Literatura académica sobre el tema "Hydroxide diffusion"
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Artículos de revistas sobre el tema "Hydroxide diffusion"
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Mizrachi, S. y M. Hunger. "Proton diffusion in calcium hydroxide". Journal of Physics: Condensed Matter 2, n.º 6 (12 de febrero de 1990): 1499–507. http://dx.doi.org/10.1088/0953-8984/2/6/009.
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Zelovich, Tamar y Mark E. Tuckerman. "OH− and H3O+ Diffusion in Model AEMs and PEMs at Low Hydration: Insights from Ab Initio Molecular Dynamics". Membranes 11, n.º 5 (12 de mayo de 2021): 355. http://dx.doi.org/10.3390/membranes11050355.
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Fuel cell-based anion-exchange membranes (AEMs) and proton exchange membranes (PEMs) are considered to have great potential as cost-effective, clean energy conversion devices. However, a fundamental atomistic understanding of the hydroxide and hydronium diffusion mechanisms in the AEM and PEM environment is an ongoing challenge. In this work, we aim to identify the fundamental atomistic steps governing hydroxide and hydronium transport phenomena. The motivation of this work lies in the fact that elucidating the key design differences between the hydroxide and hydronium diffusion mechanisms will play an important role in the discovery and determination of key design principles for the synthesis of new membrane materials with high ion conductivity for use in emerging fuel cell technologies. To this end, ab initio molecular dynamics simulations are presented to explore hydroxide and hydronium ion solvation complexes and diffusion mechanisms in the model AEM and PEM systems at low hydration in confined environments. We find that hydroxide diffusion in AEMs is mostly vehicular, while hydronium diffusion in model PEMs is structural. Furthermore, we find that the region between each pair of cations in AEMs creates a bottleneck for hydroxide diffusion, leading to a suppression of diffusivity, while the anions in PEMs become active participants in the hydronium diffusion, suggesting that the presence of the anions in model PEMs could potentially promote hydronium diffusion.
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Piana, Tatiana Dantas, Maria de Fátima Malvar Gesteira, Erica Dos Santos Carvalho, Josilene Borges Torres Lima Matos, Monica Franca, Leandro Miranda de Araújo y Silvio José Albergaria Da Silva. "Evaluation of the antimicrobial effect of calcium hydroxide combined to different vehicles". Revista Odonto Ciência 31, n.º 2 (26 de diciembre de 2016): 89. http://dx.doi.org/10.15448/1980-6532.2016.2.21522.
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Objective: To evaluate the potentiating effect of different substances in antimicrobial action of calcium hydroxide.Methods: The agar diffusion method, was used with well technique, to analyze seven substances associated to calcium hydroxide to make some pastes, they are: chlorexidine, saline, anesthetic, malvatricin, propolis, hypochlorite, paramonochlorophenol.Results: The pastes with malvatricin and paramonochlorophenol presented greater inhibition zones against Enterococcus faecalis.Conclusion: There was potentialization in antimicrobial effect of calcium hydroxide when associated to paramonochlorophenol and to malvatricin especially against Enterococcus faecalis. Low increase of the antimicrobial capacity was observed when using chlorexidine as vehicle to calcium hydroxine paste.
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Zelovich, Tamar y Mark E. Tuckerman. "(Invited) First-Principles Molecular Dynamics Investigations of Proton and Hydroxide Transport in Model Anion-Exchange- and Proton-Exchange Membranes in Nanoconfined, Low-Hydration Environments". ECS Meeting Abstracts MA2023-01, n.º 45 (28 de agosto de 2023): 2473. http://dx.doi.org/10.1149/ma2023-01452473mtgabs.
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Fuel cell-based anion-exchange membranes (AEMs) and proton exchange membranes (PEMs) have considerable potential as cost-effective, clean energy conversion devices. However, a fundamental atomistic understanding of the hydroxide and hydronium diffusion mechanisms in AEM and PEM environments is an ongoing challenge. In recent years, nano-confined structures have been exploited in the study of cost-effective and reliable polymer architectures for electrochemical devices. In this study, first-principles molecular dynamics simulations are employed to investigate the influence of the water distribution, temperature, internal geometry, cation chemistry, and presence of carbon dioxide on the diffusion rate of protons and hydroxide ions in nanoconfined geometries that serve as mimics of PEM and AEM environments and to reveal key design principles1-8. The simulations indicate that the water distribution is a determinative factor in the diffusion process, which is also arrested when carbon dioxide is present. Moreover, it is found that hydroxide diffusion in AEMs is largely vehicular or a combination of vehicular and structural while proton diffusion in PEMs is largely structural. Pairs of cations in AEMs create bottlenecks for hydroxide diffusion while the anion groups in PEMs become active participants in proton diffusion. It is found that the temperature dependence of hydroxide diffusion in AEMs is non-monotonic, exhibiting a “kink” over a particular temperature range at which dD OH ─/dT < 0, a finding that is confirmed experimentally. The presence of carbon dioxide is found to suppress hydroxide diffusion, also in agreement with experiment. Looking forward, we investigate the influence of the solvent chemistry on proton transport and propose new nanoconfined environments with the potential to enhance proton transport rates considerably using these liquids. References: Ab initio molecular dynamics study of hydroxide diffusion mechanisms in nanoconfined structural mimics of anion exchange membranes.” T. Zelovich, Z. Long, M. A. Hickner, S. J. Paddison, C. Bae, and M. E. Tuckerman J. Phys. Chem. C 123, 4683 (2019). “Hydroxide ion diffusion in anion-exchange membranes at low hydration: Insights from ab initio molecular dynamics.” T. Zelovich, L. Vogt-Maranto, M. A. Hickner, S. J. Paddison, C. Bae, D. R. Dekel, and M. E. Tuckerman Chem. Mater. 31, 5778 (2019). “Water layering affects hydroxide diffusion in functionalized nanoconfined environments.” T. Zelovich and M. E. Tuckerman J. Phys. Chem. Lett. 11, 5087 (2020). “Hydronium ion in model proton exchange membranes at low hydration: Insights from ab initio molecular dynamics.” T. Zelovich, K. I. Winey, M. E. Tuckerman J. Mat. Chem. A 9, 2448 (2021). “Non-monotonic temperature dependence of hydroxide diffusion in anion exchange membranes.” T. Zelovich, L. Vogt-Maranto, C. Simari, I. Nicotera, M. A. Hickner, S. J. Paddison, C. Bae, M. E. Tuckerman Chemistry of Materials 34 2133 (2022). “Controlling hydronium diffusivity in model proton exchange membranes.” T. Zelovich, M. E. Tuckerman J. Phys. Chem. Lett. 13, 2245 (2022). “The impact of carbonation on hydoxide diffusion in nanoconfined anion exchange membranes.” Zelovich, C. Simari, I. Nicotera, D. R. Dekel, M. E. Tuckerman J. Mat. Chem. A (2022). “Functional Groups in Anion Exchange Membranes: Insights From Ab Initio Molecular Dynamics.” T. Zelovich, D. Dekel, M. E. Tuckerman J. Membrane Sci. (submitted) Figure 1
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Leaist, Derek G. y Betty Wiens. "Interdiffusion of acids and bases•HCl and NaOH in aqueous solution". Canadian Journal of Chemistry 64, n.º 5 (1 de mayo de 1986): 1007–11. http://dx.doi.org/10.1139/v86-169.
