To see the other types of publications on this topic, follow the link: Titanium dioxide nanoparticles.
Dissertations / Theses on the topic 'Titanium dioxide nanoparticles'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Titanium dioxide nanoparticles.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
McCormick, John. "Chemistry of titanium dioxide nanoparticles." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 10.93 Mb., 224 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3220706.
Full text
2
Cadman, Christopher. "Titanium dioxide nanoparticles for photodynamic therapy." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/titanium-dioxide-nanoparticles-for-photodynamic-therapy(91717f00-c70e-4f07-8921-64caa9290b42).html.
Full textAbstract:
In the present thesis we propose the development of hybrid polymer titanium dioxide (TiO2) nanoparticles for use in biomedical applications. TiO2 exhibits high biocompatibility in the dark however, upon illumination in aqueous media with near UV light it produces an array of reactive oxygen species (ROS) which have the capability to induce death in neighbouring cells. The process of inducing cell death using a photosensitive material which produces ROS is known as photodynamic therapy (PDT) and is used to treat a wide range of maladies from psoriasis to cancer.We have demonstrated the ability to produce anatase nanoparticles with high control over their resulting size through a novel water mediated sol-gel synthetic method in benzyl alcohol, using either Ti(OnPr)4, Ti(OnBu)4 or Ti(OiPr)4 as the metal precursor. Through dynamic light scattering (DLS) analysis we have shown that the mechanism of nanoparticle growth appears to proceed through the agglomeration of primary nanoparticles formed instantly upon adding the reagents together. After synthesis the nanoparticles could be easily redispersed in aqueous media at pH2 with any further agglomeration being controlled by the parent alkoxide.After synthesis the nanoparticles were coated with PEG, conjugated to either a catechol or phosphate as ligand, in order to stabilise the nanoparticles at neutral pH. Uncoated nanoparticles exhibited good photoactive capability in the photooxidation of methylene blue. However, on coating with catechols the photoactivity of the nanoparticles was abolished. Coating with phosph(on)ates on the other hand preserved or even enhanced the photoactivity which makes this system promising for in vivo applications.At the same time this thesis also reports preliminary investigations on the use of TiO2 embedded into the walls of model drug loaded poly electrolyte multilayer microspheres for UV triggered delivery applications.
3
Mansfield, Charles M. "Phototoxic Effects of Titanium Dioxide Nanoparticles on Daphnia Magna." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc407741/.
Full textAbstract:
Titanium dioxide nanoparticles (TiO2-NP) are one of the most abundantly utilized nanomaterials in the world. Studies have demonstrated the mechanism of acute toxicity in TiO2-NP to be the production of reactive oxygen species (ROS) leading to oxidative stress and mortality in exposed organisms. It has also been demonstrated that the anatase crystalline conformation is capable of catalyzing the cleavage of water molecules to further increase the concentration of ROS in the presence of ultraviolet radiation. This photoenhanced toxicity significantly lowers the toxicity threshold of TiO2-NP to environmentally relevant concentrations (ppb). The goal of this study was to determine whether dietary uptake and accumulation of TiO2-NP in the aquatic filter feeder Daphnia magna resulted in photoenhanced toxicity. D. magna and S. caprincornatum were exposed to aqueous solutions of 20ppm and 200ppm TiO2-NP for 24hrs and then transferred to clean moderately hard water. Samples were taken at various time points, dried, and TiO2 quantified using ICP-MS. Toxicity assays were run on D. magna using three TiO2-NP (20ppm, 200ppm) exposure protocols and two ultraviolet radiation treatments. The first exposure group was exposed to aqueous solutions of TiO2-NP for the duration of the test. The second exposure group was exposed to TiO2-NP for an hour and then transferred to clean water. The third exposure group was fed S. capricornatum that had been allowed to adsorb TiO2-NP. All samples were then placed in an outdoor UV exposure system and exposed to either full spectrum sunlight (with UV) or filtered sunlight (no UV). Here we show that TiO2 uptake peaked at one hour of exposure likely due to sedimentation of the particles out of suspension, thus decreasing bioavailability for the duration of the test. Interetsingly, when D. magna were moved to clean water, aqueous concentrations of TiO2 increase as a result of depuration from the gut tract. Data also suggests these excreted particles were bioavailable and re-consumed by D. magna. These data will contribute to the understanding of TiO2-NP environmental fate and toxicity.
4
Cox, Hazel Anne. "Transport Mechanisms of Titanium Dioxide Nanoparticles in Porous Media." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/247277.
Full textAbstract:
Nanoparticles are an emerging contaminant of concern. They are used in many products and industries and, due to a lack of regulation, are entering the natural environment through our waste streams. Studies examining the transport of nanoparticles in porous media have observed divergences between data and theory. Transport data also varies greatly across studies, adding complexity to the determination of the important factors in nanoparticle transport. These main factors and key areas of deviation from theory were determined by comparing and contrasting various studies of nanoparticle transport. To further examine behavior and retention mechanisms of nanoparticles in porous media, nano-sized titanium dioxide (nano-TiO₂) was used in miscible-displacement transport experiments, followed by force measurements by Atomic Force Microscopy (AFM) between the same nanoparticles and porous media. Ionic strength ranged from 0.0015 - 30 mM, and solution chemistries were varied from pH 4.5 (favorable attachment) to 8 (unfavorable attachment). To determine the possible presence of secondary minima attachment, detachment transport experiments were performed for the unfavorable attachment conditions. Calculations were performed using DLVO theory, which is often used to describe colloid and nanoparticle retention, and compared to measured force profiles. Mass recoveries for the transport experiments ranged from 28-80%. Retention under favorable conditions was much greater than under unfavorable conditions, as was anticipated. Detachment was observed, indicating the potential presence of secondary minima. Large adhesive forces were measured by AFM and were affected by solution chemistry. Force profiles were highly variable, especially under unfavorable attachment conditions. Secondary minima were observed, even at a 0.0015 mM ionic strength. DLVO theory, while qualitatively accurate, largely under-predicted attractive and repulsive forces and their range of influence. Variability in the force profile and potential conformational changes of nanoparticle aggregates were postulated to be influential in nanoparticle transport. Retention of the nanoparticles under unfavorable conditions was postulated to involve secondary minima and the effects of surface roughness. These mechanisms, which are not represented in DLVO theory, are likely causes of the observed divergence of experimental results from theory. Improved understanding of retention mechanisms will hopefully enhance our understanding of the potential impacts of nanoparticles on the natural environment.
5
Košík, Juraj. "Determination of titanium dioxide nanoparticles in personal care products." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-240803.
Full textAbstract:
Předkládaná diplomová práce se zabývá extrakcí nanočástic oxidu titaničitého z produktů osobní péče, konkrétně opalovacích krémů a následnou charakterizací těchto částic. Počet komerčně dostupných produktů s obsahem nanočástic TiO2 se neustále zvyšuje a to se sebou přináší potřebu vyhodnotit potenciální osud a nepřímou expozici TiO2 nanošástic o různých velikostí a tvarů a zkoumat jejich celý životní cyklus. Bylo zkoumáno použití ultrafiltrace a ultracentrifugace jako extrakční metody. Dvě metody pro extrakci TiO2 nanočástic byly vyvinuty a aplikovány na vzorky opalovacích krémů. Extrahované částice mohou být použity pro ekotoxikologické studie, případně experimenty v mesokosmu. Velikost částic byla stanovena pomocí metody dynamického rozptylu světla a transmisní elektronové mikroskopie.
6
Shirley, Raphael Alexander. "Theoretical insights into the combustion synthesis of titanium dioxide nanoparticles." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609575.
Full text
7
Bhave, Radhika. "Synthesis and photocatalysis study of brookite phase titanium dioxide nanoparticles." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181250716/.
Full text
8
Ruzicka, Jan-Yves. "Synthesis of titanium dioxide nanoparticles: phase, morphology and size control." Thesis, University of Canterbury. Department of Chemistry, 2013. http://hdl.handle.net/10092/9052.
Full textAbstract:
Titanium dioxide is a well-studied and popular photocatalyst, but a number of factors still prevent its widespread use in a number of commercial applications. In this thesis we explored the synthesis of titanium dioxide nanoparticles via the sol-gel method, with the goal of creating a viable catalyst for the visible-light degradation of wastewater dyes. A number of different synthetic pathways were explored and developed, and the products categorised with respect to nanoparticle size, shape and crystallinity as well as electronic and photocatalytic properties.
9
Koopman, Mark Charles. "Titania coated hollow glass microspheres for environmental applications." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2008r/koopman.pdf.
Full textAbstract:
Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.Additional advisors: J. Barry Andrews, Krishan K. Chawla, Derrick Dean, Robert Pitt. Description based on contents viewed Feb. 13, 2009; title from PDF t.p. Includes bibliographical references.
10
Rehan, Mohammad. "In situ hydrothermal synthesis and process characterization of titanium dioxide nanoparticles." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582157.
