Cette thèse traite de la conception, la synthèse et la caractérisation de chromophores dipolaires D-π-A pour l’imagerie de fluorescence et l’imagerie photoacoustique.La première partie est consacrée à la synthèse et à l’étude de nouveaux fluorophores émettant à l’état solide dans le proche infrarouge, pour l’imagerie de fluorescence biphotonique. Afin d’améliorer les propriétés optiques à l’état solide, nous avons exploré différentes pistes en modifiant d’abord le groupement D donneur d’électron, puis le groupement A accepteur et enfin le pont π conjugué de nos structures dipolaires.La seconde partie concerne l’imagerie photoacoustique. Cette imagerie, basée sur une excitation optique et une détection acoustique, nécessite une forte absorption dans le proche infrarouge. Une des stratégies pour effectuer ce décalage bathochrome de l’absorption a été incorporation de groupements thiophènes à faible aromaticité, afin d’augmenter la délocalisation du système π. Parallèlement, nous avons aussi étudiés des hémicyanines, présentant de fortes absorptions au-delà de 650 nm.Enfin, les colorants ont été formulés en nanoparticules organiques afin d’acquérir une solubilité aqueuse pour leur application en imagerie. Deux types de nanoparticules ont été étudiés : la nanoprécipitation des colorants en présence d’un agent tensioactif, ainsi que l’encapsulation des colorants dans une matrice polymérique amphiphile stabilisée par une couche de silice. Les meilleurs chromophores ont permis l’acquisition d’images de cellules par microscopie biphotonique ainsi que d’images photoacoustiques de circuits microfluidiques et de la microvascularisation de souris in vivo. / This thesis is focused on the conception, synthesis and characterization of dipolar dyes D-π-A for fluorescence imaging and photoacoustic imaging.The first part aim to synthesize and to study new fluorophores emitting in the solid-state in the near-infrared for fluorescence imaging with two-photon excitation. In order to improve the optical properties in the solid-state, we first explored various electron donating groups D, then acceptors A and finally we modified the π bridge. In a second part, we focused on dyes for photoacoustic imaging. This technique is based on an optical excitation and an acoustic detection. It requires a strong absorption in the biological window. To red shift the absorption we incorporated a thiophene bridge with low aromaticity to increase the delocalization. We also studied several hemicyanines with strong absorption above 650 nm.Finally, dyes were formulated as water-soluble nanoparticles for their final application for imaging. Two types of nanoparticles were studied: nanoprecipitated dyes stabilized by a surfactant to increase the colloidal stability or encapsulated dyes in a amphiphilic polymer matrix stabilized with a silica shell. Those nanoparticles enabled cells imaging with biphotonic florescence imaging as well as photoacoustic imaging of a microfluidic chip and of the microvascularisation of mice ears in vivo.

A espectroscopia fotoacústica e de fluorescência foram empregadas no estudo de reação da transferência de elétrons entre um doador (Octaetil-porfirina) dois tipos de aceitadores [Diclorodiciano-benzoquinona (DDQ) e Duroquinona (DQ)] em um meio rígido [poli (metil-metacrilato)] . Foram preparados filmes nos quais a concentração de doador foi mantida constante e a de aceitador foi variada. Observou-se um aumento exponencial da amplitude do sinal fotoacústico do doador em 620 nm, com o aumento da concentração de aceitadores nos filmes. O modelo de Perrin para a supressão de fluorescência foi aplicado aos dados de fotoacústica e o raio da esfera de ação, que representa a distância crítica para a ocorrência da transferência de elétrons, foi determinado. Os resultados obtidos foram: para DDQ37 angstron e para aDQ 32 a 34angstron. Era esperado um raio maior para a DDQ devido a sua maior elétron afinidade. Também foi aplicado a estes dados o modelo de Kaneko, desenvolvido para a supressão de fluorescência. Dele se obtém a distribuição de moléculas aceitadoras incorporadas na esfera de ação. Para uma mesma concentração de aceitadores (2,8mmoldm-3) , a probabilidade de encontrar uma molécula de DDQ na esfera de ação foi 27%, enquanto que a probabilidade de encontrar uma molécula de DQ na esferade ação foi de 20%. Este resultado é, na verdade, equivalente ao encontrado no modelo de Perrin pois a probabilidade maior encontrada para a DDQ vem do fato do raio da sua esfera de ação ser maior. O valor encontrado para o raio crítico com os dados de fluorescência foi de 34 A para a DQ. Isto demonstra que as duas técnicas são complementares e que a espectroscopia fotoacústica pode ser usada para monitorar o processo de transferência de elétrons / Steady-state photoacoustic and fluorescence spectroscopy were employed