L’obtention de nanoparticules d’or nécessite le contrôle de nombreux paramètres et la compréhension du mode d’interaction entre l’or et le support. Pour cela, le choix du support est très important. Le premier volet de la thèse concerne la préparation contrôlée des catalyseurs à base d’or supporté sur les oxydes mésoporeux réductibles TiO₂, CeO₂ et Fe₂O₃ synthétisés via deux stratégies Soft et hard template en utilisant respectivement comme agents structurants le tribloc copolymère (Pluronic 123) et la silice mésoporeuse SBA-15. Les différentes techniques de caractérisation mettent bien en évidence que le taux de dépôt de l’or dépend de la concentration initiale de HAuCl₄, de la méthode de préparation (DPU, DP NaOH), de la teneur en or visée et de la nature du support ; Ces résultats sont à relier à la spéciation des espèces or en solution en fonction du pH final de la solution. Les taux de dépôt de l’or sont plus importants sur CeO₂ et ceci quelle que soit la teneur en or visée dans ce travail. Une dispersion très élevée est obtenue (la taille moyenne des particules d’or est de 2nm) sur les catalyseurs à 1% et 2%Au/CeO₂ préparés par la méthode DPU et calcinés à 400°C. Le deuxième volet de cette étude concerne l’oxydation en phase gaz d’une molécule organique modèle le toluène et l’oxydation en phase liquide d’une molécule organique modèle le phénol par des réactions de type Fenton et photo Fenton. Dans l’oxydation du toluène en phase gazeuse, les catalyseurs à base d’or supportés sur oxydes mésoporeux sont totalement sélectifs en CO₂ et H₂O. Les performances catalytiques dépendent des conditions de synthèse des catalyseurs et de la nature de l’oxyde utilisé ; le catalyseur 1%Au/CeO₂ est très actif et très stable au cours de quatre cycles successifs et au cours du temps. L’oxydation en phase liquide d’une molécule organique modèle le phénol par des réactions de type Fenton et photo Fenton a été effectuée sur les catalyseurs FeSBA-15 synthétisés via différentes stratégies : introduction du fer par voie postsynthétique et par voie hydrothermale en milieu faiblement et fortement acide respectivement à pH=6 et pH=3. Les performances catalytiques dépendent du rapport Si/Fe et de la taille des particules des espèces de fer, la taille des particules étant directement liée à la stratégie de synthèse des catalyseurs. Le catalyseur FeSBA-15(Si/Fe=60) synthétisé à pH=6 est un candidat potentiel dans la dégradation de polluants organiques par procédé Fenton et photo-Fenton en milieu neutre. / Well dispersed gold nanoparticles are the key to obtain an active gold catalyst. Obtaining gold nanoparticles requires control of many parameters and understanding of the interaction mode between gold and the support. For this reason the choice of the support is very important. The first part of this thesis concerns the controlled preparation of gold catalysts supported on reducible mesoporous oxides TiO₂, CeO₂ and Fe₂O₃ synthesized via two strategies Soft and Hard template using respectively. triblock copolymer (Pluronic 123) and mesoporous silica SBA-15 as template. This study clearly shows that the gold loading depends on the initial concentration of HAuCl₄, the method of preparation (DPU DP NaOH), theoretical gold content and the nature of the support. These results are to relate to the gold speciation which is a function of pH of the solution. The gold loading is higher on CeO₂ than on TiO₂ and Fe₂O₃ whatever the theoretical gold content. Very high gold dispersion is obtained (the gold particle size is 2 nm) on 1wt% and 2wt% Au/CeO₂ prepared by DPU and calcined at 400°C. The second part of this study concerns the toluene oxidation in the gas phase on Au/mesoporous oxide catalysts and the Fenton and photo-Fenton degradation of phenolic aqueous solutions by H₂O₂ on FeSBA-15 catalysts prepared following different synthesis routes, direct synthesis by adjusting pH at 3 and 6 and with post synthesis procedure. In the toluene oxidation in the gas phase Au/mesoporous oxide catalysts are totally selective for CO₂ and H₂O. The catalytic performances depend on the synthesis conditions of catalysts and the support; the 1wt% Au/CeO₂ catalyst is very active and exhibits a long-term stability. In the Fenton and photo-Fenton degradation of phenolic aqueous solutions the catalytic performances