Submitted by LAÍS GALVÃO CAETANO null (laisgalvao@iq.unesp.br) on 2017-02-06T13:41:04Z No. of bitstreams: 1 Dissertação Mestrado Laís Galvão Caetano.pdf: 2178003 bytes, checksum: 2239574ffc48afbca6a43b06084d326b (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-02-09T17:06:10Z (GMT) No. of bitstreams: 1 caetano_lg_me_arafo.pdf: 2178003 bytes, checksum: 2239574ffc48afbca6a43b06084d326b (MD5) / Made available in DSpace on 2017-02-09T17:06:10Z (GMT). No. of bitstreams: 1 caetano_lg_me_arafo.pdf: 2178003 bytes, checksum: 2239574ffc48afbca6a43b06084d326b (MD5) Previous issue date: 2016-12-21 / A fibroína da seda extraída dos casulos do bicho-da-sêda é um co-polímero particularmente atraente para aplicações em dispositivos fotônicos e opticoeletrônicos devido a sua transparência óptica, biocompatibilidade e propriedades mecânicas. Esta tese apresenta a obtenção de suspensões e filmes iridescentes-luminescentes de fibroína contendo nanopartículas luminescentes de carbono (“carbon dots”) obtidos a partir de carvão vegetal. As nanopartículas luminescentes de carbono apresentam biocompatibilidade, baixa toxicidade, propriedades de fotoluminescência interessantes e possibilidade de modificação da superfície. Redes de difração foram produzidas nestes filmes utilizando como molde um DVD comercial. Os materiais obtidos foram caracterizados por um conjunto de técnicas de análise: Microscopia de Força Atômica (AFM), Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (MET), Espectroscopia de absorção na região do UVVis, Espectrofotometria de absorção molecular na região do infravermelho com transformada de Fourier (FTIR) e Luminescência. Medidas de luminescência mostram que os carbon dots emitem múltiplas cores entre toda a região do visível. Planos cristalinos foram observados nas imagens de MET das nanopartículas, no qual foram asssociadas a estrutura do grafite. Pela análise de UV-Vis dos carbon dots observou-se que a absorção óptica decai gradualmente à medida em que ocorre deslocamento para o vermelho e para os filmes de fibroína observou-se um ombro referente a transição eletrônica da tirosina (aminoácido de sua composição). A partir dos espectros de FTIR observou-se que não houve mudança na estrutura da fibroína após a adição dos carbon dots. As imagens de AFM e MEV comprovam a presença dos micropadrões periódicos na superfície dos filmes. Os resultados mostraram que os filmes de fibroína contendo carbono dots tem um grande potencial para a biomedicina, principalmente devido os seus parâmetros de luminescência se extenderem em toda a região do visível e por apresentar uma matriz sustentável, com excelentes propriedades ópticas e mecânicas. / Silk fibroin extracted from silkworm cocoons is a particularly attractive copolymer for applications in photonics and optoelectronics devices due its optical transparency, biocompatibility and high mechanical strength. This thesis presents the preparation of suspensions and iridescent-luminescent films of silk fibroin containing luminescent carbon nanoparticles (carbon dots) obtained from vegetal coal. Luminescent carbon nanoparticles present high biocompatibility, low toxicity, interesting photoluminescence properties and possibility of surface modification. Diffraction gratings were produced in these films using a commercial DVD as a template. The materials obtained were characterized by a set of analysis techniques: Atomic-Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-Visible Spectroscopy, Fourier transform infrared spectroscopy (FTIR), and Luminescence. Luminescence measurements show that carbon dots emit light at the entire visible region. Crystalline planes were observed in the TEM images of the nanoparticles, where upon the graphite structure was associated. By analyzing the UV-Vis spectra of the carbon dots it was observed that the optical absorption gradually decreases as the red shift occurs. In the UV-Vis spectra of the silk fibroin films it was observed a shoulder referring to the electronic transition of the tyrosine (amino acid of its composition). From the FTIR spectra it was observed that there was no change in the silk fibroin structure after addition of the carbon dots. The AFM and SEM images confirm the presence of the periodic micro-patterns on the surface of the films. The results showed that the silk fibroin films containing carbon dots have a great potential for biomedicine, mainly due to its luminescence parameters extending throughout the visible region and due to a sustainable platform with excellent optical and mechanical properties.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Nanotechnology is a rapidly expanding field with a multitude of practical uses namely textiles, cosmetics, agriculture, and health sciences. The focus, for the purposes of this thesis, will be on carbon dots. The small size and low surface-to-volume ratio result in different physico-chemical behaviour of these particles in comparison to its significantly larger bulk-produced counterparts.

