Dissertations / Theses on the topic 'Silver-titanium nanoparticles'

Titanium dioxide nanoparticles combined with silver and hydroxyapatite (TiO₂-Ag-Hap) form a photocatalytic composite capable of oxidizing and mineralizing a wide spectrum of microbiological and chemical contaminants in water, while silver nanoparticles have long been employed for their antimicrobial properties. These materials were evaluated through an iterative series of experiments that evaluated microbial reduction, material formulation, method of application, surface-interface interactions, and reusability. The TiO₂ formulation was assessed as an antimicrobial film coated onto fabric and ceramic beads in three experimental designs: a gravity filtration column, a portable treatment capsule, and a static chamber. Colloidal floating Ag nanoparticles in solution were also assessed. Reduction of Escherichia coli, Klebsiella terrigena, MS2 bacteriophage, and Rotavirus was evaluated though standard culture-based methods. Significant microbial reduction was only observed in the static open pan design for the TiO₂-Ag-HAp materials. Colloidal silver was more effective and caused a 5 log reduction of K. terrigena, within 60 minutes, and a 5 and 4 log reduction of MS2 within 120 and 90 minutes respectively in initial trials. The anti-microbial properties of both materials were apparent, but further investigations are necessary to assess the potential of the materials for integration and development in water treatment technologies.

>Magister Scientiae - MSc
The global lack of clean water for human sanitation and other purposes has become an emerging dilemma for human beings. The presence of organic pollutants in wastewater produced by textile industries, leather manufacturing and chemical industries is an alarming matter for a safe environment and human health. For the last decades, conventional methods have been applied for the purification of water but due to industrialization these methods fall short. Advanced oxidation processes and their reliable application in degradation of many contaminants have been reported as a potential method to reduce and/or alleviate this problem. Lately, it has been assumed that incorporation of some metal nanoparticles such as magnetite nanoparticles as photocatalyst for Fenton reaction could improve the degradation efficiency of contaminants. Core/shell nanoparticles, are extensively studied because of their wide applications in the biomedical, drug delivery, electronics fields and water treatment. The current study is centred on the synthesis of silver-doped Fe₃O₄/SiO₂/TiO₂ photocatalyst. Magnetically separable Fe₃O₄/SiO₂/TiO₂ composite with core–shell structure were synthesized by the deposition of uniform anatase TiO₂ NPs on Fe₃O₄/SiO₂ by using titanium butoxide (TBOT) as titanium source. Then, the silver is doped on TiO₂ layer by hydrothermal method. Integration of magnetic nanoparticles was suggested to avoid the post separation difficulties associated with the powder form of the TiO₂ catalyst, increase of the surface area and adsorption properties. Lastly and most importantly magnetic nanoparticles upsurge the production of hydroxyl groups or reduced charge recombination. The a synthesized catalysts were characterized using Transmission Electron Microscopy, X-ray Diffraction; Infra-red Spectroscopy, Scanning Electron Microscope and Energy Dispersive Spectroscopy. Other characterization techniques includeVibrating Sample Magnetometry, Brunauer Emmett Teller analysis and Thermogravimetric analysis. The average size of the particles size is 72 nm. Furthermore the photocatalytic performances of the magnetic catalysts were assessed in comparison with that commercial titanium dioxide for the degradation of methylene blue using photochemical reactor under ultra violet light. The results showed that the photocatalytic activity was enhanced using Fe₃O₄/SiO₂/TiO₂ and Ag-Fe₃O₄/SiO₂/TiO₂ compared with that for Fe₃O₄, commercial titanium dioxide powder.

