One of the major directions of research in the area of materials science is to impart multifunctionalities to materials. Carbon stands on the top of the list to provide various multifunctional materials. It exists in all dimensions, zero (fullerene), one (carbon nanotube, CNT), two (graphene) and three (graphite) dimensions are very well-known for their versatility in various studies. They are also used in various applications in nanoelectronics, polymer composites, hydrogen production and storage, intercalation materials, drug delivery, sensing, catalysis, photovoltaics etc. Electrical conductivity of carbon can be tuned from insulator (diamond) to semiconductor (graphene) to conductor (graphite) with varying band gap. The main reason for this versatility and varied properties is that carbon can be involved in different hybridizations. Graphene, a single layer of graphite has fascinated the world during the last several years culminating in a Nobel prize for Physics in 2010. The present study is an attempt to understand the physicochemical and electrochemical properties of graphite oxide and its reduced form. Graphene oxide (GO) possesses oxygen containing functional groups such as carbonyl, carboxyl and epoxy groups distributed very randomly in the extended graphene sheet which makes it ionically conducting and electrically insulating. The AFM images of single layer of graphite (graphene) obtained from micromechanical cleavage method and that of EGO are shown in figure 1. EGO is a layered material similar to graphite and can form very stable aqueous colloids over a wide pH range of 2-11. The stability of the colloid is due to electrostatic repulsive interactions between the functional groups. EGO behaves like a molecule due to its thickness (~1 nm) and like a particle due to its two dimensional nature (lateral size can vary from nm to few microns). It behaves as amphiphilic molecule having both hydrophilic and hydrophobic nature. Figure 1d shows the STM image of EGO which clearly indicates oxidized and unoxidized regions which will impart hydrophilic and hydrophobic regions respectively. Figure 1: AFM image of (a) graphene (b) EGO. STM image of (c) HOPG and (d) EGO. The present work is related to exploring EGO as a multifunctional material. Both hydrophilic and amphiphilic nature is explored for various studies. Reduced GO (rGO) is synthesized from EGO by assembling at different interfaces (solid-liquid and liquid-air) followed by reduction. Since EGO is hydrophilic, it is brought to the air-water interface with the help of a surfactant (CTAB) through electrostatic interactions. It is reduced chemically by hydrazine vapour to rGO and electrochemically by assembling EGO on gold through electrostatic interactions between EGO and amine groups of cystamine (figure 2). The reduction process is followed by AFM, UV-Visible and in-situ Raman spectroelectrochemistry. Figure 2: Schematic of EGO self assembly, cyclic voltammogram showing electrochemical reduction and schematic for in-situ Raman spectroelectrochemistry. The next section deals with composites of EGO and polymers. EGO/polyaniline (PANI) composite is formed by electrochemical polymerization under applied surface pressure. The in-situ electrochemical polymerization of aniline in the sub-phase of Langmuir-Blodgett trough under applied surface pressure in presence of EGO at the air-water interface leads to preferential orientation of PANI in the polaronic form. This is followed by electrochemistry and Raman spectroscopy. Figure 3 shows differential pulse voltammograms of EGO/PANI obtained under two different conditions. Externally polymerized sample shows three redox peaks at 0.086/0.064 V (A/A‟), 0.390/0.430 V (B/B‟) and 0.520/0.560 mV (C/C‟) which correspond to leucoemaraldine/emaraldine, quinone/hydroquinone and emaraldine/pernigraniline redox states respectively. The peak at C/C‟ vanishes when aniline is polymerized in-trough under applied surface pressure. This implies that oxidation of emaraldine to pernigraniline becomes difficult when sample is prepared in-trough. The Raman spectroscopy clearly reveals the preferential orientation of PANI in planar polaronic structure. Figure 3. Differential pulse voltammograms for EGO/PANI complex obtained through external polymerization (black) and in-trough polymerization (red). In the next part, EGO is used as a proton conducting material for polymer electrolyte membrane fuel cell (PEMFC). EGO possesses hydrophilic and hydrophobic