyclique, rpe) et a l'etat solide (rpe, mesure de susceptibilite magnetique et diffraction des rayons x). On notera en particulier qu'une telle approche indique que les composes du type mo(rdtc)#4(tcnq) r = me et r = et possedent un comportement analogue en solution et un comportement different a l'etat solide. Dans la deuxieme partie de la these l'etude des proprietes redox et complexantes d'anions polycyanocarbones comme (cn)#2c-(cn)c#2n#- (c#1#0n#7)#-, (cn)#2c-(cn)c-n-#2#2#- (c#1#0n#8)#2#-,(cn)#2c#3c#2#- (c#1#0n#6)#2#- est abordee. L'examen des proprietes redox des anions c#1#0n#7#- et c#1#0n#8#2#- a mis en evidence la possibilite de generer les radicaux c#1#0n#7#?#2#-, c#1#0n#8#?#- et la synthese du sel de tetraalkylammonium de ce dernier a ete realisee par voie chimique ; l'etude par diffraction des rayons x du compose obtenu (et#4n)(c#1#0n#8) revele que l'anion existe en realite sous la forme du dimere (c#1#0n#8)#2#2#- et l'etude rpe a l'etat solide a mis en evidence le peuplement de l'etat triplet s = 1. L'etude des proprietes complexantes de ces anions polycyanocarbones a ensuite ete developpee. L'analyse par diffraction des rayons x des derives cu(c#1#0n#6)(h#2o)#2, cu(c#1#0n#6)(en), (en = ethylenediamine) et ag(c#1#0n#7) a montre que ces derniers etaient des polymeres ; l'etude des proprietes magnetiques des composes de cu(ii) a ete examinee
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Kirui, Joseph Kiprono. "ESR study of DMTM(TCNQ)₂." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29191.
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The ESR g-value and susceptibility measurements for DMTM(TCNQ)₂ have been studied as a function of angle made by crystal with magnetic field and temperature. The angular dependence of g-value is fitted to g² = α+βcos2θ - γsin2θ for three orthogonal directions of crystal rotation. The principal g-values are close to those expected for TCNQ compounds: g₁ = 2.0034, g₂ = 2.0030, g₃ = 2.0024. The susceptibility as a function of temperature agrees with bulk susceptibility measurements except that the maximum position occurs at about 30 K. The results of Oostra et al. for bulk susceptibility showed a maximum at around 50 K. The phase transition
reported by Visser et al. at 272 K is observed in the ESR data as a 15% decrease in susceptibility. The linewidth is remarkably anisotropic typical of TCNQ salts. The phase transition study is done for two orientations
of the crystal with the magnet field. In one of the orientations the linewidth narrows from 0.15 to 0.11 gauss and in the other it narrows from 0.24 to 0.18 gauss. In the former case there is a growth of a second line due to the twinned stack; transformation twinning takes place at the phase transition. A small level-crossing interaction is inferred from the change in relative intensities of the lines near the crossover.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Qureshi, Saleem. "Magnetic properties of TCNQ complexes." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278000.
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Beales, T. P. "Magnetic susceptibilities of TCNQ complex salts." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376162.
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Nader, G. K. "Phase changes in TCNQ complex salts." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353924.
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Broughton, Richard Anthony. "A study of zwitterionic adducts of TCNQ." Thesis, Sheffield Hallam University, 1993. http://shura.shu.ac.uk/19400/.
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Chapter 1 gives a general introduction to the field of electroactive organic compounds. The historical development of the field is outlined and then the more specific areas are described in detail. The properties of picolinium and quinolinium TCNQ salts are introduced and the extension of this to the molecules studied in this work developed. Two current areas of interest - second harmonic generation and molecular rectification - are then reviewed and the potential applications of the materials studied in this work highlighted. Chapter 2 discusses the synthesis of the materials and contrasts the two methods used. A discussion of the reaction mechanisms is given, as well as techniques for monitoring the course of reaction. The characterisation of the materials by a range of spectroscopic techniques is described. The solvatochromic behaviour of the materials is shown to conform with theoretical predictions and the observed mass spectra are shown to have some diagnostic importance. Chapter 3 gives a general introduction to Langmuir-Blodgett (LB) films starting once again from a historical perspective. The molecular requirements of suitable materials together with pressure/area per molecule measurements and the deposition process are described. The various methods available for the characterisation of LB films are described, as well as the many potential applications proposed within the general field of molecular electronics. Chapter 4 describes the experimental methods employed when using the Joyce Loebl Langmuir Trough. The importance of parameters such as cleanliness, sample purity and instrument calibration is stressed. Chapter 5 discusses the behaviour of the materials on the subphase and their resultant fabrication as LB films. The structure of the films is shown to be dependent on the hydrophobic chain length with a definite change in film structure occurring at a 15 carbon chain. Reasons for this are proposed and calculations of chromophore/hydrocarbon chain tilt angles on the basis of the proposed structure are given. A time dependent change in film structure is also discussed, as well as suggestions for future work.
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Kancono. "Complexes de transfert de charge oligothiophène/TCNQ dans les matériaux hybrides organique-inorganique : influence du TCNQ sur la structure des gels." Montpellier 2, 2001. http://www.theses.fr/2001MON20218.
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Cross, Graham Hugh. "Electrical and magnetic characterisation of a series of TCNQ salts." Thesis, Sheffield Hallam University, 1985. http://shura.shu.ac.uk/19516/.
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The electrical and magnetic properties of a series of 12 isostructural TCNQ salts of bis-pyridinium cations are reported and these properties are related to the structural characteristics. The role of the cation lattice in stabilising a regular TCNQ stack in these salts is discussed. For comparison with this series, the electrical and magnetic properties of two TCNQ salts of bis-pyridinium cations with ordered structures and two salts of dialkyldiphenylphosphonium cations are reported. Within the isostructural series of salts, the stoichiometry takes values of between 1:3 and 1:5, and the cation length determines the stoichiometry. In all these salts, the hydrated cation lattice is disordered and the TCNQs stack in regular columns. The room temperature conductivities, measured along the stacking axis, are in the range 0.05 to 500 S/cm with the highest conductivities observed in dehydrated salts having the approximate stoichiometry, 1:4.5. The 1:5 salts possess the lowest conductivity of the series and in these salts the cation lattice is partially ordered. The 1:3 and 1:4 salts are small band gap semi-conductors whereas the conductivity of the 1:5 salts is not simply activated within the experimental range of temperatures. In these salts the conductivity obeys the empirical power law: [mathematical equation]. The temperature dependence of the magnetic susceptibility of all but the 1:3 salts of the isostructural series is characteristic of a system of partially localised triplet excitons. The magnitude of the singlet-triplet exchange energy exhibits a stoichiometric dependence and is lower in the 1:5 salts where the spin concentration is lower. The magnetic susceptibility of the 1:3 salts varies with temperature according to the Curie-Weiss law. The apparent low spin concentration supports the evidence found for alloy formation in these salts where the cation lattice is partially occupied by neutral or monoquaternised base.
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Cabañas, Francisco Xavier. "A study of level crossing effects in TCNQ salts." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28632.
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ESR results for DEM(TCNQ)₂ and for MEM(TCNQ)₂ are presented as examples of TCNQ salts with and without level crossing effects. In the case of DEM(TCNQ)₂ we are performing ESR on a system with two types of spins. The latter are due to the two kinds of stacks of the acceptor TCNQ molecules in DEM(TCNQ)₂. The level crossing occurs when the g value of these two kinds of electrons are the same. This is compared to the case of MEM(TCNQ)₂ where there is only one kind of TCNQ stack and consequently no level crossing effect. It is found that g values and susceptibilities of the ESR spectra for DEM(TCNQ)₂ can be fitted very well to an interaction between the stacks of the form J ∑i,j,Si,Sj; with J > 0. This
gives an antiferromagnetic coupling between every spin on one type of stack with every spin on the other type of stack. This type of interaction is also in qualitative agreement with the published results for HMM(TCNQ)₂. The experimental results in DEM(TCNQ)₂ and MEM(TCNQ)₂ also show that there are small but significant differences in the g tensors when the temperature or the crystalline environment are changed, and consequently the g tensor in these compounds does not depend only on the orientation of TCNQ molecule in the magnetic field as previously assumed. These differences in g are typically less than 2 x 10⁻⁴.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Voss, Gleizer Bierhalz. "TCN5 - TEACHING COMPUTER NETWORKS IN A FREE IMMERSIVE VIRTUAL ENVIRONMENT." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/5425.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorTeaching technical themes in the area of Computer Networks involves difficult concepts to be understood in the traditional educational way, i.e. statically. At the same time, technological advances have created many opportunities in education, requiring the development of new pedagogical practices that contribute to the process of teaching and learning. The creation of immersive virtual environments and the addressing of issues related to context-aware computing can support this process. For that, in this dissertation it was developed an immersive virtual environment for teaching Computer Networks that uses learner context information -e.g. technology, cognitive style, and quality of context-, while providing a significant learning from the integration and interaction between users and technology. To achieve the objectives of this study, an exploratory research with a case study was performed in order to verify whether the use of an immersive virtual environment can facilitate and/or improve the process of learning the discipline of Computer Networks. The construction of this environment, named TCN5, has as basis four main elements, these being,WampServer, OpenSimulator, Sloodle and UVLEQoC Moodle, which adds features from modules like U-SEA 2.0 and SEDECA 2.0, in addition to Bootstrap theme, applying QoC parameters and metrics about the information collected in the environment, aiming to ensure the suitability of the connection for the preferences and needs of the students. In order to verify the practical feasibility of the work and the usage of the environment through mobile devices, a case study was conducted, which showed that despite mobile technologies allow the realization of most of the proposed activities, there are still some technological limitations that make difficult the usage of such devices in the educational context. At the same time, a comparative analysis between different viewers for virtual worlds was performed, pointing out advantages and disadvantages by considering aspects of available resources for processing and supported file types. Finally, a non-experimental study was conducted, using a Pedagogical Architecture, which served as the basis for the use and evaluation of the environment by a group of 25 students from the Computer Networks discipline of Computer Science program at the Federal University of Santa Maria. The results obtained during the evaluation with students accomplished the desired expectations, achieving a rating of "Excellent" on the scale of the SUS usability test and a considerable increase in the average obtained in the elaboration of the conceptual maps after using TCN5, an indication that the environment helped, at least in part, to the construction of knowledge of this group, despite the limitations and difficulties encountered during its development.
