594 resultados para nanoscience
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Research into the targeting of drug substances to a specific disease site has enjoyed sustained activity for many decades. The reason for such fervent activity is the considerable clinical advantages that can be gained when the delivery system plays a pivotal role in determining where the drug is deposited. When compared to conventional formulations where no such control exists, such as parenteral and oral systems, the sophisticated targeting device can reduce side effects and limit collateral damage to surrounding normal tissue. No more so is this important than in the area of oncology when dose-limiting side effects are often encountered as an ever present difficulty. In this review, the types of colloidal carrier commonly used in targeted drug delivery are discussed, such as gold and polymeric colloids. In particular, the process of attaching targeting capabilities is considered, with reference to antibody technologies used as the targeting motifs. Nanotechnology has brought together a means to carry both a drug and targeting ligand in self-contained constructs and their applications to both clinical therapy and diagnosis are discussed.
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AND logic gate behaviour can be recognized in chemical-responsive luminescence phenomena concerning small molecules. Though initial developments concerned separate and distinguishable chemical species as inputs, consideration of other types of input sets allows substantial expansion of the sub-field. Dissection of these molecular devices into modules, where possible, enables analysis of their logic behaviour according to supramolecular photochemical mechanisms.
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We present a theoretical analysis of a novel scheme for optical cooling of particles that does not in principle require a closed optical transition. A tightly confined laser beam interacting with a trapped particle experiences a phase shift, which upon reflection from a mirror or resonant microstructure produces a time-delayed optical potential for the particle. This leads to a nonconservative force and friction. A quantum model of the system is presented and analyzed in the semiclassical limit.
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A sandwich immunoassay for PSA/ACT complex detection based on gold nanoparticle aggregation using two probes was developed. The functionalized colloidal gold nanoparticles (AuNPs) showed highly stable not only in the presence of high ionic strength but also in a wide pH range. The functionalized AuNPs were tagged with PSA/ACT complex monoclonal antibody and goat PSA polyclonal antibody and served as the probes to induce aggregation of the colloidal particles. As a result, PSA/ACT complex was detected at concentrations as low as 1 ng/ml. This is the first time that a new aggregation sandwich-immunoassay technique using two gold probes has been used, and the results are generally applicable to other LSPR-based immunoassays.
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In this study, the stress-corrosion cracking (SCC) behaviour of laser-welded NiTi wires before and after post-weld heat-treatment (PWHT) was investigated. The samples were subjected to slow strain rate testing (SSRT) under tensile loading in Hanks solution at 37.5 C (or 310.5 K) at a constant anodic potential (200 mVSCE). The current density of the samples during the SSRT was captured by a potentiostat, and used as an indicator to determine the susceptibility to SCC. Fractography was analyzed using scanning-electron microscopy (SEM). The experimental results showed that the laser-welded sample after PWHT was immune to the SCC as evidenced by the stable current density throughout the SSRT. This is attributed to the precipitation of fine and coherent nano-sized Ni4Ti3 precipitates in the welded regions (weld zone, WZ and heat-affected zone, HAZ) after PWHT, resulting in (i) enrichment of TiO2 content in the passive film and (ii) higher resistance against the local plastic deformation in the welded regions.