Full textAbstract:
Hydrothermal synthesis of titanium dioxide (Ti02) nanoparticles has been studied in situ using synchrotron radiation energy dispersive X-ray diffraction (EDXRD) together with other analytical techniques. The main objective of this research study was to investigate the reaction kinetics and mechanisms of Ti02 crystallization under hydrothermal conditions. The nanoparticles have been produced from hydrothermal treatments of acid (HN03) and alkaline (tetrabutylammonium hydroxide; TBA) peptized sol-gels of different compositions at various temperatures, pressures and time durations. The in situ EDXRD spectra clearly showed that pure Ti02 anatase phase particles were crystallized from TBA peptized sol-gels, whereas pure Ti02 rutile phase particles were produced from the HN03 peptized sol-gels. The crystallization curves constructed from the EDXRD data showed that the rate of the particle formation increased with an increase in the hydrothermal process temperature for both types of sol-gel processes.
11
Gemmellaro, Pietro. "Titanium Dioxide Nanoparticles in the Field of Conservation of Cultural Heritage." Doctoral thesis, Università di Catania, 2012. http://hdl.handle.net/10761/964.
Full textAbstract:
This study deals with the preparation, characterization and photocatalytic activity in gas and aqueous media of undoped and doped TiO2 nanopowders and thin films.
Nanocrystalline anatase TiO2 of 25 nm size with a 1 at. % dopants were successfully prepared by the cost effective sol gel method as powders, and applied on glass substrates with spin coating method.
Techniques such thermal analyses, XRD, SEM, DLS, XPS, UV-Vis and Raman spectroscopy were used in order to characterize the obtained materials from a morphological, optical and structural point of view. Degussa TiO2 P25 nanopowder was used as a reference.
Photodegradation experiments indicated that NO2 and MO solution can be degraded in gas phase and in the aqueous TiO2 suspensions respectively. A comparison of the photocatalytic efficiency of undoped and doped TiO2 immobilized onto substrates versus catalysts in suspended form is reported.
Photocatalysis is a very promising method to face most of the problems connected with the increasing environmental pollution, and titanium dioxide, in its anatase crystallographic phase, which is one of the most investigated photocatalytic material and to be perfectly compatible with every day human activities.
12
Erdem, Ayça. "Short-term toxicity of photocatalytic titanium dioxide to bacteria under ambient conditions." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 204 p, 2008. http://proquest.umi.com/pqdweb?did=1679680941&sid=14&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
13
Rydström, Camilla. "Nanoparticles in Food - with a focus on the toxicity of titanium dioxide." Thesis, Uppsala universitet, Institutionen för farmaceutisk biovetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-209920.
Full textAbstract:
The use of nanoparticles, in many different fields, is rapidly increasing. What substances, and to what extent they exist in food and supplements, and the prevalence of such products on the market, is of interest to the Swedish National Food Agency. Answering those questions, as well as providing information regarding their potential toxicity, was the intent of this thesis. To understand the difficulties, and possibilities, in analyzing nanoparticles in food, a methods-section was included, covering the most common techniques, the theory behind them and when they may be used. It became abundantly clear that analyzing nanoparticles in food, and investigating their potential toxicity, is anything but simple, and requires a combination of many techniques. Quite surprisingly, it seems the occurrence of nanoparticles in food, as today, are not added on purpose, since not one nanosubstance to be used in food has been approved by EU. Rather, studies have revealed they originate from a nanosized fraction of food additives, such as TiO2 (E171), which has attracted particular attention in this report. This nanofraction may be as large as 40%, and the estimated total intake of TiO2 (as stated by EFSA) is 1.28 mg/kg/person, resulting in quite an amount of nano TiO2, provided the numbers are correct. The toxicity of silver has also been reviewed, since the colloidal form, which includes nanoparticles, is quite common as a health supplement. Toxicity studies are not unambiguous though, some indicate geno-and–cytotoxicity and others do not. Importantly, the toxicity studies on TiO2 have not been done on E171, but on many other forms of TiO2, whose relevance is difficult to predict. TiO2 is, however, classified as a possible carcinogen by IARC. Several groups have taken an interest in a potential relation between particle intake and various chronic inflammatory diseases, also discussed in this report. In conclusion, the size, modifications of E171 and its toxicity, requires more attention in order for food authorities to confidently ascertain healthy food for the public.
14
Lin, Ming-Yu. "Interactions between titanium dioxide nanoparticles and algal cells at moderate particle concentration." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 98 p, 2008. http://proquest.umi.com/pqdweb?did=1597633661&sid=17&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
15
Bradfield, Scott Jared. "INFLUENCE OF TIO2 ENGINEERED NANOPARTICLES ON PHOTOSYNTHETIC EFFICIENCY AND CONTAMINANT UPTAKE." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1758.
Full textAbstract:
The production of engineered nanoparticles (ENPs) is growing at an incredibly fast rate and will soon become a trillion dollar industry. At this rate of production, there is a great potential for engineered nanomaterials to be released into the environment, both intentionally and unintentionally. TiO2 ENPs are one of the most widely produced nanoparticles with a broad range of applications in paints, inks, sunscreens, cosmetics, astronautics, and air/water purification. TiO2 ENPs have been proposed for their use in agricultural settings as a UV protectant, a defense against harmful bacteria and fungi, or a catalyst for the degradation of pesticides and herbicides. Furthermore, it has been shown to increase several aspects of photosynthesis in spinach including Rubisco and Rubisco activase activity, chlorophyll synthesis, and oxygen evolution. Foliar application of TiO2 ENPs on spinach resulted in a significant increase in plant fresh weight, dry weight, chlorophyll content, net photosynthetic rate, and carboxylase activity of Rubisco. These findings have prompted investigations for the use of TiO2 ENPs as a foliar spray to promote plant growth and yield. The first main objective of this research was to determine if TiO2 ENPs has the capabilities to increase photosynthetic production in Zea mays at concentrations similar to that of the experiments performed with spinach. Secondly, it was examined if the size of the TiO2 was a factor in the increased photosynthetic response by comparing TiO2 ENPs with bulk TiO2. Finally, the determination of whether the boost in photosynthesis resulted in an increased seed quality/quantity. Another aspect of this research was to determine how the interaction of TiO2 ENPs with inorganic contaminants may affect the uptake and accumulation of the contaminants in plants. Cadmium and arsenic are two of the top ten most hazardous substances on the priority list of the Agency for Toxic Substances and Disease Registry. Sources for Cd and As contamination include atmospheric deposition resulting from mining, smelting, and fuel combustion, phosphate fertilizers, and sewage sludge. Both of these contaminants can be taken up by plant roots and translocated to the leaves and fruits, thus entering the food chain. The release of TiO2 ENPs into domestic and industrial wastewaters is expected to represent the largest release of these nanoparticles. There has been data showing that up to 99% of TiO2 ENPs that enter wastewater treatment plants are retained in the sludge. In addition, TiO2 ENPs are being used at some water treatment plants because of their strong adsorption strength for hazardous materials, such as cadmium, arsenic, and copper and also the photocatalytic breakdown of harmful organic compounds. Since sewage sludge from wastewater treatment plants is applied to agricultural lands as a soil conditioner and fertilizer, this has resulted in the introduction of an estimated 120 g kg-3 per year of TiO2 ENPs. With sewer sludge being the common factor for contamination of agricultural fields, there is a high potential for the simultaneous introduction of TiO2 ENPs and heavy metal contaminants. To date, there has been very little research done for ENP and contaminant interactions. Of the research that has been performed on the subject, the majority of it was conducted using aquatic systems involving fish and daphnids. This research has shown that the interaction of TiO2 ENPs and metal contaminants generally increases the concentration of the contaminant in the organism, however it is still unclear whether the contaminant is biologically available or if it is adsorbed to the surface of the TiO2 ENPs. This information gives rise to two alternative hypotheses on how TiO2 ENPs may affect the fate of heavy metal contaminants in a single substrate growth media. The first is that the TiO2 ENPs may sequester the heavy metals in the soil thus decreasing the amount of the heavy metals that can be taken up by the plant. The alternative is that the TiO2 ENPs could act as a carrier of the metals i.e. if the plant is able to take up the intact TiO2 ENP with heavy metals adsorbed to the surface, it could potentially increase the amount of the metals that enter the plants. The main objective of this study was to determine which of these scenarios is true for broccoli plants that were grown in cadmium and arsenate contaminated growth media.
16
Chen, Jiadong. "Shape and Hydrophobicity Effects of Titanium Dioxide Nanoparticles on Blood Plasma Protein Adsorption." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1595977372164445.
Full text
17
Burrows, Steven Preston. "Infrared Spectroscopic Measurement of Titanium Dioxide Nanoparticle Shallow Trap State Energies." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31342.
Full textAbstract:
Within the â forbiddenâ range of electron energies between the valence and conduction bands of titanium dioxide, crystal lattice irregularities lead to the formation of electron trapping sites. These sites are known as shallow trap states, where â shallowâ refers to the close energy
proximity of those features to the bottom of the semiconductor conduction band. For wide bandgap semiconductors like titanium dioxide, shallow electron traps are the principle route for thermal excitation of electrons into the conduction band.