depend on the Si/Fe ratio and the particle size of the iron species, the particle size being directly related to the synthesis strategy of the catalysts. The catalyst FeSBA-15 (Si/Fe = 60) synthesized at pH = 6 is a potential candidate in the degradation of organic pollutants by Fenton and photo-Fenton process in neutral medium. / م لخصمسقني لمعلا يف هذه ةحورطألا ىلإ نيئزج:OiT 2ب وا سطة OeC 2و , Fe2O ي خ تص الاول ال ق سم ب تح ض يرمح فزات من ال ذهبن وع من م يزوب ري ة ب مواد مدعم 3ان واع مخ ت لف ال تح ض ير. ت شخ يص ف ي ال م س ت عم لة ال ت ق ن يات مخ ت لفت ب ين ال مح ضرة ل مح فزات انال دعم ط ب ي عة ك ذا و ال مح فز ت ح ض ير وطري قة HAuCl ت ر سب معدل ي ت ع لق ل ذه با ت رك يز ع لى 4ي ع ضو جزيء و سطغازي enèuloT أك سدة ف ي ال مواد هذه ب تط ب يق ي ت ع لق ال ثان ي ال ق سم ف يال مح فز ت ح ض ير Ò طرق ك ذا و ل ت فاعل هذا ع لى ال مؤث رة ل عوامل ب درا سة ق م نا سال فا ال مذك ورة ل لمح فزات ال ف عال ية ع لان واع مخ ت لف ب وا سطة FeSBA- ي ع ضو جزيء lonehP ت فاعل ب وا سطة notneF سائ ل و سط ف ي وعمن 51 ن مح فزات ع لىوHp ال و سط Si/Fe قلعتي ةبسنب FeSBA- ريضحتلا.ادأء 1515FeSBA-15, Fenton, Phenol, Toluène, TiO و 2 CeO2, Fe2O3, SBA- ال ك لمات ال م ف تاح ية ׃م يزوب وري ة ,

L'une des stratégies mise en œuvre pour améliorer la prise en charge thérapeutique des patients concerne le développement d'outils diagnostiques sensibles et spécifiques. Les aptamères sont des oligonucléotides artificiels obtenus par SELEX avec une très haute affinité ainsi qu'une excellente spécificité pour leurs cibles. L'immobilisation de ces motifs de reconnaissance moléculaire à la surface de nanomatériaux tels que des nanoparticules d'or (AuNPs), dont les propriétés optiques et électroniques sont uniques, permet d'amplifier le signal généré par l'interaction du ligand avec sa cible. Deux systèmes de biosensing ont été élaboré en fonctionnalisant des AuNPs avec des aptamères, l'un dirigé contre la thrombine et le second dirigé contre une marque épigénétique portée par une protéine histone. La réduction des sels d'or aurique précurseurs a été réalisée en présence de PEG4 et a conduit à l'obtention d'une population homodisperse de AuNPs sphériques d'un diamètre moyen de 14 nm et présentant une isotropie de taille et de forme. Ces AuNPs ont ensuite été fonctionnalisées par des bras espaceurs de longueur variable constitués d'unités tétraéthylène glycol successives reliées entre elles par des ponts éthers ou triazoles. L'acide lipoique a été utilisé comme motif d'ancrage à la surface des AuNPs via une liaison covalente Au-S et a été couplé aux différents bras espaceurs via une réaction de Steglich. Les linkers étaient porteurs d'un groupement terminal azoture afin de réaliser le couplage par chimie-click avec les aptamères. La stratégie de détection de la thrombine utilisait les propriétés de quenching de fluorescence des AuNPs alors que la détection de l'histone était colorimétrique et mettait à profit l'effet de résonance plasmonique de surface des nanoparticules d'or. / Improving patients therapeutic care needs the development of sensitive and specific diagnostic tools. Aptamers are synthetic oligonucleotides obtained by SELEX with a very high affinity and excellent specificity for their targets. Grafting of these molecular recognition patterns onto nanomaterials such as gold nanoparticles (GNPs), which unique optical and electronic properties, can amplify the signal induce by the interaction between the ligand and its target. Two biosensing systems have been developed by GNP functionalization with aptamers, one is directed against thrombin and the second against an epigenetic mark carried by a histone protein. Gold precursors was reduced in the presence of PEO4 and led to a homodisperse population of spherical GNP with an average diameter of 14 nm and an isotropy of size and shape. GNP were functionalized with tetraethylene glycol units interconnected by ether or triazoles bridges as a linker. Lipoic acid was used as an anchor moiety onto gold surface via a covalent Au-S bond and was coupled to the spacer through a Steglich reaction. The linkers were functionalized with an azide group to perform the coupling with aptamers by click chemistry. The thrombin sensing strategy used the fluorescence quenching properties of GNPs while the histone detection involved the gold nanoparticle plasmon resonance surface effect.