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O objectivo geral desta tese foi investigar diversas estratgias de sntese de nanocompsitos hbridos de matriz polimrica, contendo nanopartculas inorgnicas com funcionalidades diversas. O interesse nestes nanocompsitos multifuncionais consiste no enorme potencial que apresentam para novas aplicaes tecnolgicas, tais como em optoelectrnica ou em medicina. No captulo introdutrio, apresenta-se uma reviso das propriedades de nanopartculas inorgnicas e nanoestruturas obtidas a partir destas, mtodos de preparao e de modificao qumica superficial, incluindo a formao de nanocompsitos polimricos, bem como a aplicao destas nanoestruturas em medicina e biologia. O estudo das propriedades de nanopartculas de ouro um importante tema em Nanocincia e Nanotecnologia. As propriedades singulares destas NPs apresentam uma estreita relao com o tamanho, morfologia, arranjo espacial e propriedades dielctricas do meio circundante. No captulo 2, reportada a preparao de nanocompsitos utilizando miniemulses de poli-estireno (PS) e poli-acrilato de butilo (PBA) contendo nanopartculas de ouro revestidas com molculas orgnicas. As propriedades pticas destas estruturas hbridas so dominadas por efeitos plasmnicos e dependem de uma forma crtica na morfologia final dos nanocompsitos. Em particular, demonstra-se aqui a possibilidade de ajustar a resposta ptica, na regio do visvel do espectro, atravs do arranjo das nanopartculas na matriz polimrica, e consequentemente o acoplamento plasmnico, utilizando nanopartculas resultantes da mesma sntese. Na generalidade, reportada aqui uma estratgia alternativa para modificar a resposta ptica de nanocompsitos, atravs do controlo da morfologia do compsito final face estratgia mais comum que envolve o controlo das caractersticas morfolgicas das partculas metlicas utilizadas como materiais de partida. No Captulo 3 apresentam-se os resultados da preparao de vrios compsitos polimricos com propriedades magnticas de interesse prtico. Em particular discute-se a sntese e propriedades magnticas de nanopartculas de ligas metlicas de cobalto-platina (CoPt3) e ferro-platina (FePt3), assim como de xidos de ferro (magnetite Fe3O4 e maguemite g-Fe2O3) e respectivos nanocompsitos polimricos. A estratgia aqui descrita constitui uma via interessante de desenvolver materiais nanocompsitos com potencial aplicao em ensaios de anlise de entidades biolgicas in vitro, que pode ser estendido a outros materiais magnticos. Como prova de conceito, demonstrase a bioconjugao de nanocompsitos de CoPt3/PtBA com anticorpos IgG de bovino. No captulo 4 descrita a preparao e propriedades pticas de pontos qunticos (quantum dots, QDs) de CdSe/ZnS assim como dos seus materiais nanocompsitos polimricos, CdSe/ZnS-PBA. Como resultado das suas propriedades pticas singulares, os QDs tm sido extensivamente investigados como materiais inorgnicos para aplicaes em dispositivos pticos. A incorporao de QDs em matrizes polimricas de particular interesse, nomeadamente devido ao comportamento ptico do nanocompsito final parecer estar dependente do tipo de polmero utilizado. As propriedades pticas dos nanocompsitos foram estudadas sistematicamente por medidas de fotoluminescncia. Os nanocompsitos apresentam propriedades interessantes para potenciais aplicaes biolgicas em diagnstico in vitro, funcionando como sondas biolgicas luminescentes.