The studies described here employ a novel infrared spectroscopic approach to determine
the energy of shallow electron traps in titanium dioxide nanoparticles. Mobile electrons within
the conduction band of semiconductors are known to absorb infrared radiation. As those electrons absorb the infrared photons, transitions within the continuum of the conduction band produce a broad spectral signal across the entire mid-infrared range. A Mathematical expression
based upon Fermiâ Dirac statistics was derived to correlate the temperature of the particles to
the population of charge carriers, as measured through the infrared absorbance. The primary
variable of interest in the Fermi â Dirac expression is the energy difference between the shallow trap states and the conduction band. Fitting data sets consisting of titanium dioxide nanoparticle temperatures and their associated infrared spectra, over a defined frequency range, to the Fermiâ Dirac expression is used to determine the shallow electron trap state energy.
Master of Science
18
Noganta, Siyasanga. "Photocatalytic degradation of organic pollutants using Ag-Fe₃O₄/SiO₂/TiO₂ nanocomposite." Thesis, University of the Western Cape, 2015. http://hdl.handle.net/11394/5208.
Full textAbstract:
>Magister Scientiae - MScThe global lack of clean water for human sanitation and other purposes has become an emerging dilemma for human beings. The presence of organic pollutants in wastewater produced by textile industries, leather manufacturing and chemical industries is an alarming matter for a safe environment and human health. For the last decades, conventional methods have been applied for the purification of water but due to industrialization these methods fall short. Advanced oxidation processes and their reliable application in degradation of many contaminants have been reported as a potential method to reduce and/or alleviate this problem. Lately, it has been assumed that incorporation of some metal nanoparticles such as magnetite nanoparticles as photocatalyst for Fenton reaction could improve the degradation efficiency of contaminants. Core/shell nanoparticles, are extensively studied because of their wide applications in the biomedical, drug delivery, electronics fields and water treatment. The current study is centred on the synthesis of silver-doped Fe₃O₄/SiO₂/TiO₂ photocatalyst. Magnetically separable Fe₃O₄/SiO₂/TiO₂ composite with core–shell structure were synthesized by the deposition of uniform anatase TiO₂ NPs on Fe₃O₄/SiO₂ by using titanium butoxide (TBOT) as titanium source. Then, the silver is doped on TiO₂ layer by hydrothermal method. Integration of magnetic nanoparticles was suggested to avoid the post separation difficulties associated with the powder form of the TiO₂ catalyst, increase of the surface area and adsorption properties. Lastly and most importantly magnetic nanoparticles upsurge the production of hydroxyl groups or reduced charge recombination. The a synthesized catalysts were characterized using Transmission Electron Microscopy, X-ray Diffraction; Infra-red Spectroscopy, Scanning Electron Microscope and Energy Dispersive Spectroscopy. Other characterization techniques includeVibrating Sample Magnetometry, Brunauer Emmett Teller analysis and Thermogravimetric analysis. The average size of the particles size is 72 nm. Furthermore the photocatalytic performances of the magnetic catalysts were assessed in comparison with that commercial titanium dioxide for the degradation of methylene blue using photochemical reactor under ultra violet light. The results showed that the photocatalytic activity was enhanced using Fe₃O₄/SiO₂/TiO₂ and Ag-Fe₃O₄/SiO₂/TiO₂ compared with that for Fe₃O₄, commercial titanium dioxide powder.
19
Bhattacharjee, Linkon. "DEGRADATION OF 1,4-DIOXANE USING METALLIC NANOPARTICLES UNDER VISIBLE LIGHT." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2655.
Full textAbstract:
1,4-dioxane is an emerging contaminant and fully miscible organic compound which has been found extensively in wastewater effluent. Conventional water treatment technologies like carbon adsorption, and air stripping are inefficient in removing this extremely mobile and persistent contaminant from water. In this study, different types of metallic nanoparticles, e.g., nanoscale zero-valent iron (nZVI), γFe2O3, and Fe(III)-doped TiO2 were used to investigate the removal of 1,4-dioxane under visible light. These nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM) and dynamic light scattering (DLS). The experiments were first carried out using deionized water (DIW) at pH 7 and pH 3. nZVI was found more efficient than other nanoparticles under visible light irradiation at pH 3. No 1,4-dioxane removal was obtained for all cases at pH 7 under visible light, or at pH 3 in dark. Moreover, light intensity also plays a significant role in 1,4-dioxane removal. Removal of 22.3%, 40.0% and >99.9% of 1.4-dioxane was reached under 2.4 mW/cm2, 2.6 mw/cm2 and 3.25 mW/cm2 light intensities, respectively, after 6 h of irradiation. The most efficient nanoparticle nZVI was applied to wastewater effluent from Carbondale Southeast Wastewater Treatment Plant. From the results, it was found that 1,4-dioxane degradation took longer time in wastewater effluent than in DIW, because of the presence of other constituents in the wastewater sample. nZVI is also capable of removing 1,4-dioxane in presence of trichloroethylene (TCE) and tetrachloroethylene (PCE) at pH 3 under visible light. In comparison, TiO2 nanoparticle is capable of degrading 1,4-dioxane under visible light or under sunlight at pH 7. Moreover, TiO2 removed 1,4-dioxane in presence of both TCE and PCE at pH 7 under visible light or sunlight. This study found a cost-effective and efficient solution for removing 1,4-dioxane from wastewater effluent that can be reused, by using metallic nanoparticles under visible light.
20
Shah, Rupal Ramesh. "The antibacterial properties of brookite phase titanium dioxide nanoparticles against methicillin-resistant Staphylococcus aureus." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202410056/.
Full text
21
Liang, Irene. "Evaluation of Immobilized Titanium Dioxide-Silver-Hydroxyapatite Nanoparticles and Colloidal Silver for Water Disinfection." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297687.
Full textAbstract:
Titanium dioxide nanoparticles combined with silver and hydroxyapatite (TiO₂-Ag-Hap) form a photocatalytic composite capable of oxidizing and mineralizing a wide spectrum of microbiological and chemical contaminants in water, while silver nanoparticles have long been employed for their antimicrobial properties. These materials were evaluated through an iterative series of experiments that evaluated microbial reduction, material formulation, method of application, surface-interface interactions, and reusability. The TiO₂ formulation was assessed as an antimicrobial film coated onto fabric and ceramic beads in three experimental designs: a gravity filtration column, a portable treatment capsule, and a static chamber. Colloidal floating Ag nanoparticles in solution were also assessed. Reduction of Escherichia coli, Klebsiella terrigena, MS2 bacteriophage, and Rotavirus was evaluated though standard culture-based methods. Significant microbial reduction was only observed in the static open pan design for the TiO₂-Ag-HAp materials. Colloidal silver was more effective and caused a 5 log reduction of K. terrigena, within 60 minutes, and a 5 and 4 log reduction of MS2 within 120 and 90 minutes respectively in initial trials. The anti-microbial properties of both materials were apparent, but further investigations are necessary to assess the potential of the materials for integration and development in water treatment technologies.
22
Foscari, Widmann Rezzonico Aurelio Giovanni <1993>. "On the colloidal behaviour of titanium dioxide nanoparticles in artificial and natural aqueous media." Master's Degree Thesis, Università Ca' Foscari Venezia, 2020. http://hdl.handle.net/10579/16389.
Full textAbstract:
The considerable growth of engineering nanomaterials (ENMs) applications in many fields has been driven by their novel physicochemical properties, which promise improved functionality. However, the extensive use and high complexity of ENMs fate processes have led concerns about their potential impact upon human and environmental health. ENMs dispersed in biological or environmental media are subjected to several processes such as dissolution, aggregation and surface transformations processes. Since there is a strong likelihood that human and biological impact from ENMs will depend on key physicochemical properties that represent the so-called exposure and hazard determinants, the investigation of interactions between ENMs and the surrounding media is of great importance for supporting the risk and safety assessment of these materials.
Among the different ENMs, titanium dioxide nanoparticles (TiO2 NPs) have been selected for this study due to their widespread use in many consumer products, very low solubility, and surface which can be easily modified.
The work presented in this thesis can be divided into: (i) the colloidal characterization of TiO2 NPs dispersed in ultra-pure water, artificial fresh water, artificial marine water, and Venice lagoon water (ii) study of the interactions between TiO2 NPs and suspended particulate matter (i.e. kaolinite as model and sediment from the Venice lagoon).
23
Chou, Hsun-Wen. "Nanotoxicology from nano titanium dioxide particle size effect on Ceriodaphnia dubia to death mechanism /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 77 p, 2008. http://proquest.umi.com/pqdweb?did=1597633671&sid=14&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
24
Bayat, Narges. "Toxicity and biological impact of metal and metal oxide nanoparticles : Focus on the vascular toxicity of ultra-small titanium dioxide nanoparticles." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116708.