The extensive use of nanoparticles (NPs) has started receiving increased attention because of the knowledge gaps regarding their fate in the environment and the possible impact on the environment and human health. The production of silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2-NPs) is increasing and it is expected that, due to their great number of applications, their concentration in waste streams will increase in the future. The presence of NPs in waste streams may affect the treatment process (e.g., composting) and, if they are not successfully removed from the waste streams, their presence in the treated waste (e.g., compost) may present an environmental risk. Composting of the biodegradable fractions of municipal solid waste (MSW) is a widely used waste management practice, mainly because it is a cost-effective treatment technology and the final product (i.e., compost) presents several benefits to the environment, particularly as a soil conditioner. The overall aim of this thesis is to assess the effect of Ag-TiO2NPs and AgNPs that may be present in the biodegradable fractions of municipal solid waste on composting and subsequent soil application of compost. For that purpose in-vessel composting of artificial municipal solid waste contaminated with commercial nanoparticles was investigated at laboratory scale, simulating a range of relevant concentration levels. Subsequently, the fate of NPs present in mature compost use as a top-layer soil conditioner was investigated using a column approach at laboratory scale. The toxicity effect of NPs present mature compost on plant growth was further investigated. The impact of NPs during composting was assessed by monitoring the temporal dynamics of organic matter (OM) using Excitation Emission Matrix (EEM) fluorescence spectroscopy. The fate of NPs following application of contaminated mature compost as a top-soil conditioner and potential release to groundwater was investigated using a column leaching experiment while the phytotoxicity of mature compost contaminated with NPs was assessed using a seed germination bioassay. Finally, to investigate further possible environmental impacts due to the application of mature compost contaminated with NPs to soils, a Life Cycle Assessment (LCA) was conducted. The impact of commercial Ag-TiO2 NPs and AgNPs on the in-vessel composting of biodegradable municipal solid waste was investigated over 21 days, using initial concentrations of 0, 5, 10, 20 and 50 mg Ag / kg of OM. Microbial activity was inhibited in the biodegradable waste reactors using 2% NaN3 to evaluate abiotic losses. Physicochemical parameters such as pH, ash content, weight loss, and the formation of humic substances (HS) were determined after 0, 4, 7, 14 and 21 days of composting and after a maturation phase. The results indicated that the presence of 2% NaN3 in biodegradable MSW inhibited effectively the microbial activity during the first week of composting. The microbial population was activated during the second week of composting but the decomposition rate was so low that did not result in the formation of humic substances (HS) following 21 days of composting when 2% NaN3 was used. Both treatments, using Ag-TiO2-NPs and AgNPs, did not show any inhibition of the decomposition process for all the tested concentrations and EEM peaks shifted towards the HS region during in-vessel composting. Higher inorganic carbon removal resulted from NP-contaminated compost with higher NP concentrations. This may indicate that the formation of humins was higher for non-contaminated compost and decreased as the NP concentration in waste increased. The shift of the peaks towards the HS region during composting for all the treatments suggested that NPs did not have an effect on humification and therefore on compost stability. The leaching properties of the NP-contaminated compost were investigated using a column leaching test. Five samples of leachate, of 50 mL each, were collected. The highest concentrations of HS were observed in the first two leaching samples. The leaching results suggested that only a low percentage of the total NPs (in weight) in compost, up to ca. 5% for Ag and up to ca. 15% for Ti, leached out from the columns, which was assumed the amount that potentially could leach to the environment. These results suggested that NPs will mainly accumulate in soils’ top layers following application of compost contaminated with NP. The phytotoxicity of NP-contaminated compost was assessed using a seed germination bioassay and the germination index was then calculated. The results indicated that the NP-contaminated compost did not present any toxic effects to cress germination. The possible environmental impacts due to the NP-contaminated compost application to soils were investigated by conducting a comparative LCA study. The LCA study indicated that the effects of NP-contaminated compost to human health and ecosystems endpoint categories increased due to the presence of NPs. The risks are associated with terrestrial ecotoxicity and human toxicity midpoint categories and are mainly attributed to the accumulation of Ag to soils.

>Magister Scientiae - MSc
Despite the wide success of antimicrobial agents against waterborne pathogens, waterborne disease continues to pose a threat to both mankind and animals. A major concern is that certain bacteria have developed resistance to antimicrobial agents, as a result of their overuse. Silver (Ag) nanoparticles are widely used for antibacterial purposes such as medical dressings. However, they are highly toxic to human cells. Hence, there is a great interest in developing next generation antibacterial nanoparticles that are as effective as Ag nanoparticles for antibacterial functions, while having less toxicity to human cells. Several methods can be used to generate these antimicrobial nanoparticles, one of which is green nanotechnology. Green nanotechnology uses natural plants such as tea to synthesise nanoparticles rather than chemicals, thus reduce human and animal harm and improve sustainability of antibacterial agents. Silver-titanium nano-composites (Ag-TiO2 NCs) were synthesised with the hydrothermal method using a tea extract from Aspalathus linearis (Rooibos, RB), and distilled water in the presence of nitrogen. The resulting structures were characterised with high resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS) analysis X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). The antibacterial characteristics of these new NCs were evaluated against 3 bacteria: Bacillus cereus, Cupriavidus metallidurans, and Escherichia coli. The optimum processing conditions to produce 6-nm spherical NPs included maintaining the temperature at 90 °C, the pH at 4.35, and using RB extract at a concentration of 2 mg/mL. The size of silver NPs was reduced in acidic conditions, agglomerated in neutral conditions, and highly reduced in alkaline conditions. Increasing the pH decreased the particle size and narrowed the particle size distribution. Gram-positive B. cereus showed slight resistance or tolerance to the Ag-TiO2 nanocomposite compared to the gram-negative bacteria E. coli and C. metallidurans. The treatment concentration required for total inhibition of E. coli and C. metallidurans growth was 100 mg/mL. Supported silver nanoparticles has shown to be a suitable way to obtain highly dispersed silver over higher surface area. This approach allowed Ag-TiO2 nanocomposite to be an efficient bactericide, with less silver amount employed.