This study aimed to improve the known microwave method to produce carbon dot nanoparticles from ethylenediamine and citric acid. Carbon dots have recently gained much attention as they have diverse applications, such as bioimaging and drug delivery reagents as cancer theranostics. Research was focused on establishing the ideal time for the synthetic reaction to produce carbon dot nanoparticles with the microwave method. After several trials, the 16-minute trial provided the best results based on Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, fluorescence spectroscopy, and ultraviolet exposure.

Les carbon dots (CDs), dernier membre de la famille des nanoparticules (NPs) carbonées à avoir été découverts, sont des particules hydrophiles quasi-sphériques qui sont généralement présentées comme biocompatibles et seulement faiblement toxiques. Ils sont facilement accessibles par voie de synthèse et peuvent être tout aussi aisément modifiés par modification chimique des groupes fonctionnels présents à leur surface. Leurs propriétés de fluorescence intrinsèques les rendent intéressants pour de nombreuses applications, notamment dans le domaine biomédical où les CDs trouvent des applications en tant que vecteurs de principes actifs, comme d’autres NPs développées dans ce domaine. Les travaux développés au cours de cette thèse visaient premièrement à identifier les propriétés physicochimiques intrinsèques des CDs qui conditionnent leur toxicité. Pour cela, le profil toxicologique d’une large collection de CDs présentant des propriétés de taille, charge et chimie de surface a été établi en utilisant des modèles in vitro et in vivo. Nous avons pu montrer ainsi que, bien que la taille des NPs joue un rôle important dans leur toxicité, elle ne constitue pas à elle seule un facteur prédictif de cette dernière. En effet, la charge et la chimie de surface régissent de façon importante les interactions entre les NPs et l’environnement biologique dans lequel elles sont introduites et, donc, leur toxicité. Le deuxième objectif de cette thèse était d’étudier le potentiel qu’offrent les CDs dans le domaine de la délivrance de gènes. Nous avons pu montrer la supériorité de CDs préparés à partir d’acide citrique et de bPEI600 sur tous les autres CDs cationiques préparés et évalués dans notre étude. Une approche systématique nous a permis d’améliorer, pas à pas, l’efficacité des CDs jusqu’à surpasser celle du bPEI25k, un agent de référence dans le domaine.Dans l’ensemble, nos études ont ouvert de nouvelles perspectives dans le domaine des NPs en apportant des éléments de compréhension des mécanismes de leur toxicité et en identifiant des conditions de production qui permettent d’optimiser leur propriétés en tant qu’agent de transfection. / Carbon dots (CDs) are the latest member of the family of carbon nanoparticles (NPs) to be discovered. They were isolated for the first time in 2004, during electrophoresis purification of carbon nanotubes. In addition to their nanometric size, these objects are almost spherical and hydrophilic, and are generally presented as biocompatible and very weakly toxic NPs. They are fairly easily accessible by synthesis and can be conveniently modified by reaction of the functional groups present on their surface (amines, carboxylic acids, alcohols, etc.). Finally, they exhibit intrinsic fluorescence properties, are relatively resistant to photobleaching, and can be excited by multi-photon irradiation. Thus, like the other members of the family of carbon NPs (graphene, nanodiamonds, fullerenes, nanotubes), CDs have remarkable properties which are the subject of intense research for applications in fields as different as those of electronics, catalysis, energy storage, imaging, and medicine. In the latter area, CDs can find applications as drug delivery systems, like other NPs successfully developed in this field. The work developed during this thesis had two distinct objectives. The first one was to identify the intrinsic physicochemical properties responsible for the toxicity of NPs. For this, the toxicological profile of a large collection of CDs produced in the laboratory and exhibiting various size, charge, and surface chemistry was characterized using in vitro lung models and mice. We found that although the size of the NPs plays an important role it is not, by itself, a predictive element of the toxicity of the NPs. The charge and the surface chemistry largely effect the interactions between the NPs and the biological medium systems and, therefore, their intrinsic toxicity. The second objective of this