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Stokes magnetically stirred diaphragm cells have been used to measure interdiffusion of hydrochloric acid and sodium hydroxide in aqueous solution at 25 °C. Expressions are developed to estimate ternary diffusion coefficients for these mixtures. The analysis reveals sharp discontinuities between the diffusion properties of HCl-rich and NaOH-rich mixtures. Although the diffusion coefficients are sensitive to concentration, accurate analytic approximations for rates of interdiffusion can be obtained by averaging coefficients along the diffusion path. When HCl and NaOH interdiffuse, proton-coupled and hydroxide-coupled diffusion operating simultaneously on opposite sides of the diffusion boundary lead to rapid diffusion of inert Na+ and Cl− species.
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Jacobson, Aaron J., Gregory D. Smith, Rallming Yang y Sujit Banerjee. "Diffusion of sulfide into Southern pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) particles and chips". Holzforschung 60, n.º 5 (1 de agosto de 2006): 498–502. http://dx.doi.org/10.1515/hf.2006.082.
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Abstract Sulfide diffusion into wood has a rapid reversible component and a much slower irreversible component. During the initial reversible phase, sulfide is unable to diffuse into parts of the wood structure, probably because of charge exclusion. The diffusion of hydroxide and sulfide into saturated wood was imaged by immersing chips in white liquor, splitting them open and then imaging the hydroxide and sulfide profiles. Sulfide moves into the interior of the chip at a faster rate than hydroxide does because it is prevented from entering some of the pores and must move deeper into the chip to access dilution water.
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Leaist, Derek G. "Moments analysis of restricted ternary diffusion: sodium sulfite + sodium hydroxide + water". Canadian Journal of Chemistry 63, n.º 11 (1 de noviembre de 1985): 2933–39. http://dx.doi.org/10.1139/v85-486.
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Ternary diffusion coefficients can be determined from restricted-diffusion experiments by evaluating zeroth and first time moments of the difference in a concentration-dependent property measured at two levels along the diffusion column. The method is used to determine ternary diffusion coefficients for aqueous sodium sulfite + sodium hydroxide solutions from conductance measurements. It is shown that these data can be analyzed to obtain the ternary diffusivity of sulfur dioxide in strongly alkaline solutions where sulfite is the major transporting species for the sulfur dioxide component. At high pH values, coupled flow of hydroxide ions leads to a significant increase in the diffusivity of the sulfur dioxide component relative to its diffusivity in pure water. Binary diffusion coefficients for aqueous sodium sulfite solutions are also reported.
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Zakaria, Myrna Nurlatifah, Yusfien Shabrina Putri, Asih Rahaju, Sri Fatmawati y Arief Cahyanto. "Inhibitory effect of calcium hydroxide combined with Nigella sativa against Enterococcus faecalis". Dental Journal (Majalah Kedokteran Gigi) 54, n.º 4 (18 de octubre de 2021): 181. http://dx.doi.org/10.20473/j.djmkg.v54.i4.p181-185.
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Background: Calcium hydroxide is the gold standard medicament for root canal treatment. Enterococcus faecalis, the primary cause of intraradicular persistent endodontic infection, is often identified even after endodontic treatment. Thymoquinone, an active ingredient of Nigella sativa, has an antimicrobial effect on both gram-negative and positive bacteria, including E. faecalis. Purpose: This study aimed to evaluate the inhibitory effect of calcium hydroxide combined with Nigella sativa extract and determine the best ratio for the combined material. Methods: This is an experimental study comprised of six groups (n = 4 per group) based on the material and its ratio, namely; (1) calcium hydroxide; (2) Nigella sativa extract; and groups of the combination of calcium hydroxide and Nigella sativa extract with a ratio (3) 70:30, (4) 50:50, (5) 30:70, (6) 10:90. The inhibitory effect against E. faecalis was evaluated by the agar well diffusion method in Muller–Hinton agar. Observation of the inhibitory zone was performed on the first, third, and seventh days. The collected data were analysed by a one-way ANOVA and LSD post hoc test. Results: Calcium hydroxide has the highest inhibitory effect, and the combination of Nigella sativa extract with calcium hydroxide ratio 50:50 was second. The inhibitory zone of these two groups was significantly higher than in any other group (p<0.05). Conclusion: Nigella sativa extract combine with calcium hydroxide did not enhance calcium hydroxide’s antimicrobial property against E. faecalis. An equal amount of Nigella sativa and calcium hydroxide is the best combination ratio, with a stable effect for up to seven days.