regions similar to nafion (sulfonated tetrafluoroethylene based fluoropolymer-copolymer) and hence it can act as a good ionically conducting membrane. EGO is incorporated in poly(vinyl alcohol) (PVA) matrix and used in the present studies. The ionic conductivity increases from 10 μS cm-1 to 370 μS cm-1 when EGO content is increased from 1wt% to 7wt% in PVA matrix. Power densities of 25 and 90 mW cm-2 are obtained for PVA and PVA/EGO membranes in H2-O2 fuel cell at 40 0C respectively. In the next section, EGO is used as receptor for simultaneous electrochemical detection of heavy metal ions such as Cd, Pb, Cu and Hg with detection limit of 5 μM, 1 pM, 5 μM and 5 μM respectively. During the process it is observed that the EGO/PbO composite can give rise to detection limit of 10 nM for arsenic. Along with detection, EGO can also be used as an effective adsorbent for inorganics (metal ions) as well as organics (dye molecules). EGO behaves as good adsorbent for heavy metal ions and cationic dyes and rGO adsorbs anionic dyes effectively. Spectroscopic techniques are used to understand the interactions between adsorbent and adsorbates. The thesis is presented as follows: Chapter 1 gives general introduction about graphene and graphite oxide with particular emphasis on the latter one. Chapter 2 gives details on the experimental methods followed, along with schematics for various adsorption processes. Chapter 3 focuses on assembling EGO at interfaces (solid-liquid and liquid-air) followed by reduction with chemical and electrochemical methods. Chapter 4 explores EGO as an amphiphilic material where EGO is assembled at air-water interface with anilinium and subsequent electropolymerization to EGO/PANI composites. EGO/PVA composite is used as electrolyte for PEMFC. Chapter 5 explores EGO as receptor for heavy metal ion detection (Cd, Pb, Cu and Hg). Chapter 6 deals with EGO as adsorbent for adsorption of inorganics (metal ions) as well as organics (dye molecules). This is followed by summary and conclusions. The appendix section gives details on the studies on preparation of exfoliated graphite with various metal ion intercalation. The covalent functionalization of EGO with metal phthalocyanines and its assembly at air-water interface forms second part of the appendix. (For figures pl see the abstract pdf file)

Submitted by (edna.saturno@ufrpe.br) on 2016-07-26T14:17:38Z No. of bitstreams: 1 Jose Armando Pires Pereira.pdf: 1552648 bytes, checksum: 8d29d0e12da5e608b1f9eafb6a0bd31c (MD5) / Made available in DSpace on 2016-07-26T14:17:38Z (GMT). No. of bitstreams: 1 Jose Armando Pires Pereira.pdf: 1552648 bytes, checksum: 8d29d0e12da5e608b1f9eafb6a0bd31c (MD5) Previous issue date: 2010-02-25 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The State of Pernambuco, the second largest producer of cachaça in Brazil, has been consolidating the quality of its cachaça and pursued, with success, paths for exporting the product. However, the levels of ethyl carbamate (EC), a recognized genotoxic carcinogen, in the cachaças and sugar cane spirits produced in Pernambuco State are still unknown. A Brazilian regulation (prepared by Ministry of the Agriculture, Livestock and Provisioning – MAPA) that limits the amount of EC in cachaça or sugar cane spirit (150 μgL-1) will come into effect from 30 June 2010. Taking into consideration a possible association between the processing of cachaça, in particular the distillation step, and its EC level, the objective of this work was to investigate the EC levels of recorded (legal) cachaças and sugar cane spirits produced in the State of Pernambuco and their technological profile. Duplicate samplings of 33 brands of cachaças and sugar cane spirits from Pernambuco State were analyzed for EC (through GC-MS) and 9 cachaça producing companies were visited to obtain details on their distillation process. In addition, the samples were analyzed for the following physiochemical parameters: alcoholic degree, volatile acidity, total sugars, total dry extract, and copper. Regarding the physiochemical parameters investigated in the 33 brands, the following percentages of nonconformity with the current MAPA regulations, per parameter, were found: alcoholic degree (27%), volatile acidity (9%), total sugars (9%) and copper (9%). According to the distillation systems applied to the 33 brands, it was found that 13 (39%) were obtained by batch distillation in pot stills (pot still cachaça) and 20 (61%) by continuous distillation