thesis was to assess the potential of CDs in the field of drug delivery as synthetic gene carriers. We were able to show the superiority of NPs prepared from citric acid and bPEI600 over all other cationic CDs produced in the laboratory. A systematic evaluation has allowed us, step by step, to improve the efficiency of these transfection agents, to exceed that of bPEI25k, a gold standard for in vitro transfection, without significant toxicity. Overall, this work opens up new horizons in NPs research that may provide 1-a better understanding of the toxicological mechanisms of NPs, especially their determinants, and 2-identification of the relationship between the CDs synthesis methods and the efficiency of these NPs as DNA transfection reagents.

Fluorescent carbon dots are a new class of carbon nanomaterials that have emerged recently, and have created a lot of interest as a potential competitor to classical semiconductor quantum dots. Carbon dots possess low toxicity, biocompatibility, easy and low-cost synthesis, and good optical properties. They show huge potential as novel and versatile nanomaterials for a wide range of applications such as bioimaging, drug delivery, chemical sensing, photocatalysis, and as sensitizers for photovoltaic solar cells. The main motivation for this research was the need to produce non-toxic, low-cost nanomaterials with good optical and electrical properties for the use in the fabrication of sustainable, inexpensive nanostructured solar cells with good efficiency. The main aims and objectives of this PhD research were: to synthesize fluorescent carbon dots from biomass-derived precursors by using the hydrothermal synthesis method, to understand and explain structural and optical properties of the as-synthesized carbon dots, and to use the carbon dots as sensitizers for nanostructured solar cells. Carbon dots (CDs) were synthesized using hydrothermal synthesis method from polysaccharides (chitosan and chitin), monosaccharide (D-glucose), amino acids (L-arginine and L-cysteine), and from real food waste in the form of lobster shells. Carbon dots were thoroughly characterized to obtain the information about their structural and optical properties. The as-synthesized carbon dots showed polydispersity and quasi-spherical morphology, with particle sizes ranging from 5-17 nm. Carbon dots showed predominantly amorphous nature, and the functional groups from the starting precursors were successfully incorporated into the as-synthesized carbon dots. Diluted solutions of carbon dots were transparent under daylight and showed blue-green photoluminescence emission under UV excitation. All carbon dots showed excitation-dependent photoluminescence emission which was more pronounced for excitation wavelengths larger than 320 nm. Chitosan CDs, L-cysteine CDs and lobster CDs also showed excitation-independent emission for excitation wavelength in the range of 200 - 320 nm. The highest fluorescence quantum yield of (43.3 ± 2.1) % was calculated for L-arginine CDs. It was concluded that the origin of light emission in carbon dots must be governed by the interplay between the absorption due to the carbon cores and the surface functional groups. Considering the application of the as-synthesized carbon dots, two types of solar cells were fabricated. Carbon dots were used as sensitizers for ZnO-nanorod-based and for TiO2-based nanostructured solar cells. Three types of carbon dots (chitosan CDs, chitin CDs and D-glucose CDs) were used as sensitizers for ZnO-nanorod-based solar cells. ZnO nanorods were successfully coated with carbon dots, and the chitosan-CDs-sensitized solar cells showed the efficiency of 0.061 %. When using layer-by-layer coating method, solar cells with combination of chitosan- and chitin-CDs as sensitizers showed the efficiency of 0.077 %. All six types of carbon dots (chitosan CDs, chitin CDs, D-glucose CDs, L-arginine CDs, L-cysteine CDs, and lobster CDs) were used as sensitizers for TiO2-based nanostructured solar cells. TiO2-based solar cells sensitized with carbon dots showed much higher efficiency compared to the ZnO-nanorod-based solar cells. L-arginine-CDs sensitized TiO2-based solar cells showed the highest efficiency of (0.362 ± 0.007) %, which was the best efficiency of all fabricated solar cells. By surveying a range of biomass-derived carbon dots, and demonstrating a clear link between functionalisation and solar cell performance, this PhD research project provides a guide to direct future development of low-cost, biomass-derived sensitizers for nanostructured solar cells.