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AKMALIA, Widya Nurul y Trimurni ABIDIN. "Diffusion of calcium ions in one-third of root canals after administration of high molecular Chitosan nanohydroxyapatite medicament (In Vitro)". Journal of Syiah Kuala Dentistry Society 6, n.º 2 (4 de enero de 2022): 92–97. http://dx.doi.org/10.24815/jds.v6i2.24190.
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ABSTRACT Calcium hydroxide is currently the gold standard medicament. Still, it has the disadvantage of leavinga residue on the surface of the root canal wall. Hence, it can interfere with the setting time and adhesion of the sealermaterial to the root canal wall. This study aims to determine the ability of calcium ion diffusion in one-third of theroot canal after administration of nanohydroxyapatite medicament with a different vehicle than calcium hydroxide.This study used 24 mandibular premolars extracted, decorated, and prepared, then grouped into four treatmentgroups. Based on the paired T-test, the study results showed no significant effect of calcium ion diffusion in group B(p = 0.739) on the 7th and 14th days. The ANOVA test results showed no significant difference in calcium ion diffusion between groups A, B, and C. on the 7th day of testing (p=0.773) and the 14th day (p=0.661). In conclusion, there was no effect and difference in the diffusion of calcium ions in the apical third after administration ofmedicament nanohydroxyapatite vehicle bidisstilled water and nanohydroxyapatite vehicle nanochitosan compared tocalcium hydroxide on the 7th and 14th day KEYWORDS: diffusion, calcium hydroxide, ion calcium, nanohydroxyapatite, nano chitosan, vehicle
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Thomas, Pinku T., Jyoti Sumi Issac, Parvathy Girija, Lekshmi S. Chandran, D. S. Arjun y A. J. Siddik. "An in vitro comparison of calcium ions release and diffusion ability of calcium hydroxide-based intracanal medicament in combination with three different vehicles like propolis, chitosan, and propylene glycol". Journal of Conservative Dentistry and Endodontics 27, n.º 2 (febrero de 2024): 190–94. http://dx.doi.org/10.4103/jcde.jcde_258_23.
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Abstract Context: Calcium hydroxide, which is an intracanal medicament, is widely used in endodontics. Improvements can be made to its effectiveness, as calcium hydroxide is dependent on the vehicle. Aim: The study aims to compare and evaluate the release and diffusion ability of calcium hydroxide when mixed with – propolis, chitosan, and propylene glycol. Methods: For this study, 33 single-rooted extracted premolar teeth have been decoronated. After the working length and enlargement of the canals had been established, different preparations of calcium hydroxide with vehicles such as propolis, chitosan, and propylene glycol were loaded into the canals. Atomic absorption spectrophotometry was used to analyze the release of calcium ions in three groups, while a digital pH meter was used to determine an acid change. Results: Atomic absorption spectrophotometry showed sustained releases of calcium ions and the digital pH meter showed increased diffusion capacity in the propylene glycol paste group in comparison to the other two groups. Conclusion: Propylene glycol vehicle made it easier to enter calcium hydroxide into the dentinal tubules.
Tesis sobre el tema "Hydroxide diffusion"
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Vidal, David. "Développement et évaluation de nouveaux séparateurs pour les batteries Nickel-Zinc". Electronic Thesis or Diss., CY Cergy Paris Université, 2023. http://www.theses.fr/2023CYUN1273.
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Les batteries nickel-zinc offrent des performances qui répondent aux exigences du stockage d'énergies renouvelables intermittentes. De plus, par rapport aux batteries lithium-ion, cette technologie est sûre, hautement recyclable et le zinc est un métal abondant. Dans ces batteries, les électrodes sont séparées par un séparateur polymère qui limite la diffusion des zincates de l'électrode de zinc vers celle de nickel tout en favorisant le transfert des ions hydroxyde. Cependant, la durée de vie de ces séparateurs limite actuellement les performances de la batterie. Il existe donc un besoin critique d'en développer des plus durables fonctionnant avec un électrolyte alcalin.Ce travail de thèse s'est d'abord axé sur l'étude des principales caractéristiques (diffusion aux ions hydroxyde, mouillabilité…) des séparateurs commerciaux Celgard traités par un revêtement hydrophile ou non, et sur leur évolution lors d'un vieillissement chimique. Cette étude a permis de corréler la désorption du revêtement hydrophile et la perte des performances observées en batterie.Afin d'améliorer leur stabilité dans le temps, un polymère hydrophile réticulé, l'alcool polyvinylique (PVA), a été introduit dans le volume poreux de plusieurs séparateurs, se différenciant par la présence ou non d'un revêtement hydrophile. La présence de ce polymère réticulé s'est avéré améliorer la mouillabilité du séparateur mais aussi la diffusion des ions hydroxyde. Ces propriétés sont conservées à la suite d'un vieillissement chimique accéléré dans l'eau ou l'électrolyte alcalin.L'introduction de surfactants en combinaison avec le PVA permet d'améliorer encore ces propriétés tandis que le PVA augmente la stabilité du séparateur au cours du vieillissement. Enfin, des tests en batterie Ni-Zn utilisant les séparateurs développés au cours de cette thèse ont confirmé ces résultats prometteursNickel-Zinc based batteries offer performances that match the requirements of the storage of the intermittency of renewable energies. Moreover, compared to Lithium-ion batteries, this technology happens to be safe, highly recyclable and zinc is an abundant metal. In these batteries, electrodes are separated by a polymer separator restricting the diffusion of zincate ions from zinc electrode towards the nickel while promoting the transfer of hydroxide ions. However, the lifetime of these separators currently limits the battery's performance. Thus, there is a critical need to develop more durable separators for batteries operating in alkaline electrolyte.This PhD work first focused on the study of the main characteristics of commercially (hydroxide diffusion, wettability, etc.) of commercial Celgard® separators, treated with a hydrophilic coating or not, and on their evolution under a chemical ageing. This study allowed correlate the desorption of hydrophilic coating with the decay in battery performances.To improve the performance stability over time, a cross-linked hydrophilic polymer, polyvinyl alcohol (PVA), was introduced into the porous volume of several separators, differentiated by the presence or absence of a hydrophilic coating. The presence of this crosslinked polymer was found to improve the separator wettability and the hydroxide ion diffusion. These properties are preserved after an accelerated chemical ageing in water or alkaline electrolyte.The introduction of surfactants in combination with PVA further improves these properties, while PVA enhances the separator's stability during aging. Finally, Ni-Zn battery tests using the separators developed during this thesis have confirmed these promising results
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Chen, Yuanxin. "POLYMER MEMBRANES FOR FLUE GAS CARBON CAPTURE AND FUEL CELL APPLICATION". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440069742.