Microbial resistance to the current available antibiotics is considered a global health problem, especially for the Multi-Drug Resistant pathogens (MDR) including methicillin resistant Staphylococcus aureus. Recently nanoparticles (NPs) have been involved in variety of antimicrobial applications due to their unique properties of antibacterial effects. However, the molecular mechanisms behind their antibacterial activity are still not fully understood. In this study, we produced silver Ag NPs (average size 27 nm) and silver-Titanium Ag-TiO2 NPs (average size 47 nm) using picosecond laser ablation. Our results showed that both laser NPs had obvious size-dependent antibacterial activity. The laser Ag NPs with a size of 19 nm and Ag-TiO2 NPs with a size 20 nm presented the highest bactericidal effect. The laser generated Ag and Ag-TiO2 NPs with concentrations 20, 30, 40, and 50 Î1⁄4g/ml showed strong antibacterial effect against three bacterial strains: E. coli, P. aeruginosa, and S. aureus, and induced the generation of reactive oxygen species (ROS), lead to cell membrane interruption, lipid peroxidation, DNA damages, glutathione depletion and the eventual cell death. Both types of laser NPs at two concentrations (2.5 and 20 Î1⁄4g/ml) showed low cytotoxicity to the in vitro cultured five types of human cells originated from the lung (A549), kidney (HEK293), Liver (HepG2), skin (HDFc) and blood vessel cells (hCAECs). The antibacterial activity of the laser generated Ag and Ag-TiO2 NPs had lasted for over one year depending on the degree of air exposure and storage conditions. Frequent air exposure increased particle oxidation and reduced the antibacterial durability of the laser generated Ag NPs. The laser generated Ag NPs had lower antibacterial activity when stored in cold compared to that stored at room temperature. The antibacterial activity of laser generated Ag and Ag-TiO2 NPs were also compared with four types of commercial based-silver wound dressings (Acticoat TM, Aquacel® Ag, Contreet ®Foam, and Urgotul® SSD) against E. coli to inform future application in this area. In conclusion, laser generated Ag and Ag-TiO2 NPs have strong bactericidal effect and low toxicity to human cells which could be a type of promising antibacterial agents for future hygiene and medical applications.

Orientador: Wilson de Figueiredo Jardim
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-19T04:25:34Z (GMT). No. of bitstreams: 1 Marcone_GlaucienePauladeSouza_D.pdf: 3873346 bytes, checksum: 7b3d84f078c155427661a732b0d8a73b (MD5) Previous issue date: 2011
Resumo: O principal objetivo deste trabalho foi estudar as interações de nanopartículas de Ag ou nanoprata (nAg ou AgNP) e nanopartículas do semicondutor TiO2 (nTiO2) com a matriz aquática, a fim de avaliar a sua toxicidade a representantes da biota aquática. Estes dois tipos de nanomateriais (NM) foram escolhidos, pois atualmente estão sendo comercializados em grande escala por apresentarem ampla aplicação industrial. Este trabalho envolveu as seguintes etapas: a) síntese de TiO2 na forma de pó e de amostras de AgNP por rotas sintéticas estabelecidas pela literatura; b) caracterização dos NM sintetizados quanto ao tamanho e a morfologia, e no caso das suspensões de AgNP foi realizada a especiação da prata a fim de nortear uma avaliação mais criteriosa sobre ecotoxicidade destas suspensões; c) avaliação da atividade bactericida das amostras de AgNP e do TiO2 sintetizados. Para isto, utilizou-se a bactéria E. coli e um sistema FIA/Condutimétrico para medir a inibição bacteriana através da produção de CO2. d) avaliação da ecotoxicidade das suspensões de AgNP e TiO2 no meio aquático. Foram utilizados os organismos aquáticos: V. fischeri (bactéria marinha), D. similis (microscrustáceo de água doce) e P. subcapitata (alga de água doce). Devido à fotoatividade do TiO2, os testes com D. similis foram adaptados, incorporando a radiação UV-A durante o teste. As amostras de AgNP foram tóxicas aos organismos aquáticos testados nas seguintes faixas de concentração: P. subcapitata (IC50 = 1-122 mg L), D. similis (CE50 = 0,5-50 mg L) e V. fischeri (CE50 = 5,2-32,2 mg L). As amostras de TiO2 se mostraram mais tóxicas para a D. similis (CE50 = 8-57 mg L) em relação ao V. fischeri (CE50 > 100 mg L). A caracterização das amostras de TiO2 e AgNP sintetizadas indicou que fatores como fotoatividade do TiO2 e a concentração de íons Ag nas suspensões de AgNP foram determinantes para a ecotoxicidade apresentada por estas amostras
Abstract: The objective of this work was to evaluate the toxicity of silver nanoparticles or nanosilver (nAg or AgNP) and TiO2 semiconductor nanoparticles to some biotic representative aquatic organisms. These two nanomaterials (NM) types were chosen because they are currently being market on a large scale due to their wide industrial application. The work was developed in accordance to the following steps: a) Synthesis of TiO2 powder and AgNP samples by current synthetic routes. b) Shape, morphology and optical characterization of TiO2 powder and AgNP synthesized samples. The Ag speciation was performed in the AgNP suspensions to improve the ecotoxicological assessment of this material; c) Bactericidal activity assessment of TiO2 and AgNP samples using E. coli. The inhibition of the bacterial growth was followed by CO2 produced using a FIA/Conductivity system; d) Ecotoxicity assessment of TiO2 and AgNP suspensions to aquatic organisms. The aquatic organisms used were V. fischeri (marine bacterium), D. similis (microcrustace freshwater) and P. subcapitata (algae freshwater). Due to the TiO2 photoactivity, the tests with D. similis were adapted by include to UV-A radiation during the whole test period. The results showed that AgNP samples were toxic to aquatic organisms in the following ranges: P. subcapitata (CI50 = 1-122 mg L), D. similis (EC50 = 0.5-50 mg L) and V. fischeri (EC50 = 5.2-32.2 mg L). The TiO2 samples were more toxic to the D. similis (EC50 = 8-57mg L) compared to V. fischeri (CE50 > 100 mg L). The characterization of TiO2 and AgNP synthesized samples indicated that factors such as TiO2 photoactivity and Ag ions concentration in AgNP suspensions were responsible to the ecotoxicity showed by this samples
Doutorado
Quimica Analitica
Doutor em Ciências

