One the most daunting technical challenges in the realization of biosensors is functionalizing transducing surfaces for the detection of biomolecules. Functionalization is defined as the formation of a bio-compatible interface on the transducing surfaces of bio-chemical sensors for immobilizing and subsequent sensing of biomolecules. The kinetics of functionalization reactions is a particularly important issue, since conventional functionalization protocols are associated with lengthy process times, from hours to days. The objective of this thesis is the improvement of the functionalization protocols and their kinetics for biosensing applications. This objective is realized via modeling and experimental verification of novel functionalization techniques in microfluidic environments. The improved functionalization protocols using microfluidic environments enable in-situ functionalization, which reduces the processing times and the amount of reagents consumed, compared to conventional methods. The functionalization is performed using self-assembled monolayers (SAMs) of thiols. The thiols are organic compounds with a sulphur group that assists in the chemisorption of the thiol to the surface of metals like gold. The two reactions in the functionalization process examined in this thesis are the SAM formation and the SAM/probe molecule conjugation. SAM/probe molecule conjugation is the chemical treatment of the SAM followed by the binding of the probe molecule to the SAM. In general, the probe molecule is selective in binding with a given biomolecule, called the target molecule. Within this thesis, the probe molecule is an antibody and the target molecule is an antigen. The kinetics of the reaction between the probe (antibody) and the target biomolecule (antigen) is also studied. The reaction between an antigen and its antibody is called the immunoreaction. The biosensing technique that utilizes the immunoreaction is immunoassay. A numerical model is constructed using the finite element method (FEM), and is used to study the kinetics of the functionalization reactions. The aim of the kinetic studies is to achieve both minimal process times and reagents consumption. The impact of several important parameters on the kinetics of the reactions is investigated, and the trends observed are explained using kinetic descriptive dimensionless numbers, such as the Damköhler number and the Peclet number. Careful numerical modeling of the reactions contributes to a number of findings. A considerably faster than conventional SAM formation protocol is predicted. This fast-SAM protocol is capable of reducing the process times from the conventional 24-hours to 15 minutes. The numerical simulations also predict that conventional conjugation protocols result in the overexposure of the SAM and the probe molecule to the conjugation reagents. This overexposure consequently lowers conjugation efficiencies. The immunoreaction kinetics of a 70 kilo-Dalton heat shock protein (HSP70) with its antibody in a hypothetical microchannel is also investigated through the FEM simulations. Optimal reaction conditions are determined, including the flow velocity and the surface concentration of the immobilized probes (antibodies). Based on the numerical results and a series of experimental studies, the fast-SAM protocol application is successfully confirmed. Moreover, the optimum reagent concentration for a given one- hour conjugation process time is determined. This functionalization protocol is successfully applied to immobilize the HSP70 antibody on gold surfaces. The use of the fast-SAM protocol and the predicted optimum conjugation conditions result in binding of the HSP70 antibody on gold, with the same or superior immobilization quality, compared to the conventional protocols. Upon implementation of a 70 μm.s^(-1) flow velocity, the reaction is observed to complete in around 30-35 minutes, which is close to the numerically predicted 30 minutes and 16 seconds. This immunoreaction time is considerably less than conventional 4-12 hour processes. The modified in-situ functionalization techniques achieved here are promising for substantially reducing the preparation times and improving the performance of biosensors, in general, and immunoassays, in particular.

Electrically conductive adhesives (ECAs) are one of the lead-free interconnect materials with the advantages of environmental friendliness, mild processing conditions, fewer processing steps, low stress on the substrates, and fine pitch interconnect capability. However, some challenging issues still exist for the currently available ECAs, including lower electrical conductivity, conductivity fatigue in reliability tests, limited current-carrying capability, poor impact strength, etc. The interfacial properties is one of the major considerations when resolving these challenges and developing high performance conductive adhesives. Surface functionalization and interface modification are the major approaches used in this thesis. Fundamental understanding and analysis of the interaction between various types of interface modifiers and ECA materials and substrates are the key for the development of high performance ECA for lead-free interconnects. The results of this thesis provide the guideline for the enhancement of interfacial properties of metal-metal and metal-polymer interactions. Systematic investigation of various types of ECAs contributes to a better understanding of materials requirements for different applications, such as surface mount technology (SMT), flip chip applications, flat panel display modules with high resolution, etc. Improvement of the electrical, thermal and reliability of different ECAs make them a potentially ideal candidate for high power and fine pitch microelectronics packaging option.