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Gao, Yang. "Low-temperature removal of hydrogen chloride from flue gas using hydrated lime as a sorbent". Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175884147.
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Giordano, Gabriela Furlan 1990. "Modificação de eletrodos com óxido/hidróxido de níquel e acoplamento em sistema de difusão gasosa para a determinação de etanol em amostras de vinho de cana-de-açúcar". [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248390.
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Orientador: Lauro Tatsuo KubotaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-27T17:12:32Z (GMT). No. of bitstreams: 1 Giordano_GabrielaFurlan_M.pdf: 2251330 bytes, checksum: a6853decc37a3f82817a0457cc141778 (MD5) Previous issue date: 2015
Resumo: Este trabalho teve como objetivo desenvolver um sistema eletroquímico capaz de detectar e quantificar etanol presente em amostras de vinho de cana-de-açúcar. Três métodos de modificação de eletrodo de níquel foram estudados visando à obtenção das espécies Ni(OH)2/NiOOH. Um dos métodos consistiu no condicionamento eletroquímico em NaOH, o outro, na oxidação química em persulfato de amônio e tratamento térmico e o terceiro, na deposição eletroquímica de Ni(OH)2 dopados com Co2+ e Cd2+, a partir de solução contendo os nitratos desses metais. Esse último apresentou resultados com maior repetibilidade de preparação e resposta. As técnicas SEM-FEG e XPS foram empregadas, a fim de caracterizar morfologicamente o Ni(OH)2 obtido e permitir determinações qualitativas e quantitativas sobre a composição química da superfície, respectivamente. Para a aplicação nas amostras empregou-se a técnica de extração por difusão gasosa através de uma membrana hidrofóbica. Assim, um módulo de extração foi construído no qual uma membrana de PTFE separou a solução de etanol - a ser analisada - de uma solução receptora de NaOH 100,0 mmol L-1, na qual o sistema eletroquímico foi acoplado. As condições aplicadas ao sistema foram otimizadas de modo a resultar em menores desvios das medidas analíticas. O vapor de etanol recolhido na solução de NaOH foi analisado utilizando o eletrodo de trabalho desenvolvido e foi possível monitorar soluções de etanol no intervalo 2,0 a 20,0% v/v. A concentração de etanol foi determinada em amostras de vinho de cana-de-açúcar por dois métodos diferentes: interpolação em curva analítica preparada em meio salino com condutividade similar às amostras e adição de padrão. Os resultados obtidos foram estatisticamente equivalentes em comparação com a técnica de FTIR, considerando nível de confiança de 95%
Abstract: This work describes the development of an electrochemical system to detect and quantify ethanol on fermentation broths. Three methods were studied to modify the electrode surface in order to obtain Ni(OH)2/NiOOH species: i) electrochemical cycling in NaOH solution; ii) chemical oxidation on ammonium persulfate and heat treatment; and, iii) electrochemical deposition of nickel, cobalt and cadmium from a solution containing the respective nitrates and application of cathodic current. The latter one showed good repeatability, therefore, an analytical curve was obtained by cyclic voltammetry technique and the analytical sensitivity was 1.2 ìA L mmol-1. Scanning electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the structures formed and allow qualitative and quantitative determination about the surface chemical composition. In order to provide selectivity to electrochemical determination of ethanol on complex samples, the electrochemical system was coupled to gas diffusion extraction through hydrophobic membrane. Thus, an extraction module was constructed in which a PTFE membrane separated the ethanol donor solution, standard or sample, from receptor solution, the electrolyte used on electrochemical analyses (100.0 mmol L-1 NaOH). The conditions applied to the system were optimized to yield repeatability on analytical measurements. In this platform, it was possible to monitor ethanol solutions in the range of 2.0 up to 20.0% v/v. Samples of fermentation broth were analyzed by two methods: direct interpolation on saline analytical curve with conductivity similar to samples and standard addition. The results were in agreement with respect to those obtained by FTIR method at 95% confidence level
Mestrado
Quimica Analitica
Mestra em Química
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Quienne, Pascale. "Mécanisme de coagulation-floculation de la silice colloi͏̈dale par les hydroxydes de fer : étude par diffusion aux petits angles des rayons X". Orléans, 1989. http://www.theses.fr/1989ORLE2024.
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Meyer, Michaël. "Synthèse et propriétés d'organisation de particules plaquettaires d'hydroxyde de nickel dispersées par voie électrostatique". Paris 6, 2003. http://www.theses.fr/2003PA066386.
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Ayturk, Mahmut Engin. "Synthesis, annealing strategies and in-situ characterization of thermally stable composite thin Pd/Ag alloy membranes for hydrogen separation". Worcester, Mass. : Worcester Polytechnic Institute, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-042307-012951/.
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Thesis (Ph.D.)--Worcester Polytechnic Institute.Keywords: composite Pd and Pd/Ag membranes, alloying, Pd/Ag barrier, intermetallic diffusion, bi-metal multi-layer BMML deposition, electroless plating kinetics, high temperature x-ray diffraction, aluminum hydroxide surface grading, porous sintered metal supports, hydrogen separation. Includes bibliographical references (leaves 279-296 ).