O ensino de temas técnicos na área de Redes de Computadores envolve conceitos difíceis de serem entendidos na forma pedagógica tradicional, ou seja, de forma estática. Ao mesmo tempo, os avanços tecnológicos criaram diversas possibilidades na educação, exigindo o desenvolvimento de novas práticas pedagógicas que contribuam para o processo de ensino e aprendizagem. A criação de ambientes virtuais imersivos e o tratamento de questões relacionadas com a computação sensível ao contexto podem auxiliar nesse processo. Para isso, foi desenvolvido nesta dissertação um ambiente virtual imersivo para o ensino de Redes de Computadores que trata informações de contexto do aluno (e.g., tecnologia, estilo cognitivo e qualidade do contexto), proporcionando ao mesmo uma aprendizagem significativa, a partir da integração e interação entre usuários e tecnologia. Para atingir os objetivos deste trabalho foi realizada uma pesquisa exploratória com estudo de caso, a fim de verificar se a utilização de um ambiente virtual imersivo pode facilitar e/ou melhorar o processo de aprendizagem da disciplina de Redes de Computadores. A construção desse ambiente, denominado TCN5, teve como base quatro elementos principais, sendo esses, o WampServer, o OpenSimulator, o Sloodle e o Moodle UVLEQoC, que agrega as características tanto dos módulos U-SEA 2.0 e SEDECA 2.0 como do Tema Bootstrap, aplicando parâmetros e métricas de QoC sobre as informações coletadas no ambiente, com o objetivo de garantir que o contexto formulado esteja adequado às preferências e necessidades dos alunos. Para verificar a viabilidade prática do trabalho quanto à utilização do ambiente por meio do uso de dispositivos móveis foi realizado um estudo de caso, que demonstrou que apesar das tecnologias móveis permitirem a realização da maioria das atividades propostas, existem ainda algumas limitações tecnológicas que dificultam a utilização desses dispositivos no contexto educacional. Ao mesmo tempo, foi realizada uma análise comparativa entre os diversos visualizadores de mundos virtuais disponíveis, apontando vantagens e desvantagens, considerando aspectos de processamento, recursos disponibilizados e tipos de arquivos suportados. Por fim, foi realizado um estudo Não-Experimental utilizando uma Arquitetura Pedagógica, que serviu como base para a utilização e avaliação do ambiente por uma turma de 25 alunos da disciplina de Redes de Computadores do Curso de Ciência da Computação da Universidade Federal de Santa Maria. Os resultados obtidos durante a avaliação com os alunos atenderam as expectativas, alcançando uma classificação Excelente na escala do teste de usabilidade SUS, bem como um aumento considerável na média obtida na elaboração dos mapas conceituais após a utilização do TCN5, um indício de que o ambiente auxiliou, pelo menos em parte, na construção do conhecimento dessa turma, apesar das limitações e dificuldades encontradas durante o seu desenvolvimento.
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Bradley, Christopher Simon. "The synthesis and characterisation of Langmuir-Blodgett film forming TCNQ adducts." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/19388/.
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Substitution reactions of TCNQ (7,7,8,8-tetracyanoquinodimethane) with suitable electron donor moieties extended the range of gamma-bridged adducts R(4)Q3CNQ and R(4)P3CNQ of which the short chain Z-beta-(l-butyl-4'-quinolinium)-alpha-cyano-4-styryldicyanomethanide (C[4]H[9](4)Q3CNQ) is a typical example. These zwitterionic D-pi-A materials (where D and A are electron donors and acceptors respectively) exhibit properties such as solvatochromism, molecular rectification and second harmonic generation. Further synthetic work concentrated on modifying the donor, the acceptor and the substitution position within these zwitterions to create a series of diverse materials for non-linear optic research. Modification of the picolinium and quinolinium systems where the TCNQ substitution is in the alpha-position, has created the extensive analogous series-R(2)Q3CNQ and R(2)P3CNQ, their properties being compared and contrasted to the original gamma-bridged adducts. The behaviour of the materials on the subphase and their resultant Langmuir-Blodgett (LB) film fabrication was studied. The abrupt change in molecular orientation in LB films of the gamma-bridged adducts occurring at R= C[15]H[31] and above was not seen in the more flatly orientated alpha-bridged adducts. Further characterisation of the LB films was performed using reflectance-absorption infrared spectroscopy (RAIRS) and surface plasmon resonance (SPR).A number of N-alkylpyridinium benzimidazolate betaine derivatives and the related betaine-TCNQ adducts were prepared and their LB film forming properties were studied.
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Yan, Bingjia. "A crystal engineering study of molecular electronic behaviour in TCNQ salts." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/392934/.
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This thesis explores the “crystal engineering” of the solid-state behaviour of a series of alkali metal TCNQ salts. This can exhibit a variety of electronic and magnetic properties, depending on the solid-state architecture. TCNQ is a good one-electron acceptor and the resulting radical anion salt is quite stable. The architectural behaviour of TCNQ salts is very dependent on the nature of the counter-cation and the stoichiometry of the material. In the present study, the effect of ionophore-encapsulation of the cation (M = Li, Na, K, Rb and Cs) has been explored using single crystal X-ray diffraction, IR, Raman, EPR and pressed discs conductivity measurements. In addition, the effect of changing the ionophore:metal cation ratio and the presence of additional TCNQ0 has been investigated. 25 new crystal structures have been obtained and analysed in detail and this has grown new insight into the impact of the effect of controlling ion pair interactions through ionophore complexation and of steric factors on the nature of TCNQ assemblies adopted. A range of solid-state motifs have been observed including some novel solid-state behaviour. In addition, the solid-state behaviour of two hydrated lanthanide TCNQ salts has been investigated.
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Shimomura, Satoru. "Studies on Syntheses and Properties of TCNQ based Porous Coordination Polymers." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142185.
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Santamaría, Prado Patricia. "Elektrokatalytische Erzeugung von Cu-TCNQ in Lösungsmittelgemischen und Charakterisierung der entstehenden Schichten." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982459327.
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Milián, Medina Begoña. "Análogos tiofénicos del TCNQ: Estudio teórico de las propiedades estructurales y electrónicas." Doctoral thesis, Universitat de València, 2004. http://hdl.handle.net/10803/10266.
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La Tesis Doctoral presenta une studio detallado de las propiedades estructurales y electrónicas de varias familias de análogos tiofénicos del TCNQ mediante la utilización de cálculos químico-cuánticos. Los sistemas estudiados son las moléculas de TCNE, TCNQ, tiofeno-TCNQ y distintos derivados de este último obtenidos por modificación de la estructura del espaciador tiofénico. Las estrategias utilizadas para modificar dicha estructura han sido: (i) extensión del sistema del anillo de tiofeno por fusión de anillos aromáticos, dando lugar a las moléculas de isotianafteno-TCNQ y su análogo de pirazina, o por introducción de grupos vinílicos; (ii) extensión lineal del esqueleto conjugado del espaciador por repetición de la unidad central de tiofeno, obteniéndose dímeros, trímeros y tetrámeros quinoides, o por fusión de anillos conservando la estructura quinoide; (iii) incorporación de grupos dadores y aceptores de electrones en la misma molécula, para dar lugar a los llamados sistemas "push-pull". Los sistemas estudiados han sido elegidos por el interés que suscitan dentro del campo de los materiales moleculares electroactivos.El objetivo del trabajo de Tesis Doctoral ha consistido en analizar la estructura molecular y electrónica de este tipo de sistemas, haciendo hincapié en la influencia de las modificaciones estructurales sobre las propiedades electrónicas de los compuestos. Concretamente, para cada familia a estudio se ha realizado la caracterización de las propiedades en estado neutro a partir de la obtención de geometrías de equilibrio, la evaluación de la transferencia de carga entre las unidades dadoras y aceptoras y la racionalización de las propiedades vibracionales. Por otra parte, se han calculado propiedades electrónicas tales como la afinidad electrónica, los estados electrónicos excitados y la transferencia de carga fotoinducida, también de los sistemas en estado neutro. Los resultados obtenidos han permitido sistematizar la evolución de las propiedades electrónicas en función de la estructura química, y se ha podido establecer una relación precisa entre ambas. Además, se ha estudiado la evolución de las propiedades estructurales y electrónicas con el proceso de dopado (generación de aniones y cationes), a través de la determinación de estructuras y la asignación de espectros vibracionales y electrónicos.La metodología principalmente utilizada ha sido la teoría del funcional de la densidad, en sus versiones independiente y dependiente del tiempo (DFT y TDDFT, respectivamente). La calidad y validez de los resultados DFT han sido calibradas mediante la utilización de otras aproximaciones metodológicas más precisas (CCSD, CCSD(T) y CASSCF/CASPT2). En general, la aplicación de los métodos de cálculo químico-cuánticos ha permitido racionalizar las propiedades estructurales y electrónicas de las distintas familias de análogos tiofénicos del TCNQ, tanto en estado neutro como reducido, incidiendo especialmente en la influencia que las modificaciones estructurales ejercen sobre las propiedades aceptoras de elctrones (afinidad electrónica, propiedades redox) de dichos compuestos.The present Doctoral Thesis deals with the theoretical study of the structural and electronic properties of TCNE, TCNQ, thiophene-TCNQ, and its derivatives. Such derivatives result from the modification of the thiophenic spacer in thiophene-TCNQ through different strategies like the extension of the p-system of the thiophene ring by fusion of aromatic rings, leading to the isotianaphthene-TCNQ and its pyrazine analogue molecules, or by introduction of vinylic groups; the linear extension of the quinonoid structure through repetition of the central thiophene moiety, leading to quinonoid dimers, trimers and tetramers, or through annelation of thiophene and benzene rings; and finally, The introduction of electron donor and electron acceptor groups in the same molecule, giving rise to the "push-pull" systems. The molecules studied have been chosen because of their interest in the field of electroactive molecular materials. Density functional theory, in its time-independent and time-dependent versions (DFT and TDDFT, respectively), has been extensively used. The quality and suitability of the DFT procedures have been calibrated by using more accurate methodological approaches (CCSD, CCSD(T), and CASSCF/CASPT2). The quantum-chemical calculations have made possible to rationalize the structural and electronic properties of the different families of thiophenic analogues of TCNQ, in their neutral and reduced states, paying special attention to the influence that the structural modifications have on the electron acceptor properties (electron affinity and redox properties) of these compounds.