The use of non-invasive methods to visualise and monitor processes inside living organisms is vital in the understanding and diagnosis of disease. The work in this thesis details the synthesis and applications of a new imaging modality; carbon dots, whose inherent fluorescence and non-toxic nature makes them attractive alternatives to more traditional ‘quantum dots’. In this thesis, different methods of carbon dot synthesis were attempted in order to produce carbon dots of the desired size and morphology. Nitrogen-containing carbon dots generated from 1,4-addition polymers provided the most successful route with optical and structural characteristics studied by TEM, UV-Vis and fluorescence spectroscopy and XPS. The biological behaviour of the carbon dots produced by this method were also evaluated. The ability of these carbon dots to up-convert when excited at long excitation wavelengths was studied. A number of biologically relevant applications of the carbon dots were studied. Using amine-functionalised carbon dots, cell targeting cargoes were conjugated and the effects of the carbon dot-cargo conjugates on cell lines were studied.

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2017-09-21T19:51:20Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tarciane_silva_pinto.pdf: 4051834 bytes, checksum: d6525c9152e47311a8695bf3eed5c6e6 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-10-09T13:37:54Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tarciane_silva_pinto.pdf: 4051834 bytes, checksum: d6525c9152e47311a8695bf3eed5c6e6 (MD5) / Made available in DSpace on 2017-10-09T13:37:54Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tarciane_silva_pinto.pdf: 4051834 bytes, checksum: d6525c9152e47311a8695bf3eed5c6e6 (MD5) Previous issue date: 2017 / Neste trabalho, Carbon Dots (CDs) obtidos a partir de celulose de algod?o e contendo 4,5 mmol.g-1 de grupos funcionais ?cidos, dos quais 63 % exibiam pKas t?picos de ?cidos carbox?licos foram usados na prepara??o de filmes automontados com os biopol?meros quitosana (QT) e col?geno (CL) a fim de verificar a morfologia, espessura e intera??es moleculares entre os componentes. A quitosana usada apresentou um total de 4,2 mmolg-1 de grupos funcionais -NH2, correspondente a um grau de desacetila??o de ~70 %. Por outro lado, o col?geno hidrolisado apresentou diferentes grupos funcionais com acidez de Br?nsted, t?picos da presen?a de diferentes amino?cidos na estrutura. Todos os filmes finos foram preparados com a t?cnica de deposi??o camada por camada (do ingl?s: Layer-by-layer (LbL)) por meio de imers?o do substrato nas diferentes solu??es. Os materiais foram caracterizados por diferentes t?cnicas, incluindo Microscopia de For?a At?mica, Espectroscopia na regi?o do UV-Vis, Espectroscopia de Resson?ncia de Plasma de Superf?cie e Titula??o Calorim?trica. Em todas as condi??es experimentais utilizadas para o crescimento dos filmes, observou-se um crescimento linear da quantidade de material depositado com o n?mero de imers?es realizadas. No entanto, diferentes condi??es das solu??es dos biopol?meros e da suspens?o de Carbon Dots produziram filmes com espessura e morfologia diferentes. Nos filmes de QT/CDs a quantidade de nanopart?culas depositadas por bicamada, com solu??o de quitosana em pH = 3,5, pH = 5 e pH = 3,5 na presen?a de 0,1 mol/L de NaCl, foram, respectivamente, 11 mg.m-2, 16 mg.m-2 e 24 mg.m-2 sendo as espessuras dos filmes, com 20 bicamadas, correspondentes a estas quantidades foram de 60, 150 e 200 nm. Este resultado ? atribu?do ao aumento da flexibilidade das cadeias polim?ricas dos biopol?meros, as quais est?o menos carregadas. Dessa forma, as cadeias podem apresentar conforma??es mais adequadas para recobrir eficientemente a estrutura das nanopart?culas quase esf?ricas. Al?m disso, o aumento da for?a