to study the electron-transfer reaction from donor molecules (Octaethyl-porphirin) to two types of acceptor molecules [Dichloro-dicyano-benzoquinone (DDQ) and Duroquinone (DQ)I in a rigid medium [poly (methyl -metacrylate)] . Films were prepared with a fixed donor concentration and severa1 acceptor concentrations. It was observed an exponential growth in the donor photoacoustic signal amplitude at 620 nm, with the increase in the acceptor concentration. Perrin model, used in fluorescence quenching, was applied to the photoacoustic data and the radius o£ an action sphere, which represents a critica1 distance for the electron transfer process, was determined. The results obtained were: for DDQ 37 angstron and for DQ from 32 to 34 angstron. It was expected a larger radius for DDQ than for DQ due to its stronger electron affinity. Kaneko\'s model, was also applied to these data. It provides the distribution o£ incorporated acceptor molecules in the action sphere. For the same acceptor concentration (2.8 mmol , the probability of finding one DDQ molecule in the action sphere was 27%, while for the DQ molecule this value was 20%. Actually, this result is equivalent to that found using Perrin model, because the larger probability obtained for DDQ comes frm the fact that its critical radius is bigger . The value obtained for the critica1 radius from the fluorescence data was 34 angstron for DQ. This shows that these two techniques are complementary and that photoacoustic spectroscopy can be used to monitor the electron transfer process

A transferência de elétrons tem sido objeto de um estudo intenso nos últimos anos, por causa da importância deste tipo de reação em processos naturais como a fotossíntese. Com isto, um progresso considerável foi conseguido na proposição de modelos para o centro de reação fotossintético, em particular utilizando o sistema-modelo porfirina-quinona. Nosso intuito e estudar o processo de transferência de elétrons da porfirina para a quinona, aleatoriamente distribuídas em uma matriz polimérica, utilizando a técnica de espectroscopia fotoacústica. A utilização de um filme de polímero como meio tem duas vantagens. A primeira e aproximar nosso sistema-modelo do processo fotossintético natural, no qual os doadores e os aceitadores de elétrons estão envoltos nas proteínas do centro de reação e, portanto, em um meio polimérico. A segunda e possibilitar a utilização desses filmes como possíveis componentes eletrônicos moleculares. Identificamos os estados eletrônicos da porfirina e da quinona e tentamos determinar o estado de cargas separadas, P+ e Q-. A partir dos espectros obtidos, determinamos a eficiência quântica de fluorescência da porfirina utilizada nos filmes. Estudamos, também, a degradação da porfirina nos filmes preparados. Por fim, verificamos o efeito da concentração crescente da quinona nos filmes preparados com a porfirina / The electron transfer phenomenon has been the subject of intense study for the last years, due to the importance of this kind of reaction in natural processes as photosynthesis. A great improvement has been achieved in the proposition of models for the photosynthetic reaction center, in particular using the porphyrin-quinone model system. Our intention is to study the electron transfer process of the porphyrin to the quinone randomly distributed in a polymeric matrix, using the photo acoustic spectroscopy. The utilization of a polymeric film as an environment has two advantages. The first is to approximate our model system to the natural photosynthetic process, in which the electron donors and acceptors are surrounded by, the proteins of the reaction center, and thus in a polymeric environment. The second is to allow the utilization of these films as possible molecular electronic components. We identified the electronic states of the porphyrin and the quinone, and we attempted to determine the charge separated electronic state. We determined the fluorescence quantum efficiency of the porphyrin films, by their photo acoustic and absorption spectra. Also, we studied the degradation of the porphyrin in the prepared films. Finally, we checked the effect of the increasing concentration of the quinone in the films prepared with the porphyrin