PhD / SYNOPSIS OF THIS THESIS The aim of this thesis is to more fully understand and explain the binding mechanism of organic molecules to the Au(111) surface and to explore the conduction of such molecules. It consists of five discreet chapters connected to each other by the central theme of “The Single Molecule Device: Conductance and Binding”. There is a deliberate concentration on azine linkers, in particular those with a 1,10-phenanthroline-type bidentate configuration at each end. This linker unit is called a “molecular alligator clip” and is investigated as an alternative to the thiol linker unit more commonly used. Chapter 1 places the work in the broad context of Molecular Electronics and establishes the need for this research. In Chapter 2 the multiple break-junction technique (using a Scanning Tunnelling Microscope or similar device) was used to investigate the conductance of various molecules with azine linkers. A major finding of those experiments is that solvent interactions are a key factor in the conductance signal of particular molecules. Some solvents interfere with the molecule’s interaction with and attachment to the gold electrodes. One indicator of the degree of this interference is the extent of the enhancement or otherwise of the gold quantized conduction peak at 1.0 G0. Below 1.0 G0 a broad range for which the molecule enhances conduction indicates that solvent interactions contribute to a variety of structures which could bridge the electrodes, each with their own specific conductance value. The use of histograms with a Log10 scale for conductance proved useful for observing broad range features. vi Another factor which affects the conductance signal is the geometric alignment of the molecule (or the molecule-solvent structure) to the gold electrode, and the molecular alignment is explored in Chapters 3 for 1,10-phenanthroline (PHEN) and Chapter 4 for thiols. In Chapter 3 STM images, electrochemistry, and Density Functional Theory (DFT) are used to determine 1,10-phenanthroline (PHEN) structures on the Au(111) surface. It is established that PHEN binds in two modes, a physisorbed state and a chemisorbed state. The chemisorbed state is more stable and involves the extraction of gold from the bulk to form adatom-PHEN entities which are highly mobile on the gold surface. Surface pitting is viewed as evidential of the formation of the adatom-molecule entities. DFT calculations in this chapter were performed by Ante Bilic and Jeffery Reimers. The conclusions to Chapter 3 implicate the adatom as a binding mode of thiols to gold and this is explored in Chapter 4 by a timely review of nascent research in the field. The adatom motif is identified as the major binding structure for thiol terminated molecules to gold, using the explanation of surface pitting in Chapter 3 as major evidence and substantiated by emergent literature, both experimental and theoretical. Furthermore, the effect of this binding mode on conductance is explored and structures relevant to the break-junction experiment of Chapter 2 are identified and their conductance values compared. Finally, as a result of researching extensive reports of molecular conductance values, and having attempted the same, a simple method for predicting the conductance of single molecules is presented based upon the tunneling conductance formula.