in columns stills (column still cachaça). The average EC concentrations varied from less than 10 μgL-1 (detection limit) up to 532.5 μgL-1. Eighteen brands (55%) contained EC levels above the MAPA regulation limit, among these brands only two came from distillation in pot stills. In comparison to columns still cachaças, lower EC levels in cachaças distilled in pot stills, particularly pot stills with the ascending and descending parts made of copper and stainless stills, respectively, were observed. In spite of the higher levels of EC in column still cachaças from Pernambuco State, they can be considered as low when compared to average levels of EC reported by other studies on column still cachaças. One of the possible reasons was the observation that producers of column still cachaça from Pernambuco State have been gradually including and excluding copper in the ascending and descending parts of their column stills, respectively. This study has confirmed that batch distillation in pot still, probably due to the removal of "heads" fraction, richer in EC precursors, combined with high reflux (ascending part) and low distillate contamination with copper (descending part), produces cachaça with very low levels of EC. / O estado de Pernambuco, segundo maior produtor de cachaça do Brasil, tem procurado consolidar a qualidade de suas cachaças e buscado, com sucesso, caminhos para exportação. Até aqui, entretanto, os níveis de carbamato de etila (CE), uma substância reconhecidamente carcinogênica, nas cachaças e aguardentes de cana pernambucanas são desconhecidos. A partir de 30 de junho de 2010 entrará em vigor a Instrução Normativa 13/2005 do Ministério da Agricultura, Pecuária e Abastecimento (MAPA) para CE, a qual estabelece uma tolerância de 150 microgramas (μg) desta substância por litro (L) de cachaça ou aguardente de cana. Tendo em vista uma possível relação entre o processo produtivo, em particular a destilação, e os níveis de CE na cachaça, a presente pesquisa teve como objetivo investigar os níveis de CE nas cachaças e aguardentes de cana produzidas legalmente no estado de Pernambuco em associação com os perfis de produção dos respectivos estabelecimentos produtores. Foram analisadas 33 marcas de cachaças e aguardentes de cana, sendo duas amostras por marca, através da técnica de cromatografia gasosa-espectrometria de massas, e visitados 9 estabelecimentos produtores para obter detalhes do processo de destilação. Complementarmente, as amostras foram analisadas quanto aos seguintes parâmetros físico-químicos: grau alcoólico real, acidez volátil, açúcares totais, extrato seco total e cobre. Do ponto de vista dos parâmetros físico-químicos investigados nas 33 marcas, foram constatados os seguintes percentuais de não atendimento a legislação vigente, por parâmetro: grau alcoólico real (27%), acidez volátil (9%), açúcares totais (9%) e cobre (9%). Relativo aos tipos de aparelho destilador utilizados para produzir as 33 marcas, constatou-se que 13 delas (39%) foram obtidas utilizando sistema de destilação descontínua em alambiques (cachaça de alambique) e 20 (61%) em sistema contínuo por meio de colunas de destilação (cachaça de coluna). As concentrações médias de CE por marca variaram desde menor que 10 μgL-1 (limite de detecção) até 532,5 μgL-1. Dezoito marcas (55 %) apresentaram níveis de CE acima do tolerado pela legislação, sendo que apenas duas delas eram provenientes de sistema de destilação em alambique. Em comparação com as cachaças de coluna, foram observados níveis de CE mais baixos para as cachaças destiladas em alambiques, especialmente os manufaturados com as partes ascendentes e descendentes de cobre e aço inoxidável, respectivamente. Apesar dos maiores níveis de CE nas cachaças pernambucanas de coluna, estes ainda podem ser considerados como baixos quando comparados aos níveis médios de CE reportados em outros estudos sobre as cachaças de coluna do Brasil. Uma das possíveis razões foi a constatação que os produtores de cachaça de coluna do estado de Pernambuco vêm gradualmente incluindo e excluindo o cobre das partes ascendentes e descendentes, respectivamente, de seus aparelhos de destilação. Este estudo confirmou que a destilação descontínua em alambique, motivada provavelmente pela remoção da fração “cabeça” do destilado, mais rica em precursores de CE, aliada com o alto refluxo (parte ascendente) e baixa contaminação do destilado por cobre (parte descendente), produz cachaças com níveis muito reduzidos de CE.

