<p>Ordinary yet unique, water is the substance on which life is based. Water seems, at first sight, to be a very simple molecule, consisting of two hydrogen atoms attached to one oxygen. Its small size belies the complexity of its action and its numerous anomalies, central to a broad class of important phenomena, ranging from global current circulation, terrestrial water and CO₂ cycles to corrosion and wetting. The explanation of this complex behavior comes from water's unique ability to form extensive three-dimensional networks of hydrogen-bonds, whose nature and structures, in spite of a great deal of efforts involving a plethora of experimental and theoretical techniques, still lacks a complete scientific understanding.</p><p>This thesis is devoted to the study of the local structure of hydrogen-bonded liquids, with a particular emphasis on water, taking advantage of a combination of core-level spectroscopies and density functional theory spectra calculations. X-ray absorption, in particular, is found to be sensitive to the local hydrogen-bond environment, thus offering a very promising tool for spectroscopic identification of specific structural configurations in water, alcohols and aqueous solutions. More specifically, the characteristic spectroscopic signature of the broken hydrogen-bond at the hydrogen side is used to analyze the structure of bulk water, leading to the finding that most molecules are arranged in two hydrogen-bond configurations, in contrast to the picture provided by molecular dynamics simulations. At the liquid-vapor interface, an interplay of surface sensitive measurements and theoretical calculations enables us to distinguish a new interfacial species in equilibrium with the gas. In a similar approach the cluster form of the excess proton in highly concentrated acid solutions and the different coordination of methanol at the vacuum interface and in the bulk can also be clearly identified.</p><p>Finally the ability of core-level spectroscopies, aided by sophisticated density functional theory calculations, to directly probe the valence electronic structure of a system is used to observe the nature of the interaction between water molecules and solvated ions in solution. Water around transition metal ions is found to interact with the solute via orbital mixing with the metal d-orbitals. The hydrogen-bond between water molecules is explained in terms of electrostatic interactions enhanced by charge rehybridization in which charge transfer between connecting molecules is shown to be fundamental.</p>

Ordinary yet unique, water is the substance on which life is based. Water seems, at first sight, to be a very simple molecule, consisting of two hydrogen atoms attached to one oxygen. Its small size belies the complexity of its action and its numerous anomalies, central to a broad class of important phenomena, ranging from global current circulation, terrestrial water and CO2 cycles to corrosion and wetting. The explanation of this complex behavior comes from water's unique ability to form extensive three-dimensional networks of hydrogen-bonds, whose nature and structures, in spite of a great deal of efforts involving a plethora of experimental and theoretical techniques, still lacks a complete scientific understanding. This thesis is devoted to the study of the local structure of hydrogen-bonded liquids, with a particular emphasis on water, taking advantage of a combination of core-level spectroscopies and density functional theory spectra calculations. X-ray absorption, in particular, is found to be sensitive to the local hydrogen-bond environment, thus offering a very promising tool for spectroscopic identification of specific structural configurations in water, alcohols and aqueous solutions. More specifically, the characteristic spectroscopic signature of the broken hydrogen-bond at the hydrogen side is used to analyze the structure of bulk water, leading to the finding that most molecules are arranged in two hydrogen-bond configurations, in contrast to the picture provided by molecular dynamics simulations. At the liquid-vapor interface, an interplay of surface sensitive measurements and theoretical calculations enables us to distinguish a new interfacial species in equilibrium with the gas. In a similar approach the cluster form of the excess proton in highly concentrated acid solutions and the different coordination of methanol at the vacuum interface and in the bulk can also be clearly identified. Finally the ability of core-level spectroscopies, aided by sophisticated density functional theory calculations, to directly probe the valence electronic structure of a system is used to observe the nature of the interaction between water molecules and solvated ions in solution. Water around transition metal ions is found to interact with the solute via orbital mixing with the metal d-orbitals. The hydrogen-bond between water molecules is explained in terms of electrostatic interactions enhanced by charge rehybridization in which charge transfer between connecting molecules is shown to be fundamental.

Le corindon pur, de formule alpha-Al_2O_3, et le béryl, de formule<br />Be_3Si_6Al_2O_18, sont des minéraux incolores. Ils deviennent colorés lorsque des ions paramagétiques sont présents en impureté. Le rubis (alpha-Al_2O_3 dopé avec du chrome) est rouge, l'émeraude (Be_3Si_6Al_12O_18 dopé avec du chrome) est verte. Le corindon dopé avec du fer est jaune, il est rose s'il est dopé avec du titane. Le saphir bleu contient à la fois du fer et du titane (alpha-Al_2O_3:Fe-Ti). La couleur est généralement interprétée dans le cadre de la théorie du champ cristallin. Elle doit donc s'expliquer par un champ cristallin spécifique autour de ces ions colorants, correspondant dans chaque cas à une structure locale (cristallographique et electronique) précise.<br /><br />Notre objectif est de décrire précisément l'environnement autour des<br />impuretés dans les gemmes. Pour cela, nous effectuons à la fois des expériences d'absorption de rayons X, et des calculs ab initio. La structure cristallographique locale déduite des mesures expérimentales est comparée à celle déduite d'un calcul de relaxation de structure par minimisation d'énergie. La comparaison directe entre les spectres d'absorption de rayons X calculés et expérimentaux nous donne des informations à la fois sur la structure cristallographique et électronique locale. Tous ces calculs utilisent la théorie de la fonctionnelle de la densité.<br /><br />Cette étude révèle que l'introduction d'une impureté dans une structure conduit à des modifications très locales du cristal autour de l'impureté. Les atomes d'oxygène de la sphère de coordination de l'impureté M (M = Fe ou Cr) dans alpha-Al_2O_3 adoptent un arrangement similaire à celui autour de M dans alpha-M_2O_3.