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Savanier, Marc. "Guides d'ondes AIgaAs oxydés pour la conversion de fréquences optiques". Paris 7, 2013. http://www.theses.fr/2013PA077120.
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Ce travail de thèse porte sur le développement des savoir-faire technologiques nécessaires à la réalisation de sources paramétriques intégrées émettant dans l'infrarouge. Pour cela, les guides d'ondes biréfringents AlGaAs/AlOx considérés, grâce à leur forte non linéarité quadratique et à la maturité des techniques de fabrication, se révèlent être un choix pertinent. La fabrication et la caractérisation d'un convertisseur de fréquence de ce type, conçu pour la conversion paramétrique descendante d'une pompe à 775 nm en paires de photons à 1550 nm, nous a permis de démontrer une efficacité de conversion normalisée de 1100 %W⁻¹cm⁻², une puissance de second harmonique de 0. 3 mW, ainsi qu'une accordabilité de 570 nm. Bien qu'à l'état de l'art des dispositifs intégrés AlGaAs, ces performances restent limitées par les pertes optiques induites par le processus d'oxydation. Afin d'établir un lien entre les pertes de propagation et les propriétés physico-chimiques de l'AlOx, nous avons étudié leur comportement spectral. Deux mécanismes de pertes ont été mis en évidence : un régime de diffusion à grande longueur d'onde, en accord avec un modèle considérant les interfaces rugueuses de l'AlOx, et un régime d'absorption à faible longueur d'onde, attribué à la présence de défauts générés par la réaction d'oxydation. Un effort de développement technologique visant à augmenter l'efficacité de nos échantillons a été entrepris suivant deux axes : l'optimisation fine du procédé d'oxydation et la mise en cavité optique des guides d'ondes. Les résultats obtenus sont très encurageants pour la réalisation de dispositifs non linéaires efficaces, et la démonstration d'un OPO intégré en particulierThis work focuses on the technological know-how necessary to fabricate integrated parametric sources emitting in the infrared. Thanks to a high quadratic nonlinearity and mature fabrication techniques, AlGaAs/AlOx birefringent waveguides are good candidates for this purpose. The fabrication and characterization of such a frequency converter, designed for the parametric down-conversion of a 775 nm pump into photon pairs at 1550 nm, led to the demonstration of a 1100 %W⁻¹cm⁻² normalized conversion efficiency, a 0. 3 mW generated second harmonic power, as well as a tunability of 570 nm. Despite these state-of-the-art performances for AlGaAs integrated devices, oxidation induced optical losses still constitute the bottleneck of this phase-matching scheme. In order to investigate their origin, in relation with the oxide properties, a study on their spectral behavior has been carried out. Two distinct mechanisms have been highlighted : scattering is the main contribution at large wavelengths whereas absorption is dominant at shorter wavelengths. While the former is qualitatively described by a model accounting for the AlOx rough interfaces, the latter has been tentatively ascribed to the presence of defects generated by the oxidation reaction. Two technological developments have then been undertaken to improve the conversion efficiency of our devices. First the propagation losses were reduced with a fine optimization of the oxidation process. Second the waveguides were placed into an integrated optical cavity to enhance the fields. The results achived through both these developments are promising for the realization of efficient nonlinear photonic devices, e. G. An integrated OPO
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Maurey, Christophe. "Etude expérimentale de la stabilisation et du soufflage des flammes de diffusion turbulentes suspendues". Rouen, 2001. http://www.theses.fr/2001ROUES001.
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Ce travail porte sur l'étude expérimentale de la stabilisation et du soufflage des flammes de diffusion turbulentes suspendues au-dessus d'un injecteur. Dans la première partie de ce travail, nous avons utilisé la fluorescence induite par laser sur le radical OH, pour effectuer une étude paramétrique et statistique sur les hauteurs et les rayons d'accrochage de la flamme suspendue. Les résultats ont montré que le comportement moyen de la flamme, est lié aux mouvements des grosses structures dans le jet turbulent. Dans la seconde partie, nous avons couplé la fluorescence induite par laser sur le radical OH avec la vélocimétrie par images de particules, afin de caractériser les propriétés dynamiques en amont de la flamme. A partir des images de fluorescence de OH, nous avons mis en évidence l'existence d'une extrémité propagative à la base de la flamme. Des mesures conditionnées de vitesses dans les gaz frais à la base de la flamme, ainsi qu'à la position de l'extrémité propagative montrent que la flamme stabilise dans une région où les vitesses de l'écoulement sont proches de la vitesse de propagation d'une flamme laminaire de prémélange. Dans la dernière partie, nous avons réalisé deux expériences afin d'étudier le mélange juste en amont de la base de la flamme. La première permet de calculer la richesse à la base de la flamme par analyse des intensités de chimiluminescence de radicaux. La seconde donne les valeurs de la fraction de mélange juste en dessous de la flamme à partir d'images de fluorescence d'un traceur injecté dans le jet central. Les résultats de ces deux investigations, tendent à prouver que le mélange inflammable en dessous de la base de la flamme devient de plus en plus pauvre lorsque la vitesse de sortie des gaz augmente. Les résultats de ces travaux ont permis de décrire les propriétés de la turbulence et du mélange de l'écoulement à la base des flammes suspendues, et de fournir des données de validation aux codes de calcul numérique.
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Laaziz, Ilham. "Etude de l'hydrolyse d'alkoxydes de titane et de zirconium par réaction d'estérification". Montpellier 2, 1990. http://www.theses.fr/1990MON20280.