Full textAbstract:
The application of nanoparticles (NPs) in different technologies has led to tremendous advancement in those fields. Moreover, there is growing interest in application of ultra-small NPs (USNPs) at 1-3 nm due to their distinct molecule like features. Parallel to these promises, there is a growing concern regarding their safety. The main goal of this thesis was to investigate the toxicity and underlying mechanisms following exposure to different metal and metal oxide NPs as well as USNPs. Their effects were studied on Saccharomyces cerevisiae, on hepatocytes and endothelial cells and finally in vivo on zebrafish embryos (Danio rerio). By selecting the rutile form of titanium dioxide (TiO2-USNPs) without intrinsic or intracellular reactive oxygen species (ROS) production, we could study biological impacts solely due to size and direct interaction with the cells. We showed that TiO2-USNPs were not cytotoxic but induced DNA damage. They had anti-angiogenic effects both in vitro and in vivo. Also, at high concentrations they caused complete mortality in zebrafish embryos exposed in water, while at lower concentrations induced delay in hatching. When injected they caused malformations. They specifically induced the differential overexpression of transcripts involved in lipid and cholesterol metabolism in endothelial cells. In hepatocytes they induced the overexpression of proteins in the electron transport chain and decreased lipids in lipid rafts. At 30 nm, TiO2-NPs, were also not cytotoxic but were genotoxic. They had no effects in vivo or on angiogenesis. However, they induced differential expression of transcripts involved in endoplasmic reticulum (ER) stress and heat shock response as well as cholesterol metabolism. This suggests a more toxic response in the cells compared to TiO2-USNPs. Single walled carbon nanotubes (SWCNTs) despite having the highest oxidative activity among the NPs studied, were not severely cyto- or genotoxic but induced expression of transcripts involved in early ER stress response. Copper oxide (CuO-NPs) was the most toxic NPs studied due to both ion release and ROS production, affecting lipid metabolism of the cells. Silver (Ag-NPs) were also cytotoxic and caused the disruption of cellular components and lipids. ZnO-NPs were not cytotoxic, did not affect cellular lipids but they increased the size of vacuoles in yeast cells. Finally by using superparamagnetic iron oxide NPs (SPIONs) with different coatings, and using a mathematical model, a nano impact index (INI) was developed as a tool to enable the comparison of nanotoxicology data.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.
25
Esterhuizen, Bevan Peter. "The effects of titanium oxide nanoparticles on cultured cells and the immune system." University of Western Cape, 2021. http://hdl.handle.net/11394/8428.
Full textAbstract:
>Magister Scientiae - MScEngineered nanomaterials derived from various bulk materials are being developed in ever larger quantities and with very diverse chemical compositions. The physical and chemical properties of the smaller nanoparticles are very different compared to their larger bulk chemicals. Titanium dioxide nanoparticles (TiO2NPs) are an example of such an engineered nanomaterial. Titanium dioxide nanoparticles are mainly used as a pigment in many applications such as glazes, enamels, plastics, pharmaceuticals, cosmetics, and it is widely used in sunscreens. Human exposure to TiO2NPs can occur both during manufacturing and use.
26
Lee, Bo Yeon. "Effect of titanium dioxide nanoparticles on early age and long term properties of cementitious materials." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44834.
Full textAbstract:
Today, with increasing global awareness and regulation of air pollution, interest in the smog-abating property of photocatalytic materials is increasing. Titanium dioxide (TiO2) is the most well known photocatalytic semiconductor and is often considered as one way of solving pollution by a passive but an effective way, particularly to reduce atmospheric nitrogen oxides (NOx=NO+NO2). This relatively new technology is already being used in some of the countries as a construction material, commercially sold as photocatalytic cement, photocatalytic pavement, self-cleaning tiles, and self-cleaning glass. Prior research has examined the photocatalytic properties of TiO2 itself, as well as TiO2-containing cement-based materials. The majority of this effort has been on characterizing and enhancing the photocatalytic efficiency. However, relatively little research was performed to assess the potential impact of the photocatalytic reaction on the "parent" or "host" material.
In this research, the focus is on the effect of photocatalysis on the composition, structure, and properties of cementitious materials, which contain titania nanoparticles at early and late ages. Fundamental examinations on the addition of these chemically non-reactive nanoparticles to cement-based materials are performed. The high surface area of nanoparticles could alter early age properties of cementitious materials, such as setting time, dimensional stability, and hydration rate. Various experimental techniques as well as mathematical modeling were used to examine and explain the early age hydration of cementitious materials when TiO2 nanoparticles are present. Further, the effects of the TiO2 on the long term durability of cement-based materials are investigated to demonstrate their suitability for long-term use in the field. The photocatalytic NOx oxidation efficiency and NOx binding capability of TiO2 containing cementitious materials are experimentally investigated. The durability of TiO2-cement is examined by various techniques on samples that went through extensive photocatalysis and environmental exposures. These investigations have led to tentative conclusions on the use of TiO2 nanoparticles in cementitious materials, and suggest avenues for future study.
27
COSTA, LAIS HELENA MOREIRA DA. "JANUS NANOPARTICLES FORMED BY GOLD AND TITANIUM DIOXIDE AS PHOTOCATALYST FOR HYDROGEN PRODUCTION FROM WATER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=36253@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Partículas que apresentam dois lados com propriedades químicas distintas são chamadas de Janus, como uma referência ao deus de duas faces da mitologia Romana. A combinação de propriedades diferentes em um mesmo sistema vem se demonstrando interessante para inúmeras aplicações. Neste trabalho, nanopartículas de ouro anfifílicas foram sintetizadas através do recobrimento seletivo dos hemisférios do núcleo metálico, por dois polímeros, sendo um hidrofóbico e outro hidrofílico. Em seguida, foi realizado o crescimento preferencial de dióxido de titânio apenas na face com recobrimento hidrofílico. Os resultados obtidos pela caracterização estrutural e físico-química confirmaram a formação de nanopartículas de ouro com um hemisfério recoberto por dióxido de titânio de baixa cristalinidade e alta porosidade, provando seu caráter Janus. As nanopartículas Janus obtidas foram testadas como fotocatalisadores para produção de gás hidrogênio a partir da água. Os resultados mostraram sua atividade superior em relação a nanopartículas formadas apenas por titânia. Portanto, este estudo descreve uma nova estratégia para obtenção de nanopartículas Janus, que podem ser utilizadas para diferentes aplicações, e ainda demonstra sua importância nas áreas de catálise e de produção de gás hidrogênio como combustível renovável.
Particles possessing two sides with different chemical properties are named Janus, as a reference to the double-faced god of Roman mythology. The combination of two different properties in the same system has been showing interesting for numerous applications. In this work, amphiphilic gold nanoparticles were synthesized by selectively coating the metallic nucleus hemispheres with two polymers, one hydrophobic and one hydrophilic. Then, a preferential growth of titanium dioxide over the hydrophilic face was performed. The results obtained by structural and physicochemical characterization confirmed the formation of gold nanoparticles with one hemisphere coated by titanium dioxide with low crystallinity and high porosity, proving the Janus character. The obtained Janus nanoparticles were tested as photocatalysts for hydrogen production from water. Results showed the superior activity in comparison to nanoparticles comprised only by titania. Thus, this study describes a new strategy to obtain Janus nanoparticles, which can be used for different applications and also demonstrates their importance in the fields of catalysis and production of hydrogen gas as renewable fuel.
28
Zhang, Huanjun. "Ag/TiO[subscript 2] nanocomposites : synthesis, characterizations and applications /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CBME%202009%20ZHANGH.
Full text
29
Rottman, Jeffrey J. "Fundamentals and Application of Porous Media Filtration for the Removal of Nanoparticles from Industrial Wastewater." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/255157.
Full textAbstract:
Increasing use of engineered nanomaterials presents concerns as some nanoparticles appear to be harmful to both human health and the environment. Effective treatment methods are required to remove problematic nanoparticles from (waste)water streams. Porous media filtration, commonly used for the removal of particulate matter, shows promise for nanoparticle treatment. The goal of this work is to investigate the potential of porous media filtration for the abatement of nanoparticles from aqueous waste streams. To this end, an automated method was developed that allows real-time and in-situ monitoring of nanoparticle transport and retention in porous media using online measurement of UV-visible absorbance or fluorescence. Development of fluorescent-core nano-silica (n-SiO₂) in controllable sizes provided an excellent tracer for nanoparticle transport in porous media. Measurement of n-SiO₂ by destructive techniques is complicated by high natural Si background levels. Fluorescence monitoring enables real-time measurement, facilitating rapid evaluation of n-SiO₂ transport. Synthesized n-SiO₂ remain in their primary sizes making an evaluation of the behavioral change of particles due to transition into the "nano" range possible. A comparison of the role of particle size on transport in porous media displayed the importance of particle number concentration as the dominance of site-specific adsorption may be obscured by simple mass concentration evaluation.T he effectiveness of different bed materials, namely, sand, activated carbon (AC), and diatomaceous earth (DE), for the removal of TiO₂ nanoparticles (n-TiO₂) from aqueous streams was investigated. DE proved promising for n-TiO₂ capture shown by its high bed capacity (33.8 mg TiO₂ g⁻¹(medium)) compared to AC (0.23 mg TiO₂ g⁻¹(medium)) or sand (0.004 mg TiO₂ g⁻¹(medium)). The presence of organic and synthetic contaminants produced varying effects on n-TiO₂ retention, mostly due to either enhanced electrostatic or steric interactions. Application of a process simulator combining physical straining with site-specific interactions, delineating physisorption from chemisorption and diffusion limited interactions, enabled the accurate fit of n-TiO₂ transport in sand, AC and DE. The fitting process revealed the advantage of DE due to increased physisorption and physical straining of n-TiO₂. Modeling of this system afforded the elucidation of controlling retention mechanisms and provides a basis for future scaling and system design.