Τις τελευταίες δεκαετίες το επιστημονικό ενδιαφέρον έχει στραφεί στη μελέτη οργανικών ημιαγώγιμων υλικών με σκοπό να κατασκευαστούν ηλεκτρονικές διατάξεις με χαμηλότερο κόστος και μεγαλύτερη απόδοση από τις εμπορικές διατάξεις με ανόργανους ημιαγωγούς, που κυκλοφορούν ήδη στην αγορά. Η οικογένεια των φθαλοκυανινών (Phthalocyanines, Pcs) ανήκει στα οργανικά υλικά που ανταγωνίζονται επάξια τους ανόργανους ημιαγωγούς στις εφαρμογές σε ηλεκτρονικές διατάξεις όπως φωτοεκπομπές δίοδοι (LEDs), τρανζίστορ επίδρασης πεδίου (FETs), φωτοβολταϊκά στοιχεία (PVs), ηλιακά στοιχεία (solar cells), αισθητήρες (sensors), διατάξεις αποθήκευσης πληροφορίας (data storage devices) και μπαταρίες (batteries). Τα υλικά αυτά είναι εύκαμπτα, εύκολα επεξεργάσιμα, με χαμηλό κόστος παρασκευής και αξιόλογη χημική και θερμική σταθερότητα, ενώ οι ηλεκτρικές και οπτικές τους ιδιότητες τα καθιστούν ελκυστικά υλικά για εφαρμογή στη μικροηλεκτρονική. Σε αυτού του είδους τις εφαρμογές παίζουν σημαντικό ρόλο οι φυσικές και χημικές αλληλεπιδράσεις που συμβαίνουν στις διεπιφάνειες μεταξύ των ενεργών οργανικών υμενίων και των υλικών που χρησιμοποιούνται ως ηλεκτρόδια, καθώς επηρεάζουν τη συμπεριφορά των διατάξεων ως προς την αγωγή του ρεύματος και επομένως τη λειτουργία τους. Καθίσταται επομένως σαφές ότι η μελέτη της ηλεκτρονικής δομής των οργανικών υμενίων και των διεπιφανειών που αυτά σχηματίζουν με μέταλλα, ανόργανους, αλλά και οργανικούς ημιαγωγούς είναι απαραίτητη και καθοριστική για την κατανόηση του τρόπου λειτουργίας των ηλεκτρονικών διατάξεων και για την εύρεση τρόπων βελτίωσης της απόδοσής τους. Στην παρούσα εργασία έγινε η πρώτη πειραματική μελέτη με φασματοσκοπίες φωτοηλεκτρονίων από ακτίνες-Χ και υπεριώδη ακτινοβολία (XPS και UPS) της ηλεκτρονικής δομής μεταλλικών φθαλοκυανινών, νικελίου (NiPc) και κοβαλτίου (CoPc), και των διεπιφανειών που σχηματίζονται κατά την απόθεση, με θερμική εξάχνωση, του οργανικού αυτού υλικού πάνω σε διάφορα υποστρώματα, σε συνθήκες υπερυψηλού κενού. Αρχικά μελετήθηκαν υμένια NiPc πάνω σε φασματοσκοπικά καθαρή επιφάνεια φύλλου πολυκρυσταλλικού χρυσού (Au) και αργύρου (Ag). Η επιλογή των μετάλλων αυτών οφείλεται στην ευρεία εφαρμογή που έχουν ως ηλεκτρόδια ή υποστρώματα σε πολλές διατάξεις, όπως FETs και LEDs. Υμένια NiPc αποτέθηκαν επίσης πάνω σε οξείδιο ινδίου-κασσιτέρου (ITO), το οποίο αποτελεί υλικό ανόδου σε OLEDs εξαιτίας της υψηλής ηλεκτρικής αγωγιμότητας και της εξαιρετικής του διαπερατότητας στο ορατό, καθώς και σε κρύσταλλο Si(100) με σκοπό να διερευνηθεί αν η παρουσία NiPc ως επίστρωση στην επιφάνεια του πυριτίου μπορεί να βελτιώσει τη λειτουργία των ανόργανων ηλεκτρονικών διατάξεων όπως τα FETs. Τέλος, μελετήθηκε η αλληλεπίδραση μεταξύ NiPc και οργανικών υλικών όπως το PEDOT:PSS και το PEDOT:PTSA, που είναι μίγματα πολυμερών και τα οποία, σύμφωνα με τη βιβλιογραφία, διευκολύνουν την έγχυση οπών σε μια διάταξη. Η χρήση του PEDOT:PTSA έχει στόχο να αντικαταστήσει σε διάφορες εφαρμογές το PEDOT:PSS του οποίου η σύνθεση είναι αρκετά περίπλοκη. Επίσης, μελετήθηκαν οι διεπιφάνειες μεταξύ υμενίων φθαλοκυανίνης κοβαλτίου (CoPc) και υποστρωμάτων πολυκρυσταλλικού χρυσού και ITO, με σκοπό να διερευνηθεί η επίδραση του κεντρικού μεταλλικού στοιχείου του μορίου της φθαλοκυανίνης, στη συμπεριφορά και τις ιδιότητες των διεπιφανειών με αντίστοιχα υποστρώματα. Από τα πειραματικά αποτελέσματα (XPS και UPS), προσδιορίζονται οι μεταβολές των ενεργειακών ζωνών των οργανικών και ανόργανων ημιαγωγών, η δομή της ζώνης σθένους και η τιμή του έργου εξόδου όλων των υλικών που χρησιμοποιούνται, καθώς και η θέση του υψηλότερου κατειλημμένου μοριακού τροχιακού (Highest Occupied Molecular Orbital, HOMO) των οργανικών ημιαγωγών (NiPc, CoPc). Επίσης προσδιορίζονται η διεπιφανειακή διπολική ροπή (eD) και το φράγμα έγχυσης οπών (Φbh) στις σχηματιζόμενες διεπιφάνειες, μεγέθη τα οποία καθορίζουν και επηρεάζουν τη μεταφορά φορτίου μεταξύ των υλικών σε επαφή κατά τον σχηματισμό της διεπιφάνειας. Η μελέτη των παραπάνω διεπιφανειών έδειξε ότι καταλληλότερο ηλεκτρόδιο για την έγχυση οπών είναι το PEDOT:PSS, καθώς το ύψος του φράγματος έγχυσης οπών στη διεπιφάνεια με υμένιο NiPc προσδιορίστηκε ίσο με 0.5 eV και είναι χαμηλότερο από αυτό που δίνουν οι διεπιφάνειες με τα μέταλλα (~0.9 eV), το ITO (1.0 eV) αλλά και το PEDOT:PTSA (0.8 eV). Από τη μελέτη της διεπιφάνειας NiPc/Si προέκυψε ότι η επιφανειακή δομή του Si(100) πιθανόν να επηρεάζει την διάταξη των μορίων της NiPc, τα οποία στα πρώτα στάδια ενδεχομένως να αναπτύσσονται στρωματικά πάνω στο υπόστρωμα, με αποτέλεσμα τα χαρακτηριστικά του οργανικού υμενίου να σχηματίζονται πλήρως στις αρχικές αποθέσεις μέχρι τα ~2 μονοστρώματα (ML). Σε κανένα από τα υπό μελέτη συστήματα δεν παρατηρήθηκε χημική αντίδραση των οργανικών μορίων με το υπόστρωμα, ενώ διαπιστώθηκε αλληλεπίδραση μέσω μεταφοράς φορτίου με σκοπό την αποκατάσταση θερμοδυναμικής ισορροπίας στη διεπιφάνεια. Επίσης, όλα τα συστήματα αποκλίνουν από τον κανόνα Schottky-Mott. Στη διεπιφάνεια NiPc/PEDOT:PSS παρατηρείται πάγωμα του επιπέδου Fermi εντός του χάσματος της NiPc. Συγκρίνοντας τα αποτελέσματα για τις δύο μεταλλικές φθαλοκυανίνες, προκύπτει ότι η παρουσία υμενίων CoPc διευκολύνει την έγχυση οπών στην επαφή με το ΙΤΟ, δίνοντας χαμηλότερες τιμές Φbh από την αντίστοιχη διεπιφάνεια με υμένια NiPc, ενώ οι διεπιφάνειες των MePcs με τον χρυσό παρουσιάζουν παρόμοια συμπεριφορά. Τέλος, έγιναν ηλεκτρικές μετρήσεις σε διατάξεις τύπου ΟFET με παχύτερα