Literatura académica sobre el tema "Alkaline nanoparticles"
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Artículos de revistas sobre el tema "Alkaline nanoparticles"
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Dutka, R. M. "Peculiarities of Ag metallic nanoparticles formation in alkaline and alkaline-earth tetraborate glasses". Functional materials 22, n.º 2 (30 de junio de 2015): 155–61. http://dx.doi.org/10.15407/fm22.02.155.
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Sánchez M., J. F., H. A. Ritacco y M. D. Sánchez. "FORMATION OF PALLADIUM NANOPARTICLES BY THE POLYOL METHOD:INFLUENCE OF ALKALINE CONDITIONS". Anales AFA 33, n.º 4 (15 de enero de 2023): 103–11. http://dx.doi.org/10.31527/analesafa.2022.33.4.103.
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The effect of sodium hydroxide (NaOH) on the size of palladium (Pd) nanoparticles obtained by the simple polyol route was studied. Nanoparticles were synthesized at room temperature using palladium(II) chloride (PdCl2) and NaOH dissolved in ethylene glycol (EG) as reduction reaction promoters. No protective agents or stabilizers were used. We monitored the reaction kinetics and the growth of the nanoparticles by UV-vis spectroscopy and their crystallinity by powder X-ray diffraction (XRD) as a function of NaOH concentration. Crystallite size was evaluated from the diffraction pattern. We found that nanoparticle growth is strongly influenced by the NaOH: Pd molar ratio. Crystallite sizes from 2 to 24 nm were obtained for molar ratios ranging from 1 to 33. At lower concentrations of NaOH, the nucleation and growth process of the nanoparticles were found to be controlled by the reduction of the Pd ion precursors.At higher concentrations, the intermediate reduction of Pd-Cl-OH species determines the nanoparticle growth rate resulting in the formation of the smallest final-size nanoparticles.
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Sutthavas, Pichaporn, Matthias Schumacher, Kai Zheng, Pamela Habibović, Aldo Roberto Boccaccini y Sabine van Rijt. "Zn-Loaded and Calcium Phosphate-Coated Degradable Silica Nanoparticles Can Effectively Promote Osteogenesis in Human Mesenchymal Stem Cells". Nanomaterials 12, n.º 17 (24 de agosto de 2022): 2918. http://dx.doi.org/10.3390/nano12172918.
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Nanoparticles such as mesoporous bioactive glasses (MBGs) and mesoporous silica nanoparticles (MSN) are promising for use in bone regeneration applications due to their inherent bioactivity. Doping silica nanoparticles with bioinorganic ions could further enhance their biological performance. For example, zinc (Zn) is often used as an additive because it plays an important role in bone formation and development. Local delivery and dose control are important aspects of its therapeutic application. In this work, we investigated how Zn incorporation in MSN and MBG nanoparticles impacts their ability to promote human mesenchymal stem cell (hMSC) osteogenesis and mineralization in vitro. Zn ions were incorporated in three different ways; within the matrix, on the surface or in the mesopores. The nanoparticles were further coated with a calcium phosphate (CaP) layer to allow pH-responsive delivery of the ions. We demonstrate that the Zn incorporation amount and ion release profile affect the nanoparticle’s ability to stimulate osteogenesis in hMSCs. Specifically, we show that the nanoparticles that contain rapid Zn release profiles and a degradable silica matrix were most effective in inducing hMSC differentiation. Moreover, cells cultured in the presence of nanoparticle-containing media resulted in the highest induction of alkaline phosphate (ALP) activity, followed by culturing hMSC on nanoparticles immobilized on the surface as films. Exposure to nanoparticle-conditioned media did not increase ALP activity in hMSCs. In summary, Zn incorporation mode and nanoparticle application play an important role in determining the bioactivity of ion-doped silica nanoparticles.
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Lee, Jae Hoon, Tae Min Kim, In-Gyu Choi y Joon Weon Choi. "Phenolic Hydroxyl Groups in the Lignin Polymer Affect the Formation of Lignin Nanoparticles". Nanomaterials 11, n.º 7 (9 de julio de 2021): 1790. http://dx.doi.org/10.3390/nano11071790.
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Alkaline soda lignin (AL) was sequentially fractionated into six fractions of different molecular size by means of solvent extraction and their phenolic hydroxyl groups were chemoselectively methylated to determine their effect on nanoparticle formation of lignin polymers. The effect of the lignin structure on the physical properties of nanoparticles was also clarified in this study. Nanoparticles were obtained from neat alkaline soda lignin (ALNP), solvent-extracted fractions (FALNPs, i.d. 414–1214 nm), and methylated lignins (MALNPs, i.d. 516–721 nm) via the nanoprecipitation method. Specifically, the size properties of MALNPs showed a high negative correlation (R2 = 0.95) with the phenolic hydroxyl group amount. This indicates that the phenolic hydroxyl groups in lignin could be influenced on the nucleation or condensation during the nanoprecipitation process. Lignin nanoparticles exhibited high colloidal stability, and most of them also showed good in vitro cell viability. This study presents a possible way to control nanoparticle size by blocking specific functional groups and decreasing the interaction between hydroxyl groups of lignin.
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Qiu, Lang, Hengbo Yin, Aili Wang, Lingqin Shen y Wei Tao. "Oxidation of 1,2-Propanediol to Carboxylic Acid Over Hydroxyapatite Nanorod-Supported Metallic Cu0 Nanoparticles". Journal of Nanoscience and Nanotechnology 20, n.º 3 (1 de marzo de 2020): 1723–31. http://dx.doi.org/10.1166/jnn.2020.16985.
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Hydroxyapatite nanorod-supported metallic Cu0 nanoparticle catalysts (Cux/HAP) were prepared by the wetness chemical reduction method. The metallic Cu0 nanoparticles were well dispersed on the surfaces of the HAP nanorods. The alkaline HAP nanorods inhibited the crystal growth of the metallic Cu0 nanoparticles. The HAP nanorods also retarded the oxidation of the metallic Cu0 nanoparticles. The Cux/HAP catalyst exhibited a higher catalytic activity for the oxidation of 1,2-propanediol with gaseous oxygen to lactic, acetic, and formic acids with the total selectivity of 70.3% even at a lower reaction temperature of 140 °C. The total selectivity of lactic, acetic, and formic acids reached 93.1% at a mild reaction temperature of 180 °C. However, the sole monometallic Cu0 nanoparticles or HAP nanorods had no catalytic activity for the oxidation of 1,2-propanediol. The metallic Cu0 nanoparticles and alkaline HAP nanorods in the Cux/HAP catalyst synergistically catalyzed the oxidation of 1,2-propanediol to carboxylic acid.