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Grassi, Henri. "Études expérimentales et théoriques du complexe de transfert de charge TEA (TCNQ)₂." Nice, 1987. http://www.theses.fr/1987NICE4116.
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Étude de la conductivité et de la diffusion thermiques ; détermination du libre parcours moyen des phonons. Mise en évidence d'une transition de phase du second ordre entre 200 et 250 K et proposition d'un mécanisme. Détermination de la répartition des charges sur les deux conformations du cation par un calcul ab-initio. Caractérisation des discontinuités réversibles de la conductivité électrique d'aiguilles du TEA (TCNQ)₂ et de mMEtbBZ (TCNQ)₂
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Bouveret, Yves. "Structure des phases modulées incommensurables basse température du conducteur unidimensionnel TTF-TCNQ." Paris 11, 1988. http://www.theses.fr/1988PA112163.
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Cette thèse a pour but d'établir la structure des phases modulées incommensurables à pression normale et à basse température des conducteurs organiques quasi-unidimensionnels TTF-TCNQ et TSeF-TCNQ. Cette étude nous a conduit à déterminer à partir de données structurales obtenues par la techniques de diffraction des rayons X, le schéma réel de la distorsion de Peierls de la phase modulée de TTF-TCNQ existant en-dessous de la plus basse température de transition ("Phase d'accrochage"), en terme de modes de déplacements inter et intra-moléculaires. Nous montrons la prépondérance des composantes de translation translations parallèles au grand axe de la molécule pour TTF et perpendiculaires au plan moléculaire pour TCNQ) par rapport aux composants de libration. Ces résultats révèlent également une importante déformation intra-moléculaire de la molécule TCNQ. Un tel comportement displacif est interprété à partir de considérations sur les orbitales moléculaires concernées par les ondes de densité de charge (ODC) sur les deux types de chaînes, ainsi que par la géométrie d'empilement des molécules à l'intérieur de ces chaînes conductrices. Cette étude structurale nous a permis de déduire la structure des ODC dans la "phase d'accrochage". Nous montrons que la transition du premier ordre à 38 K conduisant à la "phase d'accrochage", se traduit par une modulation de l'amplitude et de la phase des ODC sur les chaînes TTF et seulement par une modulation de la phase des ODC sur les chaînes TCNO. Un modèle théorique simple basé sur les interactions Coulombiennes entre chaînes voisines permet d'expliquer la plus grande stabilité de la structure des ODC adoptée par TTF-TCNQ dans la "phase d'accrochage, par rapport à la structure présumée des ODC de la phase précédente ("phase de glissement"). Ce modèle montre que cette transition s'accompagne d'un changement de mode d'interaction entre ODC dans la direction a, et rend compte des phases relatives existant entre les différentes composantes de la modulation. Enfin, nous proposons une interprétation du "mécanisme d'accrochage de cette phase modulée à la valeur particulière qa = 0. 3a*This thesis deals with the determination of the structure of the low temperature modulated phases at normal pressure of the organic quasi-one dimens10nal conductors TTF-TCNO and TSF-TCNO. This structural study by X ray diffraction techniques, leads us to express the displacement scheme of the Peierls distortions in lowest temperature modulated phase of TTF-TCNO ("locking phase") in terms of inter and intra molecular displacement modes. We show the prominence of the translation components over the liberation components of the displacements. These results reveal also an important intramolecular deformation of the TCNO molecule. Such a displacive behaviour is explained using considerations of the molecular orbitals related to the charge density wave (CDW) on the two types of chains, and the stacking configuration of the molecules inside the conducting chains. This displacement scheme allows to determine the structure of the CDW in the "locking phase". We show that the first order transition at 38 K which leads to the "locking phase", is associated to a modulation of the ampl1tude and the phase of the CDW on the TTF chains and a modulation of the phase of the cow on the TCNO chains. A simple theoretical model base on the coulombic interactions between the nearest chains, enables to explain the higher stability of the structure of the CDW determined experimentally, with respect to the structure of the previous phase ("Sliding phase"). This model shows that this transition corresponds to a change of the 1nteraction mode between the CDW m the direction of the axes, and yiels phases for each component of the modulation, in good agreement with those obtained experimentally. Finally we propose an interpretation of the "locking mechanism" for the lowest temperature phase at the special value qa = 0. 3a*
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Harberts, Megan Marie. "Materials engineering, characterization, and applications of the organic-based magnet, V[TCNE]." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440096659.
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Grassi, Henri. "Etudes expérimentales et théorique du complexe de transfert de charge TEA(TCNQ)." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376055766.
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Bouveret, Yves. "Structure des phases modulées incommensurables basse température du conducteur unidimensionnel TTF-TCNQ." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376122745.
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Crouch, David James. "Synthesis and molecular properties of zwitterionic adducts of TCNQ and other related compounds." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/3134/.
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This thesis is concerned with the synthesis and characterisation of novel TCNQ (7,7,8,8-tetracyanoquinodimethane), TMTCNQ (2,3,5,6-tetramethyl-7,7,8,8-tetracyanoquinodimethane) and TCNQF4 (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) based zwitterionic D-1t-A materials (where D and A are electron donors and acceptors respectively) of which the methylated Z-~-(N-methyl-4-quinolinium)-a-cyano-4( 2,3,5,6-tetrafluoro)styryldicyanomethanide [CH3(4)Q3CNQF4] is a typical example. Synthetic modification of the donor moiety was also undertaken, resulting in a diverse range of pyridinium, quinolinium and benzothiazolium-based materials, which may have use in nonlinear optical research. For the quinolinium system an extensive range of both 2- and 4-substituted analogues have been prepared and their properties compared and contrasted. The solvatochromic behaviour of these zwitterions was investigated in detail by dissolution in a range of organic solvents and measurement of their longest wavelength charge-transfer absorption bands using UV/Visible spectroscopy, which revealed that the substituents have a marked effect upon their solvatochromic properties. Most of the adducts studied display highly negative solvatochromism as the solvent polarity increases, in which their absorption maxima are linearly related with the normalised ENT values for the Reichardt dye. However the fluorinated quinolinium and pyridinium derivatives exhibit an unusual aggregation-induced reverse solvatochromism effect. The negative halochromic behaviour of selected zwitterions has also been investigated, with a hypsochromic shift of the longest wavelength CT absorption band being observed upon addition of electrolytes. Increased polarisation within the fluorinated R(4)Q3CNQF4 and R(2)Q3CNQF4 adducts has been indicated by solution state dipole moment measurements indicating greater nonlinear optical potential. However this increased polarisation has also been shown to be a major cause of the limited stability of these materials to photo-oxidation. The behaviour of the R(4)Q3CNQF4 and R(2)Q3CNQF4 zwitterions on the subphase and their resultant Langmuir-Blodgett film forming ability was also studied. However unlike the TCNQ-based materials the fluorinated adducts have been shown to be poor LB film forming materials.
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Fichet, Odile. "Films minces conducteurs : étude des monocouches et multicouches de dérivés amphiphiles du TCNQ." Bordeaux 1, 1992. http://www.theses.fr/1992BOR10608.
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Un enjeu de ce travail est de realiser des films minces organises et conducteurs par la technique de langmuir-blodgett. Pour ce faire, une nouvelle serie de sels du tetracyanoquinodimethane (tcnq) a ete preparee et ensuite etudiee sous forme de monocouches et de multicouches moleculaires. Il a ete montre en particulier que la chimie a la surface du bain d'un cuve de langmuir joue un role essentiel dans la formation de dimeres de tcnq a etat de valence mixte. Ces blocs moleculaires apres transfert, sont conserves et permettent d'obtenir un film conducteur. Une interpretation theorique des proprietes optiques et electriques rend compte de ces resultats et de leurs limitations actuelles
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Santos, Jaciara Nascimento. "Síntese e determinação da estrutura cristalina de um novo semicondutor molecular com aminoantraquinona (AAQ) e tetracianoquinodimetano (TCNQ) e uma contribuição à química de coordenação do TCNQ com cobre (II) em THF." Pós-Graduação em Química, 2013. https://ri.ufs.br/handle/riufs/6150.