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Esta tese descreve diversas estratgias preparativas assim como estudos de caracterizao de nanocompsitos e outras nanoestruturas, para a anlise em espectroscopia de Raman com intensificao por superfcie (SERS). Em particular foi estudada a incorporao de nanopartculas (NPs) metlicas de Ag e Au em matrizes polimricas visando avaliar o potencial destes materiais como novos substratos para SERS na deteo de molculas. O primeiro captulo consiste numa reviso bibliogrfica, onde destacado o desenvolvimento de novos substratos para SERS utilizando nomeadamente nanopartculas de Ag, Au e Cu. Numa primeira fase, esta seco apresenta uma breve descrio sobre as propriedades plasmnicas dos metais utilizados e alguns conceitos bsicos de espectroscopia de difuso de Raman. Posteriormente, descreve-se em mais detalhe o efeito de SERS, revendo-se sobretudo a qumica de materiais descrita em trabalhos recentes tendo em conta a sua utilizao como novas plataformas para anlise qumica por SERS. O captulo 2 descreve a sntese e caracterizao de nanocompsitos de poli(acrilato de butilo) obtidos atravs de polimerizao in situ por miniemulso na presena de nanopartculas de Ag. Os nanocompsitos Ag/PtBA foram investigados como novos substratos de SERS visando o desenvolvimento de novas plataformas versteis para deteo molecular. Estudos como o efeito da temperatura, pH e presso foram investigados, visando a compreenso do efeito da matriz polimrica na difuso/adsoro do analito (cido tiossaliclico) na superfcie metlica. No captulo 3, os nanocompsitos de Ag/PtBA descritos anteriormente foram investigados detalhadamente como substratos para bio-deteo em SERS, usando a adenina como analito modelo. Os nanocompsitos foram submetidos a vrios tratamentos pr-analticos para a bio-deteo da adenina. Foram realizadas experincias nos sistemas Ag/PtBA de modo a obter informao sobre o efeito do pH na deteo deste analito em solues aquosas diludas. Os nanocompsitos polimricos obtidos apresentam a vantagem de poderem ser processados utilizando tecnologia disponvel. Pelo que o estudo das suas propriedades trmicas especialmente relevante. Assim, a influncia da incorporao de NPs inorgnicas na temperatura de transio vtrea (Tg) do polmero PtBA foi investigada por meio de calorimetria diferencial de varrimento (DSC) e os resultados so apresentados no captulo 4. Estes estudos descrevem efeitos na Tg do PtBA quando analisado em nanocompsitos obtidos por diferentes mtodos (mtodos ex situ e in situ), contendo nanopartculas metlicas com diferentes distribuies de tamanho e presentes em quantidade varivel na matriz polimrica. Estes estudos possibilitaram relacionar a influncia das NPs metlicas na mobilidade das cadeias polimricas com as propriedades trmicas observadas. O captulo 5 descreve a preparao e caracterizao de materiais compsitos de base polimrica (PtBA) e NPs de Au com morfologia de bastonetes (NRs). Estes materiais foram investigados como substratos para SERS tendo originado um bom sinal de SERS na anlise de 2-2-ditiodipiridina. Investigouse igualmente o efeito da variao da morfologia das NPs metlicas (esferas e bastonetes), a razo de aspecto (R.A.) dos bastonetes e o tipo de matriz polimrica (PtBA e PnBA) no sinal de SERS. No captulo 6 descrita a utilizao da tcnica de SERS como mtodo alternativo para a monitorizao de alteraes morfolgicas de coloides de NRs de Au. Os NRs de Au foram recolhidos em diferentes fases de oxidao promovida pela presena de K2S2O8 e a sua sensibilidade como substratos de SERS foi avaliada utilizando o anio dietilditiocarbamato (DTC) como analito modelo. Os estudos foram realizados utilizando as linhas de excitao a 1064 nm e 633 nm. Este estudo demonstrou que a sensibilidade dos NRs de Au como substratos de SERS diminui medida que a sua R.A. diminui devido competitividade do CTAB (estabilizante) e o DTC pela superfcie dos NRs. de salientar que este processo acompanhado por um diferente comportamento em termos de adsoro dos dois tautmeros do DTC superfcie do metal. O captulo 7 introduz um novo tipo de compsitos para SERS, utilizando matrizes biopolimricas. Assim, descreve-se a preparao e caracterizao de nanocompsitos de carragenano e NPs de Ag. Nesta seco avaliada a utilizao destes materiais como novos substratos para a anlise em SERS, utilizando a 2-2-ditiodipiridina como molcula modelo. Descrevem-se estudos pioneiros que procuram relacionar a dependncia do sinal de SERS com a fora do gel. Para tal, realizou-se um estudo sistemtico aos nanobiocompsitos usados como substratos de SERS em diferentes condies analticas e investigaram-se as suas propriedades reolgicas. No capitulo 8 descrita a investigao de nanocompsitos de Ag/Gelatina como substratos para SERS, utilizando o anio dietilditiocarbamato como analito modelo. Realizaram-se vrias experincias para correlacionar a variao da fora do gel com o aumento do sinal de SERS bem como a diferente adsoro dos dois tautmeros do DTC superfcie do metal. Ao longo desta dissertao so apresentados metodologias distintas para a preparao e obteno de nanocompsitos com base em polmeros (sintticos ou naturais) e NPs metlicas (Ag e Au). Esta investigao no s permitiu a sntese e estudo de novos substratos para SERS mas tambm a compreenso do efeito matriz/NPs metlicas no sinal de SERS e na formao de hot spots. Este trabalho contribui para o enriquecimento na rea da Nanocincia e Nanotecnologia demonstrando a eficcia e reprodutibilidade de nanocompsitos com base em polmeros como novos substratos para SERS. Embora as propriedades ticas apresentadas por estes materiais serem aqui direcionadas para a deteo molecular pela tcnica de SERS, estes materiais podem ser investigados em outras rea tecnolgicas.