A síntese e caracterização de sistemas hetero-híbridos gerados a partir da 3,6-bi-2-piridil-1,2,4,5-tetrazina (bptz) e interações com ouro nanoparticulado são abordados nesta tese. O bptz foi estudado por meio de métodos espectroscópicos e teóricos, focalizando principalmente o efeito SERS associado à adsorção em nanopartículas de ouro. O mecanismo de transferência de carga para metais macroscópicos foi transposto para a condição nanoparticulada, envolvendo ligações químicas entre bptz e as nanopartículas. Os complexos estudados possuem fórmula geral [LmRu(µ-bptz)RuLm]Xn, com “L” indicando os ligantes periféricos 5-cloro-1,10-fenantrolina (Clphen) ou 4’-(fenil)-2,2&#8217:6&#8217,2&#8221-terpirdina (ptpy) e “X” os contra-íons. Foram investigadas suas espectroeletroquímicas eletrônica e SERS, e as mudanças de perfil vibracional foram modeladas, incorporando o mecanismo de transferências de carga entre complexo e o ouro, além dos mecanismos ressonantes e eletromagnéticos / The synthesis and investigation of heterohybrid systems encompassing 3,6-bi-2-pyridyl-1,2,4,5-tetrazine (bptz) and its ruthenium complexes associated with gold nanoparticles are dealt with in this thesis. Bptz was characterized by spectroscopic and theoretical techniques, focusing on its SERS spectra after the adsorption onto nanoparticles. The charge transfer mechanism in the SERS spectra of macroscopic metals was transposed to the nanoparticle condition, assuming the formation of chemical bonds between bptz and the nanoparticles. Complexes of general formula [LmRu(µ--bptz)RuLm]Xn, “L” the peripheric ligants 5-chlorine-1,10-phenantroline or 4’-(phenyl)-2,2&#8217:6&#8217,2&#8221-terpyrdine (ptpy), and “X” counter-ions were also investigated, with special emphasis on their electronic and SERS spectroelectrochemistry. The changes in the vibrational profiles were successfully explained by the occurrence of charge transfer between the adsorbed complex and gold, in addition to the electromagnetic and resonance mechanisms.

L'objectif de notre travail consiste en la conception de nanoparticules d'or (AuNP) monodisperses, et stables ; puis en l'évaluation de l'effet des propriétés de surface de AuNP sur leur internalisation et leur toxicité dans une lignée cellulaire (macrophages alvéolaires de rat-NR8383). Nous avons synthétisé des NP d'or soit stabilisées par les ions citrate (Au-citrate) soit fonctionnalisées par l'acide dihydrolipoïque (DHLA) (NP Au@DHLA). Nous avons montré que la densité de couverture est un paramètre crucial pour améliorer la stabilité colloïdale des AuNP dans des conditions physiologiques. Nous avons caractérisé complètement les AuNP d'un point de vue physico-chimique, en particulier en développant une méthode de dosage spectrophotocolorimétrique de l'or. Nous avons aussi étudié les effets biologiques des AuNP. Tout d'abord, en absence de cellules, nos résultats révèlent que la fonctionnalisation de surface de AuNP affecte la réactivité avec des biomolécules tels que le glutathion réduit (GSH), le S-nitrosoglutathion, et l'albumine de sérum bovin (les Au-citrate interagissant avec toutes les molécules testées), l'internalisation par les cellules (les Au-citrate sont deux fois plus internalisées) et l'état redox cellulaire (les Au-citrate diminuent de 20% le niveau intracellulaire de GSH) sans relation apparente avec la formation de ROS. En outre, les AuNP ne semblent pas induire l'expression des mRNA associées à la réponse inflammatoire (tnf), au stress oxydant (ncf1) et à l'apoptose (nfkb2), paramètres essentiels pour préserver l'intégrité de la cellule et de l'organisme, et envisager l'utilisation de ces NP comme plateforme pharmaceutique / The aim of our work was to produce highly monodisperse and stable gold nanoparticles (AuNP) with potential for biomedical applications, and to evaluate the effect of AuNP surface properties on their uptake and cytotoxicity in a cultured cell line (rat-alveolar macrophages-NR8383). We synthesized AuNP either stabilized with citrate (Au-citratte) or capped with a dithiol, i.e. dihydrolipoic acid (Au@DHLA NP). The present study shows that the surface packing density is a crucial parameter to enhance the colloidal stability of AuNP in physiological conditions. We fully characterized the considered AuNP from a physico-chemical point of view. Indeed, we optimized a spectrocolorimetric and a HPLC method to evaluate the properties of AuNP. We studied the biological effects of AuNP. Under cell-free conditions, our results reveal that AuNP coating affects their reactivity with biomolecules, i.e. reduced glutathione (GSH), S-nitrosoglutathione and bovine serum albumin (Au-citrate interact with all molecules), the cellular uptake (Au-citrate are two times more effective) and redox status (Au-citrate decrease the intracellular GSH level by ca 20%) with no apparent relationship with ROS formation. Furthermore, both AuNP appear not to induce mRNA expression related to inflammatory response (tnfa), oxidative stress (ncf1) and apoptosis (nfkb2), parameters of main importance to preserve cellular integrity and body safety, and to assure pharmaceutical platform function