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta tese apresenta as espectroscopias de fotoluminescência, excitação e fotoacústica de amostras MgGa2O4 dopadas com 0,1%, 0,5% e 1,0% de Ni2+, obtidas pelo método de estado sólido e duas amostras distintas GaNbO4-GaNb11O29-Ga2O3 dopadas com 1,0% de Cr3+, uma sintetizada por reação de estado sólido e a outra pelo método de acetato. As amostras foram identificadas por Difração de Raios X e os dados foram refinados pelo método de Rietveld. A morfologia das amostras foi observada por Microscopia Eletrônica de Varredura. Os espectros ópticos das amostras apresentaram bandas de absorção e emissão do visível ao infravermelho próximo. As transições de energia foram analisadas com base na teoria de campo cristalino e os parâmetros de energia foram obtidos a partir de espectros de absorção e das matrizes de Tanabe-Sugano. / This work presents the photoluminescence, excitation and photoacoustic spectroscopy of samples MgGa2O4 doped with 0.1%, 0.5% and 1.0% of Ni2+, obtained through solid state method and two different samples GaNbO4-GaNb11O29-Ga2O3 doped with 1.0% of Cr3+, one synthesized by solid state reaction and another by wet chemical method. The samples were identified by X Ray Diffraction and the data were refined by Rietveld method. The morphology of samples was observed by SEM. The optical spectra of samples showed emission and absorption bands from visible to near infrared. The energy transitions were analyzed based on the crystal field theory and the energy parameters were obtained from absorption spectra and Tanabe-Sugano matrices.

Multiple breath washout (MBW) of inert gas for assessment of airway disease in children is an emerging technique. In many studies Lung Clearance Index (LCI), derived from multiple breath washout of SF6, is more able to detect early or mild lung disease than standard lung function measurements. It is also able to detect very early lung disease in progressive conditions such as Cystic Fibrosis (CF). Where infants born with this condition were thought to have minimal lung disease activity, LCI is higher in these children than healthy controls. Lack of available commercial devices has hampered expansion of this technique to centres other than specialist research teams. Innocor (Innovision, Dk), a photoacoustic mass spectrometer capable of performing multiple breath washout, was adapted within this research group for use in adults. This thesis describes the setup, adaptation and validation of Innocor for use in children. In 4 studies, healthy controls, children with asthma and children with CF were recruited to perform MBW. In one study, 29 healthy controls and 31 children with asthma were recruited. Healthy controls performed 1 set of washouts, establishing a normative range. Children with asthma performed measurements before and after bronchodilator. Results showed increased LCI in children with asthma even though they were clinically stable as defined by symptoms. LCI stayed high even following bronchodilator suggesting evidence of residual airway disease in well controlled asthmatics despite adequate symptom control. To investigate short term variability of MBW measurements, two other studies recruited 18 children with CF in each. They performed measurements before and after standard physiotherapy manoeuvres and during sitting and lying posture. LCI did not change significantly after airway clearance physiotherapy, compared with children who did no intervention. Variability was high in both groups however suggesting CF lung disease is a complex interaction of changing ventilation in adjacent lung units. Lying posture induced greater changes in lung function in children with CF than controls. LCI appears to be more sensitive to this change than standard lung function measurements (spirometry). In another study 32 children with CF were recruited to perform serial lung function measurements over 18 months. These were data collected as part of the UK Cystic Fibrosis Gene Therapy Consortium (CFGTC) clinical studies in preparation for planned gene therapy trials. LCI appears comparable to FEV1 and may be able to detect another aspect of airway disease. All initial studies were performed in older children (>5yrs). The basic Innocor device is unsuitable for testing of younger patients with low breath volume and high respiratory rate. In-house adaptations following detailed lung model experimentation led to a faster analyser response, potentially capable of MBW in younger children. The second part of this thesis concerns lab experiments and an in-vivo comparison with the current gold-standard MBW device, a respiratory mass spectrometer. 16 healthy volunteers and 9 children with CF were recruited. Ages ranged from 0.4 yrs to 49 yrs. Innocor values for lung volume estimation compared favourably with the mass spectrometer. No evidence of bias caused by Innocor error was seen, however intra-test variability was rather high, reducing the precision of the results. These studies indicate Innocor is a robust, simple to use device with potential as a commercial lung function system. Modifications were made to make it suitable for use in all ages. Further development will need to focus on the patient interface and software, which is the domain of the manufacturers. The experiments contained in this thesis are therefore of interest to the wider respiratory research community as well as manufacturers of MBW devices.