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Anish, M., Ignatius Raja, K. Rahul, J. Jayaprabakar, Nivin Joy y P. Bency. "The Experimental Investigation of Heat Transfer Properties and Pressure Drop of a Corrugated Plate Heat Exchanger Using a Chemically Synthesised Zinc Oxide/Alkaline Water Nano Fluid". Journal of Nanofluids 12, n.º 2 (1 de marzo de 2023): 405–17. http://dx.doi.org/10.1166/jon.2023.1931.
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An experiment is performed to study the effects of chemically synthesized Zinc Oxide-Alkaline/water nanofluid on the pressure drop and heat convection properties of a corrugated plate heat exchanger. Nanofluids are chemically synthesised ZnO nanoparticles with diameters ranging from 200 nm to 99% purity. The weight and Reynolds number of these particles are studied to define the heat transfer properties of the finished products. The heat transfer characteristics of chemically produced ZnO are examined as a work of weight percentage and Reynolds number. In addition, the effect of adding nanoparticles to alkaline water on heat transfer coefficient is studied. The effect of increasing the nanoparticle weight concentrations and Reynolds number on the heat transfer characteristics of chemically produced ZnO-Alkaline/Water nano fluid is investigated. The results show that increasing the weight concentration of nanofluid in the corrugated plate heat exchanger enhances the heat transfer properties. At 0.2%, 0.6%, and 1.0% weight fractions of nanoparticles, the highest argumentation of the nanofluid heat transfer rate is approximately 8.6%, 16.7%, and 29.4%, respectively.
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Ikeda, Shoichiro, Akinari Nobumoto, Hideo Ono, Shinji Ono, Shinji Kawasaki y Mohamad Rusop. "Hydrophilic Carbon Nano-Particles; Preparation and Applications". Advanced Materials Research 1109 (junio de 2015): 232–37. http://dx.doi.org/10.4028/www.scientific.net/amr.1109.232.
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The hydrophilic carbon nanoparticles have been produced from synthetic graphite blocks by the electrochemical oxidation method in pure water. The resulting electrolyzed solution contains colloidal carbon nanoparticles (mean diameter is ca. 400 nm) and shows the pH value of around 2.5. The colloidal state of the solution is maintained more than a several years. After evaporation of water from the solution, carbon powders are obtained, which show a high solubility to water, namely the powder is hydrophilic. The electrolyzed solution containing carbon nanoparticles directly used as the electrical conductivity enhancer for the restoring the deteriorated lead-acid batteries by electrochemical method. The hydrophilic carbon nanoparticles were used as the environmental friendly solid-lubricant for the mechanical cutting coolants. In the case of aqueous coolants, the oily substances are used in the emulsion state in usual. By using the hydrophilic carbon nanoparticle suspension, no surfactants and no oily substances are required to maintain the suspension state. However, the cutting coolants are used in the pH values of alkaline state near 10, so the hydrophilic carbon nanoparticle solution has been neutralized by alkaline substances such as alkanolamines. In the case of oily cutting fluids for heavy duties, carbon mamo-particle powders are used after neutralized by basic barium dinonylnaphthalenesulfonate. The aqueous solutions of hydrophilic carbon nanoparticles exhibit the ability of sanitization effects to the cutting fluids and prolong the life times of them.
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Patil Machindra Balwant y Bhangale Pallavi Ravindra. "Greenery method for Synthesis of some alkali and alkaline earth metallic nanoparticles and its antibacterial screening activity". World Journal of Advanced Research and Reviews 16, n.º 3 (30 de diciembre de 2022): 494–504. http://dx.doi.org/10.30574/wjarr.2022.16.3.1356.
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In the presence study of science and technology has greater significance for the development of nanoparticles and its physicochemical properties. Alkali and alkaline earth metalic nanoparticle has synthesized by using various plant extract and metalic solution. However, biogenic reduction of metal precursors to produce corresponding metalic nanoparticle is eco-friendly, low cost, free of chemical contaminants for medical and biological applications. The synthesized Metallic nanoparticle is found to be more susceptible towards the bacterial strains.
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Chen, Qiu Ling, Wan Lin, Qiu Ling Chen y Shuang Bao Wang. "Study on the Effect of Fe3O4 Nanoparticle Dopants on the Properties of Magneto Optical Glasses". Advanced Materials Research 213 (febrero de 2011): 330–33. http://dx.doi.org/10.4028/www.scientific.net/amr.213.330.
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Fe3O4 nanoparticles doped magnetic-optical PbO-Bi2O3-B2O3 glasses were prepared and studied and the effects of Fe3O4 nanoparticle on the properties of magnetic-optical glass were analyzed. It is found that the doping of Fe3O4 nanoparticles into glasses increased the Verdet constant of magneto optical glass without evident degradation in glass transmittance. The formation of Fe3O4 nanoparticles was obtained through coprecipitation of Fe(II) and Fe(III) in alkaline media. The structure and properties of doped glasses were studied by X-ray diffraction (XRD), scanning electric microscope (SEM), UV-VIS spectray analysis and Faraday rotation test etc.
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Quinson, Jonathan, Søren Bredmose Simonsen, Luise Theil Kuhn y Matthias Arenz. "Commercial Spirits for Surfactant-Free Syntheses of Electro-Active Platinum Nanoparticles". Sustainable Chemistry 2, n.º 1 (4 de enero de 2021): 1–7. http://dx.doi.org/10.3390/suschem2010001.
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The Co4CatTM process is a simple, surfactant-free method to produce colloidal dispersions of precious metal nanoparticles in alkaline mono-alcohols. The synthesis is performed in low-boiling-point solvents and is relevant for industrial production. The robustness of the process is demonstrated by using three different commercial spirits as solvents to obtain Pt nanoparticles. The results demonstrate that careful control of the solvent purity is not needed to achieve the synthesis of stable 2 nm platinum nanoparticle colloids readily active electrocatalysts for energy conversion reactions like the methanol oxidation.
Tesis sobre el tema "Alkaline nanoparticles"
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Husar, Richard. "Investigation into the Formation of Nanoparticles of Tetravalent Neptunium in Slightly Alkaline Aqueous Solution". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-177381.
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Considering the worldwide growing discharge of minor actinides and the current need for geological disposal facilities for radioactive waste, this work provides a contribution to the safety case concerning Np transport if it would be released from deep repository sites and moving from alkaline cement conditions (near-field) to more neutral environmental conditions (far-field). The reducing conditions in a nuclear waste repository render neptunium tetravalent, which is assumed to be immobile in aqueous environment due to the low solubility solution of Np(IV). For tetravalent actinide nuclides, the most significant transport should occur via colloidal particles. This work demonstrates the formation of intrinsic neptunium dioxide nanocrystals and amorphous Np(IV) silica colloids under environmentally relevant conditions.