L’oxyde nitrique (NO) est un messager gazeux jouant de nombreux rôles physiologiques, en particulier au niveau du système cardiovasculaire. Sa biodisponibilité est limitée par sa demi-vie très courte et sa combinaison avec les thiols le stabilise et en assure le stockage et le transport. La diminution de la production endogène de NO observée dans les maladies cardiovasculaires place les médicaments donneurs de NO au centre de nouvelles stratégies thérapeutiques. Cette étude a été dédiée au développement de nouveaux matériaux réservoirs de NO. Tout d’abord, la serumalbumine (SA) a été nitrosée selon trois processus afin d’obtenir un composé mono-S-nitrosé biocompatible. Ensuite, en vue d’obtenir un réservoir à forte capacité de charge en NO, des nanoparticules d’or recouvertes par l’acide dihydrolipoïque, AuNP@DHLA ont été greffées par un nombre élevé de molécules de glutathion réduit (GSH). Il en résulte un fort pouvoir anti-oxydant des nanoparticules synthétisées (AuNP@DHLA-(GSH)n) qui devrait éviter de perturber l’état redox in vivo. De plus, ce nano-objet s’avère poly-S-nitrosable, en s’appuyant sur l’expérience acquise avec la macromolécule SA-SNO. Enfin, des nanoparticules stabilisées par les ions citrate (AuNP-citrate) très instables en condition physiologique ont été incorporées à des films multicouches de polyélectrolytes, obtenus par assemblage couche-par-couche. Il en résulte une stabilisation des AuNP et le film les contenant présente une excellente cyto/hémocompatibilité. Ces travaux ouvrent la voie à l’incorporation des nanoparticules AuNP@DHLA-(GSH)n dans un film multicouches, à leur nitrosation et au dépôt du matériau final en tant que réservoir de NO sur des dispositifs médicaux pour le traitement de maladies cardiovasculaires / Nitric oxide (NO) is a gaseous messenger playing numerous physiological roles, especially in the cardiovascular system. However, its bioavailability is limited due to a short half-life. The combination to thiols increases its stability and facilitates its storage and transport. Thus NO donor drugs represent a promising therapeutic approach in such diseases. The present study aimed at developing NO reservoirs. Firstly, serum albumin (SA) was S-nitrosated through three chemical pathways to prepare SA-SNO. Then, potential NO reservoirs with high loading capacity were developed by anchoring reduced glutathione (GSH) to dihydrolipoic acid capped gold nanoparticles, AuNP@DHLA. The obtained AuNP@DHLA-(GSH)n showed stronger antioxidant power and they will be able not to disturb the cell homeostasis. Its further poly-S-nitrosation will benefit from the S-nitrosation of SA as both macromolecular possess free thiols. In parallel, citrate ions stabilized AuNP were entrapped in multilayer polyelectrolyte films using layer-by-layer (LbL) assemblies, providing proof-of-concept of multilayer films as a useful tool to protect AuNP from degradation and increase the cyto/hemocompatibility toward biological elements. The present work opens the window to S-nitrosate AuNP@DHLA-(GSH)n either as a colloidal solution or immobilized in the multilayer system, which is expected to be applied into developing of NO eluting stent for the treatment of cardiovascular diseases

Os biossensores são dispositivos empregados para a detecção de um analito específico, podendo assim ser no controle de qualidade nos alimentos para determinar a presença de micro-organismos, toxinas ou metabólitos. O presente estudo objetiva desenvolver um biossensor condutométrico, baseado na imobilização de peroxidasse em membranas de quitosana e quitosana com nanopartículas de ouro (AuNP) para a detecção de peroxido de hidrogênio. O trabalho foi dividido em três etapas. Na primeira etapa foi estudada a obtenção de AuNP empregando agentes redutores biológicos, sendo avaliados três monossacarídeos (glicose, frutose e galactose), três dissacarídeos (sacarose, maltose e lactose), dois biopolímeros (amido e quitosana), assim como os extratos obtidos a partir das folhas de hortelã (Mentha piperita) e cascas de furtas de abacaxi (Ananas comosus), banana (Musa sp. ), maracujá (Passiflora edulis), tangerina (Citrus reticulata). A quitosana mostrou-se como o melhor agente redutor na síntese das AuNP, as quais foram empregadas na segunda etapa para a produção de membranas. Três tipos de membranas foram processadas, membranas de quitosana sem AuNP e membranas de quitosana com AuNP com concentrações de 8 e 11mM., as quais foram caraterizadas morfológica e eletricamente. Finalmente foi avaliada a imobilização da peroxidasse usando quatro tratamentos diferentes, sendo a dispersão da peroxidasse nas soluções filmogênicas precursoras das membranas a mais eficiente. A resposta elétrica destas membranas é dependente da concentração de AuNP e da presença de enzimas, e também foi alterada quando as mesmas foram expostas a soluções de tampão fosfato com diferentes concentrações de peroxido de hidrogênio. Isto constitui o principio de operação dos biossensores condutométricos desenvolvidos neste trabalho. / Biosensors are devices used for detecting a specific analyte, and thus can be used in quality control of food for determining the presence of micro-organisms, toxins or metabolites. The present study aims to develop a conductometric biosensor based on the immobilization of peroxidase in membranes of chitosan and chitosan with gold nanoparticles (AuNP) for the detection of hydrogen peroxide. The work was divided into three stages. In the first stage, methods for obtaining AuNP employing biological reducing agents were studied, evaluating three monosaccharides (glucose, fructose and galactose), three disaccharides (sucrose, maltose and lactose), two biopolymers (starch and