30
Galletti, Andrea. "Toxicity evaluation of TiO2 Nanoparticles embedded in consumer products." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11285/.
Full textAbstract:
Lo studio è orientato alla determinazione dei rischi tossici posti dalle nanoparticelle di diossido di titanio rilasciate in ambiente marino. L’organismo modello utilizzato per questo studio è la diatomea Thalassiosira pseudonana, la quale è stata scelta per la sua semplicità biologica unita alla fondamentale rilevanza nella catena alimentare e nell’ecosistema marino.
Oltre alle nanoparticelle prodotte industrialmente, questo studio ha lo scopo di determinare e confrontare la tossicità delle nanoparticelle utilizzate in alcuni prodotti di cura personale (in particolare crema solare e dentifricio), estraendole direttamente da essi.
I nostri risultati mostrano una notevole ridondanza nel legame tra la natura (il tipo) delle nanoparticelle e l’inibizione della normale crescita delle diatomee, che supera la correlazione con tutti gli altri parametri monitorati (concentrazione di nanoparticelle, tempo di esposizione, pH, carica superficiale e dimensione delle particelle stesse), sebbene gli altri parametri risultino direttamente legati agli effetti inibitori.
Tali risultati suggeriscono un’intensificazione della ricerca nell’ambito delle nanotecnologie, orientata allo sviluppo di nanomateriali “sostenibili”, ovvero dei quali sono note le potenzialità di impiego, ma anche gli aspetti negativi, che possono di conseguenza essere monitorati con maggiore consapevolezza.
31
Buzby, Scott Edward. "The effect of doping titanium dioxide nanoparticles on phase transformation, photocatalytic activity and anti-bacterial properties." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 120 p, 2008. http://proquest.umi.com/pqdweb?did=1459918071&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
32
Nelson, Kimberly Lynn. "Enhanced performance and functionality of titanium dioxide papermaking pigments with controlled morphology and surface coating." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24645.
Full textAbstract:
Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Yulin Deng; Committee Member: Arthur Ragauskas; Committee Member: Jeff Empie; Committee Member: Jeffery Hsieh; Committee Member: Preet Singh
33
Scown, Tessa M. "Uptake and effects of nanoparticles in fish." Thesis, University of Exeter, 2009. http://hdl.handle.net/10036/93696.
Full textAbstract:
Nanotechnology is a rapidly growing industry of global economic importance, with new technologies exploiting the novel characteristics of materials manufactured at the nanoscale being developed for use within the biomedical, electronic, energy production and environmental sectors. The unusual properties of engineered nanomaterials (ENMs) that make them useful in such applications have led to concerns regarding their potential impact on the environment. The aquatic environment is particularly at risk of exposure to ENPs, yet, there is currently little known about their behaviour in aquatic systems, their capacity to be taken up by aquatic organisms or their potential toxic effects. The studies that were conducted during this work sought to investigate the ecotoxicology of a range of metal and metal oxide nanoparticles using fish as a vertebrate model. In order to gain a better understanding of the uptake and effects of ENMs in fish, rainbow trout (Oncorhynchus mykiss) were exposed to nanoparticulate (34 nm) and bulk (>100 nm) titanium dioxide particles via the water column (500 and 5000 µg L-1), and to titanium dioxide nanoparticles via the diet (0.1 and 1 mg g-1 food) and via intravenous injection (1.3 mg kg-1 body weight). Uptake of titanium dioxide into the tissues of trout after waterborne and dietary exposure was found to be very low, suggesting limited bioavailability of the nanoparticles to the fish, although small amounts of uptake of titanium dioxide across the gill epithelial membrane were observed using coherent anti-stokes Raman scattering. Intravenously injected titanium dioxide accumulated and was retained in the kidneys for up to 21 days, but no adverse effect on kidney function was detected. Silver nanoparticles are already in widespread use in a variety of consumer products such as wound dressings, food containers, sock fabrics and paints, principally for their antimicrobial activity. Despite its growing commercialisation, there is little known about the environmental effects of the use of nanoparticulate silver in these products. In order to investigate these potential effects, rainbow trout were also exposed to 10 nm, 35 nm and bulk (0.6-1.6 µm) silver particles via the water column at concentration of 10 and 100 µg L-1. Uptake of silver in the gills and liver of trout occurred, with smaller nanoparticles showing a greater propensity for association with gill tissue, but with no significant differences in uptake between particles of different sizes in the liver. No increases in lipid peroxidation were detected in gills, liver or blood plasma of trout, however, expression of cyp1a2 was significantly up-regulated in exposures to 10 nm silver particles in the gill, suggesting an increase in oxidative metabolism. In an attempt to develop an effective high through-put in vitro screening assay for ENMs, the suitability of isolated rainbow trout primary hepatocytes was examined as a potential model for in vitro screening of a range of toxicological endpoints in response to nanoparticles and for studying uptake of nanoparticles into cells. The hepatocytes retained a good level of functionality after culturing as evidenced by vitellogenin production in response to the synthetic oestrogen, 17β-oestradiol. The cultured hepatocytes, however, showed limited responses on exposure to titanium dioxide, zinc oxide, cerium oxide and silver nanoparticles for lipid peroxidation and glutathione-s-transferase activity assays. Furthermore, the hepatocytes were unresponsive to the induction of these biological responses in the positive controls, suggesting they are not a good model for investigating the potential toxic effects of ENMs in terms of these endpoints. Uptake of the nanoparticles into the cells, however, was demonstrated by coherent anti-stokes Raman spectroscopy, indicating that this in vitro assay may provide a useful model for studying uptake of ENPs into cells. The studies conducted in this thesis contribute the science base regarding the bioavailability of ENPs in aquatic media as well as highlighting the importance of characterisation of ENPs in understanding their behaviour, uptake and effects in aquatic systems and in fish.
34
Stamou, Ioannis. "Impact of silver and titanium dioxide nanoparticles on the in-vessel composting of biodegradable municipal solid waste." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10051.
Full textAbstract:
The extensive use of nanoparticles (NPs) has started receiving increased attention because of the knowledge gaps regarding their fate in the environment and the possible impact on the environment and human health. The production of silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2-NPs) is increasing and it is expected that, due to their great number of applications, their concentration in waste streams will increase in the future. The presence of NPs in waste streams may affect the treatment process (e.g., composting) and, if they are not successfully removed from the waste streams, their presence in the treated waste (e.g., compost) may present an environmental risk. Composting of the biodegradable fractions of municipal solid waste (MSW) is a widely used waste management practice, mainly because it is a cost-effective treatment technology and the final product (i.e., compost) presents several benefits to the environment, particularly as a soil conditioner. The overall aim of this thesis is to assess the effect of Ag-TiO2NPs and AgNPs that may be present in the biodegradable fractions of municipal solid waste on composting and subsequent soil application of compost. For that purpose in-vessel composting of artificial municipal solid waste contaminated with commercial nanoparticles was investigated at laboratory scale, simulating a range of relevant concentration levels. Subsequently, the fate of NPs present in mature compost use as a top-layer soil conditioner was investigated using a column approach at laboratory scale. The toxicity effect of NPs present mature compost on plant growth was further investigated. The impact of NPs during composting was assessed by monitoring the temporal dynamics of organic matter (OM) using Excitation Emission Matrix (EEM) fluorescence spectroscopy. The fate of NPs following application of contaminated mature compost as a top-soil conditioner and potential release to groundwater was investigated using a column leaching experiment while the phytotoxicity of mature compost contaminated with NPs was assessed using a seed germination bioassay. Finally, to investigate further possible environmental impacts due to the application of mature compost contaminated with NPs to soils, a Life Cycle Assessment (LCA) was conducted. The impact of commercial Ag-TiO2 NPs and AgNPs on the in-vessel composting of biodegradable municipal solid waste was investigated over 21 days, using initial concentrations of 0, 5, 10, 20 and 50 mg Ag / kg of OM. Microbial activity was inhibited in the biodegradable waste reactors using 2% NaN3 to evaluate abiotic losses. Physicochemical parameters such as pH, ash content, weight loss, and the formation of humic substances (HS) were determined after 0, 4, 7, 14 and 21 days of composting and after a maturation phase. The results indicated that the presence of 2% NaN3 in biodegradable MSW inhibited effectively the microbial activity during the first week of composting. The microbial population was activated during the second week of composting but the decomposition rate was so low that did not result in the formation of humic substances (HS) following 21 days of composting when 2% NaN3 was used. Both treatments, using Ag-TiO2-NPs and AgNPs, did not show any inhibition of the decomposition process for all the tested concentrations and EEM peaks shifted towards the HS region during in-vessel composting. Higher inorganic carbon removal resulted from NP-contaminated compost with higher NP concentrations. This may indicate that the formation of humins was higher for non-contaminated compost and decreased as the NP concentration in waste increased. The shift of the peaks towards the HS region during composting for all the treatments suggested that NPs did not have an effect on humification and therefore on compost stability. The leaching properties of the NP-contaminated compost were investigated using a column leaching test. Five samples of leachate, of 50 mL each, were collected. The highest concentrations of HS were observed in the first two leaching samples. The leaching results suggested that only a low percentage of the total NPs (in weight) in compost, up to ca. 5% for Ag and up to ca. 15% for Ti, leached out from the columns, which was assumed the amount that potentially could leach to the environment. These results suggested that NPs will mainly accumulate in soils’ top layers following application of compost contaminated with NP. The phytotoxicity of NP-contaminated compost was assessed using a seed germination bioassay and the germination index was then calculated. The results indicated that the NP-contaminated compost did not present any toxic effects to cress germination. The possible environmental impacts due to the NP-contaminated compost application to soils were investigated by conducting a comparative LCA study. The LCA study indicated that the effects of NP-contaminated compost to human health and ecosystems endpoint categories increased due to the presence of NPs. The risks are associated with terrestrial ecotoxicity and human toxicity midpoint categories and are mainly attributed to the accumulation of Ag to soils.