The dissociation of the initial soluble Np(IV) complex (i.e. [Np(IV)(CO3)5]6-) induces the intrinsic formation of nanocrystalline NpO2 in the solution phase. The resulting irregularly shaped nanocrystals with an average size of 4 nm exhibit a face-centered cubic (fcc), fluorite-type structure (space group ). The NCs tend to agglomerate under ambient conditions due to the weakly charged hydrodynamic surface at neutral pH (zetapotential ~0 mV). The formation of micron-sized agglomerates, composed of nanocrystals of 2-5 nm in size, and the subsequent precipitation cause immobilization of the major amount of Np(IV) in the Np carbonate system. Agglomeration of NpO2 nanocrystals in dependence on time was indicated by PCS and UV-vis absorption spectroscopy with the changes of baseline characteristics and absorption maximum at 742 nm.
Hitherto, unknown polynuclear species as intermediate species of NpO2 nanocrystal formation were isolated from solution and observed by HR-TEM. These polynuclear Np species appear as dimers, trimers and hexanuclear compounds in analogy with those reported for other actinides.
Intrinsic formation of NpO2 (fcc) nanocrystals under ambient environmental conditions is prevented by admixing silicic acid: amorphous Np(IV) silica colloids are formed when silicate is present in carbonate solution.
Herein, the initial molar ratio of Si to Np in solution lead to the formation of Np(IV) silica particles of different composition and size where Si content determines the structure and stability of resulting colloids. Implications for different electronic structures of Np(IV) in dependence on Si content in the solid phase are given by the shift of the absorption maximum at 742 nm characteristic for Np(IV) colloids, silica excess of 5 times the magnitude of Si to Np reveal a redshift up to 6 nm in the colloidal UV-vis spectrum. Precipitation of Np(IV) particles in the ternary system results in a different coordination sphere of Np(IV) compared to the binary system, and the incorporation of Si into internal structure of Np(IV) silica colloids in coffinite-like structure is confirmed by EXAFS. TEM confirms different kinds of particle morphologies in dependence on the silica content. Silica-poor systems reveal porous particles in the micron-range which consist of irregular cross-linked hydrolyzed Np(IV) silica compartments with pores <15 nm.
In contrast, long-term stabilized and silica-enriched systems are characterized by isolated particles with an average particle size of 45 nm. Agglomerates of such isolated Np(IV) silica particles appear as consolidated amorphous solids with a densely closed surface and exhibit no internal fractures. The latter mentioned morphology of Np(IV) silica particles might facilitate the migration behavior of Np(IV) in a stabilized colloidal form under environmental conditions. The silica-enriched particles with densely closed surface are long-term stabilized as colloidal dispersion (>1 year) due to repulsion effects caused by significant surface charge. Particles synthesized from Si/Np = 9/1 carry exclusively negative surface charge in nearly the whole pH range from pH 3 to pH 10 with zetapotential = (-) 5 to (-) 30 mV. The zeta potentials of all particle systems containing silica are significantly shifted to more negative values below pH 7 where the isoelectrical point shifts from pH = 8.0 to 2.6 effecting negative charge under ambient conditions which supports electrostatic stabilization of Np(IV) particles. Particle surface charge at the slipping plane, particle size and shape necessarily depend on the initial magnitude of Si content in solution during particle formation. Particular changes of the morphology and internal structure of different Np(IV) silica colloids by aging are indicated by TEM and XPS. The composition and the crystallinity state of the initially formed amorphous phases partially changed into well-ordered nanocrystalline units characterized with fcc structure.
The presence of silicate under conditions expected in a nuclear waste repository significantly influences the solubility of Np(IV) and provoke the stabilization of waterborne Np(IV) up to concentrations of 10-3 M, exceeding Np´s solubility limit by a factor of up 10.000.
Neptunium and silicate significantly interact with each other, and thereby changing their individual hydrolysis and polymerization behavior. Silicate prevents the intrinsic formation of NpO2 NCs in fcc-structure, and at the same time, Np(IV) prevents the polymerization of silicate. Both processes result in the formation of Np(IV) silica colloids which possibly influence the migration behavior and fate of Np in the waste repositories and surrounding environments. For tetravalent actinides in general, the most significant transport in the environment would occur by colloidal particles. Therefore, Np(IV) silica colloids could have a significant implication in the migration of Np, the important minor actinide in the waste repositories, via colloidal transport.
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Facciotti, Camilla <1990>. "Development of lanthanide doped alkaline-earth fluorides core-shell nanoparticles for nanothermometry and drug delivery applications". Master's Degree Thesis, Università Ca' Foscari Venezia, 2015. http://hdl.handle.net/10579/6344.
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In this study we have worked out a new kind of nanodevices based on CaF2 and SrF2 hosts doped with lanthanide ions with upconverting properties. The main aim consists in the development of luminescent, MRI active and multifunctional nanoparticles useful in different biomedical fields. The structural, morphological and optical properties have been investigated with laser spectroscopy, X-ray diffraction technique, electron microscopy technique. The colloidal properties have been studied with the Dynamic Light Scattering technique. The encouraging results prove that the upconverting nanoparticles are good candidates as nanothermometers and nanodelivery cargo systems.
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Ntwatwa, Ziphozihle. "Formulation and evaluation of the biocompatibility of chitosan-dextran nanoparticles using a blood-brain barrier model". University of the Western Cape, 2018. http://hdl.handle.net/11394/6431.
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Magister Scientiae - MSc (Medical BioSciences)Central nervous system (CNS) infections are a therapeutic challenge. This is partly due to insufficient drug penetration across the blood-brain barrier (BBB). The BBB is a specialized, highly selective, metabolically active physiological barrier that regulates the movement of molecules into-and-out of the brain. As a result, large hydrophilic antibiotics such as colistin poorly penetrate to the CNS. Colistin is an old 'last line of defence'; a gram-negative antibiotic that has seen its clinical re-emergence due to the surge of multidrug resistance (MDR) infections. However, owing to systemic toxicity, increasing the intravenous dosage, in order to obtain higher CNS penetration, is inimical. Chitosan (CS) based nanoparticles (NPs) have been proposed as drug delivery systems across the BBB. CS is a cationic, natural polysaccharide that has the ability to be complexed with multivalent polymers like dextran (DS) thus forming CS-DS NPs. Naturally, CS has remarkable inherent features such as biocompatibility, biodegradability, ability to encapsulate poorly soluble drugs and it is favourable for endothelial cell uptake. However, polymeric NPs (even those derived from natural polysaccharides) have limited use due to toxicity. Considering the vital role of the BBB, toxicity would denote dire effects on CNS functioning. Therefore, treatment of CNS infections fringes on a deeper understanding of the interactions between drug delivery systems and the BBB.