υμένια NiPc και CoPc, τα οποία παρασκευάστηκαν με εξάχνωση πάνω σε υπόστρωμα SiO2/Si αλλά και με τα παράγωγά τους με υποκαταστάτες θειϊκές ομάδες (SO3Na), τα οποία παρασκευάστηκαν από διάλυμα με τη μέθοδο της εναπόθεσης με σταγόνα (drop-casting) ή με περιστροφή (spin-coating). Οι διατάξεις ΟFET που προέκυψαν και ιδιαίτερα αυτές των σουλφονωμένων φθαλοκυανινών νικελίου, παρουσιάζουν ικανοποιητικές ευκινησίες. Τα κύρια ηλεκτρικά χαρακτηριστικά που προκύπτουν είναι ικανοποιητικά για το είδος των εφαρμογών για τις οποίες προορίζονται τα υλικά αυτά. / Recently, there is a great interest in the application of organic semiconductor thin films as active layers in electronic devices, in order to improve their efficiency and reduce the cost of their preparation. The family of Phthalocyanines (Pcs) present some of the most promising materials that can be compared to the conventional inorganic semiconductors for application in electronic devices, such as light emitting diodes (LEDs), field effect transistors (FETs), photovoltaic cells (PVs), solar cells, gas-sensors, data storage devices and batteries. The Pcs possess beneficial properties, such as quite high conductivity, thermal and chemical stability, compatibility with plastic substrates and low cost of deposition processes and are already used in gas sensor technology and in electronic devices. In this kind of devices, the properties of the interface between the active organic layer and the materials used as electrodes (metals, inorganic and organic semiconductors) affect the device performance therefore, it is important that they be determined. The present work, concerns the first experimental study by X-Ray and UV Photoelectron Spectroscopies (XPS, UPS), of the electronic structure of the interfaces formed upon evaporating, under UHV conditions, thin films of metal phthalocyanines (MePcs), such as Nickel (NiPc) and Cobalt (CoPc), on substrates with different chemical and physical properties. The choice of the substrates depends on the materials that are applied as electrodes and substrates in conventional electronic devices. Thin films of NiPc were deposited on the clean surface of metals with different work function values (polycrystalline gold and silver foils), on Indium-Tin Oxide (ITO) coated-glass substrate, a common electrode in OLEDS due to its excellent transparency in the visible, and on a silicon wafer (Si(100) n-type) used in FET structures. Also, the interaction of NiPc with organic substrates, such as PEDOT:PSS and PEDOT:PTSA which are polymer mixtures, is investigated. It has been reported that when PEDOT:PSS is applied at the anode of a device it enhances the injection of positive charge carriers. The PEDOT:PTSA substrate is investigated in order to decide whether it can replace PEDOT:PSS in several applications, as its synthesis is simpler than that of PEDOT:PSS. Also, the interfaces formed between CoPc and polycrystalline Au foil, as well as ITO, were studied by XPS and UPS and compared with the corresponding NiPc layers, in order to determine the role of the central metal atom of the metal phthalocyanine molecule in the properties of the interface. The experimental results (XPS and UPS) provide information about the valence band structure and the work function of the materials, the position of the highest occupied molecular orbital (HOMO) of the organic semiconductor (NiPc, CoPc) and the possible shifts of the energy levels of the materials. Furthermore, factors which affect and specify the charge transfer and the carrier mobility across the interface, such as the interfacial dipole (eD) and the barrier for the injection of holes (Φbh), can be determined. The results showed that the most appropriate material for the injection of holes is PEDOT:PSS, as the Φbh at the interface with NiPc was determined equal to 0.5 eV, significantly lower than that in the case of metals (0.9 eV), ITO (1.0 eV), as well as PEDOT:PTSA (0.8 eV). The study of the NiPc/Si(100) interface showed that the structure of the Si surface might affect the arrangement of the NiPc molecules, which could lay with their molecular plane parallel to the substrate, as evidenced by the fact the characteristics of the NiPc layer are fully developed at the early steps of deposition up to ~2 monolayers. No chemical interaction was observed in any of the studied systems, while in all cases charge transfer occurs in order to achieve thermodynamic equilibration. All the interfaces divert from the Schottky-Mott rule. In the case of the NiPc/PEDOT:PSS interface, a pinning of the Fermi level at the energy gap of NiPc occurs. Comparing the results for the interfaces formed between NiPc and CoPc with polycrystalline Au foil and ITO, it is found that in the case of Au the results are similar, while in the case of ITO substrate the presence of the CoPc layer leads to lower Φbh compared to NiPc layers, which would facilitate the mobility of positive carriers injected from the anode of a device. Finally, electrical measurements were performed on OFET structures using thicker NiPc and CoPc films, prepared by thermal evaporation on SiO2/Si substrates, as well as the same MePcs substituted with SO3Na groups, which were prepared from solution by drop-casting or spin-coating. All studied OFET structures and especially those of the sulfonated MePcs showed quite promising results for such type of applications.