This research was developed with the intention of understanding the aquifer dynamics and the underground spring s preservation. In that sense, it was had as main objective to study the natural vulnerability of the Guarani Aquifer System and to analyze physiochemical parameters of the groundwater in the cities of Quaraí - Brazil and Artigas - Uruguay, due to the exploited waters of this aquifer, they be used mainly for human consumption. This way, it was used for the execution of the study, pré-existent data, field research and computer techniques. The methodology used to study the aquifer natural vulnerability leaned on in the DRASTIC Model. To characterize the groundwater, it was made analysis of physiochemical parameters in samples collected in March of 2005. As more relevant result it was verified the relation to the natural vulnerability of the aquifer in the area, that same varied of vulnerable, very vulnerable and extremely vulnerable classes. For the obtained results of the analyses of the physiochemical parameters, we stand out that the waters were classified in 5 types: CaHCO3, CaMgHCO3Cl, MgHCO3, CaMgHCO3 and CaNaHCO3. However, it is evident the importance of the accomplishment of researches of that nature, because the results can be used to manage groundwater hydrics resources in a maintainable way. On the other hand, it is waited that the obtained information and the applied methodologies in this research can subsidize addressed actions to the integrated administration of the groundwater hydrics resources between Brazil and Uruguay, mainly in the plans of use of the water, in agreement with foreseen on its legislation. / Com o intuito de compreender a dinâmica dos aqüíferos e a preservação dos mananciais subterrâneos é que se propôs desenvolver esta pesquisa. Nesse sentido, teve-se como objetivo principal estudar a vulnerabilidade natural do Sistema Aqüífero Guarani e analisar parâmetros físico-químicos das águas subterrâneas em Quarai, Brasil, e Artigas, Uruguai, devido as águas explotadas deste aqüífero serem utilizadas principalmente para consumo humano. Desta forma, utilizou-se para a execução do estudo, dados pré-existentes, pesquisa de campo e técnicas computacionais. A metodologia empregada para estudar a vulnerabilidade natural dos aqüíferos apoiou-se no Modelo DRASTIC. Para caracterizar as águas subterrâneas, fez-se análise de parâmetros físico-químicos em amostras coletadas em março de 2005. Como resultado mais relevante constatado pode-se destacar, em relação à vulnerabilidade natural dos aqüíferos da área, que a mesma variou de vulnerável, muito vulnerável a extremamente vulnerável. Quanto aos resultados obtidos das análises dos parâmetros físico-químicos, destaca-se que as águas classificaram-se em 5 tipos: CaHCO3, CaMgHCO3Cl, MgHCO3, CaMgHCO3 e CaNaHCO3. Contudo, é evidente a importância da realização de pesquisas dessa natureza, pois os resultados podem ser utilizados para gerenciar de modo sustentável os recursos hídricos subterrâneos, por outro lado, espera-se que as informações obtidas e as metodologias aplicadas nesta pesquisa possam subsidiar ações direcionadas à gestão integrada dos recursos hídricos subterrâneos entre Brasil e Uruguai, principalmente nos planos de uso da água, de acordo com o previsto na legislação de ambos os países.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Growndwater consist of strategic resources essential for public and private water supply. Therefore, the aquifer research by means of groundwater monitoring has been considered very important. In groundwater polluted potential enterprises, a system of monitoring is necessary, because it can not only allow contamination evidences previously, but also provide reference measures in order to portray the aquifer s hydrochemistry and hydrodynamics. The purpose of this study is to establish natural values and temporal variation frequency of groundwater physiochemical and hydrodynamic parameters in the area of a tank fuel in Santa Maria/RS, in an outcrop zone of Guarani Aquifer System (GAS). Therefore, the methodology consisted of: office studies in order to review the literature in the topic; field study, by the hydrogeological monitoring of seven observation wells, during 12 month, topographic work, precipitation