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Grce aux nanotechnologies, ltre humain peut matriser la matire lchelle du nanomtre soit au niveau des atomes et des molcules. Les matriaux obtenus suite ces manipulations prsentent des proprits nouvelles qui les rendent trs intressants pour nombre dapplications techniques, et ce dans tous les domaines technoscientifiques. Ainsi, les nanotechnologies sont souvent considres comme les prmisses dune profonde rvolution technologique et sociale. Toutefois, si les nanotechnologies intressent investisseurs, gouvernement, entreprises et universits, elles soulvent aussi des questions thiques, notamment au sujet de leur toxicit, de leurs retombes et de la modification de ltre humain. ces questions sajoutent plusieurs interrogations sur la gouvernance des nanotechnologies : comment, en effet, encadrer en amont le dveloppement de celles-ci pour viter dventuelles consquences nfastes en aval? Parmi ces interrogations, le rle des mdias dans les relations entre les dveloppeurs de nanotechnologies et le public est souvent mentionn. Certains voient dans les mdias un acteur auquel les chercheurs pourraient recourir pour tablir un dialogue avec le public afin dassurer un dveloppement harmonieux des nanotechnologies. Si cette recommandation semble trs pertinente, il nexiste, notre connaissance, aucune tude empirique pour en vrifier la faisabilit auprs des acteurs concerns (chercheurs, mdias, etc.). Dans le cadre de cette thse, nous avons donc voulu examiner et analyser les perceptions des chercheurs et des journalistes qubcois envers des initiatives mdiatiques pour baliser le dveloppement des nanotechnologies. Pour ce faire, nous avons procd une tude qualitative auprs de vingt (20) chercheurs en nanobiotechnologies/nanomdecine et dix (10) journalistes spcialiss en vulgarisation scientifique. Lanalyse des entretiens avec les rpondants a rvl que si les acteurs rencontrs sont favorables envers de telles initiatives, il existe plusieurs contraintes pouvant gner une telle entreprise. Suite lexamen de ces contraintes, nous avons suggr des initiatives concrtes que les chercheurs qubcois pourraient mettre en place pour mieux baliser le dveloppement des nanotechnologies laide dun dialogue avec le public. Ces suggestions consistent notamment crer des mdias privs pour les chercheurs, recourir aux mdias indpendants et investir le web. De telles initiatives, cependant, ne peuvent sobtenir quau prix dun remaniement des priorits des chercheurs.