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Kusi, Joseph, Phillip R. Scheuerman y Kurt J. Maier. "Antimicrobial Properties of Silver Nanoparticles May Interfere with Fecal Indicator Bacteria Detection in Pathogen Impaired Streams". Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etsu-works/7834.
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Silver nanoparticles (AgNPs) are expected to enter aquatic systems, but there are limited data on how they might affect microbial communities in pathogen impaired streams. We examined microbial community responses to citrate-AgNP (10.9 ± 0.7 nm) and polyvinylpyrrolidone (PVP)-AgNP (11.0 ± 0.7 nm) based on microbial concentration and enzyme activity in sediment from a pathogen impaired stream. Addition of each nanoparticle to sediment caused at least a 69% decrease in microbial concentration (1,264 ± 93.6 to 127 ± 29.5 CFU/g) and a 62% decrease in β-glucosidase activity (11.7 ± 2.1 to 1.3 ± 0.3 μg/g/h). Each AgNP reduced alkaline phosphatase activity but their effects were not statistically significant. Sediment exposed to 0.108 mg Ag/kg of AgNO3 resulted in a 92% decrease in microbial concentration and a reduced enzyme activity which was not statistically significant. Measured total silver in sediments treated with AgNPs which exhibited significant inhibition effects on the microbial community ranged from 0.19 ± 0.02 to 0.39 ± 0.13 mg Ag/kg. These concentrations tested in this study are much lower than the expected concentrations (2-14 mg Ag/kg) in freshwater sediments. The results of this study demonstrate that AgNPs can alter microbial community activity and population size, which may lead to false negative fecal indicator bacteria detection and enumeration using methods that rely on β-glucosidase activity. We conclude that the presence of AgNPs in impaired streams and recreational waters can influence pathogen detection methods, potentially affecting public health risk estimates.
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Husar, Richard [Verfasser], Thorsten [Akademischer Betreuer] Stumpf y Alexander [Akademischer Betreuer] Eychmüller. "Investigation into the Formation of Nanoparticles of Tetravalent Neptunium in Slightly Alkaline Aqueous Solution / Richard Husar. Gutachter: Thorsten Stumpf ; Alexander Eychmüller. Betreuer: Thorsten Stumpf". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://d-nb.info/1076280099/34.
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Monyoncho, Evans Angwenyi. "In-Situ and Computational Studies of Ethanol Electrooxidation Reaction: Rational Catalyst Design Strategies". Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35940.
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Fuel cells represent a promising technology for clean power generation because they convert chemical energy (fuel) into electrical energy with high efficiency and low-to-none emission of pollutants. Direct ethanol fuel cells (DEFCs) have several advantages compared to the most studied hydrogen and methanol fuel cells. First and foremost, ethanol is a non-toxic liquid, which lowers the investment of handling facilities because the current infrastructure for gasoline can be largely used. Second, ethanol can be conveniently produced from biomass, hence is carbon neutral which mitigates increasing atmospheric CO2. Last but not least, if completely oxidized to CO2, ethanol has a higher energy density than methanol since it can deliver 12 electrons per molecule. The almost exclusive oxidation to acetic acid overshadows the attractiveness of DEFCs considerably, as the energy density is divided by 3. The standard potential of acetic acid formation indicates that a reaction path including acetic acid, leads to inevitable potential losses of about 0.4 V (difference between ideal potential for CO2 and acetic acid "production").
The development of alkaline DEFCs had also been hampered by the lack of stable and efficient anion exchange membranes. Fortunately, this challenge has been well tackled in recent years,8,9 making the development of alkaline fuel cells (AFCs) which are of particular technological interest due to their simple designs and ability to operate at low temperatures (25-100 °C). In alkaline conditions, the kinetic of both the cathodic oxygen reduction and the anodic ethanol oxidation is facilitated. Furthermore, the expensive Pt catalyst can be replaced by the lower-cost and more active transition metals such as Pd.
The main objectives of this project are: i) to provide detailed fundamental understanding of ethanol oxidation reaction on transition metal surfaces in alkaline media, ii) to propose the best rational catalyst design strategies to cleave the C–C bond during ethanol electrooxidation. To achieve these goals two methodologies are used, i.e., in-situ identification of ethanol electrooxidation products using polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and mechanistic investigation using computational studies in the framework of density functional theory (DFT). The PM-IRRAS technique was advanced in this project to the level of distinguishing electrooxidation products at the surface of the nanoparticles (electrode) and in the bulk-phase of the electrolyte. This new PM-IRRAS utility makes it possible to detect molecules such as CO2 which desorbs from the catalyst surface as soon as they are formed. The DFT insights in this project, provides an explanation as to why it is difficult to break the C–C bond in ethanol and is used for screening the top candidate metals for further studies.
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Frederice, Rafael. "Fluorescência molecular em nanopartículas de sílica marcadas com quercetina e rodamina B". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-25082009-163731/.
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Nanoesferas de sílica contendo fluoróforos encapsulados (o complexo quercetina- Al+3 e o corante rodamina B) foram preparadas com alto controle de tamanho e morfologia, utilizando catálise ácida e básica do tetraetilortossilicato (TEOS). As nanopartículas obtidas apresentaram diâmetro da ordem de 200-300 nm, possuindo maior regularidade quando preparadas em meio alcalino. Nas preparações foram utilizados o método de Stöber e o método caroço-casca. Devido à hidrólise da quercetina em meio básico, as partículas funcionalizadas com o flavonóide ou com o complexo quercetina-Al+3, apresentaram maior intensidade de emissão sob catálise ácida. No caso da catálise básica, as partículas apresentaram emissão significativa quando preparadas utilizando um sol de alumina, porém foram obtidos paralelepípedos nanométricos. Os decaimentos de fluorescência para o sistema quercetina-alumina são biexponenciais, em concordância com os dois complexos quercetina-Al+3 formados no interior da nanopartícula de sílica. No caso da rodamina B, foram realizadas medidas de espectroscopia de correlação de fluorescência, que mostraram uma relação entre relaxação difusional com tamanho e autoagregação das partículas.Silica nanospheres doped with quercetin-Al+3 and rhodamine B were synthesized with high size control and morphology, using acid and basic catalysis of tetraethylorthosilicate (TEOS). The nanoparticle diameter obtained was about 200- 300 nm, with higher regularity when synthesized in alkaline media. The Stöber\'s and core-shell methods were used as preparation methods. Because the alkaline hydrolysis of quercetin, the flavonoid or the quercetin-Al+3 complex doped nanoparticles showed higher emission intensity when acid catalysis was used. When basic catalysis was performed, the particles prepared with an alumina-sol showed expressive emission intensity, but nanometric parallelepipeds were obtained. The quercetin-alumina fluorescence decays are biexponential, agreeing with the two types of quercetin-Al+3 complexes formed in the nanoparticles domain. In the case of rhodamine B, fluorescence correlation spectroscopy (FCS) measurements were performed, showing a relation between diffusion relaxation with size and aggregation behavior.