measure, hydraulic conductivity assays carried out using the method of excavated piezometer and directly in the wells (infiltration); laboratory study, by analyzing the data statistically using the statistic software SPSS® 13.0 for Windows (2004), development of tridimensional frameworks of groundwater flow and specialization cartograms of physiochemical parameters by using SURFER® 8.0 program. The results showed that the concentration of the physiochemical frameworks studied had temporal alteration in relation to months and seasons, besides variations in the spatial distribution, that indicated differences in the entrance of water in the column of the well, it happened, probably, because of the influence of different layers. It was also possible to observe variations in the water level in the seven monitoring wells from the pluviometric precipitation, indicating that they are situated in an area of GAS direct recharge. Related to the direction of the local groundwater flow, the data obtained showed that in case of fuel leak the river Vacacai-Mirim, 230 m distant of the enterprise, will be affected. In conclusion, the background variation reflects the geologic diversity in the place that has Fluvial Terrace Depository, considered permeable and, the Alemoa member of Santa Maria formation that was considered impermeable. This research contributed to the physiochemical and hydrodynamic characterization in local scale of GAS offering a background, which will subsidize environment organs, supporting in a way to allow possible groundwater contamination evidences previously. / As águas subterrâneas constituem reservas estratégicas vitais para o abastecimento público e privado. Portanto, o estudo de aqüíferos por meio do monitoramento hidrogeológico, revelase de suma importância. Em empreendimentos potencialmente poluidores da água subterrânea, faz-se necessário um sistema de monitoramento, que além de um aviso precoce da contaminação, forneça valores de referência para a caracterização hidroquímica e hidrodinâmica dos aqüíferos. O objetivo dessa pesquisa é estabelecer os valores naturais e a faixa de variação temporal de parâmetros físico-químicos e hidrodinâmicos das águas subterrâneas na área de um reservatório de combustíveis no município de Santa Maria/RS, em uma zona de afloramento do Sistema Aqüífero Guarani (SAG). Para tanto, a metodologia consistiu em: estudos de escritório a fim de revisar a literatura no tema da pesquisa; trabalho de campo, mediante o monitoramento hidrogeológico de sete poços de observação no período de 12 meses, levantamento topográfico, medidas de precipitação, ensaios de condutividade hidráulica realizados com piezômetro escavado e diretamente nos poços (infiltração); estudo de laboratório, por meio da análise estatística dos dados com auxílio do software estatístico SPSS® 13.0 for Windows (2004), construção de modelos tridimensionais do fluxo subterrâneo e cartogramas de espacialização de parâmetros físico-químicos com o Programa SURFER® 8.0. Como resultado destaca-se que as concentrações dos parâmetros físico-químicos estudados sofreram flutuações temporais mensais e sazonais, além de variações nas distribuições espaciais, o que indicou diferenças de entradas de água na coluna dos poços, ocorridas possivelmente devido à alimentação desses por diferentes camadas. Evidenciou-se que ocorreram variações do nível da água nos sete poços de monitoramento a partir das precipitações pluviométricas, indicando que os mesmos estão situados em área de recarga direta do SAG. Em relação à direção do fluxo subterrâneo local, os dados obtidos revelam que em caso de vazamento de combustíveis o Rio Vacacaí-Mirim, distando 230 m do empreendimento será afetado. Conclui-se que as variações dos valores naturais (background) refletem a diversidade geológica do local, que é marcada pela presença de Depósitos de Terraços Fluviais, considerados permeáveis e, da Formação Santa Maria Membro Alemoa, que é estimada na área de estudo como impermeável. Esse estudo contribuiu para a caracterização físico-química e hidrodinâmica em escala local do SAG fornecendo valores de referência, os quais servirão de subsídios aos órgãos gestores ambientais, auxiliando no aviso precoce de possível contaminação da água subterrânea.