Orientador: Márcia Regina de Moura Aouada
Resumo: Os curativos são agentes que, aplicados sobre uma lesão externa, auxiliam na cicatrização e cura; geralmente são de materiais leves, ordinariamente de algodão. A ideia de um curativo inteligente é fornecer um material leve, biocompátivel, biodegradável e anatômico que irá se adaptar perfeitamente para promover a cura de diferentes tipos de lesões. O objetivo deste trabalho foi melhorar as propriedades mecânicas e de barreiras em filmes de alginato de sódio. Desta forma, nanopartículas de prata com tamanho médio de 90 nm foram obtidas através de síntese química pela redução de nitrato de prata por borohidreto de sódio, e nanodispersão de dióxido de titânio obtida em equipamento de ultrassom. As nanopartículas foram inseridas na matriz de alginato juntamente com solução de sorbitol a 65%, e os filmes foram obtidos através do processo “Casting”. Posteriormente, o material foi caracterizado e os resultados das propriedades mecânicas de tensão por deformação revelaram que a presença de nanoemulsão de titânio (TiNE) e nanopartículas de prata (AgNP) na matriz de alginato aumentou a resistência à tração em aproximadamente 6,4 e 14,3%, respectivamente. Já nos filmes que tinham sorbitol, foi reduzida em 55,5%. Em contrapartida, a deformação foi aumentada em cerca de 1 a 3%. A estabilidade térmica dos filmes também sofreu um aumento (comprovada pelas técnicas de DSC e TG). Estes efeitos no aumento do elongamento e estabilidade térmica podem estar associados à formação de uma estrutura s... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Dressings are agents that, applied on an external lesion, aid and healing; Usually they are of light materials, ordinarily of cotton. The idea of an intelligent dressing is to provide a light, biocompatible, biodegradable and anatomical material that will fit perfectly to promote healing of different types of lesions. The objective of this work was to improve the mechanical and barrier properties of sodium alginate films. In this way, silver nanoparticles (AgNP) with a mean size of 75-96 nm were obtained through chemical synthesis by reduction of silver nitrate by sodium borohydride, and titanium dioxide nanoemulsion (TiNE) by dispersion in ultrasonic equipment. Through the casting process, the nanoparticles were inserted into the alginate matrix together with 65% sorbitol solution. Subsequently, the material was characterized and the results of the tensile tests revealed that the presence of TiNE and AgNP in the alginate matrix increased the tensile strength by approximately 6.4 and 14.3% respectively. In the films that had sorbitol, it was reduced by 55.5%. In contrast, the elongation rate was increased about 1 to 3%. The thermal stability of the films also increased (as evidenced by DSC and TG techniques). These effects on increasing elongation and thermal stability may be associated with the formation of a spider-like structure with more compact regions around metal NPs and regions with polymer chain spreading with predominance of M monomers due to the eletrostatic repuls... (Complete abstract click electronic access below)
Mestre

Orientador: Alessandra Nara de Souza Rastelli
Resumo: O presente estudo teve como objetivo a avaliação do efeito antibacteriano de sistemas adesivos modificados com nanopartículas (NPs) de dióxido de titânio (TiO2) decoradas ou não por prata (Ag) em diferentes concentrações, assim como o grau de conversão e a resistência de união à dentina sendo avaliada imediatamente e após três meses em saliva artificial. Os sistemas adesivos AdperTM Scotch Bond Multi Purpose e AdperTM Single Bond (3M Espe), e Clearfil SE Bond (Kuraray) foram modificados com concentrações 0 (controle); 1; 2 e 5% de NPs de TiO2 (com e sem Ag). Foram confeccionados espécimes cilíndricos em resina composta (FiltekTM Z250XT, 3M Espe) na cor A2 com matrizes metálicas (4x2mm), nos quais foram aplicados os sistemas adesivos modificados ou não, de acordo com as instruções dos fabricantes, para o teste de atividade antibacteriana por contato direto. Os espécimes foram colocados em placa de 24 poços e incubados por 18 horas a 37ºC em atmosfera de microaerofilia juntamente com 100μL de suspensão bacteriana padronizada contendo Streptococcus mutans e 900μL de BHI caldo + sacarose (1%). Para a contagem de unidades formadoras de colônias (UFC/mL), foram realizadas diluições seriadas com as soluções resultantes e 50μL dessas diluições foram plaqueadas em placas de petri contendo BHI ágar, sendo incubadas a 37ºC em 10% de CO2 por 48 horas. O grau de conversão foi avaliado por espectroscopia infravermelho por transformada de Fourier (FT-IR) para todos os adesivos modific... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The present study evaluated the antibacterial effect, the degree of conversion and the micro-shear bond strength (immediate and after three months of water storage) of modified dental adhesive systems with TiO2 or Ag/TiO2 nanoparticles at different concentrations. The adhesive systems AdperTM Single Bond (SB), AdperTMScotchTM Bond Multi Purpose (3M Espe) (SBM) and Clearfil SE Bond (Kuraray) (CB) were modified with 1.0, 2.0 and 5.0 wt% of NPs. For the direct-contact test, sterilized specimens (n=36) were made using a metallic matrix (4x2mm) with the composite resin FiltekTMZ250 XT (3M Espe), on which the dental adhesive systems were applied according to the manufacturer's instructions. Both materials were photo-activated using a LED light-curing unit (LED Radii Plus, SDI). The specimens were placed in a 24-well plate with 100μL of Streptoccocus mutans standardized suspension on their surfaces, 900μL of BHI broth and incubated for 18 hours at 37ºC under an atmosphere containing 5% CO2. A six-fold serial dilution was performed with the resultant solutions. Fifty microliters (50μL) from each dilution was retrieved and spread on brain-heart infusion agar plates and incubated at 37°C under an atmosphere containing 5% of CO2 for 48h and the colony forming units (CFU's) were registered. For the evaluation of the DC, the specimens were made by the modification of the dental adhesive systems with all concentrations of nanoparticles and stored for 24hs at 37ºC in an incubator. The FTIR analysis was conducted using an attenuated total reflectance unit (ATR) at a 4cm-1 resolution and 64 scans. For the micro-shear bond strength test, One hundred and twenty six standardized dentin specimens were made from bovine incisors and divided into twenty-one groups. The control and modified adhesive systems were applied on the surfaces ...(Complete abstract electronic access below)
Mestre