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Nunes, Andreia. "Hybrid mesoporous materials for the oxidative depolymerization of lignin into valuable molecules". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1024.
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La lignine est un des polymères naturels les plus abondants et le seul constituant de la biomasse basé sur des unités aromatiques et, à ce titre, représente une ressource renouvelable prometteuse pour la production durable de molécules organiques plus complexes. Les travaux de cette thèse portent sur le développement de matériaux catalytiques capables de transformer sélectivement la lignine en molécules fonctionnelles de base, hautement oxygénées, et l'étude de leur mise en oeuvre en condition alcaline oxydante en utilisant le peroxyde d'hydrogène comme donneur d'oxygène. Différentes familles de matériaux hybrides de type SBA-15 à base de titane, Au/titane, Ag/titane et Fe(TAML) ont tout d'abord été synthétisées et entièrement caractérisées. Des études catalytiques comparatives ont ensuite été réalisées afin d'évaluer leurs performances en termes de degré de dépolymérisation et distribution de produits. Le catalyseur présentant le plus fort potentiel, le matériau TiO2 supporté sur SBA-15, a ensuite été soumis à des études de réactivité plus poussées afin d'optimiser les différents paramètres réactionnels (température, temps de réaction et quantité d'oxydant) permettant d'atteindre en présence d'un excès d'oxydant jusqu'à 90 %pds de conversion de la lignine et à 80°C un rendement en bio-huile de 50%pds constituée principalement d'acides carboxyliques et molécules aromatiques potentiellement valorisablesLignin is one of the most abundant natural polymers and the only biomass constituent based on aromatic units and as such represents a promising renewable resource for the sustainable production of complex organic molecules. This dissertation reports on the development of catalytic materials capable of selectively transform lignin into basic functional molecules with high oxygen content and the study of their performance under alkaline oxidative conditions, using hydrogen peroxide as oxygen donner. Different families of hybrid materials based on the SBA-15 scaffold were first synthesized by incorporation of titanium, Au/titanium, Ag/titanium and Fe-TAML and completely characterized. Comparative catalytic studies were then accomplished in order to evaluate their performance in terms of degree of depolymerization and product distribution. The catalyst with the highest potential, the TiO2 based SBA-15 material, was then submitted to further reactivity studies in order to optimize the different reaction parameters (temperature, reaction time and quantity of oxidant). In the presence of an excess of oxidant, conversions up to 90 wt. % were obtained, whereas a temperature of 80 °C allowed to obtain a yield in bio-oil of 50 wt. %, which is mainly composed of carboxylic acids and aromatic molecules with potential to be further valorized
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Queiroz, Adriana Coêlho. "Síntese e estudo da atividade eletrocatalítica de óxidos de metais de transição e de nanopartículas de prata e ouro para a reação de redução de oxigênio". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-25102011-170304/.
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A reação de redução de oxigênio (RRO) foi estudada em eletrocatalisadores formados por nanopartículas de óxidos puros e mistos de metais de transição de Mn, Co e Ni, além de estrutura tipo espinel, e por nanopartículas de Ag, Au e Ag3M (M= Au, Pt, Pd e Cu) suportadas em carbono Vulcan, em eletrólito alcalino. Os óxidos de metais de transição foram sintetizados por decomposição térmica de seus respectivos nitratos e as nanopartículas a base de prata e ouro foram sintetizadas por redução química com borohidreto. Os eletrocatalisadores foram caracterizados por Difratometria e Espectroscopia de Absorção de Raios X (somente para os óxidos de transição). Os materiais a base de óxidos de manganês, mostraram-se com alta atividade para a RRO, para os quais os resultados espectroscópicos in situ evidenciaram a ocorrência da redução do Mn(IV) para Mn(III), na região de início da RRO. Assim, as atividades eletrocatalíticas foram associadas à ocorrência da transferência de elétrons do Mn(III) para o O2. Entretanto, apresentaram forte desativação após ciclagem potenciodinâmica, o que foi associado à formação da fase Mn3O4, conforme indicado por difratometria de Raios X, após os experimentos eletroquímicos, que é eletroquimicamente inativa. Já o material formado pela estrutura do tipo espinel de MnCo2O4 apresentou alta atividade e estabilidade frente à ciclagem e à RRO. A alta atividade eletrocatalítica foi relacionada a ocorrência do par redox CoII/CoIII em maiores valores de potencial em relação ao CoOx e MnOx, devido a interações entre os átomos de Co e Mn no reticulo espinélico. Contrariamente ao observado nos óxidos com maior quantidade de manganês, o espinel mostrou-se altamente estável, o que foi associada à não alteração de sua estrutura no intervalo de potenciais que a RRO ocorre. Para os materiais bimetálicos a base de prata e ouro, os experimentos eletroquímicos indicaram maior atividade eletrocatalítica para o material de Ag3Au/C. Neste caso, a alta atividade foi associada a dois efeitos principais: (i) a um efeito sinergético, no qual os átomos de ouro atuam na região de ativação, favorecendo a adição de hidrogênio e os átomos vizinhos de prata proporcionam a quebra da ligação O-O, conduzindo a RRO pelo caminho de quatro elétrons por molécula de O2; (ii) ao aumento força da ligação Ag-O, devido à interação da Ag com o Au, resultando em maior atividade para a quebra da ligação O-O, aumentando a atividade da Ag para a RRO, em relação à atividade da Ag pura. Assim, a RRO apresentou menor sobrepotencial e maior número de elétrons em Ag3Au/C, quando comparado com as demais nanopartículas bimetálicas.The oxygen reduction reaction (ORR) was studied on electrocatalysts composed by pure and mixed transition metal oxides of Mn, Co, and Ni, including spinel-like structures, and by Ag, Au, and Ag3M/C (M= Au, Pt, Pd e Cu) bimetallic nanoparticles, in alkaline electrolyte. The transition metal oxides were synthesized by thermal decomposition of their nitrates, and the silver and gold-based nanoparticles by chemical reduction using borohydride. The electrocatalysts were characterized by X-Ray Diffraction and X-Ray Absorption Spectroscopy (in the case of the metal oxides). The manganese-based oxide materials showed high activity for the ORR, in which the in situ spectroscopic results evidenced the Mn(IV) to Mn(III) reduction, in the range of the ORR onset. In this case, the electrocatalytic activities were correlated to the transfer of electron from Mn(III) to O2. However, they presented strong deactivation after several potentiodynamic cycles, which was ascribed to the formation of the electrochemically inactive phase of Mn3O4, as indicated by the XRD results, after the electrochemical experiments. On the other hand, the MnCo2O4 spinel-like material showed high activity and stability for the ORR. Its high electocatalytic activity was attributed to the CoII/CoIII redox pair, taking place at higher potentials, in relation to that of the CoOx e MnOx pure phases, due to the Co and Mn interactions in the spinel lattice. Contrarily to the behavior observed for the manganese-based materials, the spinel oxide presented high stability, which was ascribed to the non alteration of its crystallographic structure in the range of potentials tha the ORR takes place. For the Au and Ag-based materials, the electrochemical experiments indicated higher electrocatalytic activities for Ag3Au/C. In this case, its higher activity as associated to two main aspects: (i) to a synergetic effect, in which the gold atoms act in the activation region, facilitating the hydrogen addition, and the neighboring Ag atoms promoting the O-O bond breaking, leading the ORR to the 4-electrons pathway; (ii) to the increased Ag-O bond strength, due to the electronic interaction between Ag and the Au atoms, resulting in a faster O-O bond breaking, enhancing the electrocatalytic activity of the Ag atoms in the Ag3Au/C nanoparticle, in relation to that on the pure Ag. Therefore, the ORR presented lower overpotential and higher number of electrons in the Ag3Au/C electrocatalyst, when compared to the other investigated bimetallic nanoparticles.
