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Conducting and semiconducting polymers, consisting of delocalized π-electrons, have been studied for the past three decades. These materials have shown novel physical properties with interesting applications in batteries, detectors, light emitting diodes, field effect transistors, solar cells, biosensors etc. Nevertheless the charge transport properties are yet to be understood in detail due to the complexity of the system, especially due to the interplay of quasi-one dimensionality (q-1D), disorder, localization and electron-electron interactions(EEI). A combined investigation of both conductivity and spin lattice relaxation time, especially at very low temperatures and high magnetic fields, is really lacking in conducting polymers. In this thesis a set of experiments – dc conductivity, magnetoresistance (MR), Nuclear Magnetic Resonance (NMR) spin lattice relaxation time (T1) measurements, magnetic susceptibility amd ac conductivity have been carried out in conducting polymers. NMR being a local probe it is possible to get the nanoscopic scale charge transport mechanism. Further, this helps to develop a consistent understanding among a wide range of the physical properties in conducting polymers. In this thesis author has reported the results of experiments at ultra low temperature (mk) and ultra high magnetic field which give more insight about the roles of electron-electron interaction(EEI) and disorderin charge transport properties. This thesis describes a detailed study of charge transport and NMR relaxation in three representative conducting polymers namely polypyrrole(PPy)., poly-3-methylthiophene(P3MT) and poly3-hexylthiophene(P3HT). The emphasis is to understand the charge transport phenomena and NMR relaxation, especially at ultra low temperatures (down to 20 mk) and high magnetic field (up to 23.4 T). The NMR T1 relaxation mechanisms are discussed in terms of (i) Korringa relaxation, (ii) relaxation due to spin diffusion to paramagnetic centers (SDPC) amd (iii) reorientation of symmetric groups, depending upon the temperature range.

Orientador: Prof. Dr. Caetano Rodrigues Miranda / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, Santo André, 2018. / A pasta de cimento 'e um material complexo, heterog¿eneo e poroso com excelentes propriedades que o tornam um aglutinante adequado para aplica¸c¿oes em constru¸c¿oes. A qualidade e a durabilidade do cimento t¿em uma forte rela¸c¿ao com a 'agua contida nele. Embora uma boa compreens¿ao das intera¸c¿oes complexas entre os poros do cimento e os flu'ýdos confinados 'e necess'aria para resolver os atuais problemas de durabilidade, at'e ent¿ao nenhum modelo foi bem sucedido na captura de todos os processos e o papel da 'agua no cimento continua a ser uma 'area de pesquisa ativa. Com o intuito de contribuir para a compreens¿ao atual da estrutura do cimento, este trabalho se concentrou no estudo dos processos din¿amicos que acontecem na nanoescala da 'agua confinada em poros de cimento. Utilizamos simula¸c¿oes atom'ýsticas que v¿ao desde primeiros princ'ýpios at'e din¿amica molecular para estudar a principal fase de hidrata¸c¿ao, ou seja, hidrato de silicato de c'alcio (C¿S¿H), modelado por uma estrutura de tobermorita com defeitos. A partir de primeiros princ'ýpios, investigamos a morfologia da superf'ýcie da tobermorita a qual rege as intera¸c¿oes da 'agua com o modelo C-S-H. Demonstramos que a tobermorita forma cristais pseudo-hexagonais e a faceta mais est'avel 'e a (004). A fim de explorar sistemas maiores, checamos a transferabilidade do potencial cl'assico CLAYFF na descri¸c¿ao dos componentes do cimento atrav'es de um estudo comparativo entre simula¸c¿oes de mec¿anica molecular e DFT. Embora as frequ¿encias calculadas com DFT e CLAYFF sejam diferentes, as propriedades estruturais e termodinâmicas apresentam grande concord¿ancia, indicando que o potencial CLAYFF 'e adequado para nossos c'alculos. Um par¿ametro importante para quantificar a din¿amica da 'agua no nanoconfinamento 'e o tempo de relaxa¸c¿ao T2. Para validar a metodologia implementada na determina¸c¿ao te'orica do tempo de relaxa¸c¿ao T2, realizamos simula¸c¿oes para a 'agua confinado dentro de nanoporos de calcita (1¿6 nm). Observamos que a din¿amica translacional 'e a principal respons'avel pela relaxa¸c¿ao de spin das mol'eculas de 'agua pr'oximas 'a superf'ýcie. O tempo de relaxa¸c¿ao T2 para mol'eculas de 'agua adsorvidas na superf'ýcie 'e menor e independente do tamanho de poro, no entanto, uma relaxa¸c¿ao de spin do tipo bulk 'e observada no centro dos poros maiores que 3 nm. Buscando elucidar as diversas propriedades da 'agua nanoconfinada em poros C¿S¿H, dividimos nosso estudo em tr¿es partes. Inicialmente, nos dedicamos a compreender os efeitos de confinamento da 'agua entre camadas (< 1 nm) e poros de gel (1¿5 nm) do modelo C-S-H, assim como suas influ¿encias nas intera¸c¿oes de superf'ýcie. A natureza hidrof'ýlica da superf'ýcie C¿ S¿H 'e evidenciada pela din¿amica lenta da 'agua que interage diretamente com a superf'ýcie. Entre as camadas, a 'agua se encontra praticamente im'ovel e exibe propriedades similares aquelas observadas em 'agua super-resfriada. Na sequ¿encia, investigamos o transporte da 'agua dentro da pasta de cimento implementando a relaxa¸c¿ao de troca do tipo 2D T2¿T2 RMN entre poros de gel com 1 nm e 4 nm conectados entre si. Nossos resultados mostraram que h'a trocas de mol'eculas de 'agua entre poros com um tempo caracter'ýstico de troca de 18 ns. Finalmente, conclu'ýmos nossos estudos considerando a natureza particulada do C¿S¿H a fim de estabelecer uma conex¿ao entre os fen¿omenos observados nas escalas nano e meso. Demonstramos que a 