From the Proceedings of the 1972 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 5-6, 1972, Prescott, Arizona / The need for increased control of seepage from both natural and artificial small ponds and lakes has become more apparent with the increased frequency of their construction and use on the farm, ranch, and in recreational urban use. Seepage control methods are also becoming more numerous. Unfortunately, comparisons as to effectiveness, longevity and costs are not readily available. This paper investigates some control techniques being used in this region and evaluated them according to the above criteria. Emphasis was on the use of available physiochemical methods other than rubber membranes and concrete liners. Examples of the types of controls in use include plastic, soil compaction aids, hydrophobic chemicals and monovalent cation applications, such as sodium chloride. Some examples of the use of these methods in Arizona are shown and the results of some field comparison tests conducted using 8 x 8 square foot double -ringed infiltrometers presented. Recommendations are made of additional research that should be undertaken to improve the technology of the control of seepage losses.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-08T13:12:58Z No. of bitstreams: 1 Tese - Gildete.pdf: 3864174 bytes, checksum: 31674065a4332deeca217025e7b4eb0b (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-08T13:41:06Z (GMT) No. of bitstreams: 1 Tese - Gildete.pdf: 3864174 bytes, checksum: 31674065a4332deeca217025e7b4eb0b (MD5) / Made available in DSpace on 2016-09-08T13:41:06Z (GMT). No. of bitstreams: 1 Tese - Gildete.pdf: 3864174 bytes, checksum: 31674065a4332deeca217025e7b4eb0b (MD5) / Neste trabalho buscou-se avaliar a qualidade das águas da Bacia Hidrográfica do Rio Joanes utilizando os resultados das determinações dos parâmetros físico-químicos: cor, pH, turbi- dez, sólidos totais dissolvidos, oxigênio dissolvido, DBO, DQO, amônia, nitrito, nitrato, fósforo e condutividade elétrica e dos metais e metalóides antimônio, arsênio, bário, berílio, boro, cádmio, chumbo, cobalto, cobre, cromo, ferro, lítio, manganês, mercúrio, níquel, pra- ta, selênio, vanádio e zinco nas águas brutas desta bacia, durante o monitoramento realizado pela EMBASA-Empresa Baiana de Águas e Saneamento no período de 2006-2007. Alguns metais e metalóides como antimônio, arsênio, berílio, boro, níquel, prata e selênio apresen- taram resultados abaixo dos respectivos limites de detecção não tendo, portanto, nenhuma variação de valores por isso não foram utilizados nas discussões. A análise multivariada de dados usando o método da PCA foi utilizada com o objetivo de identificar os fatores deter- minantes, naturais e antrópicos da qualidade das águas superficiais da bacia supracitada. Através da PCA verificou-se que as variáveis CE, DBO, DQO, fósforo, sólidos totais, turbi- dez, OD, Ag, Hg, Mn, V, Cr, Cu e Fe foram as mais importantes para a qualidade destas águas e estão associadas ao lançamento de esgotos doméstico e industriais nos corpos hídri- cos, sem tratamento adequado. Ficou evidenciada a interferência antrópica pelos altos níveis de fósforo e amônia encontrados ao longo da bacia sinalizando a necessidade urgente de intervenções mais efetivas. / This work aimed to evaluate the water of the basin of the Joanes River through the results of the study of the physiochemical parameters: color, pH, turbidez, dissolved total solids, dis- solved oxygen, DBO, DQO, ammonia, nitrite, nitrate, electric conductivity and of the met- als and metalloids antimony, arsenic, barium, beryl, boron, cadmium, lead, cobalt, copper, chrome, iron, lithium, manganese, mercury, nickel, silver, selenium, vanadium, and zinc, as determined in the raw waters of this basin in the period of 2006-2007. Some of the metals and metalloids antimony, arsenic, beryl, boron, nickel, silver, and selenium yield results below their limits of detection, without variation in values. As a results, they were not in- cluded in the discussion. Multivariate analysis using PCA was used to identify the determin- ing natural and anthropogenic factors of the quality of surface waters of the basin. Through PCA, the study shows that the variables CE, DBO, DQO, phosphor, total solids, turbidez, OD, Ag, Hg, Mn, V, Cr, Cu e Fe, were the most important factors for the water quality and these are associated with the release of domestic and industrial sewers in the body of water without adequate treatment. The anthropogenic interference evidenced by the high match levels of phosphor and ammonia found along the basin in the study signals an urgent need for effective interventions.