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Brazeau, Nicolas. "Palladium-Based Catalysts for Ethanol Electrooxidation in Alkaline Media". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32201.
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Direct ethanol fuel cells have been shown to be a good alternative to internal combustion engines in order to reduce the CO2 emissions. In this study, Pd and Pd-based nanocatalysts were deposited on various supports (carbon black, graphene, SnO2, CeO2, TiO2, TiO2 nanotubes and SnO2/TiO2 nanotubes) and their effects on the catalytic properties of the deposited metal for ethanol oxidation in alkaline media are studied. These modifications to the catalytic systems have shown to cause an increase in the reaction rate at the surface of the catalyst and to reduce the overpotential of the ethanol oxidation reaction. Two different promotion mechanisms have been identified. Firstly, the supply of OH- ions at the metal-support interface facilitates the oxidation of adsorbed molecules on neighbouring Pd sites. Secondly, an increase in electron density of Pd nanoparticles with increasing support reducibility modifies the adsorption strength of ethanol and its oxidation intermediates.
Capítulos de libros sobre el tema "Alkaline nanoparticles"
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Baglioni, Piero, David Chelazzi, Rodorico Giorgi, Huiping Xing y Giovanna Poggi. "Alkaline Nanoparticles for the Deacidification and pH Control of Books and Manuscripts". En Nanoscience and Cultural Heritage, 253–81. Paris: Atlantis Press, 2016. http://dx.doi.org/10.2991/978-94-6239-198-7_9.
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Nguyen, Tan No, Huu Quoc Phong Le y Anh Tuan Le. "Activation of Nanoparticle and Alkaline Environment on Fly Ash Geopolymer Mortar". En Lecture Notes in Civil Engineering, 361–70. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-3303-5_29.
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Poggi, Giovanna, Nicole Bonelli, Rodorico Giorgi y Piero Baglioni. "La chimica dei nanocomposti e la loro applicazione al restauro dei manoscritti". En Dalla tutela al restauro del patrimonio librario e archivistico. Venice: Edizioni Ca' Foscari, 2018. http://dx.doi.org/10.30687/978-88-6969-215-4/022.
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Cellulose-based artifacts are susceptible to fast degradation due to the presence of detrimental components and to the action of environmental pollutants. As a result, the acidity of pristine material increases, promoting the acid-catalysed depolymerisation of cellulose that alters the mechanical properties of paper. In this paper, the use of innovative dispersions of alkaline earth metal hydroxide nanoparticles will be discussed as a method of counteracting the degradation of paper. The application of the most recent formulations of nanoparticles dispersions for the deacidification of artworks will be highlighted. Finally, the usage of innovative gel formulations for the cleaning of cellulose-based artworks will be discussed.
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Wu, Chengfan, Rui Zhang, Wei Du, Liang Cheng y Gaolin Liang. "Alkaline phosphatase-triggered self-assembly of near-infrared nanoparticles for the enhanced photoacoustic imaging of tumors". En Methods in Enzymology, 111–44. Elsevier, 2021. http://dx.doi.org/10.1016/bs.mie.2021.06.028.
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Jolivet, Jean-Pierre. "Conclusion". En Metal Oxide Nanostructures Chemistry. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190928117.003.0012.
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Metal oxide nanostructures are of major interest in technology. It is therefore essential to have a full understanding of the phenomena involved in the aqueous synthesis of nanoparticles, so that their properties can be adjusted to a desired application. Understanding these phenomena is also important in other fields, for instance, in geology and environmental sciences, enabling us to explain the presence and formation of a given mineral. The precipitation of metal oxy(hydroxi)des is a complex phenomenon initiated by hydroxylation of the cations in solution and resulting from condensation of the hydroxylated species. Therefore, the acidity of the cations is the main characteristic of their reactivity. Three main parameters are essential in predicting and rationalizing the behavior of metal cations in water: the formal charge (the oxidation degree), size, and electronegativity, which determine the degree of polarization of the oxygenated ligands. One may thus define five classes of cations: . . . The too weakly polarizing cations that form only aquocomplexes unable to condense and to precipitate; for instance, the alkaline cations M+, The cations that condense by olation and form polycations and hydroxides, typically, the divalent cations and also Al3+. The cations that condense by olation and oxolation and form oxyhydroxides and oxides (such as Cr3+, Fe3+, and Mn3+). The cations that condense essentially by oxolation and form oxides that are more or less hydrated (Ti4+, Mn4+, V5+). The cations that form anionic oxocomplexes and exhibit no trend toward condensation, typically, MnVII. . . . This series thus includes cations of increasing polarizing power, that is cations of increasing oxidation degree and electronegativity. Precipitation usually generates nanosized particles. In a system that is not continuously fed, in which a limited amount of matter is available in the reactor, the nucleation step is always sudden and easy enough, allowing lower supersaturation and creating nuclei that have stopped growing because of the too low concentration in soluble precursor. That does not, however, exclude an intense dynamics of dissolution–crystallization because of the evolution of the criticality of the particle size during the decrease in supersaturation.
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Wong, Kin y Vitaly V. Kresin. "PHOTOIONIZATION OF ALKALI NANOPARTICLES AND CLUSTERS". En Latest Advances in Atomic Cluster Collisions, 223–32. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2004. http://dx.doi.org/10.1142/9781860946806_0020.