35
Ochola, Rispah Janet. "The preparation and study of photocatalysts : from core-shell palladium-titanium dioxide nanoparticles to iridium(III) complexes." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63140.
Full text
36
Hessler, Christopher Mark. "The Influence of Capsular Extracellular Polymeric Substances on the Toxicological Interaction Between Titanium Dioxide Nanoparticles and Planktonic Bacteria." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1321645743.
Full text
37
Das, Prajna Paramita. "Enhancement of photoactivity by synthesizing nanotube-nanoparticle composites of TIO₂ and CdS for generation of hydrogen via splitting of water." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460754.
Full text
38
Adhikari, Pratima. "IMPACT OF ENGINEERED TITANIUM DIOXIDE AND ZERO-VALENT IRON NANOPARTICLES ON CARBON DIOXIDE FIXATION BY AN AQUATIC MICROBIAL COMMUNITY: EFFECT AT ENVIRONMENTALLY RELEVANT CONCENTRATIONS." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2856.
Full textAbstract:
AN ABSTRACT OF THE THESIS OFPratima Adhikari, for the Master of Science degree in Civil Engineering, presented on June 30, 2021, at Southern Illinois University Carbondale.TITLE: IMPACT OF ENGINEERED TITANIUM DIOXIDE AND ZERO-VALENT IRON NANOPARTICLES ON CARBON DIOXIDE FIXATION BY AN AQUATIC MICROBIAL COMMUNITY: EFFECT AT ENVIRONMENTALLY RELEVANT CONCENTRATIONSMAJOR PROFESSOR: Dr. Jia LiuThe purpose of this study is to investigate the effect of engineered nanoparticles (ENPs) on carbon dioxide reduction by aquatic microbial communities. Titanium dioxide (TiO2) nanoparticles and nanoscale zero-valent iron (nZVI) of different concentrations (10, 1, 0.1, 0.01, 0.001 mg/L and control), both environment-relevant and higher than the environmental concentrations as prediction for future concentrations, were selected. An anaerobic microbial community from the campus lake of Southern Illinois University Carbondale was studied. Different humic acid concentrations (100, 10, and 1 mg/L) were considered under pH 6.0 - 9.0. The research was conducted in two phases: 1) Transformation of TiO2 and nZVI nanomaterials in simulated environmental conditions, and 2) Inoculation of microbial community to the pristine nZVI nanoparticles as well as environmentally transformed nanoparticles, i.e. TiO2 and nZVI, to study their impacts on carbon dioxide reduction. The nanoparticles were suspended in a medium that simulates the aqueous environment for the growth of anaerobic bacteria. The nanoparticle suspension was kept in the simulated medium for 12 h light and 12 h dark for a period of one month and the transformed nanoparticles were then used for the study in its interaction with the microbial community. When the microbial community was inoculated, carbon dioxide gas was purged inside the vials to ensure no oxygen present in the vials. These samples were then monitored for a period of 2-3 weeks to see the carbon dioxide reduction. The results showed that the transformed nZVI had significant impact on the reduction of carbon dioxide concentration, whereas pristine nZVI and transformed TiO2 nanoparticles did not have significant impact on the reduction of carbon dioxide concentrations in the vials. The spearman correlation coefficient value showed that there is a somewhat monotonic relation between the reduction of carbon-dioxide and organic carbon formation for transformed TiO2 nanoparticles, however, for the transformed nZVI no such correlation was found. From this study, we can state that certain microbial communities can increase the rate of carbon dioxide fixation when exposed to the transformed zerovalent iron nanoparticles. This study can provide guidance on the industrial usage and environmental release of ENPs that are related to carbon fixation.
39
Lundqvist, Maria J. "Quantum chemical modeling of dye-sensitized titanium dioxide : ruthenium polypyridyl and perylene dyes, TiO₂ nanoparticles, and their interfaces /." Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7141.
Full text
40
Lundqvist, Maria J. "Quantum Chemical Modeling of Dye-Sensitized Titanium Dioxide : Ruthenium Polypyridyl and Perylene Dyes, TiO2 Nanoparticles, and Their Interfaces." Doctoral thesis, Uppsala universitet, Kvantkemi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7141.
Full textAbstract:
Quantum chemical calculations have been used to model dye-sensitized nanostructured titanium dioxide systems that can be used in solar cells for solar energy to electricity conversion. Structural, electronic and spectral properties of isolated dyes and both bare and dye-sensitized TiO2 have been calculated with density functional theory, providing detailed information about both the separate parts and the dye-TiO2 interface. The connection between the geometry, the ligand field splitting and the lifetime of the triplet metal-to-ligand charge transfer (MLCT) excited state has been explored for a series of ruthenium polypyridyl dyes. Moreover, the relative energetics of MLCT and metal centered triplet excited states have been studied for a number of such systems. It was found that small alterations of the polypyridyl ligands can result in significant changes in ligand field splitting and in the energetics of the triplet states. Attachment of the dyes to the TiO2 surface is achieved via anchor and spacer groups. The influence of such groups on various properties of the dye and their ability to act as mediators of photo-induced surface electron transfer has been studied. Delocalization of the lowest unoccupied dye orbital onto the spacer and/or anchor group indicates that certain unsaturated groups can mediate electron transfer. With a combination of methods that enables efficient computations and a scheme for construction of metal oxide clusters, chemical models for bare TiO2 nanocrystals in the 1-2 nm size range have been developed. The electronic structures show well-developed band structures with essentially no electronic band gap defect states. Atomistic models of the interface between TiO2 nanocrystals and Ru(II)-bis-terpyridine dyes, the so-called N3 dye as well as perylene dyes are reported. Electronic coupling strengths, which provide estimates for the electron injection times, are extracted from the interfacial electronic structure and the lowest electronic excitations are calculated.
41
Kobese, Nokubonga. "Synthesis of silver doped titanium dioxide nanocomposites using tea extract from Aspalathus linearis and evaluation of their antibacterial effects." University of the Western Cape, 2018. http://hdl.handle.net/11394/6779.
Full textAbstract:
>Magister Scientiae - MScDespite the wide success of antimicrobial agents against waterborne pathogens, waterborne disease continues to pose a threat to both mankind and animals. A major concern is that certain bacteria have developed resistance to antimicrobial agents, as a result of their overuse. Silver (Ag) nanoparticles are widely used for antibacterial purposes such as medical dressings. However, they are highly toxic to human cells. Hence, there is a great interest in developing next generation antibacterial nanoparticles that are as effective as Ag nanoparticles for antibacterial functions, while having less toxicity to human cells. Several methods can be used to generate these antimicrobial nanoparticles, one of which is green nanotechnology. Green nanotechnology uses natural plants such as tea to synthesise nanoparticles rather than chemicals, thus reduce human and animal harm and improve sustainability of antibacterial agents. Silver-titanium nano-composites (Ag-TiO2 NCs) were synthesised with the hydrothermal method using a tea extract from Aspalathus linearis (Rooibos, RB), and distilled water in the presence of nitrogen. The resulting structures were characterised with high resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS) analysis X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). The antibacterial characteristics of these new NCs were evaluated against 3 bacteria: Bacillus cereus, Cupriavidus metallidurans, and Escherichia coli. The optimum processing conditions to produce 6-nm spherical NPs included maintaining the temperature at 90 °C, the pH at 4.35, and using RB extract at a concentration of 2 mg/mL. The size of silver NPs was reduced in acidic conditions, agglomerated in neutral conditions, and highly reduced in alkaline conditions. Increasing the pH decreased the particle size and narrowed the particle size distribution. Gram-positive B. cereus showed slight resistance or tolerance to the Ag-TiO2 nanocomposite compared to the gram-negative bacteria E. coli and C. metallidurans. The treatment concentration required for total inhibition of E. coli and C. metallidurans growth was 100 mg/mL. Supported silver nanoparticles has shown to be a suitable way to obtain highly dispersed silver over higher surface area. This approach allowed Ag-TiO2 nanocomposite to be an efficient bactericide, with less silver amount employed.
42
Al-Jubory, Aliaa Rasheed. "Titanium dioxide nanoparticle uptake across the isolated perfused intestine of rainbow trout : physiological mechanisms and a comparison with Caco-2 cells." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1586.