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Ce travail decrit l'etude de l'hydrolyse d'alkoxyde de titane, de zirnonium et de leur melange par reaction d'esterification. Les differents produits obtenus sont des sols, cristaux, gels ou precipites. Ces differentes phases ont ete caracterisees par l'intermediaire de techniques spectroscopiques (ir, rmn), par analyse thermique (atg, atd) ainsi que par diffusion des rayons x aux petits angles, diffusion de la lumiere et thermoporometrie. La resolution structurale des trois composes cristallins: ti#6(o#ipr)#8(oac)#8o#4, zr#6ti#3(opr)#1#6(oac)#8o#6, zr#9(o#npr)#1#8(oac)#6o#6 a permis de preciser l'arrangement structural des ligands alkoxy et acetate ainsi que la presence de liaison m-o-m. L'ensemble de ces resultats permet de mettre en evidence la similitude entre les structures des gels et celles des cristaux
Capítulos de libros sobre el tema "Hydroxide diffusion"
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Winkelmann, J. "Diffusion of hydrogen (1); water (2); potassium hydroxide (3)". En Gases in Gases, Liquids and their Mixtures, 2299. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-49718-9_1785.
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Winkelmann, J. "Diffusion of oxygen (1); water (2); potassium hydroxide (3)". En Gases in Gases, Liquids and their Mixtures, 2320. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-49718-9_1804.
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Winkelmann, J. "Diffusion of oxygen (1); water (2); sodium hydroxide (3)". En Gases in Gases, Liquids and their Mixtures, 2321. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-49718-9_1805.
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Santos, Diogo M. F. y César A. C. Sequeira. "Chronoamperometric Determination of Diffusion Coefficients for Borohydride Anions in Sodium Hydroxide Solutions". En Diffusion in Solids and Liquids III, 583–89. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-51-5.583.
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Winkelmann, J. "Diffusion of carbon dioxide (1); water (2); potassium hydroxide (3)". En Gases in Gases, Liquids and their Mixtures, 2277. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-49718-9_1765.
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Winkelmann, J. "Diffusion of carbon dioxide (1); water (2); sodium hydroxide (3)". En Gases in Gases, Liquids and their Mixtures, 2278. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-49718-9_1766.
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Winkelmann, J. "Diffusion of sodium hydroxide (1); carbon dioxide (2); water (3)". En Gases in Gases, Liquids and their Mixtures, 2296. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-49718-9_1782.
Texto completoActas de conferencias sobre el tema "Hydroxide diffusion"
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Schwenzer, Birgit, John Gomm y Daniel Morse. "Biologically Inspired Vapor-Diffusion Route to Metal Hydroxide Films at Low Temperatures: Synthesis, Conversion and Applications". En 2006 International Conference on Nanoscience and Nanotechnology. IEEE, 2006. http://dx.doi.org/10.1109/iconn.2006.340604.
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Shinohara, Kyosuke y Yasuhiko Sugii. "Micro Chemical Reaction Flow Measurement Using PIV and LIF Technique". En ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45757.
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Using micro PIV technique and micro LIF technique, velocity distributions and pH distributions of chemical reacting flow in micro fluidic device were measured. The micro fluidic device was Y-junction channel. In order to generate a neutralization reaction, acetic acid and ammonia hydroxide were introduced into each channel respectively. The results of velocity profiles of the chemical reacting flow corresponded closely to the theoretical profile of Poiseuille’s flow. This was characteristic of laminar flow. The results of pH distribution of the chemical reacting flow showed two kinds of distribution. In one case interface was straight and mixing was not noticeable at higher flow speed. In the other hand mixing or molecular diffusion due to chemical reaction definitely caused at lower flow rate. Applying both results we compared the experimental diffusion with theoretical value. In one case the experimental result corresponded close to theoretical value. However, it did not agree with theory in the other case. The results indicate that acetic acid and ammonia hydroxide mixed faster than theory in micro scale.
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Zecevic, Strahinja, Edward M. Patton y Parviz Parhami. "Direct Carbon Fuel Cell With Molten Hydroxide Electrolyte". En ASME 2004 2nd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2004. http://dx.doi.org/10.1115/fuelcell2004-2496.
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Historically, despite its compelling cost and performance advantages, the use of molten hydroxide electrolytes has been ignored by DCFC researches, primarily due to the potential for formation of carbonate salt in the cell. This paper describes the electrochemistry of a patented medium-temperature DCFC based on molten hydroxide electrolyte, which overcomes the historical carbonate formation. An important technique discovered for significantly reducing carbonate formation is to ensure high water content of the electrolyte. Water helps hydrolysis of the carbonates and reduces formation of peroxide and superoxide ions that may react with carbon dioxide producing carbonate ions. High water content can be achieved by maintaining a humid atmosphere above the melt. To date, four successive generations of medium temperature DCFC prototypes have been built and tested at SARA Inc. to demonstrate the technology, all using graphite rods as their fuel source. The cells all used a simple design in which the cell containers served as the air cathodes and successfully demonstrated delivering more than 40 A at 0.3 V with the current density exceeding 200 mA/cm2. The basic feature of this simple cell design is that the cathode is not traditional gas fed electrode type. It is a non-porous electrode structure made of an inexpensive Fe-Ti alloy and gaseous oxygen is introduced into the cell by bubbling humid air through the electrolyte. Results obtained indicated that the cell operation was under a mixed activation-Ohmic-mass transfer control. The activation control is mainly due to slow anode oxidation of carbon, the Ohmic control is mainly due to a large electrode spacing whereas the mass transfer control is most likely because of slow diffusion of oxygen species (O2, O22−, O2−, and H2O) to the cathode surface. Cell performances are improved in the new generation cell design, which has been recently built, and which enables faster mass transfer of the reaction species and a lower voltage drop across the electrolyte. In the new design, the cathode is a separate perforated component of the cell that allows the use of a larger surface area electrode and for the electrode spacing to be varied.
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Joe, Hyun-Jong y Barclay G. Jones. "Modeling of Porous Crud Layer Based on Effects of Diffusion and Water Radiolysis on Anomalous Porous Crud Deposition on Fuel Pin Surfaces in PWRs". En 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22602.