Doutoramento em Biologia
Over 11 million tons of nanomaterials (NMs) have been produced in 2012 and predictions point the increase in production. Despite predictions and extended usage via consumer products and industry, the understanding of the potential impact of these materials on the environment is virtually absent. The main aim of this thesis is to understand how a selected group of nanomaterials (metal based particles) may impact soil invertebrates, with special focus on the mechanisms of response. Since a case-by-case Environmental Risk Assessment (ERA) of all the emerging contaminants (particularly NMs) is impossible, among others due to time and cost reasons, to gain understanding on the mechanism of action and response is very important to reach a common paradigm. Understanding the modes of action provides predictive characters in cross particle extrapolation. Besides, it also provides insight for the production of new and sustainable materials. Overall, the effects of the selected NMs (Copper and Silver, Titanium and Zirconium oxides) and the respective salt forms, were investigated at the gene expression (using high-throughput tools, microarray and qPCR technology), biochemical (using enzymatic assays for analysis of oxidative stress markers) and organism (survival and reproduction as in OECD test guidelines) levels, this using standard soil species (Enchytraeus albidus, Enchytraeus crypticus, Eisenia fetida). Gene expression analysis provided valuable information on the mechanisms affected by each of the NMs. The gene expression profile highlighted a (nano)material signature and the effect of the duration of exposure. The functional analyses integrated with the biochemical and organism data, revealed a good understanding power. The biochemical parameters (oxidative stress related) were distinct across the materials and also influenced by duration of exposure and concentration. The standardized organismal responses differed the least between the various materials. The overall outcome is that, in this context of NMs effect assessment, gene expression and enzymatic assays introduced a very important knowledge gap, which could not had been achieved by the standard organismal effects alone. A reoccurring issue with some metal based NMs is the possible dissolution and subsequent release of ions that then causes toxicity e.g. Cu-NPs or Ag-NPs release Cu2+ or Ag+. The oxidation state of the particles was investigated, although this was not the focus of the thesis. The study of fate, e.g. dissolution of NPs, is also only in its beginning and the appropriate techniques are currently being developed. The results showed a specific nanoparticle effect. The UV exposure with titanium dioxide nanoparticles increased its effect.
Em 2012 foram produzidas mais de 11 milhões de toneladas de nanomateriais (NMs) e as perspetivas apontam para um aumento na produção. Apesar das previsões e o uso extensivo em produtos de consumo e indústria, o conhecimento é praticamente inexistente no que diz respeito ao potencial impacto destes materiais no ambiente. O principal objetivo desta tese é compreender o impacto de um grupo de NMs selecionados (NMs de base metálica) em invertebrados de solo, com especial incidência nos mecanismos de resposta. Uma vez que a avaliação de risco ambiental feita caso-a-caso para todos os contaminantes emergentes (particularmente NMs) é impossível, devido, entre outros fatores, ao tempo e custos necessário, a compreensão dos mecanismos de ação é muito importante para alcançar paradigmas comuns. A compreensão dos modos de ação fornece os caracteres com valor preditivo para a extrapolação entre partículas. Além disso, também fornece informação para a produção de novos materiais sustentáveis. Em suma, os efeitos dos NMs selecionados (Cobre e Prata, Óxido de Titânio e Zircónio) e do respetivo sal, foram investigados ao nível dos genes (utilizando a ferramentas de alto varrimento, tecnologia de “microarrays” e PCR em tempo real), bioquímico (utilizando ensaios enzimáticos para a análise de marcadores de stress oxidativo) e do organismo (sobrevivência e reprodução, tal como nos protocolos OCDE), utilizando espécies modelo ecotoxicológicas (Enchytraeus albidus, Enchytraeus crypticus, Eisenia fetida). A análise da expressão de genes forneceu informação importante sobre os mecanismos afetados por cada um dos NMs testados. Os perfis de expressão genéticos evidenciaram uma assinatura do (nano)material e o efeito do tempo de exposição. A análise funcional integrada com os dados bioquímicos e de organismo revelou um bom poder de entendimento. As respostas dos parâmetros bioquímicos (relacionados com stress oxidativo) foram distintas entre os materiais testados e também influenciados pelo tempo de exposição e concentrações testadas. As respostas padronizadas ao nível do organismo foram as que mostraram menor diferenciação entre os vários materiais testados. De um modo geral, e neste contexto de avaliação de efeitos de NMs, a expressão de genes e ensaios enzimáticos, apresentaram um papel muito importante no preenchimento de lacunas que não podería ter sido alcançado através dos efeitos no organismo isoladamente. Um assunto recorrente relativo a alguns NMs de base metálica tem a ver com a possível dissolução e subsequente libertação de iões que a posteriori causam toxicidade, p.e. Cu-NPs ou Ag-NPs libertam Cu2+ ou Ag+. O estado de oxidação das partículas foi investigado, apesar deste não ser o foco da tese. O estudo do destino, p.e. dissolução de NPs, está ainda apenas no seu início e as técnicas apropriadas estão presentemente a ser desenvolvidas. Os resultados mostraram um efeito específico das nanopartículas. A exposição UV com o dióxido de titânio aumentou o seu efeito.