La peau est l'organe le plus grand du corps humain et représente ~10% de la masse corporelle. La bonne qualité de son état et de ses fonctionnalités est primordiale pour la santé d'un individu. La sécheresse cutanée constitue un phénomène commun dans différents dysfonctionnements physiopathologiques. Grâce à ses propriétés de protection de l'organisme vis-à-vis de son environnement, le stratum corneum (SC) est considéré comme le principal élément contrôlant l'hydratation. Ce travail de thèse, associant des développements techniques et méthodologiques, a conduit à la mise en évidence par microspectroscopie Raman confocale, des mécanismes moléculaires impliqués dans les phénomènes de sécheresse cutanée. Le lien moléculaire entre hydratation et stress mécanique du SC ex vivo est décrit de manière approfondie impliquant lipides et protéines tissulaires. Ces travaux ont également porté sur la caractérisation des modifications supramoléculaires responsables des déformations du SC sous stress mécanique. En parallèle, ce travail illustre l'intérêt des spectroscopies vibrationnelles comme outil d'évaluation des mécanismes d'action des produits hydratants.Le caractère non-invasif de la spectroscopie Raman a permis d'exploiter les fortes potentialités de cette technique en transposant in vivo l'utilisation des descripteurs spectraux obtenus ex vivo. Ainsi, nous avons développé une approche in vivo couplant la spectroscopie Raman et la méthode des moindres carrés partiels (PLS) pour la quantification indirecte de différents paramètres physico-chimiques et fonctionnels du SC y compris les lipides et l'eau conduisant à une caractérisation globale du statut physiopathologique du SC.

Une nouvelle famille de porphyrines chirales bridées a été mise au point dans le but d'accéder à des systèmes présentant un processus redox irréversible, lié à une bistabilité conformationnelle, dans le but de les appliquer dans le domaine des mémoires moléculaires. Ces nouvelles porphyrines sont constituées de deux brides ancrées sur les quatre positions meso par des groupes cyclohexyle. Une amine secondaire a été insérée au centre des brides dans le but d'obtenir des métalloporphyrines présentant une seule conformation à l'équilibre pour une longueur de bride, un métal et un degré d'oxydation donnés et pour favoriser un changement conformationnel en fonction du degré d'oxydation d'un métal comme le manganèse. Pour cela, une nouvelle voie de synthèse des porphyrines bridées par pré-fonctionnalisation du dialdéhyde autour de la fonction amine a été conçue. Les porphyrines ont été caractérisées par spectroscopie RMN, spectroscopie UV-Visible et dichroïsme circulaire. Les conformations des bases libres, des complexes de zinc(II) et de nickel(II) ont été déterminées par RMN proton. Pour une longueur de bride de 9 atomes avec une amine secondaire, les conformations des complexes de zinc(II) et de nickel(II) sont respectivement αααα et ααββ. En partant de ce modèle, les complexes de manganèse(II) et de chloromanganèse(III) ont été synthétisés et caractérisés par spectroscopie UV-Visible, dichroïsme circulaire et RMN du carbone 13 afin d'étudier si des changements de conformation en fonction du degré d'oxydation du métal ont lieu. / A new family of chiral bridled porphyrins was designed in order to access systems presenting an irreversible redox process linked to a conformational switch. Such systems could be of high interest in the field of molecular memories. These new porphyrins are made of two bridles anchored to the four macrocycle meso positions through cyclohexyl groups. The first objective is to introduce a secondary amine in the centre of the bridles in order to allow metalloporphyrins with defined bridle length and specific metal with a given oxidation degree to be only under one conformation at equilibrium. The second objective is to favor a conformational switch dependent on the oxidation state of a redox metal such as manganese. To reach these goals, a new porphyrin synthetic pathway was established. The key steps of this new protocol were the synthesis of the bridle built around the central amine with two terminal aldehyde functions required for the macrocyle formation. Porphyrins were studied by NMR, UV-Visible and circular dichroism spectroscopies. The conformations of free base porphyrins, zinc(II) complexes and nickel(II) complexes were determined by 1H NMR. For a bridle with a chain length of 9 atoms including the secondary amine, the zinc(II) complex presents only an αααα conformation and nickel(II) complex an ααββ conformation. From these structural models, manganese(II) and chloromanganese(III) complexes were synthesised and characterised by UV-Visible spectroscopy, circular dichroism and 13C NMR in order to study the possible conformational switches dependent on the Mn redox state.

Ce travail a pour objet de synthétiser de nouveaux matériaux hybrides organiques-inorganiques, de types silsesquioxanes pontants. La structure locale et les propriétés de luminescence sont caractérisées en vue d’applications potentielles dans le domaine de la photonique durable comme les concentrateurs solaires.Dans ce contexte, trois familles distinctes de matériaux sont synthétisées, basées sur six précurseurs pouvant s’auto-assembler à travers des liaisons hydrogènes et dont les parties sililées peuvent être poly-condensées lors de la réaction sol-gel. Ces précurseurs diffèrent par leur sous structure organique i.e. 1) structure linéaire où la partie organique est basée sur le groupement malonamide (P2-m et P4-m); 2) structure linéaire dans laquelle un aromatique sépare deux groupements amide et/ou thioamide (P(UU), P(UT) and P(TT)) et 3) une structure à trois embranchements dont la partie organique est basée sur des groupements amides (t-UPTES (5000)).Les deux hybrides organiques inorganiques (M2-m et M4-m) résultant de l’hydrolyse condensation des précurseurs P2-m et P4-m sont synthétisés en présence de lanthanides. On étudie l’impact de la présence d’un ou deux groupes malonamides sur la structure locale et les propriétés de photoluminescence.Les hybrides organiques-inorganiques (H(UU), H(UT) and H(TT)) sont obtenus par hydrolyse condensation des précurseurs des précurseurs (P(UU), P(UT) and P(TT)). Des composés organiques modèles des trois sous structurels organiques sont également synthétisés. L’impact de la substitution du groupement urée par le groupement thio-urée sur la structure locale des modèles et des hybrides est étudié par spectroscopie vibrationnelle. Les mécanismes de compressions et les propriétés optiques des matériaux sont ensuite analysés à la lumière des différents types de liaisons hydrogènes (urée-urée, urée-thio-urée et thio-urée--thio-urée) mises en évidence dans ces composés.es hybrides basés sur les précurseurs t-UPTES(5000) sont synthétisés selon différentes stratégies. En changeant la concentration de HCl et d’eau ou en effectuant la synthèse dans un environnement contrôlé, on montre une amélioration des propriétés optiques de ce système, en particulier, le rendement quantique absolu et le coefficient d’absorption. De plus, les mécanismes de recombinaison responsables de l’émission sont étudiés à travers la comparaison entre les propriétés de luminescence des modèles organiques et inorganiques.Finalement, de par leur affinité pour les ions lanthanides les précurseurs P2-m and P4-m ont été dopés par des ions Eu3+. La structure locale des hybrides correspondants montre une coordination entre l’hybride et l’hôte. Grâce à un rendement quantique de luminescence très élevé pour ces matériaux, des concentrateurs solaires luminescents peuvent être développés présentant un maximum de rendement quantique absolu de 0.60+/-0.06 et un