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The reaction of 1-aminoanthraquinone with 7,7,8,8-tetracyanoquinodimethane in dichloromethane yielded the charge-transfer complex with semiconducting characteristics, C14H9NO2·C12H4N4. The molecules have maximum deviations from the mean planes through the non-H atoms of 0.0769 (14) Å for an oxo O atom and 0.1175 (17) Å for a cyano N atom, respectively. The dihedral angle between the two planes is 3.55 (3)°. In the crystal, molecules are stacked into columns along the a-axis direction. Pairs of N-H...N and N-H...O interactions connect the molecules perpendicular to the stacking direction. Additionally, an intramolecular N-H O hydrogen-bond interaction is observed for 1-aminoanthraquinone. A charge transfer is present, since the electrical resistivity falls with increasing temperature indicating semiconducting characteristics. From the resistivity data, an Arrhenius development ln(1/R) versus 1/T gives a mainly linear behaviour, from which a small barrier for the thermally activated transport of 1.25 eV can be derived. Dark brown crystals, suitable for X-ray analysis, were obtained by the slow evaporation of the solvent. Elemental analysis: Calc. 73.1 C, 3.1 H, 16.4 N; found 72.8 C, 3.4 H, 16.6 N. The melting point was determined by differential scanning calorimetry to 520 K. Exothermic decomposition occurs at 555 K. This work is already published (Oliveira et al., Acta Cryst. (2013). E69, o301). The coordination chemistry of tetracyanoquinodimethane was investigated with a reaction with Cu (II) in tetrahydrofurane. The results were analyzed with infrared, thermal analysis and cyclic voltammetry data and showed the coordination through the cyano groups of tetracyanoquinodimethane and the metal center.A reação da 1-aminoantraquinona com o 7,7 ,8,8 -tetracianoquinodimentano em diclorometano resultou na formação de um complexo de transferência de carga com características de um semicondutor, com fórmula C14H9NO2·C12H4N4. As moléculas possuem um desvio máximo do plano ideal através dos átomos não-hidrogenóides de 0,0769(14) Å para um oxigênio do grupo oxo e de 0,1175(17) Å para um grupo ciano. O ângulo entre os planos formados pelas moléculas é de 3,55(3)º. No cristal, as moléculas estão empilhadas em colunas ao longo da direção cristalográfica a. Pares de interações de hidrogênio do tipo N-H...N e N-H...O conectam as moléculas de forma perpendicular à direção do empilhamento. Adicionalmente, uma ligação de hidrogênio intramolecular é observada para a 1-Aminoantraquinona. Uma transferência de carga está presente, tendo em vista que a resistência elétrica cai com o acréscimo da temperatura, indicando características de um semicondutor. A partir dos dados da resistência elétrica, a equação de Arrhenius ln(1/R) x 1/T fornece um comportamento preponderantemente linear, do qual uma pequena barreira térmica para o transporte de carga de 1,25 eV pode ser derivada. Cristais com coloração marrom escuro, adequados para a análise via difração de raios-X em monocristal podem ser obtidos pela lenta evaporação do solvente. Análise elementar: Calc. 73,1 C, 3,1 H, 16,4 N; encontrado experimentalmente 72,8 C, 3,4 H, 16,6 N. O ponto de fusão foi determinado via calorimetria diferencial e o valor é de 520 K. Uma decomposição exotérmica ocorre em 555 K. Os dados deste trabalho já estão publicados em Oliveira et al., Acta Cryst. (2013). E69, o301. A química de coordenação do tetracianoquinodimetado foi investigada com uma reação com cobre (II) em tetrahidrofurano. Os resultados foram analisados via espectroscopia no infravermelho, análise térmica e voltametria cíclica, que mostraram a coordenação através do grupo ciano do tetracianoquinodimetano com o centro metálico.
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Houser, Christopher L. "Synthesis of New Molecule-Based Magnets using Bridging Organic Radicals." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/91440.
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Several new families of organic acceptors that are candidates as building blocks of molecule-based ferrimagnets were synthesized and characterized. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The magnetic networks were synthesized by reacting each acceptor with V(CO)6. The magnets synthesized in this study were characterized using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Although some combinations failed to yield magnetically ordered materials, others exhibited ordering temperatures in the range of 95 K – 260 K. The ordering temperatures and saturation magnetizations were compared among families of acceptors and correlated with individual properties of the acceptors such as reduction potential and structure.Doctor of Philosophy
Several new families of organic molecules have been created and examined for use as building blocks of molecule-based magnets. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The 3-D magnetic scaffoldings were created by combining an individual organic molecule in one of the families listed above with vanadium. The magnets created in this study were examined using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Some of the combinations of the organic molecules with vanadium failed to result in a 3-D magnetic scaffolding and showed no magnetic properties. Others showed magnetic properties in the below certain temperatures in the range of 95 K – 260 K. The magnetic properties were compared among families of molecules and correlated with individual properties of each molecule such as electronic effects and structure.
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Luz, Rita de Cássia Silva. "Desenvolvimento de sensores eletroquímicos à base de filmes com TCNX (tetracianoquinodimetano e tetracianoetileno) para a determinação de compostos fenólicos." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248406.
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Orientador: Lauro Tatsuo KubotaTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Neste trabalho é descrito o desenvolvimento de sensores eletroquímicos à base de compostos com TCNX (tetracianoetileno e tetracianoquinodimetano) para a determinação de compostos fenólicos. Para este propósito foram preparados eletrodos de carbono vítreo modificados com tetracianoetileneto de lítio (LiTCNE) e bis(tetracianoquinodimetaneto) de bis(fenantrolina) de cobre (lI) [Cu(phen)2(TCNQ)2], ambos imobilizados em filmes de poli-l-lisina (PLL). Após esta etapa, o eletrodo modificado com LiTCNE/PLL foi testado para verificar a capacidade de eletrocatálise da reação de redução de p-nitrofenol enquanto que o eletrodo modificado com Cu(phen)2(TCNQ)2/PLL foi utilizado para a oxidação de catecol. As técnicas utilizadas para a realização deste trabalho foram a voltametria cíclica, voltametria de varredura linear, amperometria, voltametria de pulso diferencial e voltametria de onda quadrada, as quais foram utilizadas para estudar o comportamento dos eletrodos modificados, para a otimização dos parâmetros experimentais, obtenção dos parâmetros cinéticos e caracterização analítica dos sensores. Os hidrodinâmicos foram realizados com o objetivo de obter maiores informações sobre os processos de redução e oxidação de p-nitrofenol e catecol, respectivamente, sobre os eletrodos modificados. Através do gráfico de Koutech-Levich foi possível obter os valores para o coeficiente de difusão e constante de velocidade da reação (k) para os analitos em estudo. Os valores do coeficiente de difusão e de k, determinados para o p-nitrofenol, foram de 9,03 x 10 cm s e 1,65 x 10 mol L s, enquanto que para o catecol, os valores do coeficiente de difusão e de k, foram de 4,6 x 10 cm s e 1,3 x 10 mol L s, respectivamente. O aumento na velocidade de reação, tanto para o p-nitrofenol como para o catecol, foi atribuído à eficiente transferência eletrônica entre as espécies estudadas e os compostos eletroativos imobilizados nas superficies dos eletrodos de carbono vítreo. O eletrodo modificado com filme de LiTCNE/PLL apresentou uma ampla faixa de resposta linear, sensibilidade, limite de detecção e quantificação de 0,001 a 5 mmol L, 42,90 mA cm L mmol, 0,3 e 1,0 nmol L (n= 10), respectivamente, para o de p-nitrofenol, enquanto que o eletrodo modificado com Cu(phen)2(TCNQ)2/PLL apresentou uma faixa de resposta linear, sensibilidade, limite de detecção e quantificação de 0,005 a 5 mmol L (n=8), 16,10 mA cm, 1,5 e 5,0 nmol L, para o catecol. Após a aplicação destes sensores em amostras de interesse, estudos de adição e recuperação dos analitos foram realizados para avaliar a exatidão dos métodos e verificou-se que em ambos os casos foi possível uma percentagem de recuperação entre 98,87 e 104,5% para o p-nitrofenol e 99,1 e 100,1 % para o catecol
Abstract: In this work is describing the development of electrochemical sensors based on TCNX (tetracyanoquinodimethane and tetracyanoethylene) for phenolics compound determination. For this purpose glass carbon electrodes were modified with lithium tetracyanoethylenide (LiTCNE) and bis (tetracyanoquinodimethanide) of bis (phenantroline) of copper (II) [Cu(phen)2(TCNQ)2], both immobilized at films of poly-l-lysine (PLL). After this step, the modified electrode with LiTCNE/PLL was tested to verify the electrocatalysis capacity of the reduction of p-nitrofenol and the electrode modified with Cu (phen)2(TCNQ)2/PLL for the catechol oxidation. The techniques used for the accomplishment of this work were the cyclic voltametry, linear sweep voltametry, amperometry, differential pulse voltametry, and square wave voltametry, which were used to study the behavior of the modified electrodes, for the experimental parameters optimization, for the attainment of the kinetic parameters and analytical characterization of the sensors. Hydrodynamic studies were carried out with the aim to get information on the reduction processes and oxidation of p-nitrofenol and catechol, respectively, on the modified electrodes. Through the Koutech-Levich plot it was possible to obtain the values for the diffusion coefficient (Do) and kinetic constant of the reaction (k) for the analyte in study. The values of the diffusion coefficient and k, determined for p-nitrofenol, were 9,03 x 10 cm s and 1,65 10 x mol L s, whereas for catechol, the values of Do and k were 4,6 x 10 cm s e 1,3 x 10 mol L s, respectively. The increase of the reaction rate for p-nitrofenol and catechol was attributed to the efficient electron transfer between the studied species and immobilized electroactives species on superface the glassy carbon electrodes surface. The electrode modified with LiTCNE/PLL presented a wide linear response range, as well as sensitivity, detection and quantification limit of 0,001 up to 5 mmol L, 42,90 mA cm L mmol, 0,3 and 1,0 nmol L (n=10) for the p-nitrophenol, whereas the electrode modified with [Cu(phen)2(TCNQ)2], presented a linear range, sensitivity, detection and quantification limit of 0,005 a 5 mmol L (n=8), 16,10 mA cm, 1,5 e 5,0 nmol L, respectively, for catechol. After the application of these sensors in samples of interest, studies of addition and recovery of the analytes were carried out to evaluate the error of the methods and was verified that in both the cases a recovery percentages between 98,8 and 104,5% for p-nitrofenol and, 99,1 e 100,1 % for catechol
Doutorado
Quimica Analitica
Doutora em Ciências
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Mabrouk, Manel. "Structure électronique des couches minces organiques." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4343.