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Many studies have been undertaken to understand crud formation on the upper spans of fuel pin clad surfaces, which is called axial offset anomaly (AOA), is observed in pressurized water reactors (PWR) as a result of sub-cooled nucleate boiling. Separately, researchers have considered the effect of water radiolysis in the primary coolant of PWR. This study examines the effects of radiolysis of liquid water, which aggressively participate in general cladding corrosion and solutes within the primary coolant system, in the terms of pH, temperature, and Linear Energy Transfer (LET). It also discusses the effect of mass transfer, especially diffusion, on the concentration distribution of the radiolytic products, H2 and O2, in the porous crud layer. Finally it covers the effects of chemical reactions of boric acid (H3BO3), which has a negative impact on the mechanisms of water recombination with hydrogen, lithium hydroxide (LiOH), which has a negative effect on water decomposition, dissolved hydrogen (DH), and some trace impurities.
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Prakash, Raghu V., C. Anish y Dhinakaran Sampath. "Modeling Electric-Potential for a Crack Subjected to Corrosion Under Static and Cyclic Loading". En ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-85773.
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Abstract High strength steels are increasingly being used in applications such as ship hulls and oil and gas pipelines which are subjected to corrosive environment. These steel grades exhibit more than an order of magnitude higher crack growth rates in corrosive environments compared with the crack growth rates in air. A mathematical model is developed based on the slip dissolution mechanism to evaluate the chemistry and potential distributions in the occluded crack. The species distribution due to diffusion and ion migration is evaluated by considering the effect of ferrous hydroxide formation on the transport properties in the electrolyte. It is also found that the potential and pH drop in the crack is affected by the crack tip stress and strain fields. The dissolution of iron at the crack tip is enhanced by the pH drop. Both steady state and transient numerical studies are carried out to determine the evolving crack geometry. Thus, by considering reactions inside the crack, a better representation of the species and potential distributions can be obtained.
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Yamaguchi, Akira, Takashi Takata, Hiroyuki Ohshima y Kazunori Suda. "Sodium-Water Reaction and Thermal Hydraulics at Gas-Liquid Interface: Numerical Interpretation of Experimental Observations". En 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89615.
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In a sodium-cooled fast reactor development, coupled phenomena of thermal-hydraulics and chemical reaction of sodium and water vapor are of importance from the safety viewpoint. However, the sodium-water reaction (SWR) phenomena are generally complex and the experimental measurement technology is not well matured. Therefore, a numerical simulation is used for the investigation of the SWR. In this paper, a new computer program has been developed and the SWR in a counter-flow diffusion flame is studied by a numerical simulations and an experiment as well. In the computer program, Navier-Stokes equations and chemical reaction equations are solved interactively. In addition, a dynamic equation of airborne particulates is coupled with the governing equations of thermal hydraulics. A source of the particulates is the chemical reaction products, i.e. sodium hydroxide and sodium oxide. The SWR experiment is decided based on the numerical simulation. To obtain a stable reaction flame and to measure the temperature and reaction product distributions, the flow field in the experimental cell needs to be optimized. The numerical simulation is useful for designing experiments of complex phenomena and for obtaining the data. The computations are compared with experimental data. It has been demonstrated that the computational fluid dynamics code coupled with chemical reaction well predict the SWR.
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Kawaguchi, Munemichi. "Phase-Field Model for Recrystallization of Impurities in Sodium Coolant". En 2021 28th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/icone28-65721.
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Abstract In researches and developments (R&Ds) on sodium (Na) management technology, the experimental data related to a cold trap and a plugging meter have been accumulated in each country because the impurities such as sodium oxide (Na2O), sodium hydride (NaH) and/or sodium hydroxide (NaOH) in Na coolant accelerate the corrosion on the stainless-steel surface. The cold trap has stainless-steel wire mesh and wall where the saturated impurities are recrystallized to remove the impurity in the Na coolant. Similarly, the plugging meter has stainless-steel orifice where the saturated impurities are recrystallized to measure the saturation concentration (plug temperature). The recrystallization is common physical chemistry phenomena, in which is dominated by the temperature and the concentration. To date, a phase-field model (PFM) has been developed extensively as a powerful tool to predict microstructure evolution of micro–meso scale. Especially, the PFM has some simulation merits: it can calculate movement of interface without explicit trace of the interface (calculate robustly the large deformation), and this simulation results are known to be consistent with the thermodynamics data. In this study, we developed the simulation models for complex recrystallization of one impurity in Na coolant using the PFM, and confirmed that the simulation results are reasonable for the experimental data with the operating experience. In the simulation results for the one impurity of Na2O or NaH, we concluded that the kinetics of recrystallization was determined by the solubility and/or diffusion behavior in liquid Na.
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Gadala, Ibrahim M. y Akram Alfantazi. "Bicarbonate, Temperature, and pH Influences on the Passivation of API-X100 Pipeline Steel in Simulated Groundwater Solutions". En 2014 10th International Pipeline Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/ipc2014-33180.
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The influence of bicarbonate ion (HCO3−) concentration and related environmental parameters such as pH and temperature on the passivation of API-X100 pipeline steel is the focus of this investigation. NS4 solution simulating groundwater trapped under disbonded coatings at regions where near-neutral stress corrosion cracking (SCC) occurs was used as a reference. Bicarbonate content in the solutions was increased steadily and the critical HCO3− concentration at which passivation becomes evident is found using potentiodynamic polarization sweeps. Multi-step dissolution is observed especially in higher pH solutions, owing to the involvement of hydroxide ions (OH−) in the adsorption of hydrous Fe(OH)2. Dynamic electrochemical impedance spectroscopy (DEIS) is used to study and compare interfacial processes in active, pre-passive, passive, and trans-passive regions. The results of the potentiodynamic and DEIS tests achieve good agreement. The protective properties of the passive film formed at three different HCO3− concentrations (critical passivation and two higher concentrations) and temperatures (25, 50, and 75 °C) are studied. The combined effect of HCO3− and temperature resulted in a pH range from ∼6.7 to 9.3 for the nine conditions in the corresponding test matrix. Passive films were formed at a suitable anodic potential and then studied with electrochemical impedance spectroscopy (EIS), Mott-Schottky, and cyclic voltammetry (CV) tests. Evidence of adsorption and diffusion, in addition to significant resistance from the passive film, is observed and accounted for in the equivalent circuit, which achieved good correspondence when fitted with the experimental data. The protective properties of the overall passive film are enhanced with increased bicarbonate and decreased temperature. Positive slopes in the Mott-Schottky plots reveal the n-type semi-conductive behavior of the passive films in all conditions and the CV results highlight the proposed reaction sequences occurring in different potential scan regions. CV measurements also confirm the enhanced protective properties of passive films with increased bicarbonate and lower temperatures observed in the EIS analysis.