chitosan), as well as the extracts obtained from the leaves of mint (Mentha piperita) and husks dost thou pineapple (Ananas comosus), banana (Musa sp), passion fruit (Passiflora edulis), mandarin (Citrus reticulata). Chitosan exhibited the best behavior as reducing agent for the synthesis of AuNP, which were employed in the second step for the production of membranes. Three types of membranes were processed, chitosan membranes without AuNP and chitosan membranes with AuNP with concentrations of 8 and 11mM, which were morphologically and electrically characterized. Finally the peroxidase immobilization was evaluated using four different procedures, being the dispersion of the peroxidase in filmogenic solutions precursor of membranes the more efficient. The electrical response of these membranes, depends on the AuNP concentration and the presence of enzymes, and was also altered when they were exposed to hydrogen peroxide containing phosphate buffer solutions. This constitutes the principle of operation of the conductometric biosensor developed in this work.

Made available in DSpace on 2017-07-21T19:25:48Z (GMT). No. of bitstreams: 1 Vinicius Mariani.pdf: 12327357 bytes, checksum: 1e83d3e17afc9ea8500a2b6e3adf5a5f (MD5) Previous issue date: 2015-03-05 / The optical properties as well as thermal transport nanoparticles attract great attention due to the possibilities of applications and research in basic physics. Among the most studied systems are gold nanoparticles by presenting a plasmon resonance frequency in the visible wavelength. However, the manner in which generate heat when excited optically and how the surface plasmon can be used as a probe medium in which the particles are dispersed have been little explored. In this work we present an experimental study of the thermal lens effect of lyotropic liquid crystals doped with gold nanoparticles, under cw 532 nm optical excitation, and a study of how the surface plasmon resonance of colloidal gold can probe the local ordering of a anisotropic media. Spherical gold nanoparticles of approximately 12 nm were synthesized by the Turkevich’s method and the two lyotropic liquid crystals were prepared with a ternary mixture of sodium dodecyl sulfate (SDS) and potassium laurate (KL) with 1-decanol (1-DeOH ) and water. The lyotropic matrix with SDS induced the formation of nanoparticle aggregates, leading to a broad and a red shift of the plasmon resonance band. The nonlinear refraction index of thermal origin increases as a power law with respect to particle density, being possible to adress this behavior with the presence of nanopaticles clusters. In the case of liquid crystal composed of KL, we studied the reentrant isotropic - nematic calamitic - isotropic phase transitions, monitoring the plasmon resonance of the nanoparticles. For transitions at low temperatures, isotropic reentrant to nematic, the resonance band has a red-shift of 7 nm which can be assigned mainly with the increase of the dielectric constant due to a change in the shape anisotropy of the micelles. On the other hand, in the high temperature transition, the maximum absorption wavelength suffer a slight extra red-shift which may be due to a small change in the correlation length. / As propriedades ópticas, assim como as de transporte térmico em nanopartículas atraem grande atenção devido as possibilidades de aplicações e pesquisa em Física básica. Entre os sistemas mais estudados estão as nanopartículas de ouro por apresentar uma frequência de ressonância de plasmon no comprimento de onda do visível. No entanto a forma com que geram calor quando excitadas opticamente e como a superfície de plasmon pode ser utilizada como sonda do meio em que as partículas estão dispersas têm sido pouco exploradas. Neste trabalho apresentamos um estudo experimental do efeito de lente térmica de cristais líquidos liotrópicos dopados com nanopartículas de ouro, sobre a excitação óptica de 532 nm, e um estudo de como a ressonância de plasmon de superfície do ouro coloidal pode sondar o ordenamento local de um meio anisotrópico. Nanopartículas esféricas de ouro em torno de 12 nm foram sintetizadas pelo método de Turkevich e dois cristais líquidos liotrópicos foram preparados com uma mistura ternária de dodecil sulfato de sódio (SDS) ou laurato de potássio (KL) com 1-decanol (1-DeOH) e água. A matriz liotrópica com SDS induziu a formação de agregados de nanopartículas, levando a um alargamento e deslocamento da banda de ressonância de plasmon para o vermelho. O índice de refração não linear de origem térmica aumenta como uma lei de potência em relação à densidade de partículas, sendo possível relacionar seu comportamento com a presença de agregados. No caso do cristal líquido composto por KL, estudamos as transições de fase isotrópica reentrante - nemática calamítica e posteriormente para a fase isotrópica em alta temperatura, monitorando a ressonância de plasmon das nanopartículas. Para transições em baixas temperaturas, isotrópica reentrante para nemática, a banda de ressonância tem um deslocamento de 7 nm para o vermelho que pode ser associado principalmente com o aumento da constante dielétrica devido a uma alteração na anisotropia de forma das micelas. Por outro lado, para transição em alta temperatura, o comprimento de onda do máximo de absorção sofre um sutil deslocamento extra para o vermelho o qual pode ser devido à uma pequena mudança no comprimento de correlação.