Magister Scientiae - MSc / A novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(η5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, Γ, of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 M, 6.92 M and 7.01 M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively. / South Africa

Magister Scientiae - MSc / Indinavir is a potent and well tolerated protease inhibitor drug used as a component of the highly active antiretroviral therapy (HAART) of HIV/AIDS, which results in pharmacokinetics that may be favourable or adverse. These drugs work by maintaining a plasma concentration that is sufficient to inhibit viral replication and thereby suppressing a patient’s viral load. A number of antiretroviral drugs, including indinavir, undergo metabolism that is catalysed by cytochrome P450-3A4 enzyme found in the human liver microsomes. The rate of drug metabolism influences a patient’s response to treatment as well as drug interactions that may lead to life-threatening toxic conditions, such as haemolytic anaemia, kidney failure and liver problems. Therapeutic drug monitoring (TDM) during HIV/AIDS treatment has been suggested to have a potential to reduce drug toxicity and optimise individual therapy. A fast and reliable detection technique, such as biosensing, is therefore necessary for the determination of a patient’s metabolic profile for indinavir and for appropriate dosing of the drugs. In this study biosensors developed for the determination of ARV drugs comprised of cysteamine self-assembled on a gold electrode, on which was attached 3-mercaptopropionic acid-capped palladium telluride (3-MPA-PdTe) or thioglycolic acid-capped palladium telluride (TGA-PdTe) quantum dots that are cross-linked to cytochrome P450-3A4 (CYP3A4) in the presence of 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide. The quantum dots were synthesized in the presence of capping agents (3-MPA or TGA) to improve their stability, solubility and biocompatibility. The capping of PdTe quantum dots with TGA or 3-MPA was confirmed by FTIR, where the SH group absorption band disappeared from the spectra of 3-MPA-PdTe and TGA-PdTe. The particle size of the quantum dots (< 5 nm) was estimated from high resolution transmission electron microscopy (HRTEM) measurements. Optical properties of the materials were confirmed by UV-Vis spectrophotometry which produced absorption iii bands at ~320 nm that corresponded to energy band gap values of 3 eV (3.87 eV) for TGAPdTe (3-MPA-PdTe) quantum dots. The electrocatalytic properties of the quantum dots biosensor systems were studied by cyclic voltammetry (CV) for which the characteristic reduction peak at 0.75 V was used to detect the response of the biosensor to indinavir. Results for indinavir biosensor constructed with 3-MPA-SnSe quantum dots are also reported in this thesis. The three biosensors systems were very sensitive towards indinavir; and gave low limits of detection (LOD) values of 3.22, 4.3 and 6.2 ng/mL for 3-MPA-SnSe, 3-MPA-PdTe and TGA-PdTe quantum dots biosensors, respectively. The LOD values are within the ‘maximum plasma concentration’ (Cmax) value of indinavir (5 - 15 ng/mL) normally observed 8 h after drug intake.

Ce travail porte sur l’étude des interfaces semi-conducteur/diélectrique et semiconducteur/électrode dans les transistors organiques à effet de champ (OFETs). En effet, le transport et l’injection des charges se trouvent affectés par la qualité de ces interfaces.L’objectif est donc la compréhension de l’influence des caractéristiques morphologiques(rugosité, énergie de surface) et électroniques (travail de sortie) du diélectrique ou del’électrode sur les performances des OFETs.Dans un premier temps, des OFETs sur substrats de silicium à base de pentacène ontété fabriqués et les interfaces traitées à l’aide de monocouches auto-assemblées (SAMs). Legreffage des SAMs tels que l’OTS8 ou l’OTS, en neutralisant les groupes hydroxyles et enprésentant une surface apolaire, conduit à une réduction de la densité de pièges en surface. Deplus, les pièges présents dans la couche active et dus aux joints de grains sont moinsnombreux grâce à une croissance 2D en larges grains du pentacène sur OTS. Cesmodifications de l’interface sont mises en évidence par une réduction de la tension de seuil,de la pente sous le seuil ainsi que de l’hystérésis. Le transport ainsi favorisé des chargespermet une amélioration de la mobilité jusqu’à 0,6 cm2/Vs.Nous nous sommes également intéressés à l’interface semi-conducteur/électrode et àsa modification par des SAMs fluorés tels que le PFBT, le PFHT et le PFDT. L’influence desSAMs est présente tant au niveau morphologique, en améliorant la continuité de croissance dupentacène