Doutoramento em Biologia
A nanotecnolgia tem tido um impacto significativo em muitas áreas devido às peculiares propriedades dos nanomateriais (NM). O crescent uso de NM em diversos sectores da indústria veio aumentar a preocupação, a nível científico e legislativo, em desenvolver produtos mais benéficos mas com menor impacto ecológico. Uma das maiores limitações de ambos os sectores, científico e legislativo, é a capacidade de detectar e caracterizar NM. Diversas técnicas têm vindo a ser desenvolvidas durante as últimas décadas, mas a maioria apresenta limitações na capacidade de análise de NM em matrizes complexas. Geralmente é necessário combinar várias técnicas analíticas para obter dados satisfatórios. Neste estudo focamonos em algumas dessas limitações. Com o uso de técnicas complementares foi possível desenvolver um método de detecção e caracterização de nanopartículas (NP) em matrizes complexas mais robusto e compreensivo. O foco foi dado ao desenvolvimento de métodos alternativos de detecção e caracterização de partículas de titânio em produtos comerciais, e de prata em ambiente marinho e organismos marinhos. Foi proposta a combinação de análises por AF4/UVVis/ MALS/DLS, após extracção por CO2 supercrítico, para detecção de NP de titânio em cremes solares. Este método poderá ser adaptado à caracterização de NP de titânio em águas recriacionais. A detecção de NP de prata em águas marinhas baseou-se na combinação das técnicas de AF4/UV-Vis/DLS, que poderão ser usadas, por exemplo, na avaliação do potencial tóxico de águas residuais em zonas costeiras. Propôs-se a determinação da concentração de NP por análise de ICP-MS no entanto recomendou-se o uso de TEM para identicação da sua forma. A caracterização de NP de prata mostrou-se limitada devido à instabilidade destes materiais em presença de elevada carga iónica e matéria orgânica dissolvida. Além disso, para estudos de internalização, propôs-se o uso do método desenvolvido para detecção e localização de NP de prata em células. O método, baseado em análise por TEM-EDX, foi optimizado para análise 3D de células intactas. Espera-se que este método se torne útil na avaliação dos mecanismos de acção de NP, visto permitir identificar interacções entre NP e elementos cellulares.
Nanotechnology is having a significant impact in many application fields due to the peculiar properties of nanomaterials. The rapid uptake of nanotechnology innovation to products onto the market has stimulated scientific and regulatory activities aimed at maximizing the products benefits, while minimizing their potential adverse ecological impact. One of the key problems of both scientific and regulatory development is the detection and proper characterization of nanomaterials. Several techniques have been developed during the last decades, but most of them have shortcomings, especially when analysing nanomaterials in complex matrices. The combination of several techniques is usually required to obtain enough data to characterize a nanomaterial. In this work we addressed some of the limitations of existing methods. By using complementary techniques it was possible to develop more complete and robust methods for detection and characterization of silver and titanium dioxide nanoparticles in complex matrices. In particular, this research focused on the development of alternative approaches for detecting and characterizing titania nanoparticles in consumer products and silver nanoparticles in sea water and marine organisms. A combination of AF4/UVVis/ MALS/DLS analysis, after spCO2 extraction, was proposed for titania nanoparticle detection in sunscreen lotions but this method could be also adapted to characterize titania nanoparticles in recreational waters. Detection of silver nanoparticles in sea water was based on the combination of AF4/UV-Vis/DLS techniques, which could be used, for instance, to determine the toxic potential of waste water discharges in coastal areas. Determination of nanoparticles concentration was proposed by ICP-MS while TEM was recommended for shape determination. The characterization of silver nanoparticles was shown limited due to the instability of the material in the presence of high ionic strength and dissolved organic matter. Furthermore, detection and localization of silver nanoparticles in cells was developed as proxy for uptake studies. A method based on TEM-EDX analysis was optimized for whole cell imaging in 3D. This method showed the ability to identify nanoparticle interactions with cell elements and therefore is expected to become a useful tool in the mechanism of action research field.