Made available in DSpace on 2017-07-24T19:37:54Z (GMT). No. of bitstreams: 1 Dhesmon Lima.pdf: 3726533 bytes, checksum: d3be37b6257d9747cd2404bc48091086 (MD5) Previous issue date: 2016-02-26 / In this work, glassy carbon paste electrodes (GCPE) were modified with porphyran- capped gold nanoparticles (GCPE/AuNps-PFR) and applied for the determination of an anticancer drug, 5-fluorouracil (5-FU), by using differential pulse voltammetry (DPV). The PFR polysaccharide was isolated from commercial Nori seaweed, and its characterization was carried out by FTIR and 13C-NMR as well as by determining its total sugar and sulfate contents, which resulted in 82.8% and 11.9%, respectively. These experiments confirmed the chemical identity and purity of the extracted polysaccharide, which was used as reducing and capping agent to the synthesis of gold nanoparticles (AuNps-PFR). The temperature and the concentrations of AuCl4- and PFR for the AuNps-PFR synthesis were optimized by a 23 full factorial design including a central point assayed in triplicate. The smallest particles were produced with 128.7 nm by employing a temperature of 70 °C and concentrations of 2.5 mmol L-1 for AuCl4- and 0.25 mg mL-1 for PFR. The characterization of the AuNps-PFR nanocomposite was performed by UV-VIS, FTIR and DLS spectroscopies, FESEM, zeta potential and XRD. The UV-VIS spectrum showed an absorption at 524 nm (plasmon band), with no significant changes in its shape and absorption frequency for 90 days. This observation suggests that the AuNps-PFR are stable in suspension, which is in good agreement with the zeta potential of -30.5 mV obtained for the sample. The FTIR spectrum revealed that interactions between the AuNps and the PFR may exist, as a consequence of displacements in the frequency of the bands in the AuNps-PFR spectrum compared to that obtained for the PFR individually. The electrochemical characterization of the porphyran modified GCPE (GCPE/PFR) was carried out by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of the Fe(CN)63-/4- probe, revealing that the polysaccharide had a positive effect on the electrode response, since higher current values and a lower charge transfer resistance for the electrochemical probe redox process were achieved compared to the unmodified GCPE. Even better responses were obtained after the modification of the GCPE with the synthetized AuNps-PFR, as a consequence of the high electrical conductivity and large surface area displayed by the nanocomposite. The 5-FU was oxidized on the GCPE/AuNps-PFR surface according to an irreversible, pH dependent and diffusion controlled mechanism, showing an anodic wave at +1,1 V in BR buffer solution 0.04 mol L-1. The highest current value for 5-FU determination was achieved in BR buffer with pH 8.0, by DPV; therefore, this value was chosen for the further analysis. A linear relationship was observed between the anodic peak potential and the pH of the medium with a slope of -69 mV pH-1, demonstrating that the same number of protons an electrons participate in the 5-FU oxidation mechanism. The GCPE/AuNps-PFR exhibited a linear relationship between the peak current and 5-FU concentration over the range of 29.9 to 234.0 μmol L-1, with low detection (0.66 μmol L-1) and quantification limits (2.22 μmol L-1). Besides the good sensitivity for detecting 5-FU, the modified electrode showed reproducibility, and its response was not influenced by interfering compounds such as glucose, urea, albumin, ascorbic acid, Na+ and K+, suggesting its potential application to determine 5-FU in biologic matrices. The practical utility of the developed sensor was demonstrated for the quantification of 5-FU in pharmaceutical injection sample. A good average recovery percentage of 104.0% was achieved, with an acceptable relative standard deviation of 2.25%. So, these results could