Full textAbstract:
The wide use of nanoscale materials in food and health care products raises the concern of their possible uptake across the gastrointestinal tract, but very limited data are available on their uptake kinetics, and the potential hazards for humans. In this study, the uptake mechanism of titanium dioxide (TiO2) across the isolated perfused fish intestine and human intestinal Caco-2 cells were evaluated. The in vitro preparation of the whole gut sac and the isolated perfused intestine of rainbow trout were performed using both bulk and nano TiO2 in a concentration of 1 mg l-1 for up to 4 h. The results showed that the Ti from both bulk and TiO2 NPs were mainly accumulated in the mid and hind intestine, with 80% or more of the accumulation in the mucosa rather than the underlying muscularis. Perfused intestines showed a saturable, time-dependent accumulation of the Ti from TiO2 and the uptake of Ti from exposure to NPs was faster than that of the bulk form. The uptake of Ti from exposure to TiO2 NPs increases 10 fold when the CO2 in the gas mixture was lowered to 0.5%. Subsequently, further investigation on the mechanisms of uptake of TiO2 was applied using different kinds of inhibitors. Adding 10 mmol l-1 cyanide did not stop Ti uptake from TiO2 exposures, and 100 µmol l-1 vanadate (ATPase inhibitor) caused a 2.8 fold reduction in the net uptake rate of Ti for the TiO2 NP exposure. Luminal additions of 120 IU ml-1 nystatin (endocytosis inhibitor) blocked the uptake of Ti from both bulk and TiO2 NPs treatments. The results indicate that Ti accumulation from TiO2 exposures was sensitive to both nystatin and vanadate; the former suggesting that there is an endocytosis involvement in the uptake of TiO2 across the intestinal epithelium. Human intestinal Caco-2 cell showed a steady, saturable and time-dependent accumulation of Ti over 24 h exposures to 1 mg l-1 TiO2 (for all forms of TiO2). A scanning electron microscope study indicated the appearance of the particles underneath the cells, increasing the evidence of the Ti uptake from different forms of TiO2 by Caco-2 cells. Both nystatin and vanadate increase the accumulation of TiO2 which suggests interference of these drugs with endocytic pathways. All the data in the thesis demonstrates Ti uptake across the intestinal epithelium from TiO2 exposures involving CO2-dependent and nystatin-sensitive mechanisms. The results in this thesis have contributed to some understanding on the behaviour, uptake and effects of the TiO2 NPs across the intestine; and highlight the possible dietary hazard of the NPs to human health.
43
Odame-Ankrah, Charles Anim. "Studies of Titanium Dioxide Nanoparticles and Surfactants Effects, Singly and in Combinations, on Luminescence Intensity of Some Aromatic Compounds." Digital Commons @ East Tennessee State University, 2009. https://dc.etsu.edu/etd/1799.
Full textAbstract:
Luminescence techniques are sensitive, selective, and widely used in analysis. Luminescence intensity is attenuated by quenchers. This research has focused on the use of surfactants such as CTAB, SDS, and TX-100 singly or together with TiO2 nanoparticles to evaluate their individual and combined effects on some fluorescent aromatic compounds such as pyrene, fluoranthene, anthracene, phenanthrene, and carbazole. Rutile phase TiO2 was synthesized using the low temperature sol-gel method. Carbazole and phenanthrene were severely quenched by all surfactants singly or in combination with TiO2. Anthracene and fluoranthene showed some enhancement in their luminescence intensity. The most dramatic effect was observed on the fluorescence intensity of pyrene. Pyrene showed enhanced fluorescence after degassing the solution alone or with the addition of the surfactants alone or in combination with TiO2 after degassing. These results showed that surfactants and TiO2 nanoparticles either singly or in combination should be useful for analysis employing luminescence techniques.
44
Cohignac, Vanessa. "Réponse macrophagique à des nanoparticules manufacturées : effets de leurs caractéristiques physico-chimiques sur l’autophagie." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1185/document.
Full textAbstract:
L'exposition à des nanoparticules manufacturées (NP) peut entraîner des effets sur la santé, notamment au niveau respiratoire, où elles peuvent induire des phénomènes de remodelage pulmonaire. Toutefois, les mécanismes cellulaires sous-jacents à ces effets et l'influence des caractéristiques physico-chimiques des NP dans ces effets sont encore loin d'être compris. L'objectif de cette thèse était d'évaluer la réponse macrophagique à des NP présentant différentes caractéristiques physico-chimiques (taille/longueur, composition chimique, forme, structure cristalline ou propriétés de surface) en se concentrant particulièrement sur leurs effets sur l'autophagie. Nous avons montré que l'exposition de macrophages murins à des nanotubes de carbone multi-parois (MWCNT) induisait un blocage de l'autophagie tandis que l'exposition à des NP sphériques induisait une autophagie fonctionnelle. Le blocage du flux autophagique par les MWCNT est associé à une accumulation de lysosomes non fonctionnels. Par ailleurs, les MWCNT induisaient une réponse oxydante et pro-inflammatoire plus importante que les particules sphériques qui pourrait être lié à leur blocage de l'autophagie. Ces résultats montrent un rôle prépondérant de la forme des nanomatériaux sur le processus autophagique, et ouvrent de nouvelles voies pour l'interprétation et la compréhension de la toxicité des nanomatériauxL'exposition à des nanoparticules manufacturées (NP) peut entraîner des effets sur la santé, notamment au niveau respiratoire, où elles peuvent induire des phénomènes de remodelage pulmonaire. Toutefois, les mécanismes cellulaires sous-jacents à ces effets et l'influence des caractéristiques physico-chimiques des NP dans ces effets sont encore loin d'être compris. L'objectif de cette thèse était d'évaluer la réponse macrophagique à des NP présentant différentes caractéristiques physico-chimiques (taille/longueur, composition chimique, forme, structure cristalline ou propriétés de surface) en se concentrant particulièrement sur leurs effets sur l'autophagie. Nous avons montré que l'exposition de macrophages murins à des nanotubes de carbone multi-parois (MWCNT) induisait un blocage de l'autophagie tandis que l'exposition à des NP sphériques induisait une autophagie fonctionnelle. Le blocage du flux autophagique par les MWCNT est associé à une accumulation de lysosomes non fonctionnels. Par ailleurs, les MWCNT induisaient une réponse oxydante et pro-inflammatoire plus importante que les particules sphériques qui pourrait être lié à leur blocage de l'autophagie. Ces résultats montrent un rôle prépondérant de la forme des nanomatériaux sur le processus autophagique, et ouvrent de nouvelles voies pour l'interprétation et la compréhension de la toxicité des nanomatériaux
45
Chen, Cheng [Verfasser], and Ljiljana [Akademischer Betreuer] Fruk. "Novel Strategies for the Preparation and Functionalization of Noble Metallic and Titanium Dioxide Nanoparticles / Cheng Chen. Betreuer: Dr. L. Fruk." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1060425378/34.
Full text
46
Zahed, Nizar Bassam. "Formation of Meso-Structured Multi-Scale Porous Titanium Dioxide by Combined Soft-Templating, Freeze-Casting and Hard-Templating Using Cellulose Nanocrystals." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/99386.
Full textAbstract:
This thesis identifies a facile and versatile technique for creating multi-scale porous titania with tunable meso-scale morphology. Three templating approaches were simultaneously utilized in achieving this; namely, soft-templating by template-free self-assembly of an aligned macroporous structure, freeze-casting for the preservation of particle dispersion found in suspension, and hard-templating by the use of cellulose nanocrystals (CNCs) as sacrificial material. A systematic study was conducted wherein three synthesis parameters (water content, alcohol solvent content, and drying method) were varied in the hydrolysis of titanium tetra-isopropoxide (TTIP) by the sol-gel method to determine their contribution to the formation of multi-scale porous titania exhibiting aligned macrochannels and mesoporosity. The optimal synthesis settings for producing multi-scale porous titania were identified as H2O/TTIP molar ratio of 30, without any isopropanol (acting as solvent), and freeze-drying after freezing at -40�C. Subsequently, CNCs were added in various quantities (0-50vol%) to the hydrolysis of TTIP using these optimized settings to achieve more direct and precise control of the final titania meso-structure. Morphological studies revealed that the final titania bodies maintained the formation of macrochannels 1-3 μm in diameter as a result of hydrolysis in excess water in the absence of an organic solvent and exhibited successful templating mutually affected by CNC addition and freeze-casting. Freeze-drying preserved particle dispersion in the colloid suspension, hindering agglomeration otherwise found after oven-drying and enhanced the CNCs� role of disrupting titania aggregation and increasing interconnectivity. Thus, meso-structured multi-scale porous titania was prepared by a combined templating strategy using template-free self-assembly, freeze-casting, and CNC hard-templating.MS
47
McCracken, Christie Joy. "Toxicity of Food-Relevant Nanoparticles in Intestinal Epithelial Models." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437688702.
Full text
48
Boery, Mirella Nagib de Oliveira. "Obtenção controlada das nanopartículas e das fases cristalinas do dióxido de titânio." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264812.