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Ce mémoire de thèse présente les travaux de recherche sur les monocouches auto-organisées organométalliques. Nous avons étudié théoriquement les propriétés structurales, électroniques et magnétiques des structures bidimensionnelles TM-Pc (Pc : phtalocyanine) et TM-TCNB (TCNB : tétracyanobenzène) où TM représente le métal de transition de la série 3d, 4d ou 5d. Les calculs sont faits avec la méthode de la théorie de la fonctionnelle de la densité en tenant compte du terme de Hubbard (DFT+U) en utilisant le code de simulation VASP (Vienna Ab-initio Simulation Package). En plus, l’adsorption de la molécule de Fe-Pc sur la surface d’Or Au(111) a été étudiée avec les méthodes SGGA et SGGA+UThis thesis presents research work on self-organized metal-organic monolayers. We have theoretically investigated the structural, electronic and magnetic properties of two-dimensional TM-Pc (Pc: phthalocyanine) and TM-TCNB (TCNB: tetracyanobenzene) where TM is the transition metal for the 3d, 4d or 5d series. The calculations are performed by density functional theory taking into account the Hubbard term (DFT+U) using the VASP simulation code (Vienna Ab-initio Simulation Package). In addition, the adsorption of the Fe-Pc molecule on the gold surface Au(111) was studied via SGGA and SGGA+U
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Kornelsen, Kevin E. "Far-infrared reflectivity measurements including thin films of ice and a mosaic of TTF-TCNQ crystals." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25905.
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The main objective of this thesis project involved the design and construction of a reflectance module to be used with a far infrared Fourier spectrometer. This module would be used for specular reflectivity measurements with small samples at temperatures between liquid helium and room temperature.
Early tests of this reflectance module were used to investigate some of the interesting changes in the far infrared spectrum which result from ice condensation on the sample surface. With the condensing substrate at temperatures between 130 and 200K the condensation is in a crystalline phase and can drastically reduce the intensity of the reflected radiation. The effects are most significant in the spectral range between 150 and 300cm⁻¹. Substrate temperatures lower than 130K lead to condensation of ice in a vitreous phase which does not have such a large effect on the far infrared spectrum.
Modifications were made to the reflectance module design to eliminate the unpredictable effects of ice condensation and a final set of tests were performed measuring the reflectance of a mosaic of TTF-TCNQ crystals. The resulting data shows much of the fine structure which has been observed in other measurements using bolometric techniques.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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GHEZZAL, ELHASSANE. "Realisation et caracterisation de composites conducteurs par transfert de charge entre le cuivre et le tetracyanoquinodimethane (tcnq)." Nice, 1992. http://www.theses.fr/1992NICE4563.
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La reaction de transfert de charge entre un donneur et un accepteur d'electrons a fait l'objet de plusieurs etudes experimentales et theoriques. En 1985, notre groupe a montre qu'une telle reaction peut avoir lieu directement a l'etat solide par broyage mecanique des deux reactants ou par leur simple mise en contact. Le but de notre travail a ete de realiser cette reaction entre un donneur metallique, le cuivre, et l'accepteur, le tetracyanoquinodimethane (tcnq), et de caracteriser les produits qui en resultent par l'etude de differentes proprietes electriques et optiques. Les melanges passifs (non reactifs) obtenus sans broyage a partir de proportions variables de poudres de cuivre metallique et de tcnq, ont un comportement percolatif. La reaction de transfert de charge a l'etat solide necessite un broyage mecanique prolonge des produits passifs. Les composites obtenus sont caracterises par un transfert de charge tres faible et une diminution importante de leur conductivite electrique avec le temps de broyage. Ceci est explique par le fait que le broyage ne fractionne pas les grains de cuivre, et la reaction prend lieu sur leur surface. Le produit de la reaction enrobe ces grains conducteurs d'une couche peu epaisse mais isolante; d'ou la chute de la conductivite malgre le faible rendement de la reaction. A l'aide du modele de forces d'oscillateurs, base sur les intensites relatives de certaines bandes d'absorption infrarouge du tcnq, applique d'abord aux melanges solide-solide teai/tcnq (teai=iodure de triethylamine), nous avons verifie que l'introduction d'acetonitrile (solvant de tcnq) augmente considerablement le rendement de la reaction entre le cuivre et tcnq. Pour certaines concentrations en cuivre, les composites obtenus par cette voie presentent des bandes d'absorption inhabituelles en ir pour des composes a base de tcnq. Nous avons lie cette anomalie a la formation d'especes ioniques du tcnq possedant plus d'une charge par molecule (tcnq## par exemple); hypothese qui semble assez bien correlee avec la faible conductivite electrique des composes pour les memes concentrations en cuivre. Par ailleurs, le signe du pouvoir thermoelectrique des composites cu/tcnq est lui aussi fortement influence par leur composition. L'etude des caracteristiques i=f(v) de ces materiaux, montre qu'ils ont un comportement proche de celui des thermistances: il est du au caractere thermiquement active de leur conductivite electrique. Pour les composites presentant des spectres anormaux d'absorption ir, cet effet s'accompagne, quand le courant applique depasse un certain seuil, d'un phenomene d'hysteresis. Il traduit une transition de phase, sous l'effet du courant electrique, d'un etat de haute impedance vers un etat de faible impedance. Les systemes retrouvent leur etat initial quelques semaines apres la coupure du courant applique. L'etude des spectres ir, du pouvoir thermoelectrique et de l'energie d'activitation avant et apres la transition indique que ce changement est du a une transformation chimique des composites qui pourrait etre representee par les equilibres suivants: cu#+#2tcnq##cu#+tcnq#+cu#0 ou cu#+#+tcnq##cu#+tcnq#. Du fait de certains aspects de leurs proprietes, les composites cu/tcnq que nous avons realises pourraient etre utilises, par exemple, comme des thermistances, des systemes a resistances electrique variables, pour le stockage d'informations
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Wolf, Hilke. "Data Quality Bench-Marking for High Resolution Bragg Data." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://hdl.handle.net/11858/00-1735-0000-0022-5DE2-A.
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Riou, Laurent. "Mecanismes de fixation cellulaire de tcn-noet, un nouveau traceur radioactif de la perfusion myocardique." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10111.
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Les maladies cardiovasculaires representent la premiere cause de mortalite en france. L'ischemie myocardique est principalement responsable de ces accidents. Le diagnostic de l'ischemie myocardique est actuellement effectue grace a la realisation de scintigraphies myocardiques apres injection d'un traceur radioactif du debit sanguin coronaire, le thallium 201. Cependant, le thallium 201 presente des inconvenients (dosimetrie elevee, energie d'emission mal adaptee, cout de production eleve). Le technetium-99m est un isotope mieux adapte (dosimetrie faible, energie d'emission bien adaptee, cout de production faible). Plusieurs complexes techneties ont ete proposes en remplacement du thallium 201, mais aucun ne presente le meme comportement. Le thallium 201 reste donc le traceur de debit le plus utilise. Tcn-noet est un nouveau complexe technetie presentant le meme comportement que le thallium 201 chez le chien et chez l'homme. Ce traceur est actuellement en essais cliniques de phase iii. L'objectif de ce travail est la determination des mecanismes de fixation cellulaire de tcn-noet. Les etudes realisees in vitro sur cardiomyocytes de rats nouveau-nes indiquent que la fixation cellulaire du traeur est independante de l'etat metabolique des cellules. Cette fixation est inhibee et augmentee par des drogues inhibant et activant, respectivement, les canaux calciques voltage-dependants membranaires. Compte-tenu de l'utilisation frequente des antagonistes calciques en pratique clinique, l'effet du verapamil, du diltiazem et de la nifedipine sur la fixation cardiaque de tcn-noet a ete evalue sur le modele du cur isole et perfuse de rat. Ces drogues sont sans effet sur l'activite cardiaque en tcn-noet. De meme, le verapamil n'affecte pas la fixation myocardique de tcn-noet in vivo chez le chien. Ceci peut s'expliquer par une fixation du traceur ex-vivo et in vivo sur l'endothelium vasculaire, qui ne presente pas de canaux calciques voltage-dependants. En conclusion, tcn-noet est le premier complexe technetie presentant le meme comportement que le thallium 201. In vitro sur cardiomyocytes, ses mecanismes de fixation cellulaire impliquent les canaux calciques voltage-dependants. L'effet d'inhibiteurs de ces canaux n'est pas mis en evidence ex vivo et in vivo, ce qui suggere qu'un traitement par inhibiteurs calciques n'affectera pas la fixation myocardique de tcn-noet en pratique clinique.
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Полудненко, Т. В. "Вплив домішок Li-тетраціанохінодіметана на електропровідність планарно орієнтованого нематичного рідкого кристала Е25М." Thesis, Київський національний університет технологій та дизайну, 2019. https://er.knutd.edu.ua/handle/123456789/13887.
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Ajlani, Abdallah. "Elaboration de polyéthylène conducteur par inclusion de sel (TTF-TCNQ) : caractérisation électrique et propriétés de détection chimique en phase gazeuse." Lyon 1, 1994. http://www.theses.fr/1994LYO10248.