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Lambert, Richard. "Electrochemical and Chemical Promotion by Alkalis with Metal Films and Nanoparticles". En Catalysis and Electrocatalysis at Nanoparticle Surfaces. CRC Press, 2003. http://dx.doi.org/10.1201/9780203912713.pt5.
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Wang, S., L. Jiang, Y. Li y D. Li. "Immobilization of alkali protease with magnetic nanoparticles modified by amino-silane". En Frontiers of Energy and Environmental Engineering, 565–68. CRC Press, 2012. http://dx.doi.org/10.1201/b13718-132.
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Aguado, Andrés y José M. López. "Chapter 3 Computer simulation of the solid-liquid phase transition in alkali metal nanoparticles". En Nanomaterials: Design and Simulation, 59–83. Elsevier, 2007. http://dx.doi.org/10.1016/s1380-7323(06)80005-1.
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de Ménorval, L. C. y F. Rachdi. "Formation of alkali nanoparticles in NaY zeolite cages and in AlPO4-5 molecular sieves: NMR studies". En Studies in Surface Science and Catalysis, 2019–26. Elsevier, 1997. http://dx.doi.org/10.1016/s0167-2991(97)80668-4.
Texto completoActas de conferencias sobre el tema "Alkaline nanoparticles"
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Jung, Seunghwan y Debjyoti Banerjee. "A Simple Analytical Model for Specific Heat of Nanofluid With Tube Shaped and Disc Shaped Nanoparticles". En ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44372.
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In this study we present a simple analytical model for estimating the specific heat capacity of nanofluids containing tube shaped and disc shaped nanoparticles dispersed in a solvent. The model includes the effect of an ordered liquid layer formed at the solid-liquid interface between a tube or disc shaped nanoparticle and the liquid phase. The size and thermo-physical properties of the ordered liquid layer are calculated based on the results of molecular dynamic (MD) simulation. The model is applied to nanofluid dispersed carbon nanotube (CNT) nanoparticles with tube shape in a liquid phase of alkaline metal carbonate salt eutectic mixture (Li2CO3:K2CO3 in 62:38 molar ratio). In addition, the specific heat of nanofluid with graphite nanoparticles with disc shape is calculated using the simple analytical model. The alkaline salt mixture as well as the corresponding nanofluid has potential applications as thermal energy storage (TES) material for solar thermal energy conversion. Hence, the specific heat is an important thermo-physical property for determining the thermal efficiency of the solar thermal energy system. To identify the effect of particle size and mass concentration, the specific heat capacity is plotted as a function of particle size and mass concentration. The experimental data is used to validate the simple analytical model for the effect of particle shape on the specific heat. The results show that the specific heat of nanofluid increases with the mass concentration of nanoparticles. Furthermore, nanoparticles with diameters less than 6 nm can cause anomalous enhancement in the specific heat of nanofluid. The results also show that tube shaped nanoparticles are more effective in enhancing the specific heat capacity of nanofluids than disc shaped nanoparticles due to the higher specific surface area of tube shaped nanoparticles compared to disc shaped nanoparticles of similar mass.
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McLellan, Claire A., Chris P. Siefe, Stefan Fischer, Jason R. Casar, Dayne F. Swearer, Miriam B. Goodman y Jennifer A. Dionne. "Alkaline-earth Rare-earth Upconverting Nanoparticles as Bio-compatible Mechanical Force Sensors". En CLEO: Science and Innovations. Washington, D.C.: OSA, 2020. http://dx.doi.org/10.1364/cleo_si.2020.sth3m.5.
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Sen, Debasis, Avik Das y Jitendra Bahadur. "Dissolution of amorphous SiO2 nanoparticles at high alkaline pH: Real time SAXS investigation". En DAE SOLID STATE PHYSICS SYMPOSIUM 2018. AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5112874.
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Samba, Mohammed A., Hafsa A. Hassan, Mahjouba S. Munayr, Moataz Yusef, Abdelkareem Eschweido, Hamed Burkan y Mahmoud O. Elsharafi. "Nanoparticles EOR Aluminum Oxide (Al2O3) Used As a Spontaneous Imbibition Test for Sandstone Core". En ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10283.
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Abstract There are three types of oil production energy operations, primary recovery, secondary recovery and enhanced oil recovery (EOR). EOR consider as the last period for production operations. Where the EOR classify into many types such as thermal injection, gas injection, microbial EOR and chemical flooding. Chemical flooding classified into many types such as polymer, surfactant, alkaline and nanoparticles (NP). NP can be classified into many types such as Iron Oxide (Fe2O3), Aluminum Oxide (Al2O3) and Magnesium Oxide (MgO) etc. In this study NP Aluminum oxide (Al2O3) were used to enhance the oil recovery. The main objective of this study is to use the Nanoparticles EOR (Al2O3) and know it is effect on increasing the extraction of oil from cores. The big motivation of using Al2O3 that it is easy to extract it from raw clay. However, the raw clay is available in Libya and using it will be more economic than using other method of chemical EOR. Nanoparticles EOR Aluminum oxide (Al2O3) used as a spontaneous imbibition test for sandstone core samples after saturated by crude oil. A spontaneous imbibition test consisting of two scenarios of nanoparticle solution (Al2O3) with change temperature and compared with one scenario of distilled water. The spontaneous imbibition test was performed in this study at room temperature to oven temperature (30C°, 40C°, 50C°, 60C°, 70C°). The results shown that the oil recovery increases with the increase of the concentration of nanoparticle (Al2O3) and increase the temperature. The higher oil recovery was 76.04% at NP (Al2O3) concentration 1%. Finally, oil swelling and adsorption (NP (Al2O3) with oil drops) have been noticed during the extraction of oil. Thus, the gravity force will be higher than the capillary force.
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"Synthesis of Graphene Supported Nickel and Cobalt Nanoparticles and Their Applications for Methanol Oxidation in Alkaline Medium". En May 22-24, 2017 Kuala Lumpur (Malaysia). IIE, 2017. http://dx.doi.org/10.15242/iie.e0517019.
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Patlolla, Anita K. y Paul B. Tchounwou. "Abstract 5463: Serum aminotransferases and alkaline phosphatases as biomarkers of hepatotoxicity in sprague-dawley rats exposed to silver nanoparticles". En Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL. American Association for Cancer Research, 2012. http://dx.doi.org/10.1158/1538-7445.am2012-5463.
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Assef, Y., P. Pourafshary y H. Hejazi. "Controlling Interactions of Colloidal Particles and Porous Media During Low Salinity Water Flooding and Alkaline Flooding By MgO Nanoparticles". En SPE EOR Conference at Oil and Gas West Asia. Society of Petroleum Engineers, 2016. http://dx.doi.org/10.2118/179768-ms.