L'auto-organisation de nanoparticules métalliques dans un support est un moyen efficace et peu coûteux de produire des systèmes plasmoniques pouvant être utilisés pour des applications d'affichage couleur actif, de codage d'image et de sécurité. De tels systèmes nanocomposites doivent être synthétisés sous forme de films stables qui pourraient être enduits sur tout type de surface pour un traitement laser. Cette thèse de doctorat porte sur l 'auto - organisation induite par laser de couches minces nanocomposites d' argent et d 'oxyde de titane mésoporeux.Dans ce travail, nous étudions d'abord la synthèse de couches minces mésoporeuses de TiO2 à l'aide d'un processus hydrolytique, facile à mettre en œuvre, pour fournir des films cristallisés à partir de 100 ° C. sont rapportés dans ce travail. En outre, les mécanismes de croissance des nanocristaux dans les films mésoporeux de TiO2 sont étudiés sous la forme de mesures ellipsométriques mettant en évidence son effet sur la porosité et la cristallinité du film avec la température de recuit.La deuxième étude démontre la fabrication de différentes structures nanocomposites à l'aide de la technique de balayage laser femtoseconde, déclenchant la croissance et l'auto-organisation de nanoparticules d'argent à l'intérieur d'une matrice de titane amorphe poreuse donnant lieu à des couleurs dichroïques plasmoniques. Une recherche plus approfondie sur l'étude paramétrique de ces nanocomposites donne lieu à différentes nanostructures à deux régimes de vitesse de balayage différents, qui se forment à la surface et sont noyées en dessous en raison de l'excitation de la surface et des modes guidés. La flexibilité de cette technologie de marquage laser permet également de fabriquer des nanostructures hybrides composées de différents types de nanostructures adjacentes, entrelacées pour couvrir de grandes surfaces. Une extension de cette étude est conclue sur des substrats plastiques / flexibles pour encoder des images imprimées diffractives. Ici, les nanostructures de surface (LIPSS) sont formées en utilisant le contrôle de la polarisation du laser et donc de l'orientation du réseau, qui est utilisé pour coder des images de niveau de gris qui peuvent être observées dans les modes de diffraction.De plus, cette étude se conclut en produisant trois multiplexages d'images qui peuvent être observés dans trois modes sélectionnés d'observation sous lumière blanche en réflexion avec lumière non polarisée et transmission entre polariseurs pour deux angles de polarisation différents. Cela est dû au fait que la biréfringence et le dichroïsme du film peuvent être contrôlés pour produire des gammes de couleurs sans précédent pour le multiplexage. Un tel traitement laser intelligent sur des films minces nanocomposites donne lieu à des applications artistiques et de sécurité en codant différentes images jusqu'à trois sous la même zone
Self-organization of metallic nanoparticles in a medium is an efficient and a low-cost way to produce plasmonic systems that can be used for applications to active colour display, image encoding, and security. Such nanocomposite systems must be synthesized in form of stable films which could be coated on any kind of surface for laser processing. This doctoral thesis focuses on laser‐induced self‐organization of nanocomposite thin films of silver and mesoporous titania.In this work, we first investigate synthesizing mesoporous TiO2 thin films using hydrolytic process, which is easy to implement, to provide crystallized films starting at 100°C. First activation energies in mesoporous TiO2 films using Raman spectroscopy in combination with the phonon quantum confinement model are reported in this work. Further, growth mechanisms of nanocrystals in mesoporous TiO2 films are investigated in form of ellipsometric measurements highlighting its effect on film porosity and crystallinity with annealing temperature.The second study demonstrates fabrication of different nanocomposite structures using femtosecond laser scanning technique, triggering growth and self-organization of silver nanoparticles inside porous amorphous titania matrix giving rise to plasmonic dichroic colours. Further investigation on the parametric study of such nanocomposites gives rise to different nanostructures at two different scan speed regimes, which are formed at the surface and are embedded below due to excitation of surface and the guided modes. The flexibility of this laser-based marking technology also allows to fabricate hybrid nanostructures composed of different adjacent nanostructure types, interlaced to cover large areas. An extension of this study is concluded on plastic/flexible substrates to encode diffractive printed images. Here surface nanostructures (LIPSS) are formed by using the control of laser polarization and thus grating orientation, which is used to encode grey-level images that can be observed in diffraction modes.Further, this study is concluded by producing three image multiplexing which can be observed in three selected modes of observation under white light in reflection with non-polarized light and transmission between polarizers for two different polarization angles. This is due to the fact that the film birefringence and dichroism can be controlled to produce unprecedented colour gamuts for multiplexing. Such smart laser processing on nanocomposite thin films gives rise to artistic and security applications by encoding different images up to three under same area

UV disinfection of drinking water is becoming more common as water utilities attempt to control the formation of disinfection byproducts. While most organisms are readily inactivated by UV, certain viruses require a large fluence for adequate disinfection. In this study, photocatalytic silver doped titanium dioxide nanoparticles were investigated for their capability to enhance the UV disinfection of Bacteriophage MS2. The inactivation kinetics were compared to the base TiO2 material and silver nanoparticles. Inactivation of MS2 was enhanced by doping TiO2 with 8 and 10 wt. % silver, while no enhancement was observed with 4 and 6 wt. % silver. In order to determine the inactivation mechanism, alcohol scavengers were employed to eliminate the effects of hydroxyl free radical. When nAg/TiO2 was used as the catalyst, the alcohols significantly decreased the inactivation rate, but did not completely eliminate the virucidal activity. When P25 TiO 2 was used, no virus inactivation was observed.