à la jonction diélectrique/électrode qu’au niveau électronique en augmentant letravail de sortie de l’électrode. La réduction de la résistance de contact RC souligne clairementces modifications et conduit à des mobilités maximales de 0,6 cm2/Vs. Par la suite, nousavons choisi de modifier ces deux interfaces dans un même dispositif, ce qui nous a permisd’atteindre des mobilités moyennes élevées de 1,3 cm2/Vs.La dernière partie de ces travaux a été dédiée à la fabrication d’OFETs basse tension àbase de pentacène ou de C60 sur substrats de verre. Le caractère basse tension de cesdispositifs est rempli grâce à l’utilisation d’un diélectrique composé de deux couches : undiélectrique à forte constante diélectrique, l’oxyde d’aluminium, et une fine couche d’undiélectrique à faible constante diélectrique comme les SAMs (C8-PA ou C18-PA) ou lespolymères (PMMA ou PVT). Cette combinaison permet d’atteindre des mobilités(m = 0,4 cm2/Vs) encourageantes pour des OFETs de type n ainsi que de faibles hystérésis(<0,1 V) dans le cas d’OFETs de type p. / The charge transport and injection are strongly dependant of the semiconductor/dielectric and semi-conductor/electrode interfaces quality. Therefore, this studyfocuses on these interfaces in organic field effect transistors (OFETs). The goal is theunderstanding of the relation between the dielectric (roughness, surface energy) or electrode(work function) characteristics and the OFETs performances.First, we investigate the influence of the interfaces modification by SAMs (SelfAssembled Monolayers) in pentacene based OFETs on silicon substrates. Due to the SAMsgrafting such as OTS8 or OTS, the hydroxyls groups are neutralized and the dielectric showsan apolar surface leading to the reduction of the charge traps density. Moreover, a 2Dpentacene growth with large grains on OTS surface contributes to the decrease of the chargetraps density in the bulk. The threshold voltage, subthreshold swing and hysteresis decreasesgive rise to these modifications. The improvement of the charge transport allows us to reachmobility up to 0.6 cm2/Vs.Then, we investigate the electrode surface treatment by fluorinated SAMs such asPFBT, PFHT or PFDT. The better pentacene layer continuity and the increased electrodework function emphasize the morphologic and electronic influences of the SAMs. Thesemodifications lead to the contact resistance reducing and in consequence to an enhancedmobility up to 0.6 cm2/Vs. Finally, devices with a combination of the interfaces treatmentpresent high mean mobility of 1.3 cm2/Vs.On the final part of this study, we concentrate on low voltage C60 or pentacene basedOFETs on glass substrates. Using a dielectric composed of a high-k dielectric as AlOx and athin layer of a low-k dielectric such as phosphonic SAMs (C8-PA or C18-PA) or polymers(PMMA or PVT) allow us to achieve this low voltage condition. The mobility obtained withn-type OFETs (m = 0.4 cm2/Vs) and the small hysteresis (<0.1 V) in p-type OFETs arepromising.

Ce mémoire est consacré à la synthèse et la caractérisation de complexes bis-terdentates de ruthénium pour leur potentielle utilisation dans des triades photosensibles, ou pour la fabrication de dispositifs photosensibles. La première partie se concentre sur les propriétés photophysiques de deux complexes de RuII bis-terdentates. Le premier est un complexe homoleptique, formé de ligands tridentates comprenant deux sous-unités carbène (CNC), le second est un complexe hétéroleptique composé d'un ligand CNC et d'une terpyridine. Ce complexe hétéroleptique est luminescent à température ambiante, contrairement à ses deux complexes parents homoleptiques. Les propriétés électrochimiques et photoélectrochimiques de complexes de type [M(tpy)2]2+ (M=FeII ou RuII), dont les ligands terpyridine sont substitués par des groupements thiols, sont étudiées dans une seconde partie. Ces complexes électropolymérisent de manière organisée sur des électrodes d'or, par oxydation des thiols en disulfures. Ces propriétés ont été utilisées pour construire des diades [RuII]-[FeII] sur des électrodes d'or, dont le photocourant a pu être mesuré. Dans le dernier chapitre, les propriétés photophysiques et d'électropolymérisation du complexe de ruthénium décrit dans le chapitre 2 sont utilisées pour tenter de fabriquer un transistor pho-toactivable. / This thesis deals with the synthesis and characterization of several bis-terdentate complexes, and their potential use for the construction of photoactive molecular triads, or the fabrication of photoactive devices. The first chapter focuses on the photophysical properties of two new bis-terdentate RuII com-plexes. The first one is a homoleptic complex containing two N-heterocyclic