rendement de conversion optique de 12.3% dans la région spectrale (300-380 nm). / The present work aims to synthesize new organic-inorganic hybrid materials, bridge silsesquioxanes type, and characterize the local structure and photoluminescence properties overlooking potential applications in the area of sustainable photonics, namely, in solid-state lighting as luminescent solar concentrators.In this context, three distinct families of materials based on six precursors which differ in their structural organization are synthesized, i.e. precursors with structure: 1) linear where the organic component is based on malonamide group (P2-m and P4-m); 2) linear which is added an aromatic ring whose organic part is based on amide and/or thioamide (P(UU), P(UT) and P(TT)) and 3) tri-branched which the organic component is based on amide group (t-UPTES (5000)).Two organic-inorganic hybrids (M2-m and M4-m) which results from hydrolysis and condensation of the precursors P2-m and P4-m are synthetized. The role of the presence of one or two malonamide groups is studied in terms of local structure and photoluminescence properties.Three organic-inorganic hybrids (H(UU), H(UT) and H(TT)) based on (P(UU), P(UT) and P(TT)) aresynthesized and structurally characterized aiming to study the role of the hydrogen bond in the self-assembling of these materials. The presence of different types of hydrogen bonds (bifurcated, linear and cyclic) induces different conformations which affect the physical properties (mechanical and optical) of the materials.Hybrids based on t-UPTES(5000) precursor are synthesized based on different synthesis strategies. Changing the concentration of HCl and water content as well as the synthesis in a controlled environment allow the improvement of the optical properties of this system, in particular, the absolute quantum yield and the absorption coefficient. In addition, it is studied the recombination mechanisms responsible for the emission through the comparison between the corresponding photoluminescence properties of the organic and inorganic models.Finally, due to the structural simplicity of the precursors and affinity with lanthanide ions, P2-m and P4-m precursors are doped with Eu3+. The local structure of the corresponding hybrids shows local coordination between the ion and host. Efficient materials concerning the quantum yield values lead to the development of luminescent solar concentrators with a maximum absolute quantum yield of 0.600.06 and optical conversion efficiency in the absorption spectral region (300-380 nm) of 12.3%.

Magnetorheological fluids (MRFs) are non-colloidal stable suspensions of polarizable mesoscale soft magnetic particles, usually metallic Fe-particles, in a carrier liquid such as oil or water; the solidity of which can be tuned by varying the applied magnetic field strength. Magnetorheological fluids are agile candidates for impact mitigation due to their tunable “solidity”, quick and complete reversibility of physical states, durability and reusability in comparison to their mechanical counterparts. The highly desirable property of an MRF is its yield strength and hence the conventional MRFs are Fe-based. However, uncoated Fe-particles suffer from poor chemical and thermo-oxidative stabilities, poor sedimentation stability and redispersibilities necessitating the coatings / additives; which always lead to compromised performance when used in MRFs. An alternative (to Fe) magnetic filler phase is the use of magnetic oxide particles. Soft magnetic spinel ferrites and garnets (though with moderate yield strength in an MRF) with their excellent chemical, thermo-oxidative and sedimentation stabilities, ready-redispersibility, less stringent synthesis and preservation conditions, lower cost, need no stabilizers and additives make them potential contenders for use in MRFs which can provide reliable MR performance. As the microstructure and magnetic nature of particles have direct influence on the MR property, the effects of these were studied by preparing MRFs with magnetic oxide particles of different sizes and shapes. These MRFs were simple bi-phasic as magnetic oxide particles were dispersed in versatile carrier fluid (silicone oil) without any additives; where the magnetic fill fraction was decided based on off state viscosity and the wettability criteria. As the MRFs in a device can undergo different stress / strain conditions of varying amplitudes and frequencies during their service, such a response was studied in laboratory using magnetorheometer via different modes of operation which mimic the service conditions. By varying the applied magnetic field strength and applied shear conditions, the performance of MRFs was evaluated and correlated to the physical and magnetic properties of the particles. Such a study provides a basis for the choice of magnetic phase in MRFs and their required concentration in the base fluid to provide highest efficiency. The dynamic yield strengths (field dependent yield stress) of MRFs extracted from steady shear measurements showed that the yield strength was strongly dependent on the saturation magnetization as well as on the microstructure of the particles used in MRF. The yield strength scaled with the saturation magnetization, magnetic fill fraction and applied magnetic field strength due to stronger magnetic column formation. The stability of MRFs (via the absence of wall slip) was found to depend predominantly on the microstructure of magnetic particles in the fluid such that MRFs containing structured particles showed the absence of wall slip while the MRFs containing irregular shaped powder particles showed poor stability via the occurrence of wall slip. The steady shear tests highlight the importance of using particles of definite shape with superior magnetic properties at a certain magnetic fill fraction for an efficient and reliable MR performance. The MRFs subjected to different oscillatory shear conditions showed that sturdier structures form in-field (exhibited via high gain modulus or low loss factor) when the particles have certain shapes (and size distribution) which result in high surface contact and are highly magnetic. Hence, the MRF containing Fe3O4 micro-octahedrons with high magnetization and large surface area for contact with other octahedron showed the large value of gain modulus and low loss factor compared to all other MRF samples. Poly-dispersity in spheres was found to be advantageous over monodisperse spherical magnetic particles due to void-bridging effects that strengthen the magnetic structuration. The irregular shaped particles based MRFs showed lower gain (higher loss factor) due to weak structuration. Anomalously high loss factor observed for rod shaped LZFP particles based MRF at medium strains and low field strengths is attributed to the rotation hindrance and low density of particles. The polydisperse particles based MRFs showed need for higher applied field strengths to decrease the loss and irregular particles based MRFs showed noisy response. The magnetosweep results showed that shape anisotropic particles based MRFs respond faster to applied field manifested as a faster decrease in loss factor with field. With magnetorheological parameters showing high dependence on the physical and magnetic nature of particles, oscillatory shear tests can serve as a means to select and assess the suitability of these particles for magnetorheological fluid for specific applications. The time dependent magneto-mechanical behaviour such as creep-recovery in MRFs showed that the strain recovery was dependent on the microstructure and magnetic nature of the particles such that fluids containing structured particles with high