The application of photoacoustic (PA) phenomena to medical imaging has been investigated for more than a decade. To implement this modality, one may choose between two types of laser sources, pulsed or continuous wave (CW). This selection affects all features of the imaging technique. Nowadays pulsed lasers are the state-of-the-art technique in the PA research. In this work, various features of the alternative frequency-domain (FD) PA were investigated. An axially symmetric transfer function model of PA wave generation and a Krimholtz-Leedom-Matthaei (KLM) transducer model were developed and used to analyze the experimental results. The controllable parameters of the FD-PA were optimized to improve the signal-to-noise ratio (SNR), contrast, axial resolution and depth detectivity. For example, it was shown that employing the optimal chirp bandwidth can enhance the SNR by more than 10 dB. In addition to the image produced by the cross-correlation amplitude, the phase of the correlation signal was used as a separate channel. A statistical method was introduced to generate an image from this phase channel, and also to filter the PA amplitude channel. A study was also performed to compare FD PA and the prevalent pulsed method. Various features of both methods were examined experimentally using a dual-mode PA system and under the condition of maximum permissible exposure (MPE). The SNRs of both methods were evaluated theoretically and experimentally. It was shown that at low frequencies, both modalities generate comparable SNRs, and at high frequencies pulsed PA produces superior SNRs and depth detetivity. However, by increasing the laser power and decreasing the chirp duration within the safety limits, the SNR and depth detectivity of the FD-PA method are enhanced considerably. The main cause to achieve lower experimental SNRs than theoretical predictions for pulsed PA response was shown to be the oscillating baseline, which can be partially eliminated by filtering.

The application of photoacoustic (PA) phenomena to medical imaging has been investigated for more than a decade. To implement this modality, one may choose between two types of laser sources, pulsed or continuous wave (CW). This selection affects all features of the imaging technique. Nowadays pulsed lasers are the state-of-the-art technique in the PA research. In this work, various features of the alternative frequency-domain (FD) PA were investigated. An axially symmetric transfer function model of PA wave generation and a Krimholtz-Leedom-Matthaei (KLM) transducer model were developed and used to analyze the experimental results. The controllable parameters of the FD-PA were optimized to improve the signal-to-noise ratio (SNR), contrast, axial resolution and depth detectivity. For example, it was shown that employing the optimal chirp bandwidth can enhance the SNR by more than 10 dB. In addition to the image produced by the cross-correlation amplitude, the phase of the correlation signal was used as a separate channel. A statistical method was introduced to generate an image from this phase channel, and also to filter the PA amplitude channel. A study was also performed to compare FD PA and the prevalent pulsed method. Various features of both methods were examined experimentally using a dual-mode PA system and under the condition of maximum permissible exposure (MPE). The SNRs of both methods were evaluated theoretically and experimentally. It was shown that at low frequencies, both modalities generate comparable SNRs, and at high frequencies pulsed PA produces superior SNRs and depth detetivity. However, by increasing the laser power and decreasing the chirp duration within the safety limits, the SNR and depth detectivity of the FD-PA method are enhanced considerably. The main cause to achieve lower experimental SNRs than theoretical predictions for pulsed PA response was shown to be the oscillating baseline, which can be partially eliminated by filtering.