carbene-based ligands (CNC) allowing close-to-perfect octahedral coordination geometry. The second one is a heteroleptic complex bearing a CNC ligand and an ancillary terpyridine ligand. This second complex displays room temperature luminescence whereas both homoleptic terpyridine-based and CNC-based RuII complexes are only luminescent at 77 K. The second chapter describes the electrochemical properties of a [M(tpy)2]2+-type (M = RuII or FeII) complex bearing thiol groups on both of the terpyridines are described. These complexes display electropolymerization properties through oxidation of thiols into disulfides. This phenomenon happens only on gold, suggesting that the polymer chains organize on the surface of the electrodes. Moreover, self-assembled monolayers of the RuII complexes were formed on gold, and their ability to exchange charges with the electrode upon irradiation was studied. Finally, self-organisation and electropolymerization properties were used to form [RuII]-[FeII] diads on a gold surface, and their photoresponse was recorded. The last chapter describes the attempts to construct a molecular photosensitive device by electropolymerizing the RuII complexes depicted in the second chapter in nanogaps between gold electrodes.

L'ingénierie tissulaire consiste à assembler de façon intelligente des cellules et des matériaux biocompatibles dans le but de créer des tissus artificiels. Pour la construction de tissus en laboratoire, il est indispensable d'élaborer des matériaux qui miment cet environnement. Dans ce cadre, la collaboration entre les scientifiques de différents domaines (matériaux, chimie, biologie, biochimie) s'avère nécessaire. L'ingénierie du muscle squelettique est prometteuse pour remplacer le tissu musculaire endommagé et pour le traitement des maladies du muscle, mais aussi pour les essais pharmaceutiques. Dans ce but, les matériaux avec les propriétés mécaniques et chimiques contrôlées sont requis -- pour l'amplification et la différenciation in vitro de cellules souches musculaires, mais aussi pour l'étude de la myogenèse sur des microenvironnements contrôlés 2D et dans les matrices 3D. Dans ce travail, nous avons utilisé la technique d'assemblage couche par couche (LbL, layer-by-layer) pour deux buts. Le premier a été de développer de nouveaux films biomimétiques possédant des propriétés biochimiques et mécaniques parfaitement contrôlées, pour étudier les interrelations entre ces deux paramètres sur les processus cellulaires. En plus, nous avons associé ces films biomimetiques aux substrats avec la topographie contrôlée, afin de guider la formation du tissu. Dans un second temps, nous avons utilisé la technique LbL pour organiser les cellules en structures 3D. Nous avons ainsi crée des microtissus d'épaisseur contrôlée, qui pourraient être utilisés en tant que modèles de tissus artificiels pour les applications thérapeutiques ou pour les évaluations de médicament en industrie pharmaceutique. / Tissue engineering approach consists in combining cells, engineering and biomaterials to improve the biological functions of damaged tissues or to replace them. Production of “artificial tissues” is still challenging and requires collaboration of scientists from different domains like cell biology, chemistry, materials and polymer science. Skeletal muscle tissue engineering holds promise for the replacement of muscle due to an injury and for the treatment of muscle diseases, such as muscle dystrophies or paralysis, but is also required for pharmaceutical assays. To this end, materials with tunable mechanical and biochemical properties for myoblast expansion and differentiation in vitro, as well as for the studies of myogenesis on controlled 2D microenvironments or in 3D scaffolds, are crucially needed. In this work, we use layer-by-layer (LbL) assemblies for two goals. The first consisted in the development of multifunctional biomimetic thin films for the control of skeletal muscle cell fate on 2D substrates. We use LbL films made of polypeptides, which can be stiffened by chemical cross-linking and can be specifically functionalized by grafting of biomimetic peptides onto their surface. In addition, we combined the peptide-grafted films with substrate microtopography. Such approach is promising for the development or multifunctional materials that combine the different stimuli present in in vivo ECM, among them physical and biochemical cues, but also microtopography. In the second part, we use LbL assemblies for the construction of 3D skeletal muscle microtissues. This allows to rapidly build 3D muscle tissues and is promising for the in vitro construction of physiologically relevant skeletal muscle tissue models.