Full textAbstract:
Orientador: Carlos Kenichi SuzukiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-19T01:50:40Z (GMT). No. of bitstreams: 1 Boery_MirellaNagibdeOliveira_M.pdf: 2280722 bytes, checksum: de44802a3f6daef5829060dbc3396bce (MD5) Previous issue date: 2011
Resumo: Este estudo acerca da obtenção controlada das nanopartículas e das fases cristalinas do dióxido de titânio investiga os parâmetros de deposição: fluxo de hidrogênio e oxigênio e, consequentemente, a razão dos gases H2/O2 na deposição pelo método aerossol em chamas. O objetivo é verificar a influência desses parâmetros no tamanho do cristalito, das nanopartículas e nas proporções das fases cristalinas (anatásio e rutilo) do dióxido de titânio (TiO2). Nas amostras caracterizadas são utilizadas as técnicas de difração de raios-X (DRX) e microscopia eletrônica de varredura (MEV). Atualmente o semicondutor TiO2 é um material muito utilizado na fotocatálise heterogênea, por isso muitos pesquisadores tentam otimizar as suas características a fim de obter um máximo de atividade fotocatalítica desse nanomaterial. Através do método aerossol em chamas, nanopartículas de TiO2 foram produzidas pela hidrólise e oxidação do tetracloreto de titânio (TiCl4), com a razão H2/O2 variando entre 0,17 e 3,00, possibilitando estabelecer as condições ideais para se produzir anatásio ou rutilo como única fase, ou a associação de anatásio mais rutilo. Observou-se que a razão H2/O2 possui uma relação direta com as fases cristalinas do dióxido de titânio e com o crescimento dos cristalitos das nanopartículas de TiO2, sendo possível neste trabalho produzir nanopartículas de TiO2 com fase cristalina e tamanho das nanopartículas controladas sem tratamento térmico. Após o tratamento térmico os cristalitos de TiO2 não tiveram grande aumento, mas como esperado, a fase cristalina predominou o rutilo
Abstract: This study aimed to investigated the deposition parameters: flow of hydrogen and oxygen, and consequently the ratio of gases H2/O2 on deposition by flame aerosol method in order to check the influence of these parameters on the crystallite size, and proportions of nanoparticles crystalline phases (anatase and rutile) of titanium dioxide (TiO2), and the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nowadays semiconductor TiO2 is a material widely used in photocatalysis, because of this, many researchers try to optimize their characteristics in order to achieve maximum photocatalytic activity of this nanomaterial. Through the flame aerosol method, nanoparticles of TiO2 were produced by hydrolysis and oxidation of titanium tetrachloride (TiCl4), with reason H2/O2 ranging between 0.17 and 3.00, making it possible to establish the ideal conditions to produce pure anatase , pure rutile or association of anatase more rutile. It was observed that the reason H2/O2 has a direct relationship with the crystalline phases of titanium dioxide and the growth of crystallites of TiO2 nanoparticles, it was possible to produce nanoparticles of TiO2 with controlled crystalline phase and size of nanoparticles without heat treatment. After heat treatment, the crystallites of TiO2 have no significant increase, but as expected, the rutile crystalline phase predominated
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
49
Marcone, Glauciene Paula de Souza. "Avaliação da ecotoxicidade de nanopartículas de dióxido de titânio e prata." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249642.
Full textAbstract:
Orientador: Wilson de Figueiredo JardimTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-19T04:25:34Z (GMT). No. of bitstreams: 1 Marcone_GlaucienePauladeSouza_D.pdf: 3873346 bytes, checksum: 7b3d84f078c155427661a732b0d8a73b (MD5) Previous issue date: 2011
Resumo: O principal objetivo deste trabalho foi estudar as interações de nanopartículas de Ag ou nanoprata (nAg ou AgNP) e nanopartículas do semicondutor TiO2 (nTiO2) com a matriz aquática, a fim de avaliar a sua toxicidade a representantes da biota aquática. Estes dois tipos de nanomateriais (NM) foram escolhidos, pois atualmente estão sendo comercializados em grande escala por apresentarem ampla aplicação industrial. Este trabalho envolveu as seguintes etapas: a) síntese de TiO2 na forma de pó e de amostras de AgNP por rotas sintéticas estabelecidas pela literatura; b) caracterização dos NM sintetizados quanto ao tamanho e a morfologia, e no caso das suspensões de AgNP foi realizada a especiação da prata a fim de nortear uma avaliação mais criteriosa sobre ecotoxicidade destas suspensões; c) avaliação da atividade bactericida das amostras de AgNP e do TiO2 sintetizados. Para isto, utilizou-se a bactéria E. coli e um sistema FIA/Condutimétrico para medir a inibição bacteriana através da produção de CO2. d) avaliação da ecotoxicidade das suspensões de AgNP e TiO2 no meio aquático. Foram utilizados os organismos aquáticos: V. fischeri (bactéria marinha), D. similis (microscrustáceo de água doce) e P. subcapitata (alga de água doce). Devido à fotoatividade do TiO2, os testes com D. similis foram adaptados, incorporando a radiação UV-A durante o teste. As amostras de AgNP foram tóxicas aos organismos aquáticos testados nas seguintes faixas de concentração: P. subcapitata (IC50 = 1-122 mg L), D. similis (CE50 = 0,5-50 mg L) e V. fischeri (CE50 = 5,2-32,2 mg L). As amostras de TiO2 se mostraram mais tóxicas para a D. similis (CE50 = 8-57 mg L) em relação ao V. fischeri (CE50 > 100 mg L). A caracterização das amostras de TiO2 e AgNP sintetizadas indicou que fatores como fotoatividade do TiO2 e a concentração de íons Ag nas suspensões de AgNP foram determinantes para a ecotoxicidade apresentada por estas amostras
Abstract: The objective of this work was to evaluate the toxicity of silver nanoparticles or nanosilver (nAg or AgNP) and TiO2 semiconductor nanoparticles to some biotic representative aquatic organisms. These two nanomaterials (NM) types were chosen because they are currently being market on a large scale due to their wide industrial application. The work was developed in accordance to the following steps: a) Synthesis of TiO2 powder and AgNP samples by current synthetic routes. b) Shape, morphology and optical characterization of TiO2 powder and AgNP synthesized samples. The Ag speciation was performed in the AgNP suspensions to improve the ecotoxicological assessment of this material; c) Bactericidal activity assessment of TiO2 and AgNP samples using E. coli. The inhibition of the bacterial growth was followed by CO2 produced using a FIA/Conductivity system; d) Ecotoxicity assessment of TiO2 and AgNP suspensions to aquatic organisms. The aquatic organisms used were V. fischeri (marine bacterium), D. similis (microcrustace freshwater) and P. subcapitata (algae freshwater). Due to the TiO2 photoactivity, the tests with D. similis were adapted by include to UV-A radiation during the whole test period. The results showed that AgNP samples were toxic to aquatic organisms in the following ranges: P. subcapitata (CI50 = 1-122 mg L), D. similis (EC50 = 0.5-50 mg L) and V. fischeri (EC50 = 5.2-32.2 mg L). The TiO2 samples were more toxic to the D. similis (EC50 = 8-57mg L) compared to V. fischeri (CE50 > 100 mg L). The characterization of TiO2 and AgNP synthesized samples indicated that factors such as TiO2 photoactivity and Ag ions concentration in AgNP suspensions were responsible to the ecotoxicity showed by this samples
Doutorado
Quimica Analitica
Doutor em Ciências
50
Puthur, Jayapalan Amal Raj. "Properties of cement-based materials in the presence of nano and microparticle additives." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49104.
Full textAbstract:
Cement clinker production is a highly resource and energy intensive process and contributes substantially to annual global anthropogenic greenhouse gas emissions. One potential pathway to reduce the environmental footprint of cement-based materials is through the reduction of clinker content in concrete by partial replacement of cement with fillers. In this investigation, the partial replacement of cement with chemically inert nano and microsized fillers of titanium dioxide (TiO₂) and limestone was examined. The effects of nano and micro fillers on early-age properties, long-term properties, photocatalytic properties (for TiO₂-cement mixtures) and life cycle costs were measured and compared. Investigation of early-age properties shows that nanoparticles increase rate and degree of early cement hydration and chemical shrinkage due to heterogeneous nucleation effect. In contrast, coarser microparticles (>3µm in this research) maintain or marginally decrease the rate and degree of early cement hydration and decrease chemical shrinkage due to a dilution effect. In addition, temperature sensitivity of hydration reactions increases in the presence of nanoparticles. Investigation of long-term properties shows that pore size refinement is possible with the partial replacement of cement with nanoparticle fillers. But the long-term tests of filler-cement mixes also demonstrate that, compared to ordinary portland cement mix, the strength decreases and permeability increases. Analysis of photocatalytic properties of TiO₂-cement mixtures showed a lack of an appropriate testing procedure for nitrogen oxide (NOₓ) gas conversion by cement-based materials. Thus, a new standardized procedure and photocatalytic efficiency factor for characterizing photocatalytic NOₓ binding by cementitious materials is proposed. Life cycle analysis demonstrates that although inclusion of TiO₂ increases initial environmental impact of cementitious materials, the innovative photocatalytic properties of TiO₂ could improve sustainability. Life cycle analysis also shows that partial replacement of cement with limestone decreases environmental impact of cementitious mixtures due to lower processing “costs” of limestone compared to cement. Thus, the results from the current research demonstrate that variation of dosage and particle size of inert fillers can be used to tailor properties and structure of cement-based materials and that environmental sustainability can be improved by partial replacement of cement with inert fillers that introduce additional functionalities or fillers with lower embodied-energy and emissions.