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The present work is an attempt to understand the characteristics of high energy ball milling on the structural, electrical and magnetic properties of some normal spinets in the ultra fine regime, Magnetism and magnetic materials have been a fascinating subject for the mankind ever since the discovery of lodestone. Since then, man has been applying this principle of magnetism to build devices for various applications. Magnetism can be classified broadly into five categories. They are diamagnetic, paramagnetic, ferromagnetic antiferromagnetic and ferrimagnetic. Of these, ferro and ferri magnetic materials assume great commercial importance due to their unique properties like appropriate magnetic characteristics, high resistivity and low eddy current losses. The emergence of nanoscience and nanotechnology during the last decade had its impact in the field of magnetism and magnetic materials too. Now, it is common knowledge that materials synthesized in the nanoregime exhibit novel and superlative properties with respect to their coarser sized counterparts in the micron regime. These studies reveal that dielectric properties can be varied appreciably by high-energy ball milling in nanosized zinc ferrites produced by coprecipitation method. A semi conducting behaviour was observed in these materials with the Oxygen vacancies acting as the main charge carrier for conduction, which was produced at the time of coprecipitation and milling. Thus through this study, it was possible to successfully investigate the finite size effects on the structural, electrical and magnetic properties of normal spinels in the ultra fine regime
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Over the past few years, a little word with big potential has been rapidly entering into the world's consciousness-'nano'. Nanoscience and technology is a multidisciplinary field, involving the fabrication and understanding of matter at the finest level of a few nanomters.This thesis is about the synthesis and laser induced studies of nanosized ZnO,a versatile material with a wide range of applications.After synthesizing colloids and films of nano ZnO,the samples are studied using different optical methods.Interactions of intense laser beams with nanosized particles are found to open up many interesting scenarios with possible applications in the field of photonics.
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Department of Physics, Cochin University of Science & Technology
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This thesis Entitled INVESTIGATIONS ON THE STRUCTURAL, OPTICAL AND MAGNETIC PROPERTIES OF NANOSTRUCTURED CERIUM OXIDE IN PURE AND DOPED FORMS AND ITS POLYMER NANOCOMPOSITES.Synthesis and processing of nanomatelials and nanostmctures are the essential aspects of nanotechnology. Studies on new physical properties and applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology,crystal structure and chemical composition.Recently, several methods have been developed to prepare pure and doped CeO2 powder, including wet chemical synthesis, thermal hydrolysis, flux method, hydrothermal synthesis, gas condensation method, microwave technique etc. In all these, some special reaction conditions, such as high temperature, high pressure, capping agents, expensive or toxic solvents etc. have been involved.Another hi gh-li ght of the present work is room temperature ferromagnetism in cerium oxdie thin films deposited by spray pyrolysis technique.The observation of self trapped exciton mediated PL in ceria nanocrystals is another important outcome of the present study. STE mediated mechanism has been proposed for CeO2 nanocrystals based on the dependence of PL intensity on the annealing temperature. It would be interesting to extent these investigations to the doped forms of cerium oxide and cerium oxide thin films to get deeper Insight into STE mechanism.Due to time constraints detailed investigations could not be canied out on the preparation and properties of free standing films of polymer/ceria nanocomposites. It has been observed that good quality free standing films of PVDF/ceria, PS/C61l8, PMMA/ceria can be obtained using solution casting technique. These polymer nanocomposite films show high dielectric constant around 20 and offer prospects of applications as gate electrodes in metal-oxide semiconductor devices.
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The development of new materials has been the hall mark of human civilization. The quest for making new devices and new materials has prompted humanity to pursue new methods and techniques that eventually has given birth to modern science and technology. With the advent of nanoscience and nanotechnology, scientists are trying hard to tailor materials by varying their size and shape rather than playing with the composition of the material. This, along with the discovery of new and sophisticated imaging tools, has led to the discovery of several new classes of materials like (3D) Graphite, (2D) graphene, (1D) carbon nanotubes, (0D) fullerenes etc. Magnetic materials are in the forefront of applications and have beencontributing their share to remove obsolescence and bring in new devices based on magnetism and magnetic materials. They find applications in various devices such as electromagnets, read heads, sensors, antennas, lubricants etc. Ferromagnetic as well as ferrimagnetic materials have been in use in the form of various devices. Among the ferromagnetic materials iron, cobalt and nickel occupy an important position while various ferrites finds applications in devices ranging from magnetic cores to sensors.