Submitted by Veronica Neshmi Salaues Mendoza (neshmi_salaues@hotmail.com) on 2018-04-18T15:18:38Z No. of bitstreams: 1 Salaues_M_Dissert_Araraiq.pdf: 2461056 bytes, checksum: b0790442c72a5c574565c09b578075df (MD5) / Approved for entry into archive by Ana Carolina Gonçalves Bet null (abet@iq.unesp.br) on 2018-04-18T19:43:41Z (GMT) No. of bitstreams: 1 mendonza_vns_me_araiq_int.pdf: 2392917 bytes, checksum: 3697fdc59d96b5ae59f7207b7abe76e6 (MD5) / Made available in DSpace on 2018-04-18T19:43:41Z (GMT). No. of bitstreams: 1 mendonza_vns_me_araiq_int.pdf: 2392917 bytes, checksum: 3697fdc59d96b5ae59f7207b7abe76e6 (MD5) Previous issue date: 2018-03-13 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O sucesso no tratamento de muitos tipos doenças passa pela detecção seletiva e sensível de biomarcadores proteicos que permitam um diagnóstico precoce. A dengue é uma doença infecciosa de diagnóstico clínico impreciso e diagnóstico laboratorial demorado e custoso, a qual não possui tratamento ou vacina efetivos. Portanto se requer de ferramentas diagnósticas precisas, baratas e portáveis que permitam o diagnóstico rápido para realizar um tratamento adequado de sintomas e identificar os focos infecciosos para prevenir o espalhamento da doença. Um biomarcador útil na detecção da dengue, é a proteína NS1 que vem sendo utilizada com sucesso em diferentes plataformas de diagnóstico. Porém, nenhuma das plataformas oferecidas a nível comercial, consegue combinar a precisão, portabilidade, baixo custo e facilidade de manuseio. Portanto, o melhoramento de ditas ferramentas é o foco de bastantes pesquisas. Neste trabalho se apresenta uma plataforma que se amostra útil para a detecção de diferentes biomarcadores, incluindo a proteína NS1. Esta plataforma combina o uso de uma técnica eletroquímica como é a Espectroscopia de Capacitância Eletroquímica (ECE), com o uso de peptídeos redox e está baseada na funcionalização de eletrodos de ouro mediante formação de monocamadas auto-organizadas (SAM) confeccionadas com um peptídeo redox (Fc-Glu-Gli-Ser-Gli-Ser-Cys) desenhado para ser ancorado em superfícies metálicas, ao mesmo tempo que tem capacidade de ancorar uma sonda redox e um bioreceptor na mesma estrutura/molécula, com a vantagem adicional que a SAM obtida tem propriedades anti-incrustantes desejáveis em biossensoriamento. Ensaios realizados com a proteína NS1 permitiram a detecção de esta proteína em concentrações de 2 µg/ml. / Success in the treatment of many kinds of illnesses depends on the selective and sensitive detection of protein biomarkers that allow an early diagnosis. Dengue is and infectious disease of imprecise clinical diagnostic and delayed and expensive laboratorial diagnostic. This disease does not have an effective vaccine or treatment. Therefore, precise, cheap and portable diagnostic tools are necessary to allow a fast diagnostic in order to treat the symptoms, identify focuses of infection, and thus prevent the spreading of the disease. A useful biomarker in the detection of dengue is the protein NS1, which has been successfully used in different diagnostic platforms. However, none of the commercially available platforms combines precision, portability, low cost and user friendliness. Consequently, the improvement of such tools is object of ample research. This work, introduces a platform, which is useful for the detection of various biomarkers, including the protein NS1. This platform combines the usage of an electrochemical technique such as Electrochemical Capacitance Spectroscopy (ECS) and the use of redox peptides. It is based in the functionalization of gold electrodes through formation of Self Assembled Monolayers (SAM) formed by a redox peptide (Fc-Glu-Gli-Ser-Gli-Ser-Cys) designed to bind to metallic surfaces as well as to anchor a redox probe and a bioreceptor in the same structure/molecule. It presents the additional advantage of forming anti-fowling SAMs, which is a highly desirable property for biosensing. Tests made with NS1 protein allowed the detection of this protein in concentrations as low as 2 µg/ml. / 190233/2015-0