Thermoacoustic tomography (TAT) is a newly emerging modality in biomedical imaging. It combines the good contrast of electromagnetic and good resolution of ultrasound imaging. The mathematical model of TAT is the observability problem for the wave equation: one observes the data on a hyper-surface and reconstructs the initial perturbation. In this dissertation, we consider several mathematical problems of TAT. The first problem is the inversion formulas. We provide a family of closed form inversion formulas to reconstruct the initial perturbation from the observed data. The second problem is the range description. We present the range description of the spherical mean Radon transform, which is an important transform in TAT. The next problem is the stability analysis for TAT. We prove that the reconstruction of the initial perturbation from observed data is not H¨older stable if some observability condition is violated. The last problem is the speed determination. The question is whether the observed data uniquely determines the ultrasound speed and initial perturbation. We provide some initial results on this issue. They include the unique determination of the unknown constant speed, a weak local uniqueness, a characterization of the non-uniqueness, and a characterization of the kernel of the linearized operator.

During the last few years the scientific interest in chalcogenides glasses has been provoked on account of their properties and new application possibilities. These materials exhibit electrical and optical properties, which make them useful for several potential applications. Specifically the threshold and memory switching behavior and the infrared transmission of many of these glasses make the materials to be well suitable for use in memory devices and in fiber optics. Multicomponent glasses have been found to be more useful for many of these applications since the properties could be tailored for the specific uses. On account of this there has been great deal of interest in recent years in understanding the composition dependent variations of physical properties in these glasses. Models based on network topology and chemical ordering have been proposed to explain the composition dependence of physical properties. The Chemically Ordered Covalent Network (COCN) model is one of the best efforts put forth in this subject. This model predicts distinctive physical properties of these glasses for compositions at which there is a maximum number of heteropolar bonds. A physical model based on changes in network topology with composition has been proposed recently. This model predicts the rigidity to percolate in the network at the mean coordination number <r> = 2.40. This critical value of <r> at which the rigidity percolates is called the mechanical threshold or the rigidity percolation threshold. One more argument based on medium range interactions, existing in these glassy networks, suggests that the mechanical threshold should occur at <r> = 2.67. A general lack of consensus in the existing experimental reports on the mechanical threshold in some chalcogenides glasses prevents one from identifying the correct threshold value of <r>. A systematic study of the composition dependence of glasses with a large glass-forming region is necessary to resolve this controversy. The correct threshold value of <r> and the reason for the departure from this value in the other cases is the first step towards verifying the applicability of this model to chalcogenide glasses. Glasses belonging to IV — V — VI groups are natural candidates for this study because of their large glass forming region. It also seems possible to isolate the chemical threshold from interfering with the mechanical threshold in some of these glasses. In device applications of any semiconductor the optical and the electrical band gaps need to be varied and this is commonly done by doping. The large density of valence alteration pairs and intrinsic disorder of amorphous semiconductors counter-balances the effects of external additives. As a result, it is hard to electrically dope these materials. Non-equilibrium experimental techniques have been used to some extent, but one of the limitations is that they are confined to the thin film state. The finding that p to n type conduction sign changes can be induced by Bi and Pb in bulk Ge-M (M= S, Se and Te) glasses has therefore created special interest. This thesis deals with Ge-Se glass matrix doped with Te, Bi and Pb. The optical, thermal and electrical properties have been studied. The present thesis work is arranged in several chapters. The basic introduction of chalcogenide glasses is given in chapter one. This includes an introduction to chalcogenide glasses followed by a brief discussion on the important structural models, the possible defects in chalcogenide glasses and the electrical, optical and thermal properties of chalcogenide glasses. The second chapter discusses the experimental techniques used in the present investigations. The basic principles and theory behind the experiments, the experimental setup and the experimental procedure leading to the determination of