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L'utilisation des materiaux organiques, habituellement isolants, envahit depuis quelques annees le domaine de l'electronique grace a la mise en evidence de proprietes conductrices. Le genie chimique permet aujourd'hui aux materiaux moleculaires d'atteindre des proprietes semiconductrices. Le domaine des polymeres, a caractere essentiellement amorphe, est par contre moins explore bien qu'il permette d'obtenir sous forme composite des proprietes interessantes pour l'electronique. Dans ce travail nous presentons les criteres d'elaboration d'un materiau composite dont nous evaluons les aptitudes a etre utilise dans une structure de capteur de gaz. Le materiau composite est constitue d'un polyethylene faible densite dans lequel un sel (ttf-tcnq) se developpe en dendrites lors d'un traitement physico-chimique. Les conditions, teneur en sel, temperature, vitesse de sechage, trempe, permettent d'obtenir une distribution uniforme de dendrites donnant un chemin de percolation pour de tres faibles teneurs en sel (0,3 pour cent). Le materiau a ete elabore sous forme de film mince, pour realiser des structures metal/composite/metal utilisees pour la caracterisation electrique. En courant continu, la conductivite montre l'existence d'un mode de conduction ohmique a faible champ auquel se superpose une conduction par injection. L'existence du phenomene de percolation sur ces deux modes de conduction, implique une interpretation de la conduction du composite par les methodes des milieux effectifs. En courant alternatif (jusqu'a 10mhz), les mesures permettent de proposer un modele d'impedance de la structure. Par une interpretation des pertes dielectriques, un domaine de frequences, caracteristique du composite est mis en evidence: des hypotheses d'interpretation sont proposees. La structure ainsi caracterisee est ensuite soumise a des essais de sensibilite a la pollution d'un flux d'argon par differents gaz (o#2, no#2, co#2, vapeur d'eau). Des resultats prometteurs sont presentes, en particulier pour des pollutions inferieures a 100ppm en co#2
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Angel, Ceballos Isandra Fortuna. "Late Pleistocene deglaciation histories in the central Mérida Andes (Venezuela)." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAU002/document.
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Les Andes de Mérida (Venezuela) est caractérisé par la présence de morphologie glaciaire bien préservée entre 2400-4978 m. Les études de ces morphologies glaciares font la contribution pour mieux comprendre et reconstruire la Dernière Glaciation aux Andes Vénézuéliennes. La reconstruction de la Dernière Glaciation (connue dans la région comme Glaciation Mérida) était limitée par la disponibilité de chronologie glaciaire. Cette thèse fait sa contribution à la reconstruction de la Dernière Glaciation et à la connaissance du paléoclimat depuis le Pléistocène Superieur. La méthodologie a involucré l´analyse géomorphologique et l´étude géochronologique. La morphologie glaciaire a été datée avec la technique de nucléides cosmogéniques produits in-situ (10Be). Cette technique est appropriée pour dater les matériels riches en quartz et la période d´intérêt. Les inférences des conditions paleoclimatiques ont été faites sur la base des analyses de la paléo ELA.Des différentes dynamiques glaciares ont été identifiées aux Andes centrales de Mérida. Dans les vallées de Mucubají et Mucuchache, la dynamique a été caractérisée par plusieurs étapes de avancé-arrêt des glaciaires dans un recul général de la glace. Dans les vallées de Gavidia et Mifafí, la disparition des glaciares a été très rapide avec la vitesse de recul plus haute (entre 4-7 km/ky). Divers caractéristiques morpho métriques comme la pente du fond de la vallée, la topographie de la zone d´accumulation (cirques glaciares avec les murs très incliné), des surfaces de la zone d´accumulation et son orientation ont aussi contrôlé les différents dynamiques glaciares.Les avancées des glaciares ont été identifiées entre 2500-4200 m. Les avancées glaciares pendant le MIS 3 ont été reconnues à Sierra Nevada. Ces avancées ont été liées aux hautes précipitations dans le nord de l´Amérique de Sud produites par l´activité de la Zone de Convergence Intertropical. Ces avancées ont été aussi reliées aux conditions plus chaudes et humides dans l´Hémisphère Nord (aussi ces conditions ont été identifiées aux Andes vénézuéliennes et sont connues comme l´Interstadío El Pedregal). Les avancées glaciares pendant le Dernière Maximum Glaciares ont été enregistrées en Sierra Nevada á Mucubají et Las Tapias entre 3100-3600 m. Principalement, les avancées glaciares MIS 2 sont arrivées pendant l´Oldest Dryas-El Caballo Estadío à 17 ka. Ces avancées glaciares ont été reliées aux températures froides dans l´Hémisphère Nord et les températures plus froides enregistrées dans les carottes de glaciares tropicaux.Mots clésDatation par cosmogéniques produits in-situ, morphologie glaciaire, Pléistocène, Dernière Glaciation, LGM, paléo ELAThe central Mérida Andes (Venezuela) landscape is characterized by the presence of well-preserved glacial landforms located between 2400 and 4978 m a.s.l. Geomorphological studies of these glacial landforms significantly contribute to the Venezuelan Andes glaciations reconstructions. However, Last Glaciation (locally called Mérida Glaciation) was poorly reconstructed because of limited chronological data. This dissertation attempts to contribute to the Last Glaciation reconstruction and paleoclimate knowledge since the late Pleistocene. Accordance this necessity, the methodology involved geomorphological analysis and geochronological study. Glacial landforms were dated based on the Terrestrial Cosmogenic Nuclide dating (10Be). This method is suitable for date quartz-rich materials and for the period of interest. To deduce paleoclimate conditions an analysis based on paleo ELA was developed.In the central Mérida Andes different Late Pleistocene glacier dynamics were identified. In the Mucubají and the Mucuchache valleys, successive stages of glacier stop-advance were identified during an overall glacier withdrawal. In the Gavidia and Mifafí valleys, glacier withdrawal was rapid with the highest retreat rates (between 4-7 km/ky). Morphometric features as glaciers bottom valley slopes, accumulation zone topography (glaciers cirques with steep walls), areas and orientation controlled different glaciers dynamics.Glacier advances were evidenced between 2500-4200 m. MIS 3 glaciers advances has been recognized in the Sierra Nevada. These were related to the highest runoff in the north of South America produced by the Intertropical Convergence Zone (ITCZ) and the local warm and wet climate conditions (locally named El Pedregal Interstadial). LGM glacier advances were recorded in Sierra Nevada in the Mucubají and Las Tapias between 3100-3600 m. MIS 2 Glaciers advances mainly occurred during the Oldest Dryas- El Caballo Stadial at around 17 ka. These glaciers advances correlate to the cold temperatures in the North Hemisphere and the coldest temperatures recorded in tropical ice cores.KeywordsTerrestrial cosmogenic nuclides dating, TCN, cosmogenic dating, glacial landforms, Andes Mérida, Venezuela. Pleistocene, Last Glaciation, LGM, paleo ELA, tropic paleoclimate
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Viklund, Joel. "Synthesis of sequential data." Thesis, Uppsala universitet, Avdelningen för systemteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-443542.
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Good generative models for short time series data exist and have been applied for both data augmentation and privacy protection purposes in the past. A common theme for existing generative models is that they all use a recurrent neural network (RNN) architecture, which makes the models limited regarding the length of the sequences. In real world problems, we might have to deal with data containing longer sequences, and it is such data we in this thesis attempt to synthesize. By combining the recently successful TimeGAN framework with a temporal convolutional network component architecture, we generate synthetic sequential data for two toy data sets: sequential MNIST and multivariate sine waves. The results strongly indicate, although relying solely on a visual inspection, that the model manage to capture long temporal dynamics over time and also relations between different features for the multivariate sine waves data set. In order to make our model applicable for real world data sets, we suggest two improvements. Firstly, the validation of the generated data should not only rely on visual inspection, but also ensure that the synthetic data has the same statistical distribution. Secondly, depending on the task, model refinements such that the synthetic samples look even more realistic should be made.
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Cappussi, Francesco. "Sintesi e caratterizzazione di cristalli charge-transfer da derivati di [1]Benzotieno[3,2-b][1]benzotiofene e tetracianochinodimetano." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23428/.
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Scopo di questa tesi è stato lo studio mediante tecniche spettroscopiche di cristalli di complessi a trasferimento di carica (CT) con caratteristiche di semiconduttori, ottenuti a partire da una coppia di composti organici che presentassero rispettivamente le proprietà di donatore e
accettore di carica. La nostra attenzione si è focalizzata sulla formazione di CT binari contenenti un derivato
asimmetrico del benzotieno-benzotiofene (BTBT) denominato Ph-BTBT-C10 come donatore, e da derivati fluorurati del tetracianochinodimetano (TCNQ) come accettori, per la progettazione di sistemi a potenziale comportamento ambipolare. Il TCNQ è infatti un ottimo accettore,
soprattutto nei suoi derivati fluorurati, e la semi-conducibilità di tipo n che presentano molti dei
suoi complessi può essere accompagnata a quella di tipo p proprio quando il donatore è una molecola asimmetrica. Il lavoro di tesi è consistito in primo luogo nella preparazione di cristalli misti mediante metodi da soluzione o per via meccanochimica, prediligendone la crescita in fase bulk piuttosto che in film sottile al fine di permetterne la futura caratterizzazione strutturale tramite diffrazione di
raggi X. Alla sintesi è seguita la caratterizzazione mediante spettroscopie IR, Raman e UV. Si è anche eseguita una stima quantitativa del grado di trasferimento di carica che determina la formazione del complesso mediante la misura dello spostamento delle frequenze dei modi vibrazionali del TCNQ che sono sensibili a variazioni della densità di carica sull’accettore.
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Aguirre, Brockway Romina Pía. "Efecto de algunos factores genético-ambientales sobre el tamaño de camada al nacimiento en cerdos. I. Tamaño de la Camada Nacidos Vivos (TCNV)." Tesis, Universidad de Chile, 2006. http://repositorio.uchile.cl/handle/2250/134133.