saturation magnetization showed higher recovery (due to better in-field structuration) compared to the irregular shaped and lower magnetization particles based MRF counterparts. The endurance of the MRFs (sustenance of strength of the MRF) under sustained stress conditions were estimated by a novel method which showed that MRFs containing ‘structured’ particles with high saturation magnetization showed high creep strength. In case of spherical particles based MRFs, the polydispersity of particles was found to aid in better column strength due to void-filling. The high surface contact between rod-shaped particles in the fluid resulted in good creep-strength among all MRFs. Among all the particles, the octahedron shaped Fe3O4 particles with large surface contact coupled with high saturation magnetization makes the Fe3O4 micro-octahedron particles based MRF the best amongst all the MRFs studied in this work. In case of irregular shaped particles based MRFs, the creep strength lagged behind the yield strength suggesting that such MRFs are not suitable for applications which demand sustained strength over prolonged action of stresses. Thus, the present work highlights the importance of considering the physical and magnetic properties of magnetic particles while selecting them for application specific MRFs where high endurance is sought. The stress relaxation behaviour of MRFs showed an overall high strength (via relaxation moduli) for MRFs containing particles with definite shape and high magnetization values (increased structure strength). However, the rod shaped particles based MRF did not witness increased strain limit with increased field strength, probably due to the mass flow in fluid due to higher inter-particle interaction than the interaction with applied field. The observation of increase in critical strain with increase in field for MRFs containing irregular shaped particles is only due to the higher number of particles resulting in overall increase in viscosity with field. Among all the MRFs, octahedron Fe3O4 particles with superior magnetic properties and large surface contact between facets showed highest critical strain for flow, which is in corroboration with other magnetorheological studies discussed so far. The creep-recovery and stress relaxation behaviours of MRFs are rarely studied, yet very important when selecting an MRF for an application which seeks high retention of MR strength over prolonged action of stress or strains. A comparison of particle shapes used in the MRFs suggests that although both octahedron shaped and rod shaped particles make high surface contact during structuration, the former is better due to lack of rotation hindrance, thus useful for preparing quickly responding MRFs. The inadequacies in th e conventio nal FOMs are address ed by a new FOM which is based o n a wholistic approach formulated consideri ng all relev ant physical and magnetic paramete rs of the particles. Also, the individ ual terms of this FOM help in selecting a particular MRF for a specific application. The FOM is as follows: λ – sedimentation constant (time taken by the MRF to sediment to about 1/eth of its total volume) With the MRFs containing octahedron shape d Fe3O4 pa rticles showing the highest FOM followed by s pheres (mod erate value ) which are succeeded by irregular powder samples based MRFs, the FO M observed in all MRF cases follow the same trend as observed by results from different magnetorheologi cal studies. Hence, the highest F4 (or FAB) observed for Fe3O4 octahedron particles based MR F in comparison to a ll other MR Fs (including Fe-based) is justified by the o Mbserved large yield strength, creep-resistance, low density and ready-redispersibilities, validating the FOM. The entire thesis is organized as follows. Chapter 1 details the motivation for the present research work, introduction to the material of interest (Magnetorheological fluid) with overview of different areas of potential applications, important properties of MRF, the current status of MRF, the challenges / issues needed to be addressed followed by choice of alternate materials for addressal of these drawbacks faced by conventional (Fe based) MRFs. Chapter 2 explains the synthesis of magnetic-oxide particles of different sizes and shapes by following different synthesis techniques. This is followed by the structural, microstructural and magnetic properties characterizations carried out by employing different, standard characterization techniques. The procedure for preparation of MRFs from the synthesized magnetic oxide particles is discussed. The basis of carrier fluid selection and magnetic particle concentration in MRF is explained. Chapter 3 gives a background to magnetorheology, in terms of the instrumentation (magnetorheometer), the relation between the magnetorheological parameters and the instrumental parameters (conversion factors), the different operating modes and the relevance of characterization modes in terms of practical applications, the procedure of different characterizations and the standard response behavior of MRFs to the characterizations. Chapter 4 is comprehensive characterization of all the MRFs subjected to steady shear conditions at various applied fields. The detailed analyses in terms of MR response are given with respect to the structure, microstructure, magnetic nature, and magnetic fill fraction of the magnetic particle in the fluid. Chapter 5 is extensive study of all the MRFs subjected to dynamical shear conditions at various applied fields. The magnetorheological responses of MRFs under different dynamical conditions (amplitude sweep, frequency sweep and magnetosweep) are analyzed in regard to role of microstructure, magnetic nature and magnetic fill fraction of the magnetic particle in the fluid. Chapter 6 explains the creep-recovery response of MRFs for the best magnetic fill fraction, decided from the steady and dynamical shear responses for all concentrations of MRFs. The recovered strain is analyzed with respect to a range of applied field strength and stress values. The creep strength determined from this study is correlated to the microstructure and magnetic nature of particles constituting the MRFs. Chapter 7 elaborates the stress relaxation behaviour of MRFs for the best magnetic fill fraction, decided from the steady and dynamical shear responses for all concentrations of MRFs. The stress relaxation (plateau values) moduli for the MRFs extracted at various applied field strength and strain values are analyzed to estimate the critical stress for flow in MRFs. This relationship between the critical stress that an MRF can withstand and the microstructure and magnetic nature of the particles in the fluid are investigated. Chapter 8 is about the study of sedimentation stability (and the redispersibility) of magnetic oxide particles based MRFs and the comparison of these properties with Fe- based MRFs. The role of mass-density and microstructure of particles in the fluid on sedimentation rate is briefly explained. Chapter 9 compares the important outcome of all the magnetorheological characterizations for all the studied MRFs in terms of extent and speed of response, the sedimentation stability and eases of redispersibility, and relates the observations to the physical and magnetic properties of the magnetic particles. The method of developing a new figure of merit based on a wholistic approach for assessing the efficiency and reliability of MRF is discussed which overcomes the shortcomings of conventional figures of merit. Chapter 10 summarizes the important findings of research work and highlights the validity of the new figure of merit in assessing ‘reliability and performance’ of MRFs.