Recentemente, nanopartículas (NP) de FePt de fase tetragonal de face centrada (fct) em sistemas auto-organizados tem sido sintetizados como potenciais candidatos para gravação magnética de ultra-alta densidade (UHMR), devido a sua elevada anisotropia magnetocristalina. Entretanto, o alinhamento magnético de NP esféricas tem sido constantemente um problema, pois os eixos de fácil magnetização das NP permanecem randomicamente orientados nas três direções. Na tentativa de superar os problemas decorrentes da falta de alinhamento magnético, trabalhos recentes sugerem que NP alongadas em sistemas auto-organizados orientados perpendicularmente a superfície do substrato como possível solução para a textura e alinhamento magnético. Até o presente momento, as sínteses de nanobastões (NB) e de nanofios (NF) de FePt reportadas na literatura levam a obtenção de NP na fase cúbica de face centrada (fcc), a qual possui baixa anisotropia magnetocristalina e se mostrou termicamente instável, resultando em NP esferoidais após o processo de recozimento para a transformação da fase fcc para fct. Neste trabalho, NP de Fe55Pt55 com tamanho e composição química controlada e morfologia de nanofios e nanobastões foram sintetizadas através da adequação do método do poliol modificado. Além disso, as condições de sínteses foram ajustadas para a obtenção direta das NP na fase fct. Sistemas auto-organizados de NB orientados longitudinalmente ou perpendicularmente em arranjos hexagonais compactos foram obtidos utilizando, respectivamente, ácido oléico (AO) e oleilamina (Oam) ou hexadecilamina (HDA) como agentes espaçadores. Sistemas de NB orientados perpendicularmente com alinhamento magnético devido à anisotropia de forma combinado com as propriedades magnéticas resultantes da fase parcialmente tetragonal obtida sugerem um forte candidato a aplicação em UHMR com densidade de gravação magnética na ordem de terabits/pol2. / Recently, self-assembled FePt nanoparticles (NP) in face-centered tetragonal phase (fct) has been synthesizes as potential candidates for Ultra-High Magnetic Recording Systems (UHMR) due to high magnetocrystalline anisotropy. However, the magnetic alignment of these self-assembled fct-FePt nanoparticles also has been a constant limiting factor, since the axes of easy magnetization of spherical nanoparticles are presented randomly oriented in three directions. Concerning to avoid these restrictions arising from magnetic alignment, one-dimensional NP perpendicularly oriented on the magnetic medium surface has been reported as a possible solution for texture and magnetic alignment. To date, the reported nanorods (NR) and nanowires (NW) synthesized in the literature showed face centered cubic phase (fcc) which present poor magnetocrystalline anisotropy, instead the fct desirable phase, and were found to be thermally unstable resulting in spheroidal NP after annealing required to phase transformation from fcc to fct. In this work, Fe55Pt45 NP with morphologies varying from nanospheres, NR with different lengths up to NW were synthesized by a modified polyol process. Furthermore, the synthesis conditions were adjusted to obtain FePt NP directly in fct phase. Either longitudinal or perpendicular self-assembled NR systems in a hexagonal compact array were obtained using oleic acid (OA) and oleylamine (Oam) or hexadecylamine (HAD), respectively, as molecular organic spacers. Perpendicularly oriented NR system led to magnetic alignment due to shape anisotropy and combined with the magnetic properties due to partial tetragonal phase suggest a strong future candidate to ultra-high magnetic density recording applications capable to achieve density of Terabits/in2.