Le procédé de mise en forme des tôles métalliques, généralement oxydées, par emboutissage est en pleine évolutionpour répondre à de nouveaux besoins : intervalles de tolérances dimensionnelles de plus en plus étroits, productionen grande série à faible coût, apparition de nouvelles nuances de matériaux, souci écologique. La réussite d’une telleopération est prédominée par le contrôle du frottement au niveau du contact entre tôle à former et outil enmouvement relatif. Pour ce faire, nous proposons dans cette thèse de fonctionnaliser la surface de la tôle en ygreffant des molécules organiques auto-assemblées, par simple immersion dans une solution contenant les moléculesréactives. Le couple métal/molécule retenu pour cette étude est un substrat massif de cuivre pur avec des moléculesd’acides alkylphosphoniques (CnH2n+1PO(OH)2) dans le but d’établir une corrélation entre les propriétésphysicochimiques des films ainsi formés et leur comportement tribologique. La réponse en frottement a été étudiéepar deux moyens de simulation expérimentale des conditions de contact (tribomètres bille/plan et étirage-plan). Nousavons considéré l’influence des trois facteurs de préparation de substrat suivant μ la nature de surface juste avant safonctionnalisation (présence d’une couche d’oxyde ou d’hydroxyde), le nettoyage de surface aux ultrasons après safonctionnalisation (élimination des espèces physisorbées) et la longueur de chaîne alkyle de la moléculeorganophosphonique (n=4, 12 et 16). Bien que la formulation de cette fonctionnalisation soit simple (élaborée àpartir d’une seule molécule), les techniques d’investigation de surface (PM-IRRAS, XPS, électrochimie, MEB,…)montrent que les films auto-assemblés sont constitués d’une bicouche de bonne qualité de greffage et de propriétésanticorrosion. Cette bicouche est composée d’une première monocouche de molécules chimisorbées à la surface (ouSAM) sur laquelle est déposée une deuxième couche d’amas physisorbés. D’autre part, notre étude a montréégalement que les amas physisorbés ont un rôle primordial dans le comportement tribologique du film auto-assemblé(abaissement et stabilité du coefficient de frottement et prévention contre le grippage). / Sheet metal forming processes are quickly evolving to meet new requirements of deep drawing such as: continuousminimization of dimensional tolerances intervals, cost efficiency at mass production, appearance of new materialstypes, environmental concern. The success of such operation is predominated by controlling friction at the contactbetween the metal sheet and forming tool in relative motion. In the present work, we propose to functionalize themetal sheet surface using grafting of self-assembled organic molecules by simple immersion in a solution containingthe reactive molecules. Consequently, thin film of alkylphosphonic acid (CnH2n+1PO(OH)2) was grafted on copperoxide substrate in order to establish a correlation between the physicochemical properties of the films andtribological behavior. Frictional response was studied by two experimental means of contact conditions (stripdrawing testing and ball-on-plane tribometer). The influence of three factors for the preparation of substrate wasconsidered. Firstly, the nature of its surface just before functionalization including the presence of an oxide orhydroxide layer was studied. Then, the ultrasonic surface cleaning after functionalization (removal physisorbedspecies) and finally, the alkyl chain length of the organophosphonic molecule (n = 4, 12 and 16). Although theformation of this functionalization is simple (made from a single molecule), the surface investigation techniques(PM- IRRAS , XPS, electrochemistry , SEM, .., etc.) show that self-assembled films consist of a bilayer with a goodgrafting quality and anticorrosion properties. The bilayer is composed of a first monolayer of molecules chemisorbedon the surface (or SAM) on which a second layer of physisorbed species is deposited. Furthermore, this study alsoshowed that the physisorbed species have a key role in the tribological behavior of self-assembled film (lower andstable friction coefficient and high resistance to galling).