i?nica da solu??o de Carbon Dots tamb?m contribui para o aumento de material depositado devido ? forma??o de aglomerados sob estas condi??es. Nos filmes de CL/CDs, a quantidade de nanopart?culas depositadas, com solu??o de col?geno em pH = 3,16, pH = 5 e pH = 3,16 na presen?a de 0,1 mol/L de NaCl, foram 2,3 mg.m-2, 6,46 mg.m-2 e 6,41 mg.m-2, respectivamente. No entanto, a energia de intera??o, obtida por calorimetria isot?rmica, ? maior em pH baixo. Em geral, a quantidade de material depositado nos filmes de col?geno ? bem inferior ?s observadas para os filmes de QT/CDs e, consequentemente, filmes com espessuras entre 40 e 50 nm. Al?m disso, n?o foi observada varia??o significativa entre as massas depositadas nestes filmes com o aumento do pH e for?a i?nica. Estes resultados podem estar relacionados ? menor ?carga parcial positiva? sobre as cadeias da prote?na em rela??o a quitosana, observada pelos potenciais zeta nestas condi??es. Por fim, os resultados aqui apresentados sugerem que as estruturas dos filmes, isto ?, morfologia e espessura, podem ser facilmente controladas e reproduzidas manipulando-se as condi??es das solu??es dos biopol?meros, al?m do tradicional n?mero de imers?es. Em adi??o, o estudo pode contribuir para o desenvolvimento de uma nova classe de dispositivos de alto desempenho, como sensores e superf?cies fotoativas. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / In the present work, Carbon Dots (CDs), obtained from cotton cellulose and containing 4.5 mmol g-1 of acid functional groups, of which 63% exhibited typical pKa?s compared to carboxylic acids, were used in the preparation of self-assembled films with the biopolymers Chitosan (QT) and Collagen (CL) in order to verify the morphology, thickness and molecular interactions among the components. The chitosan used in this work had a total of 4.2 mmol g-1 of functional groups ?NH2, corresponding to a deacetylation degree of ~70%. On the other hand, the hydrolyzed collagen showed different functional groups with Br?nsted acidity typical to the presence of different amino acids in the structure. All the thin films were prepared using the Layer-by-layer method (LbL) by immersing the substrate in different solutions. The materials were characterized by several techniques, such as Atomic Force Microscopy, UV-Vis Spectroscopy, Surface Plasmon Resonance and Calorimetric Titration. It was observed, in all experimental conditions for the growth of the films, a linear increase in the amount of deposited material with the number of immersions performed. However, different conditions of the biopolymer solutions produced films with different thickness and morphology. In the films QT/CDs the amount of nanoparticles deposited per bilayer, with the chitosan solution at pH = 3.5, pH = 5 and pH = 3.5 with the presence of 0.1 mol L-1 of NaCl, were, respectively, 11 mg m-2, 16 mg m-2 and 24 mg m-2 with the thickness of the film, at 20 bilayers, at 60, 150 and 200 nm. This result is associated to the increase in the flexibility of the polymeric chains of the biopolymers, which are less charged. Thus, the chains can present conformations that are proper to cover more efficiently the structure of the almost spherical nanoparticles. Furthermore, the increase of the ionic strength of the Carbon Dots solution also contributes to the increase of the material deposited due to the formation of agglomerates in these conditions. In the films CL/CDs, the amount of nanoparticles deposited, with the collagen solution at pH = 3.16, pH = 5 and pH3.16 in the presence of 0.1 mol L-1 of NaCl, were 2.3 mg m-2, 6.46 mg m-2 and 6.41 mg m-2, respectively. However, the interaction energy, obtained by isothermal calorimetry, is higher in low pH. In general, the amount of material deposited on the collagen films is much lower than that