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Memoria para optar al Título Profesional de Médico VeterinarioChile, según información reciente de USDA, se encuentra en el sexto lugar de los principales exportadores de carne porcina del mundo. Para responder a esta demanda, los productores de cerdos se han preocupado de mejorar sus índices productivos, entre los que se encuentra el tamaño de camada nacidos vivos (TCNV). Dentro de este marco se inserta este trabajo que tuvo por objetivo, conocer el efecto del número ordinal de parto (NOP), mes de monta (MM), número de inseminaciones artificiales (NIA), criadero, partero y maternidad, sobre el TCNV dentro de 2 líneas genéticas porcinas. La variable TCNV se definió como el número de lechones nacidos vivos por parto. El trabajo se realizó con un total de 11.096 registros obtenidos de 5 criaderos industriales de la VI Región de Chile. El promedio general para el TCNV encontrado fue de 11,62 ± 3,12 lechones, observándose que la línea genética L-42 (Landrace x Large White), es superior a la línea genética Large White (LW) (11,89 ± 3,19 y 11,14 ± 2,89, respectivamente). Los resultados muestran un importante efecto del NOP sobre el TCNV en ambas líneas genéticas (p ≤ 0,05). El MM no constituye un factor de variación para el TCNV, tanto en la línea genética L-42 como el la línea genética LW (p > 0,05), pero se observó una tendencia a un incremento del TCNV para las inseminaciones realizadas en invierno. Con respecto al NIA, se observa un aumento no significativo del TCNV cuando las hembras son inseminadas 3 o 4 veces durante el estro (p > 0,05). El efecto criadero o plantel no fue significativo, para las líneas genéticas estudiadas. (p > 0,05) El efecto partero constituye una fuente de variación sobre el TCNV (p ≤ 0,05), para ambas líneas genéticas, respectivamente, mientras que el efecto maternidad no afectó el TCNV (p > 0,05).
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Kormoš, Lukáš. "2D molekulární systémy na površích." Doctoral thesis, Vysoké učení technické v Brně. CEITEC VUT, 2021. http://www.nusl.cz/ntk/nusl-438774.
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Molekulárne systémy predstavujú jeden zo smerov súčasného výskumu nových nanoelektronických zariadení. Organické molekuly nachádzajú uplatnenie v rôznych aplikáciách, ako sú napríklad solárne články, displeje alebo kvantové počítače. Rast vysokokvalitných molekulárnych vrstiev s požadovanými vlastnosťami často vyžaduje využitie samousporiadavaných štruktúr, hlboké pochopenie rozhrania kovu a organických molekúl a tiež dynamiky rastu molekulárnych vrstiev. Predkladaná práca sa zaoberá predovšetkým samousporadanými štruktúrami bifenyl-dikarboxylovej kyseliny (BDA) na Cu (1 0 0) a Ag (1 0 0), ktoré boli skúmané v UHV s využitím STM, XPS a LEEM. V prípade BDA-Ag je podrobne opísaných niekoľko chemicky a štrukturálne odlišných molekulárnych fáz. Ďalej boli BDA a TCNQ molekuly skúmané na grafene pripravenom na Ir (1 1 1). Okrem toho sa organo-kovové systémy syntetizovali depozíciou atómov Ni a Fe s molekulami TCNQ a BDA. Záverečná časť tejto práce popisuje povrchovú syntézu grafénových nanoribonov (7-AGNR) na špecicky štrukturovanom substráte Au (16 14 15) z prekurzorových molekúl DBBA. Rekonštrukcia povrchu po raste bola analyzovaná pomocou STM a elektronické vlastnosti 7-AGNRs pomocou ARPES.
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PASQUALINI, ROBERTO. "Nouvelle methode de synthese de complexes de technetium comportant le cur (tcn)2+ : application a la preparation de radiopharmaceutiques." Paris 11, 1995. http://www.theses.fr/1995PA112386.
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A l'echelle macroscopique, la reduction de l'ion pertechnetate par la triphenyl phosphine en presence de hcl et d'une base de schiff bianionique tridentee (h#2l) derivee du dithiocarbazate de methyle, a conduit a un complexe neutre comportant le cur (tco)#3#+, de formule tcocil#0. Cette meme reaction, effectuee avec #9#9#mtc, n'a pas abouti au complexe attendu #9#9#mtcocil mais elle a produit une nouvelle espece radiochimiquement pure, dont la structure n'a pu etre que partiellement approchee par les etudes utilisant des techniques analytiques radiochimiques. Sa caracterisation complete n'a ete possible qu'apres analyse par diffraction des rayons x des cristaux obtenus par une synthese a haute dilution en utilisant #9#9tc. La structure pyramidale a base carree du complexe, de formule tcnlpph#3#0, a confirme les resultats obtenus a l'echelle des indicateurs et a mis en evidence la formation d'une liaison triple tcn. La structure du complexe, ainsi que sa facilite a subir des reactions d'echange de ligands, a prouve qu'il etait possible d'obtenir des radiopharmaceutiques techneties contenant le cur (#9#9#mtcn)#2#+ a partir de #9#9#mtco#4- par une reaction simple. Nous avons pu montrer que la formation d'especes contenant le cur (#9#9#mtcn)#2#+ a partir de #9#9#mtco#4- etait le resultat d'une reaction generale dans laquelle l'ion pertechnetate est reduit en presence d'un ligand comportant l'arrangement chimique >n-n<. Le choix d'une phosphine hydrosoluble comme la tris (m-sulfophenyl) phosphine et du ligand donneur d'ion n#3#- s-methyl, n-methyl dithiocarbazate a permis la fabrication, a l'echelle industrielle, d'une trousse pour la preparation de radio pharmaceutiques nouveaux contenant le cur (#9#9#mtcn)#2#+ en milieu sterile et apyrogene
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Roberts, Vincent. "Kelvin Probe Examination of Organic/Metallic Semiconductors." Ohio University Honors Tutorial College / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1340137774.
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Chen, Chia-Yi. "Chemically Tailored Organic-Based Magnets to Exploit Optical Control of Magnetization and Depth-Resolved Magnetization in V[TCNE]x~2 via Polarized Neutron Reflectivity." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1293405276.
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Shawulienu, Kezilebieke. "Scanning tunneling microscopy and spectroscopy of metal organic complexes : from single atoms to extended networks." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE005/document.
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La recherche actuelle dans le domaine des nanosciences, l’assemblage supramoléculaire d’atomes métalliques et de molécules sur des surfaces ouvre la voie à des composants fonctionnels, utiles dans une multitude d’applications comme l’Optoélectronique, le magnétisme et la catalyse. Il a été démontré que dans certains cas, l’état de Spin Haut et une forte anisotropie magnétique apparaissent suite à un transfert d’électron entre ligands, surface et atome métallique. Le but de cette thèse porte sur l’auto-assemblage des 1,2,4,5-Tetracyanobenzene (TCNB) et des coordinations nanostructurelles des Fe-TCNB sur une surface d’Au(111). La formation de ces structures est conduite par les interactions non-covalentes. La spectroscopie à effet tunnel (STS) révèle que la molécule de TCNB est physisorbée sur la surface d’Au(111). Une analyse détaillée des spectres dI/dV effectués sur une monocouche de TCNB sur une surface d’Au(111) montre que la molécule de TCNB a un transfert de charge négligeable sur ce substrat avec une énergie d’adsorption de 0,5 eV par molécule. Les mesures STS révèlent un gap HOMO-LUMO de 3 eV, comme le prédit la théorie. En contrôlant les paramètres de fabrication, des composants nanostructurels avec différentes compositions chimiques ou des arrangements moléculaires ont été synthétisés. Les propriétés électroniques ont été caractérisées par une analyse spectroscopique dI/dV locale sur les centres métalliques à différentes étapes de formation des complexes Fe-(TCNB)x (x=4, 2). La déposition à très basse température forme un état intermédiaire métastable. Les données STM montrent que l’angle que forment le trièdre Fe-N-C est de 120°. La spectroscopie tunnel révèle que le Fe et la molécule de TCNB gardent leur identité spectroscopique, le Fe garde ses états de surface de la même façon que s’il avait été déposé seul sur une surface d’Au(111). Ceci indique que les molécules de TCNB sont virtuellement dans le même état électronique qu’avant la déposition du Fe. La situation change lorsque ce dépôt est effectué à température ambiante. Une augmentation de température agit sur l’interaction des composants transformant ainsi la formation en un complexe monomère de Fe(TCNB)4 avec un angle Fe-N-C de 180°. La spectroscopie STS sur ce complexe suggère fortement que la liaison de coordination est formée entre le Fe et la molécule de TCNB. Les calculs DFT soutiennent ces conclusions. Plus loin, une structure a été réalisée par la synthèse d’un réseau Fe(TCNB)2. Ce réseau a une structure carrée avec une séparation régulière entre les atomes de Fe. Les informations électroniques de la structure sont données par la molécule de FePc (où Pc représente la molécule de Phthalocyanine) pour identifier les pics de résonnance du spectre du réseau de Fe(TCNB)2. Une similitude apparait dans les spectres dI/dV effectués sur l’atome de Fe et sur les ligands dans les deux systèmes, indiquant que le Fe ressent un environnement similaire quand il est entouré de TCNB ou quand il est à l’intérieur d’une Phthalocyanine. Une analyse plus détaillée basée sur la formation des liaisons métal-ligands a été discutéeIn the bottom up approach of today’s nanoscience, the supramolecular assembly of metal atoms and molecules on surfaces is leading to functional compounds, relevant to many applications in optoelectronics, magnetism, and catalysis. It has been found that in some cases high magnetic spin states and strong magnetic anisotropy appear as a result of electron transfer between ligands, surface and metal atom. The focus of this thesis lies on the self assembling of 1,2,4,5-Tetracyanobenzene (TCNB) and Fe-TCNB coordination nanostructures on the Au(111) surface. The structural formation is directed by the non covalent interactions. Scanning tunneling spectroscopy (STS) reveal that the TCNB molecules are physisorbed on Au(111) surface. By detail analysis of the dI/dV spectra above the TCNB monolayer on the Au(111) surface, we found that the TCNB molecules on Au(111) shows a negligible charge transfer with Au(111) substrate and a small adsorption energy of 0.5 eV per TCNB molecules. STS measurement provide a HOMO-LUMO gap of 3 eV in agreement with DFT calculations. By controlling the fabrication parameters, surface coordination nanostructures with different chemical composition or molecular packing have been synthesized. The electronic properties have been characterized by the local dI/dV analysis of the metal centers at different steps of a Fe-(TCNB)x (x=4, 2) complexes formation. At low temperature deposition, first form an ordered metastable intermediate. STM data yield the bond angle between the Fe-N-C is 120°. The scanning tunneling spectroscopy reveal that Fe atoms and the TCNB molecules keep their identity while the Fe atoms localize the surface-state electrons similar to what they do on the bare Au(111) surface. This result indicates that the TCNB molecules are virtually in the same electronic state as before the Fe adsorption. The situations are different when the deposition performance at room temperature. When the temperature is changed, to room temperature, the original entities transform into the Fe(TCNB)4 monomer complexes with 180° Fe-N-C bond angles. The STS above the Fe(TCNB)4 complex strongly suggest that the coordination bond had been formed between the Fe atom and the TCNB ligands. DFT calculations support the conclusions and drawn from experimental studies and assist the interpretations of experiment. Further structural complexation is achieved by the synthesis of Fe(TCNB)2 network. The network has a square structure with a regular separation of the magnetic Fe atoms in the network. The electronic information is gathered from the spectroscopic labeling of FePc to identify some of the resonances of the Fe(TCNB)2 network. There are similar features are found in the dI/dV spectra above the Fe atoms and ligand in both system, indicating that the Fe somehow feels a similar environment from the TCNB ligands in the network and in the FePc molecules. Further analysis of this feature have been disused by means of metal-ligand bond formation
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Veder, Jean-Pierre M. "The development of a rigorous nanocharacterization scheme for electrochemical systems." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/2119.