'agua confinada dentro do ambiente C¿S¿H edge-edge apresenta uma din¿amica semelhante ao caso das superf'ýcies planares. / Cement paste is a complex, heterogeneous and porous material with outstanding properties that make it a suitable binder for construction applications. The quality and durability of cement have a strong relationship with the water contained in it. While a good understanding of the complex interactions between the cement pores and the confined fluids is necessary to solve the current durability issues, no single model has been successful in capturing all the processes so far and the role of water in cement still remains an area of active research. To contribute to the current understanding of cement structure, this work has focused on studying the dynamical processes happening at the nanoscale of water confined in cement pores. We employ atomistic simulations ranging from first principles to molecular dynamics to study the main hydration phase, i.e calcium silicate hydrate (C¿S¿H), modeled by a defected tobermorite structure. Starting from first principles, the surface morphology of tobermorite which governs the interactions of water with the C¿S¿H model was investigated. It was shown that tobermorite forms pseudohexagonal crystals and the most stable facet is the (004). To upscale the calculations, the transferability of CLAYFF in the description of cementitious materials was tested through a comparative molecular mechanics and DFT study. Although the frequencies calculated with DFT and CLAYFF differ, the structures and thermodynamic quantities agree quite well, making CLAYFF a reasonable potential for our cement calculations. An important parameter to quantify water dynamics in nanoconfinement is NMR T2 relaxation time. To underpin the implemented methodology for theoretical determination of T2 relaxation time, simulations were performed for water confined within calcite nanopores (1¿6 nm). It was revealed that translational dynamics are the main contribution to spin relaxation of near surface water molecules. The T2 relaxation time for water molecules directly adsorbed on the surface is short and pore size independent, however a bulk¿like spin relaxation is observed at center of pores larger than 3 nm. To disentangle the diverse properties of water nanoconfined in C¿S¿H pores, the study of water within C¿S¿H was subdivided into three parts. The first part was dedicated to understanding the relative effect of the C¿S¿H surface and progressive confinement to water confined in the interlayer (< 1 nm) and gel pores (1¿5 nm) of C¿S¿H model. The hydrophilic nature of the C¿S¿H surface is evidenced by the slow dynamics for the water interacting directly with the surface. Within the interlayer, water is highly immobile and exhibits similar properties as those observed in supercooled water. Next, transport within cement paste was investigated by implementing 2D T2¿T2 NMR exchange relaxation between a 1 nm and 4 nm gel connected pores. We showed that there is water exchange in gel pores quantified by an exchange time of 18 ns. Lastly, the particulate nature of C¿S¿H is taken into consideration to facilitate bridging the gap between the atomistic and the mesoscale cement understanding. It was shown that water confined within the C¿S¿H edge¿edge environment portrays similar dynamics as in the C¿S¿H planar surfaces.

This thesis focuses on two aspects of Quantum Information Processing (QIP) and contains experimental implementation by Nuclear Magnetic Resonance (NMR) spectroscopy. The two aspects are: (i) development of novel methodologies for improved or fault tolerant QIP using longer lived states and geometric phases and (ii) implementation of certain quantum algorithms and theorems by NMR. In the first chapter a general introduction to Quantum Information Processing and its implementation using NMR as well as a description of NMR Hamiltonians and NMR relaxation using Redfield theory and magnetization modes are given. The second chapter contains a study of relaxation of Pseudo Pure States (PPS). PPS are specially prepared initial states from where computation begins. These states, being non-equilibrium states, relax with time and hence introduce error in computation. In this chapter we have studied the role of Cross-Correlations in relaxation of PPS. The third and fourth chapters, respectively report observation of cyclic and non-cyclic geometric phases. When the state of a qubit is subjected to evolution either adiabatically or non-adiabatically along the surface of the Bloch sphere, the qubit sometimes gain a phase factor apart from the dynamic phase. This is known as the Geometric phase, as it depends only on the geometry of the path of evolution. Geometric phase is used in Fault tolerant QIP. In these two chapters we have demonstrated how geometric phases of a qubit can be measured using NMR. The fifth and sixth chapters contain the implementations of “No Deletion” and “No Cloning” (quantum triplicator for partially known states) theorems. No Cloning and No Deletion theorems are closely related. The former states that an unknown quantum states can not be copied perfectly while the later states that an unknown state can not be deleted perfectly either. In these two chapters we have discussed about experimental implementation of the two theorems. The last chapter contains implementation of “Deutsch-Jozsa” algorithm in strongly dipolar coupled spin systems. Dipolar couplings being larger than the scalar couplings provide better opportunity for scaling up to larger number of qubits. However, strongly coupled systems offer few experimental challenges as well. This chapter demonstrates how a strongly coupled system can be used in NMR QIP.