Depuis la première observation du phénomène de Diffusion Raman Exaltée de Surface (DRES) en 1974 de nombreuses méthodes ont été développées pour contrôler l'arrangement de nanostructures métalliques sur une surface dans le but d'augmenter le signal de diffusion Raman. La valeur du facteur d'amplification de la DRES résulte principalement de l’accroissement localisé du champ électromagnétique pour des surfaces métalliques nanostructurées. Des études antérieures ont révélé que l'espacement nanométrique entre les nanoparticules constituait des zones de forte exaltation appelées «points chauds». Nous avons développé et breveté une méthode de lithographique assistée par AFM permettant la fabrication de surfaces métalliques. Il a été démontré que cette méthode fournissait une approche relativement simple pour réaliser d’une part des surfaces reproductibles à géométrie contrôlée à l’échelle nanométrique, et d’autre part des surfaces modèles pour étudier l'influence de la géométrie des motifs sur l'effet DRES. Afin d'étudier la relation entre les propriétés optiques et la géométrie de nos systèmes la résonance plasmon localisée de surface (LSPR) et le facteur d'exaltation du champ électrique local ont été simulés par éléments finis. Les zones de forte exaltations ont été localisées sur les nanostructures par microscopie par photoémission d'électrons (PEEM) et l'effet DRES a été démontré en effectuant des mesures Raman avec plusieurs molécules cibles. Les corrélations effectuées entre les résultats de PEEM, les calculs du champ local et les facteurs d’exaltation Raman seront présentées en lien avec les paramètres géométriques des motifs de nanostructures. / Since the first observation of Surface Enhanced Raman Scattering (SERS) in 1974 a variety of methods have been developed to physically control the arrangement of metallic nanostructures onto a surface in order to enhance Raman signals. The magnitude of the SERS enhancement factor is mainly driven by the enhanced local electromagnetic field in nanostructured metal surfaces. Gaps between adjacent nanoparticles give rise to strong enhancement effects, often referred as ‘hot spots’. One way to produce highly efficient SERS substrates is to develop a reproducible system of interacting metal nanostructures capable of high field enhancement.We patented a force-assisted Atomic Force Microscopy lithographic method allowing the fabrication of a metallic substrate. It will be shown that this method also provides a relatively simple approach to realize reproducible patterns with controlled geometry that can be used to study the influence of specific pattern geometry on SERS phenomenon.In order to investigate the relationship between optical properties and pattern geometries, localized surface plasmon resonance (LSPR) and local electric field enhancement are simulated.Whereas electric field enhancement regions (hot spot) have been observed on the top of the nanostructures with PhotoEmission Electron Microscopy (PEEM), SERS effect has been demonstrated by performing Raman measurements using several probe molecules. Correlations between PEEM measurements, Raman exaltation and local field calculations are presented in relation with the geometrical parameters of the nanostructured patterns.

Na primeira parte deste trabalho foi estudada a interação da porfirina catiônica meso-tetrakis N-metil-4-piridil (TMPyP) e a porfirina aniônica meso-tetrakis 4-fenilsulfonato (TPPS4) nas formas de base livre com sistemas modelos de membrana biológica (micelas iônicas, micelas mistas e vesículas de fosfolipídios) em soluções aquosas, através das técnicas de absorção ótica, espalhamento de luz ressonante (RLS do inglês \"resonante light scattering), fluorescência e SAXS, do inglês \"Small Angle X-Ray Scattering\". As curvas de SAXS das micelas catiônicas de CTAC (cloreto de cetiltrimetilamônio) foram ajustadas como um elipsóide prolato na ausência e na presença de 2-10 mM de TPPS4. Os dados de SAXS mostraram que a presença da porfirina TPPS4 modifica o centro hidrofóbico micelar, levando a formação de micelas menores. Através das análises dos dados de SAXS das micelas de SDS (dodecilsulfato de sódio) observamos que a forma da micela na ausência e na presença de 2-10 mM TMPyP apresenta a forma de um elipsóide prolato sem mudanças. Entretanto, o coeficiente de ionização, diminuiu com o aumento da concentração de porfirina, sugerindo a \"blindagem\" da carga aniônica do SDS pela porfirina catiônica. A supressão de fluorescência da TPPS4 e TMPyP foi estudada na ausência e na presença de diferentes micelas de surfactantes, tais como as de SDS, CTAC, HPS (N-hexadecil-N,N,dimetil-3-amônio-1-propano sulfato) e TX-100 (t-octil-fenoxi-polietoxi-etanol). O iodeto de potássio (KI) foi utilizado como supressor. Os gráficos de Stern-Volmer dos dados de fluorescência no estado estacionário foram ajustados pela equação quadrática, incluindo a supressão dinâmica (KD) e estática (KS). Os valores de KS são muito menores do que os valores de KD. Os resultados da TMPyP são consistentes com as constantes de ligação reportadas na literatura: uma redução significativa de supressão acontece para a TMPyP na presença de SDS, e uma redução moderada é observada para o sistema TMPyP-HPS e quase nenhuma mudança é vista para a TMPyP na presença de TX-100. Para o sistema CTAC-TPPS4 um aumento na supressão foi observado quando comparada com a TPPS4 em tampão puro. Isto provavelmente é associado ao acúmulo de iodeto na interface da micela catiônica. A atração entre a cabeça polar do CTAC e I-, e a repulsão entre SDS e I-, aumenta e reduz a supressão de fluorescência, respectivamente, das porfirinas que se localizam na interface micelar. A pequena supressão da TPPS4 em TX-100 é coerente com a forte ligação entre a TPPS4-TX-100 reportada na literatura. A TPPS4 e a TMPyP na presença de concentrações baixas dos surfactantes CTAC e SDS, respectivamente, apresentaram formação de agregados pré-micelares. A adição de surfactante neutro, TX-100, reduziu o efeito de agregação, acompanhada pelas várias técnicas espectroscópicas utilizadas neste trabalho. Portanto, sob condições onde temos a máxima formação de agregados (porfirina-surfactante), a titulação da TPPS4 com micelas de 40%CTAC-60%TX-100 e a TMPyP com micelas de 80%SDS-20%TX-100 não foi suficiente para eliminar a agregação, apesar da diminuição significativa do efeito de supressão de fluorescência e da intensidade de luz espalhada. A interação da TMPyP com 1-Palmitoil-2-Oleoil-sn-Glicero-3-fosfocolina (POPC), 1-Palmitoil-2-Oleoil-sn-Glicero-3-[Fosfo-rac-(1-glicero)] (POPG) e a mistura POPC + POPG é predominantemente devido à contribuição de eletrostática. O aumento da carga negativa, devido à adição de POPG, favorece a interação das vesículas com a porfirina catiônica. Na segunda parte deste trabalho foram estudados os efeitos de três surfactantes na estrutura oligomérica da hemoglobina extracelular gigante de Glossoscolex paulistus (HbGp) na sua forma oxi. O estudo com o SDS, CTAC e HPS permitiu diferenciar os efeitos de cargas opostas