observed for the QT/CDs films and, consequently, films thickness are 40 and 50 nm. Besides that, it was not observed any significant variation between the masses deposited in these films with the increase of the pH and the ionic strength. These results may be associated to the lower ?partial positive charge? on the protein chains in relation to the chitosan, observed by the zeta potentials in these conditions. The presented results suggest that the structures of the films, i.e. morphology and thickness, can be easily controlled and reproduced manipulating the conditions of the biopolymer solutions and the number of immersions. Additionally, the study may contribute to the development of a new class of high performance devices, such as sensors and photoactive surfaces.

Carbonaceous materials, especially in micro and nanoscale, are useful in optical, energy storage, electronic, and biomedical devices or technologies. Techniques have been developed for preparation and modification of the carbonaceous materials, while it is still challenging to tailor the properties of carbonaceous materials effectively and economically. Laser is a powerful tool in academic and industrial laboratories, which also plays important roles in the preparation and modification of high-performance carbonaceous nanomaterials. In this study low-cost hydrothermal synthesis, high-temperature annealing, and Laser ablation (LAL) methods are developed to prepare functionalized carbon nanomaterials and modify their electrochemical and optical properties. Sub-micro hollow carbon spheres are synthesized via hydrothermal carbonization and high-temperature activation without any templates. Good capacitive properties are obtained after activation. The electrochemical properties of the activated carbon spheres depend on the media of the activation. The capacitance of the activated carbon spheres significantly increases with the addition of water as an activation agent. Carbon dots (CDs) are synthesized via a facile and economic hydrothermal (HTC) process using both small-molecule sugar (Xylose) and ground soybean residuals as precursors. The photoluminescence (PL) properties of the as-prepared and further-treated CDs are systematically studied. For the xylose-synthesized CDs, the initial green PL emission disappears after high-temperature treatment at 850 ℃ for 2 h. With further LAL treatment in NH4OH solutions, the PL emission is re-acquired, and a blue shift in emission is observed. Thus, the LAL is found to be an effective method to modify the CDs and their PL properties. For the nitrogen-doped soybean waste-derived carbon particles, they show strong blue emissions, which essentially disappear after 850 ℃ annealing for 2 hours in an argon flow. Then, PL appears again after laser ablation in a 10% NH4OH solution. The conversion from the blue emission to no emission and then back to blue emission again implies the effect of the functional groups on the PL properties of the CDs.

>Magister Scientiae - MSc / The interest in carbon-based nanomaterials, such as carbon-nanodots and graphene, has grown exponentially because these materials have unique properties and applications in the medical, electronic, clean energy and several other fields for biochemical sensing, energy conversion, photocatalysis, optoelectronics, etc. Carbon dots were discovered in 2004, yet very little research has been done on the colloidal stability thereof. Nanomaterials such as carbon dots will inescapably make their way to natural waters with an unknown environmental fate. Therefore, it is of great importance to understand the behaviour of carbon dots under the influence of certain environmental conditions such as pH, ionic strength, and in the presence of natural organic matter. / 2022

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