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This thesis reports on a methodology for the nanocharacterization of complex electrochemical systems. A series of powerful techniques have been adapted and applied to studies of two scientifically important electrochemical systems; namely polymer membrane solid-state ion-selective electrodes (ISEs) and electrochemically generated tetracyanoquinodimethane (TCNQ) charge-transfer materials. These studies have mainly encompassed the use of neutron reflectometry (NR), electrochemical impedance spectroscopy (EIS), secondary ion mass spectrometry (SIMS), small angle neutron scattering (SANS), synchrotron radiation / Fourier transform-infrared microspectroscopy (SR / FT-IRM), synchrotron radiation / X-ray photoelectron spectroscopy (SR / XPS) and synchrotron radiation / grazing incidence X-ray diffraction (SR / GIXRD). Significantly, an NR technique has been specially developed to enable simultaneous EIS measurements through the development and refinement of a novel electrochemical / reflectometry cell. Furthermore, the development of a versatile electrochemical cell that is capable of allowing SR / GIXRD measurements to be made in practically any conceivable electrochemical problem has also been of great significance.The investigation of polymer membrane solid-state ISEs focused on the problem of water layer formation at the buried polymer interface after prolonged exposure to an analyte. Initially, a rigorous surface and materials characterization scheme was developed and applied to plasticized poly(vinylchloride) (PVC) coated wire electrodes (CWEs) that are known to be adversely affected by water layer formation. It was determined that water and the associated ions from the sample analyte were transported through the PVC membrane. This resulted in the formation of a water layer (approximately 120 Å thick) at the substrate / ion-selective membrane interface. The results of the study suggested that this event occurred after 3 to 20 hours of constant exposure to solution. Moreover, the water layer at the buried interface was found to contain traces of plasticizer, whilst nanodroplets of water were also found in the membrane. The former is evidence for the exudation of plasticizer from the PVC membrane into the water layer at the buried interface.Further investigations on a solid-state ISE utilizing a hydrophobic poly(methylmethacrylate) / poly(decylmethacrylate) (PMMA / PDMA) copolymer as the ion-selective membrane revealed that water was transported through the membrane at a far slower rate than that of plasticized PVC ISEs. In fact, a regular ISE of this type severely restricted water accumulation at the buried interface, with such an event occurring after 460 hours. In addition, water was restricted to accumulation as droplets at the buried interface, as opposed to continuous water layers. A negligible amount of water was found in the bulk of this hydrophobic polymer membrane.Given CWEs are susceptible to forming water at the buried interface, it is customary to employ solid-contact (SC) underlayers. The primary function of the SC is to provide an appropriate mechanism for ion-to-electron transduction. Certain SCs are also theorized to discourage the formation of water layers. The results of this thesis revealed that a hydrophobic poly(3-octylthiophene-2,5-diyl) (POT) SC can prevent the formation of a water layer in SC ISEs altogether. This is not only achieved through the hydrophobic nature of POT, but also through the fact that the underlayer of POT is able to cover any imperfections at the buried interface, which water can use as a site for accumulation.By contrast, a hydrophilic polymer SC, known as poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS), was found to scavenge available traces of water at the buried interface. Instead of forming a well defined water layer or even water-droplets at the buried interface, the PEDOT:PSS SC system was found to soak up all traces of water transported through the ion-selective membrane to the buried interface. Water was detected in the PEDOT:PSS vii underlayer in a miscible state and not as a separate phase as observed with the CWE systems.The mechanism for ion-to-electron transduction in electroactive polymer SCs was also investigated. The study was performed in order to address the extent to which charger-transfer events occur throughout the underlying polymer SC. By studying the electrochemical doping of POT with [3,5-bis(triflouro-methyl)phenyl]borate (TFPBˉ) ions it was shown that the ion-to-electron transduction process is surface confined. This outcome demonstrates that the performance of various SCs does not depend on the thickness of the polymer film. In fact, it is proposed that the sparing use of the SC material may possibly achieve better charge-transfer performance. Such a hypothesis is based on the reduced electron path through the SC, hence reducing the probability that electrons are hindered by impurities and film imperfections. The suggestion of surface confined charge-transfer events also supports previous notions that the effectiveness of SCs is based on the capacitive nature of the material.The final part of the thesis deals with the characterization of the structure and morphology of TCNQ-based charge-transfer materials. Due to the lack of prior research on the electrochemical syntheses and structures of these materials, Cd(TCNQ)2 and Zn(TCNQ)2 were studied. By using SR / GIXRD together with synchrotron powder diffraction, the electrochemically synthesized Cd(TCNQ)2 was found to be crystallographically similar to the powder sample. Subtle differences between the two materials were evident; however, it was found that the major phase of non-hydrated Cd(TCNQ)2 phase was present in both samples. Notably, this phase was found to have a tetragonal unit cell, with cell parameters: a = 16.78Å and c = 8.83Å.Finally, a potential-dependant voltammetric study was carried out on a Zn(TCNQ)2 system. This was done in order to investigate the effects of electrodepositing Zn(TCNQ)2 under different electrochemical conditions. It was found that the material electrocrystallized prior to, or at, the peak potential for reduction of TCNQ to TCNQˉ comprised two layers. The upper layer was shown to consist of a densely packed and highly amorphous layer of Zn(TCNQ)2, while the lower layer was a crystalline phase of Zn(TCNQ)2. The material deposited at a potential after the peak suggested that only the crystalline phase of Zn(TCNQ)2 was present. This finding is significant for two reasons. First, in electrochemistry, it demonstrates that the in situ SR / GIXRD technique can be used to interrogate electrode reaction products under different voltammetric conditions. Next, it is important in the manufacture of electrocrystallized materials, where it demonstrates that complete control of the morphology and major phases is possible and that SR / GIXRD is a useful research tool to study the process.
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Almqvist, Olof. "A comparative study between algorithms for time series forecasting on customer prediction : An investigation into the performance of ARIMA, RNN, LSTM, TCN and HMM." Thesis, Högskolan i Skövde, Institutionen för informationsteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-16974.
Full textAbstract:
Time series prediction is one of the main areas of statistics and machine learning. In 2018 the two new algorithms higher order hidden Markov model and temporal convolutional network were proposed and emerged as challengers to the more traditional recurrent neural network and long-short term memory network as well as the autoregressive integrated moving average (ARIMA). In this study most major algorithms together with recent innovations for time series forecasting is trained and evaluated on two datasets from the theme park industry with the aim of predicting future number of visitors. To develop models, Python libraries Keras and Statsmodels were used. Results from this thesis show that the neural network models are slightly better than ARIMA and the hidden Markov model, and that the temporal convolutional network do not perform significantly better than the recurrent or long-short term memory networks although having the lowest prediction error on one of the datasets. Interestingly, the Markov model performed worse than all neural network models even when using no independent variables.
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Berti, Matteo. "Anomalous Activity Detection with Temporal Convolutional Networks in HPC Systems." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/22185/.
Full textAbstract:
Detecting suspicious or unauthorized activities is an important concern for High-Performance Computing (HPC) systems administrators. Automatic classification of programs running on these systems could be a valuable aid towards this goal. This thesis proposes a machine learning model capable of classifying programs running on a HPC system into various types by monitoring metrics associated with different physical and architectural system components. As a specific case study, we consider the problem of detecting password-cracking programs that may have been introduced into the normal workload of a HPC system through clandestine means.
Our study is based on data collected from a HPC system called DAVIDE installed at Cineca. These data correspond to hundreds of physical and architectural metrics that are defined for this system. We rely on Principal Component Analysis (PCA) as well as our personal knowledge of the system to select a subset of metrics to be used for the analysis. A time series oversampling technique is also proposed in order to increase the available data related to password-cracking activities. Finally, a deep learning model based on Temporal Convolutional Networks (TCNs) is presented, with the goal of distinguishing between anomalous and normal activities.
Our results show that the proposed model has excellent performance in terms of classification accuracy both with balanced (95%) and imbalanced (98%) datasets. The proposed network achieves an F score of 95.5% when training on a balanced dataset, and an AUC-ROC of 0.99 for both balanced and imbalanced data.