confirm the promising analytical performance of the modified electrode for the electroanalysis of 5-FU in real samples. / Neste trabalho, eletrodos de pasta de carbono vítreo (EPCV) foram modificados com nanopartículas de ouro estabilizadas no polissacarídeo sulfatado porfirana (PFR) e aplicados para a determinação do agente antitumoral 5-fluorouracil (5-FU), utilizando voltametria de pulso diferencial (VPD). A PFR foi extraída a partir de alga Nori comercial, e sua caracterização foi realizada por FTIR, RMN-13C e pela determinação dos teores de carboidratos totais e de grupos SO42-, os quais resultaram em 82,8% e 11,9%, respectivamente. Tais experimentos confirmaram a pureza e a identidade química do polissacarídeo extraído, que foi empregado como agente redutor e estabilizante para a síntese de nanopartículas de ouro (AuNps-PFR). A temperatura, a concentração do precursor AuCl4- e a concentração de PFR empregadas para a síntese das AuNps-PFR foram otimizadas por meio de um planejamento fatorial 23 com triplicata no ponto central. Um menor tamanho de partícula (128,7 nm) foi alcançado ao se empregar uma temperatura de 70 °C e concentrações de AuCl4- e PFR iguais a 2,5 mmol L-1 e 0,25 mg mL-1, respectivamente. As AuNps-PFR obtidas foram caracterizadas pelas espectroscopias UV-VIS, FTIR e DLS, MEV-FEG, potencial zeta e DRX. O espectro de UV-VIS mostrou uma banda em 524 nm (banda plasmon), que não apresentou variações significativas na forma e frequência de absorção durante 90 dias. Tais observações sugeriram que as AuNps-PFR são estáveis em suspensão, o que corrobora com o potencial zeta de -30,5 mV obtido para a mesma. O espectro de FTIR evidenciou a existência de interações entre as AuNps e a PFR, devido a deslocamentos das bandas apresentadas no espectro das AuNps-PFR em relação ao obtido para a PFR. A caracterização eletroquímica do EPCV/PFR, realizada por voltametria cíclica (VC) e espectroscopia de impedância eletroquímica em meio da sonda Fe(CN)63-/4-, evidenciou que o polissacarídeo conferiu aos eletrodos maiores valores de corrente e menor resistência à transferência de carga para o processo redox da sonda eletroquímica em comparação aos eletrodos não modificados. Respostas de corrente ainda maiores foram obtidas ao se empregar o EPCV/AuNps-PFR, como uma consequência da elevada condutividade e alta área superficial apresentada pelas nanopartículas. Por VC, verificou-se que o 5-FU foi oxidado irreversivelmente na superfície do EPCV/AuNps-PFR segundo um mecanismo dependente do pH e controlado por difusão, apresentando um processo anódico em +1,1 V em tampão BR 0,04 mol L-1. O pH do tampão BR para a determinação de 5-FU foi otimizado por VPD, tendo-se observado um máximo de corrente em pH 8,0, valor empregado para a obtenção das curvas analíticas. A relação linear observada entre o potencial de pico e o pH do meio com inclinação de -69,0 mV pH-1 evidenciou que o mesmo número de prótons e elétrons estão envolvidos no processo de oxidação. O EPCV/AuNps-PFR apresentou linearidade de resposta na faixa de 29,9 a 234,0 μmol L-1 de 5-FU, com limites de detecção e de quantificação iguais a 0,66 e 2,22 μmol L-1, respectivamente. Além da boa sensibilidade ao 5-FU, o EPCV/AuNps-PFR apresentou reprodutibilidade de resposta, e não sofreu interferência significativa de compostos como glicose, ácido ascórbico, ureia, albumina e íons Na+ e K+, sugerindo sua potencial aplicação para a determinação de 5-FU em matrizes biológicas. O eletrodo modificado foi aplicado para a quantificação do 5-FU em formulação farmacêutica comercial injetável, tendo-se obtido uma porcentagem média de recuperação igual a 104,0, com desvio padrão relativo dentro dos limites aceitáveis (2,25%). Confirma-se, deste modo, o bom desempenho analítico do sensor e da metodologia voltamétrica desenvolvida para a eletroanálise do 5-FU em amostras reais.