Indiana University-Purdue University Indianapolis (IUPUI) / Purpose: Dental sealant forms a physical barrier to prevent pit and fissure caries; therefore, the retention rate becomes a main factor of the sealant’s effectiveness. Electrospun nylon-6/N6 nanofibers have shown good mechanical properties, such as high tensile strength and fracture toughness. Chitosan/CH has received significant attention due to properties such as antibacterial activity. The purpose of this study was to synthesize and evaluate the effect of incorporating N6 and CH electrospun nanofibers on the physical-mechanical and antibacterial properties of an experimental resin-based sealant. Methods and Materials: Nanofiber synthesis: N6 pellets were dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol at a concentration of 10wt%. Practical-grade chitosan was dissolved in trifluoroacetic acid and dichloromethane (60:40 TFA/DCM) at 7 wt%. Electrospinning parameters were optimized in order to fabricate defect-free N6 and chitosan nanofiber mats. Morphological and chemical characterizations were performed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively after vacuum drying the mats for 48 h. The average fiber diameter was determined from SEM images by measuring the diameter of 120 fibers using ImageJ software. Experimental Sealant: N6 and CH electrospun mats (3×3cm2) were immersed into a resin mixture of BIS-GMA/TEGDMA. Once no bubbles were seen, the resin-modified N6 and CH mats were put on a glass plate, light-cured (“TRIAD 2000”) for 2 min and then submitted to a cryomilling process to obtain a fine micron-sized powder. Three different filler levels (1 wt%, 2.5 wt%, 5 wt%) were used to prepare the N6 and CH incorporated resin-based sealants. Additionally, a commercially available resin-based sealant and the experimental resin mixture (unfilled) were used as controls. Three-point flexural testing, Vickers microhardness testing, and agar diffusion testing were performed on the experimental sealants and the commercial sealant. Data were analyzed by one-way ANOVA and Fisher's Protected Least Significant Differences Pair-wise comparisons between groups (5%). Results: The average fiber diameter for N6 was found to be 503±304 nm and 595±411 nm for CH. No significant difference was found between fiber diameter (p = 0.0601). FTIR confirmed the characteristic peaks for N6 ((CO-NH and [-(CH2)5-].) and CH (N-H and C2F3O2-). CH-5% group had significantly higher (p = 0.0000) FS (115.3±4.5 MPa) than all other groups. CH-1% and CH-2.5% groups had significantly higher FS than the control (unfilled) (p = 0.0016 and p = 0.0033 respectively); Helioseal Clear (p = 0.0000), and nylon groups. N6-5% had significantly higher flexural strength than Helioseal Clear (p = 0.0013) and N6-2.5% (p = 0.0250). CH-1% had significantly higher hardness values than all other groups, and CH-5% (p = 0.0414) had significantly higher values than N6-2.5%. No antibacterial inhibition was seen in any of the tested groups. Conclusions: CH and N6 nanofibers were successfully prepared via electrospinning and used to modify the experimental resin-based dental sealants. The overall results indicated that CH-containing sealants presented the highest flexural strength and hardness; however, none of the CH groups displayed antimicrobial properties. Further investigation is needed to enhance the physico-mechanical properties of the experimental resin-based sealants using nylon-6 and CH.