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Taviot-Guého, C., F. Leroux, F. Goujon, P. Malfreyt y R. Mahiou. "Étude du mécanisme d'échange et de la structure des matériaux hydroxydes doubles lamellaires (HDL) par diffraction et diffusion des rayons X". En UVX 2012 - 11e Colloque sur les Sources Cohérentes et Incohérentes UV, VUV et X ; Applications et Développements Récents, editado por E. Constant, P. Martin y H. Bachau. Les Ulis, France: EDP Sciences, 2013. http://dx.doi.org/10.1051/uvx/201301016.
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Chen, Kok Hao y Jong Hyun Choi. "DNA Oligonucleotide-Templated Nanocrystals: Synthesis and Novel Label-Free Protein Detection". En ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11958.
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Semiconductor and magnetic nanoparticles hold unique optical and magnetic properties, and great promise for bio-imaging and therapeutic applications. As part of their stable synthesis, the nanocrystal surfaces are usually capped by long chain organic moieties such as trioctylphosphine oxide. This capping serves two purposes: it saturates dangling bonds at the exposed crystalline lattice, and it prevents irreversible aggregation by stabilizing the colloid through entropic repulsion. These nanocrystals can be rendered water-soluble by either ligand exchange or overcoating, which hampers their widespread use in biological imaging and biomedical therapeutics. Here, we report a novel scheme of synthesizing fluorescent PbS and magnetic Fe3O4 nanoparticles using DNA oligonucleotides. Our method of PbS synthesis includes addition of Na2S to the mixture solution of DNA sequence and Pb acetate (at a fixed molar ratio of DNA/S2−/Pb2+ of 1:2:4) in a standard TAE buffer at room temperature in the open air. In the case of Fe3O4 particle synthesis, ferric and ferrous chloride were mixed with DNA in DI water at a molar ratio of DNA/Fe2+/Fe3+ = 1:4:8 and the particles were formed via reductive precipitation, induced by increasing pH to ∼11 with addition of ammonium hydroxide. These nanocrystals are highly stable and water-soluble immediately after the synthesis, due to DNA termination. We examined the surface chemistry between oligonucleotides and nanocrystals using FTIR spectroscopy, and found that the different chemical moieties of nucleobases passivate the particle surface. Strong coordination of primary amine and carbonyl groups provides the chemical and colloidal stabilities, leading to high particle yields (Figure 1). The resulting PbS nanocrystals have a distribution of 3–6 nm in diameter, while a broader size distribution is observed with Fe3O4 nanoparticles as shown in Figure 1b and c, respectively. A similar observation was reported with the pH change-induced Fe3O4 particles of a bimodal size distribution where superparamagnetic and ferrimagnetic magnetites co-exist. In spite of the differences, FTIR measurements suggest that the chemical nature of the oligonucleotide stabilization in this case is identical to the PbS system. As a particular application, we demonstrate that aptamer-capped PbS QD can detect a target protein based on selective charge transfer, since the oligonucleotide-templated synthesis can also serve the additional purpose of providing selective binding to a molecular target. Here, we use thrombin and a thrombin-binding aptamer as a model system. These QD have diameters of 3∼6 nm and fluoresce around 1050 nm. We find that a DNA aptamer can passivate near IR fluorescent PbS nanocrystals, rendering them water-soluble and stable against aggregation, and retain the secondary conformation needed to selectively bind to its target, thrombin, as shown in Figure 2. Importantly, we find that when the aptamer-functionalized nanoparticles binds to its target (only the target), there is a highly systematic and selective quenching of the PL, even in high concentrations of interfering proteins as shown in Figure 3a and b. Thrombin is detected within one minute with a detection limit of ∼1 nM. This PL quenching is attributed to charge transfer from functional groups on the protein to the nanocrystals. A charge transfer can suppress optical transition mechanisms as we observe a significant decrease in QD absorption with target addition (Figure 3c). Here, we rule out other possibilities including Forster resonance energy transfer (FRET) and particle aggregation, because thrombin absorb only in the UV, and we did not observe any significant change in the diffusion coefficient of the particles with the target analyte, respectively. The charge transfer-induced photobleaching of QD and carbon nanotubes was observed with amine groups, Ru-based complexes, and azobenzene compounds. This selective detection of an unlabeled protein is distinct from previously reported schemes utilizing electrochemistry, absorption, and FRET. In this scheme, the target detection by a unique, direct PL transduction is observed even in the presence of high background concentrations of interfering negatively or positively charged proteins. This mechanism is the first to selectively modulate the QD PL directly, enabling new types of label free assays and detection schemes. This direct optical transduction is possible due to oligonucleotidetemplated surface passivation and molecular recognition. This chemistry may lead to more nanoparticle-based optical and magnetic probes that can be activated in a highly chemoselective manner.
Informes sobre el tema "Hydroxide diffusion"
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Environmental Assessment for the sale of excess lithium hydroxide stored at the Oak Ridge K-25 Site and the Portsmouth Gaseous Diffusion Plant. Office of Scientific and Technical Information (OSTI), abril de 1993. http://dx.doi.org/10.2172/10173192.
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