the physical properties are given here. These include information about Differential Scanning Calorimetry (DSC), Photo acoustic (PA) spectroscopy and Photoluminescence studies. In the third chapter the experimental investigations on Ge-Se-Te glasses are presented. The chapter starts with the preparation and characterization of these glasses. It then gives an account of the earlier studies on Ge-Se-Te glasses that are relevant to the present work. The results of the DSC and PA studies are discussed in the following two sections. In the systems with Gex Se80-x Te20 and Gex Se75.x Te25, glasses with less than 20 at. % of Ge do not show any crystallization peak due to Se rich content. But Te and Ge-rich glasses show strong crystallization tendency. The composition dependence of Tg of this glassy system gives an evidence for the occurrence of the topological threshold or mechanical threshold at <r> = 2.40 and chemical threshold at <r> = 2.67. These can be explained on the basis of COCN model. The optical band gap and thermal diffusivity studies also show anomalous behavior at <r> = 2.40 and <r> = 2.67. The experimental results on Ge-Se-Te glasses are summarized in the last section of this chapter. The investigations on Bi doped Ge-Se and Ge-Se-Te glasses are given in the fourth chapter. The chapter starts with a brief introduction of preparation, characterization and a short review of earlier work. In PA studies the anomalous behavior is observed in thermal diffusivity and thermal diffusion length plot at 8-9 at. % of Bi doping of the Ge-Se and Ge-Se-Te glasses where the conduction changes from p to n type. These results are explained on the basis of percolation model and the formation of Bi2Se3 microcrystalline phase. Finally these results are summarized at the end of the chapter. The fifth chapter is devoted to the investigations on Pb doped Ge-Se glasses. It is arranged in five sections; preparation and characterization, earlier work, Photo acoustic and Photoluminescence studies. In PA studies the composition dependence of thermal diffusivity show anomalous behavior at x =F 9 at % of Pb in Pbx Ge42-x Sesg glasses and y = 21 at. % of Ge in Pb2o Gey Seso-y glasses where the conduction changes from p to n type. After that it reaches the maximum. After the conduction sign changes the conductivity increases with addition of respective Pb and Ge concentration in both series of glasses, which is reflected in thermal diffusivity value also. The results have been explained on the basis of COCN model. From PL studies, the PL intensity is high in un-doped Ge42 Scss glasses. With the addition of Pb into Ge-Se system the PL intensity goes down drastically up to 9 at. % of Pb, beyond 9 at. % the PL intensity is approximately the same up to 15 at. %. In the last section the results are summarized. Chapter six summarizes the essential features of the work reported in the thesis. These conclusions are drawn from the present and the earlier reported studies on Ge-Se-Te glasses, Bi doped Ge-Se and Ge-Se-Te glasses and Pb doped Ge-Se glasses. Finally based on the present experimental results, some future work has been suggested which could throw some light on a better understanding of/? to n transition and defects state of these glasses. It is worth extending the microscopic phase separation studies in these glasses. Highly sensitive experimental techniques are needed in this regard. Also some simulation work like Monte-Carlo simulation and Molecular dynamics simulation needs to be undertaken for understanding the microscopic phase separation and the role of defects in carrier type reversal in these glassy materials. All the references cited in the thesis are collected and listed at the end of the thesis.

The recent increase in survival rates of most cancers is due to early detection greatly aided by medical imaging modalities. Combined ultrasound and photoacoustic imaging provide both morphological and functional/molecular information which can help to detect and diagnose cancer in its earliest stages. However, both modalities can benefit from the use of contrast agents. The objective of this thesis was to design, synthesize, and test a nano-sized, dual contrast agent for combined ultrasound and photoacoustic imaging named Photoacoustic nanoDroplets. This agent consists of liquid perfluorocarbon nanodroplets with encapsulated plasmonic nanoparticles. These dual contrast agents utilize optically triggered vaporization for photoacoustic signal generation, providing significantly higher signal amplitude than that from the traditionally used mechanism, thermal expansion. Upon pulsed laser irradiation, liquid perfluorocarbon undergoes a liquid-to-gas phase transition generating giant photoacoustic transients from these dwarf nanoparticles. Once triggered, the gaseous phase provides ultrasound contrast enhancement. Demonstrated in this work are the design, synthesis, characterization, and testing of Photoacoustic nanoDroplets in phantom and animal studies, and preliminary work into adapting these agents into targeted, drug delivery vehicles for simultaneous detection, diagnosis, and treatment of diseases. / text