da cabeça polar dos surfactantes na dissociação da estrutura oligomérica e na autoxidação da hemoglobina. A interação do HPS com HbGp foi claramente menos intensa que a interação desta hemoglobina com os surfactantes catiônico (CTAC) e aniônico (SDS). Provavelmente, esta menor interação da HbGp com HPS, quando comparada com o SDS e o CTAC, é devido a menor atração eletrostática entre o HPS e os sítios iônicos da proteina. Dados espectroscópicos foram discutidos e comparados com os da literatura, afim de compreender a interação hemoglobina-surfactante, e como o ponto isoelétrico ácido (pI) pode influenciar na relação da estrutura-atividade das hemoglobinas gigantes extracelulares. As amostras de HbGp foram estudadas por espalhamento de luz dinâmico (DLS do inglês \"Dynamic light scattering\"). Na faixa de pH 6.0 a 8.0, HbGp é bastante estável e a distribuição de tamanho das partículas é monodispersa com um diâmetro hidrodinâmico médio (Dh) de 27 nm. O aumento dos valores de pH (pH>9.0) induziu um processo de dissociação irreversível, resultando num valor do Dh menor (10 nm). A diminuição do Dh sugere uma dissociação completa da hemoglobina. Em pH>9,0 a cinética de dissociação é lenta, com um mínimo 24 h para ser completada. As constantes cinéticas de dissociação aumentam progressivamente, com o aumento do valor do pH. As curvas de melting point para HbGp apresentaram dissociação oligomérica e desnaturação da proteina em função do pH. Os processos de autoxidação e dissociação estão intimamente relacionados, de modo que a dissociação da proteina oligomérica promove um aumento na velocidade de autoxidação e vice-versa. / In the first part of this work interactions of the cationic meso tetrakis (4-N-methilpyridil) porphyrin (TMPyP) and meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS4) in the free base forms with membrane model systems (ionic micelles, mixed micelles and phospholipids vesicles) in aqueous solutions, have been investigated by optical absorption, resonance light scattering (RLS), fluorescence and SAXS (Small Angle X-Ray Scattering). The best-fit SAXS curves were obtained assuming for cetyltrimethylammonium chloride (CTAC) micelle a prolate ellipsoidal shape in the absence and upon incorporation of 2-10 mM TPPS4. SAXS results show that the presence of TPPS4 impacts on micellar hydrophobic core, leading to a micellar reassembling into smaller micelles. SAXS data analysis demonstrated a prolate ellipsoidal shape for sodium dodecyl sulfate (SDS) micelles; no significant changes in shape and size were observed for SDS-TMPyP co-micelles. Moreover, the ionization coefficient, &alpha;, decreases with the increase of the porphyrin concentration, suggesting the \"screening\" of the anionic charge of SDS by the cationic porphyrin. These results are consistent with optical absorption, fluorescence and RLS spectroscopies data, allowing to conclude that neutral surfactants present a smaller interaction with the cationic porphyrin as compared with ionic surfactants. Fluorescence quenching of TPPS4 and TMPyP is studied in aqueous solution and upon addition of micelles of SDS, CTAC, N-hexadecyl-N,N-dimethyl-3-ammonio-1- propanesulfonate (HPS) and t-octylphenoxypolyethoxyethanol (Triton X-100). Potassium iodide (KI) was used as quencher. Steady-state Stern-Volmer plots were best fitted by a quadratic equation, including dynamic (KD) and static (KS) quenching. KS was significantly smaller than KD. For TMPyP quenching results are consistent with reported binding constants: a significant reduction of quenching takes place for SDS, a moderate reduction is observed for HPS and almost no change is seen for Triton X-100. For CTAC-TPPS4 system an enhancement of quenching was observed as compared to pure buffer. This is probably associated to accumulation of iodide at the cationic micellar interface. The attraction between CTAC headgroups and I-, and repulsion between SDS and I-, enhances and reduces the fluorescence quenching, respectively, of porphyrins located at the micellar interface. The small quenching of TPPS4 in Triton X-100 is consistent with strong binding as reported in the literature. Anionic TPPS4 and cationic TMPyP in the presence of low concentrations of the surfactants CTAC and SDS, respectively, showed formation of aggregates, monitored by optical absorption, fluorescence and resonance light scattering intensity (RLS). The addition of nonionic surfactant, Triton X-100, reduced the effect of aggregation monitored by the various techniques used in the present work. Therefore, under conditions for the maximum of aggregate formation (porphyrin-surfactant), apparently, the CTAC: TX-100 ratio equal to 40:60 and SDS:TX-100 ratio equal to 80:20 are not sufficient to eliminate aggregation, despite the significant decrease of the quenching effect of fluorescence and of the light scattering intensity. The interaction of TMPyP with 1-Palmitoyl-2-Oleoyl-sn- Glycero-3-Phosphocholine (POPC), 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-rac-(1- glycerol)] (POPG) and the mixture POPC+POPG is predominantly due to the electrostatic contribution. The increase of the negative charge, due to addition of POPG, favors the interaction of vesicles with the cationic porphyrin. On the second part of this work the effects of three surfactants upon the oligomeric structure of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) in the oxy - form was studied. The use of SDS, CTAC and HPS has allowed to differentiate the effects of opposite headgroup charges on the oligomeric structure dissociation and hemoglobin autoxidation. Furthermore, the interaction of HPS with HbGp was clearly less intense than the interaction of this hemoglobin with cationic (CTAC) and anionic (SDS) surfactants. Probably, this lower interaction with HPS is due to the lower electrostatic attraction between the HPS surfactant and the protein surface ionic sites when compared to the electrostatic interaction between HbGp and cationic and anionic surfactants. Spectroscopic data are discussed and compared with the literature in order to improve the understanding of hemoglobin-surfactant interaction as well as the acid isoelectric point (pI) influence of the giant extracellular hemoglobins on its structure-activity relationship. HbGp samples were studied by dynamic light scattering (DLS). In the pH from range 6.0 to 8.0, HbGp is stable and a monodisperse size distribution with a z-average hydrodynamic diameter (Dh) of 27±1 nm is observed. More alkaline pH (pH>9.0) induced an irreversible dissociation process, resulting in smaller Dh of 10±1 nm. Dh decrease suggests a complete hemoglobin dissociation. At pH 9.0 the dissociation kinetics is slow, taking a minimum of 24 h to be completed. Dissociation rate constants progressively increase at higher pH. Melting curves for HbGp showed oligomeric dissociation and protein denaturation as a function of pH. Autoxidation and dissociation processes are intimately related, so that oligomeric protein dissociation promotes the increase of autoxidation rate and vice-versa.