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Rizvi, Syed Muhammad Mujtaba, Yousof Nayfeh, Baha El Far y Donghyun Shin. "Use of Silica Coated Zinc Nanoparticles for Enhancement in Thermal Properties of Carbonate Eutectic Salt for Concentrated Solar Power Plants". En ASME 2020 14th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/es2020-1710.
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Abstract Concentrated Solar Power (CSP) is one of the most efficient mega-scale renewable Energy sources. However, the overall cost of energy production is not viable for commercial usage and supplanting with fossil fuels or energy produced by nuclear ways. Its operational cost mainly lies in the electrical and thermal systems of the plant. The thermal system comprises of heat storage and heat transfer system. Any enhancement to heat storage or transfer system will directly reduce the cost of operation and increase the yield. Conventionally, oils stable up to 400C were used to transfer and store heat, however more recently, molten salts have been operational in the field for purpose of heat transfer but still, their thermal storage and conduction are limited. The current work explores the possibility of boosting the thermal storage capacity of molten salts through the latent heat of added phase change materials and increasing the specific heat at the same time by adding silica encapsulated zinc nanoparticles. We studied the advantage of adding coated Zn nano-sized particles to carbonate eutectic mixture for enhanced thermal energy storage and heat capacity enhancement. Zinc particles (40nm–60nm) obtained from the commercial sources were coated with silica shells using the solgel process under alkaline conditions. The nano-capsules were then dispersed in a mixture of carbonate salts. A differential scanning calorimeter was employed to characterize the thermal properties of the mixture. Tranmission electron miocroscopy was employed to characterize nanoparticles and electron diffraction Spectroscopy was performed to characterize materials and strcutures involved.
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Radt, Benno, Jesper Serbin, Björn I. Lange, Reginald Birngruber y Gereon Hüttmann. "Laser generated micro- and nanoeffects: inactivation of proteins coupled to gold nanoparticles with nano- and picosecond pulses". En European Conference on Biomedical Optics. Washington, D.C.: Optica Publishing Group, 2001. http://dx.doi.org/10.1364/ecbo.2001.4433_16.
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Background: Protein denaturation in the fs-ns time regime is of fundamental interest for high precision applications in laser tissue interaction. Conjugates of colloidal gold coupled to proteins are presented as a model system for investigating ultrafast protein denaturation. It is expected that irradiation of such conjugates in tissue using pico-up to nanosecond laser pulses could result in effects with a spatial confinement in the regime of single macromolecules up to organelles. Materials and Methods: Experiments were done with bovine intestinal alkaline phosphatase (aP) coupled to 15 nm colloidal Gold. This complex was irradiated at 527 nm/ 532 nm with a variable number of pico- and nanosecond pulses. The radiant exposure per pulse was varied from 2 to 50 mJ/cm2 in the case of the picosecond pulses and 10 to 500 mJ/cm2 in the case of the nanosecond pulses. Denaturation was detected as a loss of protein function with the help of the fluorescence substrate 4MUP. Results and Discussion: Irradiation did result in a steady decrease of the aP activity with increasing radiant exposures and increasing number of pulses. Inactivations up to 80% using 35 ps pulses at 527 nm with 50 mJ/cm2 and a complete inactivation induced by 16 ns pulses at 450 mJ/cm2 are discussed. The induced temperature in the particles and the surrounding water was calculated using Mie’s formulas for the absorption of the nanometer gold particles and an analytical solution of the for heat diffusion. The calculated temperatures suggest that picosecond pulses heat a molecular scaled area whereas nanosecond pulses could be used for targeting larger cellular compartiments. It is difficult to identify one of the possible damage mechanisms, i.e. thermal denaturation or formation of micro bubbles, from the dependance of the inactivation on pulse energy and number of applied pulses. Therefore experiments are needed to further elucidate the damage mechanisms. The observed inactivation dependencies on applied energy and radiant power can not be explained with one or two photon photochemistry. In conclusion, denaturing proteins irreversibly via nanoabsorbers using pico-/ nanosecond laser pulses is possible. The expected confinement of the heat to the nanoabsorbers suggests that denaturation of proteins with nanometer precision could be possible with this approach. However, the mechanism of protein inactivation, which is part of present investigations, is crucial for the precision of such nanoeffects.
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Yang, Hongjoo y Debjyoti Banerjee. "Study of Specific Heat Capacity Enhancement of Molten Salt Nanomaterials for Solar Thermal Energy Storage (TES)". En ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75338.
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The overall thermal efficiency of solar power plants is highly sensitive to the operating characteristics of the Thermal Energy Storage (TES) devices. Enhancing the operating temperature of TES is imperative for enhancing the thermal efficacy of solar power plants. However, material property limitations for high temperature operation severely limit the choice of materials for TES. Molten salts and their eutectics are promising candidates for high temperature operation of TES. To enhance the thermal and operational efficiency of TES, the thermo-physical properties such as the specific heat capacity and thermal conductivity of the materials need to be maximized. The specific heat capacity (Cp) of molten salt is relatively smaller than other conventional TES materials. Recent studies have shown that addition of nanoparticles to molten salts can significantly enhance their specific heat capacity. Several transport and energy storage mechanisms have been proposed to account for these enhancements. Primarily, the layering of solvent molecules due to inter-molecular forces (due to competition between adhesive and cohesive forces) is observed at solid-liquid interface, leading to the formation of a more dense or “compressed layer” of solvent molecules on the dispersed nanoparticles. The formation and existence of the compressed layer has been demonstrated experimentally and from numerical predictions (e.g., Molecular Dynamics/ MD models). To verify the enhancement of specific heat capacity of molten salt nanofluids, the influence of compressed layer has been explored in this study. This implies that for the same amount (or concentration) of nanoparticle, the ratio of surface/volume of the individual nanoparticles can change significantly depending on the nanoparticles size and shape — which in turn can affect the mass fraction of the compressed layer formed on the surface of the nanoparticles. In this study, the specific heat capacity of the molten salt nanomaterials was investigated for: (a) silica nanoparticles in eutectic mixture of alkali chloride salt eutectics, and (b) silica nanoparticles in an eutectic mixture of alkali carbonate salts eutectics. The effect of the particle size distribution was considered in this study and it was observed that smaller nanoparticles contribute a larger proportion to the observed specific heat capacity enhancements. The size of distribution of the nanoparticles in the molten salt mixture/ nanomaterial (nanocomposites and nanofluids) was measured by using Scanning Electron Microscopy (SEM), and subsequently the actual number of nanoparticles (as a function of size) that were dispersed in molten salt fluid was calculated. The specific heat capacity of molten salt nanomaterial was calculated using a classical mixing model and by accounting for the contribution from the compressed layer in the mixture.