L’objectif de cette thèse est de contrôler les propriétés optiques des nanoparticules d’or greffées de polymère en modulant les propriétés structurales de la couche protectrice de polymères. Des nanoparticules greffées de polymères thermosensibles avec une large gamme de masse molaire et différents degrés d’hydrophobicité sont synthétisées par la méthode de « grafting-to ». La DNPA est utilisée pour caractériser les propriétés structurales de la couche protectrice de polymère. Les spectres d’absorption sont modélisés en utilisant la théorie de Mie. Nous démontrons que la sensibilité de la SPR à la propriété diélectrique du solvant diminue progressivement avec la fraction volumique de la couche de polymère jusqu’à devenir quasi-nulle; dans ce dernier cas de figure, la SPR est dite « gelée » par la couche de polymère. Un déplacement significatif de la bande de SPR vers le rouge est induit (un changement de couleur se produit) dû à une transition de collapse de la couche de polymère avec la température. La gamme de température pour induire ce déplacement dépend du degré d’hydrophobicité du polymère et de la salinité. Une partie important de cette thèse est également consacrée aux propriétés des nanoparticules d’or greffées de polymères à l’interface air-eau. La technique de Langmuir est utilisée pour former des films minces dont la distance entre particule est contrôlée par la compression, la longueur des chaînes du polymère greffé et la température. Les propriétés structurales des films minces sont étudiées en déterminant la conformation de la couche de polymère greffée et l’organisation du cœur de l’or par la réflectivité de neutron et de X, respectivement. Les mesures de réflectivité nous permettent également d’évaluer et d’améliorer la stabilité des films minces pour un meilleur control de la distance entre particule, aspect important pour l’optimisation de la SPR. Enfin, les propriétés optiques des nanoparticules d’or à l’interface sont mesurées par des mesures de transmission. / In this thesis, the objective is to control the polymer-grafted gold nanoparticles optical properties (SPR) by tuning the protecting polymer shell structural properties. Gold nanoparticles grafted with thermosensitive polymers with a large range of molecular masses and different degrees of hydrophobicity are synthesized by “grafting-to” technique. SANS is employed to characterize the protecting polymer shell structural properties. The absorption spectra are modeled using the Mie Dipolar theory. It is shown that the gold nanoparticle sensitivity to external solvent is progressively reduced with increasing polymer volume fraction of the nanocomposite until the SPR is frozen by the polymer shell. In this case, the SPR mode becomes insensitive to the dielectric properties of the solvent. SPR is also red-shifted (a color change occurs) by thermally inducing the collapse of the polymer shell. The temperature and the extent of the red-shift are controlled by the graft polymer hydrophobicity and salinity. An important part of this thesis is also dedicated to the polymer-protected gold nanoparticles behaviour at the air-water interface. The Langmuir balance technique is used to build interfacial layers whose interparticle distance is modulated by compression, polymer graft chain length and temperature. The interfacial layer structural properties are determined by studying both the polymer graft layer conformation and the gold core organization with neutron and X-ray reflectivities. These reflectivitity measurements also enable us to evaluate and ameliorate the surface layers stability for a better control of the interparticle distance that is important for optimizing the SPR of the surface layer.

A síntese e caracterização de sistemas hetero-híbridos gerados a partir da 3,6-bi-2-piridil-1,2,4,5-tetrazina (bptz) e interações com ouro nanoparticulado são abordados nesta tese. O bptz foi estudado por meio de métodos espectroscópicos e teóricos, focalizando principalmente o efeito SERS associado à adsorção em nanopartículas de ouro. O mecanismo de transferência de carga para metais macroscópicos foi transposto para a condição nanoparticulada, envolvendo ligações químicas entre bptz e as nanopartículas. Os complexos estudados possuem fórmula geral [LmRu(µ-bptz)RuLm]Xn, com “L” indicando os ligantes periféricos 5-cloro-1,10-fenantrolina (Clphen) ou 4’-(fenil)-2,2&#8217:6&#8217,2&#8221-terpirdina (ptpy) e “X” os contra-íons. Foram investigadas suas espectroeletroquímicas eletrônica e SERS, e as mudanças de perfil vibracional foram modeladas, incorporando o mecanismo de transferências de carga entre complexo e o ouro, além dos mecanismos ressonantes e eletromagnéticos / The synthesis and investigation of heterohybrid systems encompassing 3,6-bi-2-pyridyl-1,2,4,5-tetrazine (bptz) and its ruthenium complexes associated with gold nanoparticles are dealt with in this thesis. Bptz was characterized by spectroscopic and theoretical techniques, focusing on its SERS spectra after the adsorption onto nanoparticles. The charge transfer mechanism in the SERS spectra of macroscopic metals was transposed to the nanoparticle condition, assuming the formation of chemical bonds between bptz and the nanoparticles. Complexes of general formula [LmRu(µ--bptz)RuLm]Xn, “L” the peripheric ligants 5-chlorine-1,10-phenantroline or 4’-(phenyl)-2,2&#8217:6&#8217,2&#8221-terpyrdine (ptpy), and “X” counter-ions were also investigated, with special emphasis on their electronic and SERS spectroelectrochemistry. The changes in the vibrational profiles were successfully explained by the occurrence of charge transfer between the adsorbed complex and gold, in addition to the electromagnetic and resonance mechanisms.