碩士
國立臺灣科技大學
化學工程系
105
This study mainly focus on the research of photocatalysis and antibacterial properties of silver nanoparticle modified titanium dioxide. Here, commercially available P25 is used as the powder source. Spray process is applied on film fabrication, and the temperature applied in film fabrication process were controlled, both high temperature and room temperature process were trailed, for the deposition of silver nanoparticle, photo-assisted reduction was applied. In the degradation processes, methyl orange aqueous solution was chosen as an indicating material in the study of photocatalysis, and by analyzing the results, all the degradation profiles of silver modified titanium dioxide photocatalysts follows pseudo-first order degradation process, which indicates methyl orange was adsorbed on the surface of catalysts, then reacted with OH radicals for its further degradation. Here, by modifying silver nanoparticle, the photo degradation property of titanium dioxide catalyst is significantly enhanced, which may be caused by the surface plasmon resonance of silver nanoparticle, which could induce the dipole-dipole interaction with titanium dioxide, and enhance the formation of electron-hole pair, thus improve the photo degradation capability. In the research, the silver modified powder catalysts has a best degradation rate constant of 0.0418 min-1, for the film catalysts, the room temperature and the high temperature fabricated film has an optimum rate constant of 0.0145 min-1 and 0.0155 min-1, respectively. In the exams of antibacterial property, both E. coli and S. aureus were chosen for the test. As the results from the antibacterial test, under dark condition, even with high silver loading concentration, the catalyst films can only inhibit the growth of E. coli, however, the high concentration silver loaded catalyst film shows an effective inhibition for both kind of microorganisms.

碩士
國立清華大學
生醫工程與環境科學系
103
In this study, we divided as mono-culture and BBB model system to explore the toxicity effect of TiO2 (3-5nm ST-01, 30-50nm ST-21) and Ag NPs (<10nm). In vitro BBB model by co-culture endothelial cells (bEnd.3) and astrocytes (ALT) were established to estimate whether BBB dysfunction. Accordingly, four works will be examined after exposing nanoparticles 24 hours, all of which are cell viability, uptake potential, intracellular reactive oxygen species (ROS), and cytokines (MCP-1). In addition, the integrity of BBB was estimated by measuring the tranendothelial electrical resistance (TEER), calculating the permeability and observing the tight junction protein expression. On the other hand, we also compare the condition with or without lipopolysaccharide (LPS), which is assumed as the inflammatory situation. Consequently, we found that the toxicity mechanism of Ag-NPs and TiO2 NPs in the cells were trend to follow the way by producing ROS to gradually induce cell death. BBB were influenced by this two kind of nanoparticles to decrease TEER value, disrupt tight junction proteins and increase permeability of nanoparticles. The reason of this were associated with ROS generation and cytokines secretion. Furthermore, we found that Ag-NPs were more noxious than TiO2 NPs according to the lower lethal dosage (2ppm) and higher permeability in the BBB model. On the other hand, LPS treatment would stimulate MCP-1 release to make severer effect on BBB model although it did not have significant influence with co-culture nanoparticles.

Light scattering and surface Plasmon calculations were done on a variety of novel geometries using the DDSCAT software package, which simulates the scattering of objects using the discrete dipole approximation method. Calculations were done on core shell nanoparticles consisting of a silver shell and a TiO2 core in order to determine changes in the extinction spectrum and the near field patterns. Several geometries were tested, including spheres, cylinders, and hexagons, each of varying size and number. It was determined that when geometries were coupled together, there was significant near field enhancement where the geometries were in contact. This enhancement along with the increase in extinction in the visible region of the light spectrum makes these nanoparticles idea for solar cell technology, where they would increase efficiency.

碩士
國立臺灣大學
生物環境系統工程學研究所
107
Silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2 NPs) have been widely applied in disinfectant and sunscreen spray for their antimicrobial efficacy and high absorptivity to ultraviolet. However, lung adverse response may be induced by inhalation of airborne NPs while using spray products. Studies have proved the toxic effects of inhaled AgNPs and TiO2 NPs. Related health risk was considered to exist in the application of sprays containing AgNPs or TiO2 NPs. Therefore, we aimed to estimate potential human health risk of inhaled AgNPs and TiO2 NPs by integrating the exposure analysis and murine-related effect data. The compartmentalized physiologically based alveolar deposition model and the physiologically based lung models were employed to predict the lung AgNPs and TiO2 NPs burden for long-term exposure. A Hill-based dose-response model was used to describe the relationship between lung inflammation and NPs accumulation. The Weibull threshold model was used to estimate the threshold accumulated amounts causing specific levels of maximum neutrophils elevation effect. Moreover, the probabilistic risk model and hazard quotients were used to estimate the potential health risk. Results of risk assessment indicate that the risk probability was about 50% that the hazard quotient estimates of AgNPs-containing deodorant with a count median diameter ≈30 nm exceeded 1. Application of TiO2 NPs-containing spray with lotion of lowest viscosity and larger emitted volumn per action would pose highest relative risk. Based on the most conservative threshold accumulated amounts and application scenarios, we estimated the suggested upper limits of daily exposure duration for AgNPs-containing sprays (median: 2.29 h day-1, 95% confidence interval: 0.83–6.36 h day-1), daily using amounts (58.37 g, 23.82–144.05 g; 39.29 g, 10.85–145.50 g) and pressing number (38, 16–97; 66, 18–245) for both AgNPs and TiO2 NPs-containing sprays, respectively, as recommendation for consumers in using nanomaterial-containing spray products. This study provided a mechanistic approach for estimating potential health risk for long-term exposure to airborne AgNPs and TiO2 NPs from spray products and recommendation for daily application.