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Jiang, XuewenSustainable Methods for Cyanotoxin Treatment and Discovery of the Cyanophage
Master of Science, The Ohio State University, 2017, Food Science and Technology
Cyanobacterial harmful algal bloom (CHABs) has been a great concern due to the detrimental effects on ecosystem, animal and human health. Overgrowth of CHABs causes hypoxia and some species produce unpleasant odor compounds. More importantly, multiple toxins (cyanotoxins) produced by CHABs can be harmful to animal and human health by damaging internal organs, including liver, kidney, reproductive and neurological systems. Water-mediated activities are believed to be the common exposure routes for human to these toxins. Many studies reported that these toxins can be accumulated into food or dietary supplements via contaminated water, since the guideline for agriculture and aquaculture water use is not established yet. Therefore, strategies for controlling both CHABs and their toxins are important and imperative for protecting environmental and food safety. Chapter 1 summarized the literature review about CHABs and their toxins, and identified knowledge gaps. Furthermore, previous research regarding to cyanophages and their ecological roles are also reviewed because understanding of cyanophage, natural predators of cyanobacteria, is critical to understanding the bloom formation and evolution. Among the cyanotoxins, the most abundant cyanotoxin is microcystin (MC), which is a seven-amino-acid peptide, consisting of more than 150 congeners. MC shows toxicity via inhibiting protein phosphatase 1 and 2A, and generate reactive oxygen species (ROS), leading to cell apoptosis in the involved organs. MCs are chemically stable against sunlight, extreme pH and boiling, therefore, it is difficult to treat the contaminated water once MCs are released. Physical, chemical and biological methods have been applied to treat MCs in water, but few of them can be successfully applied for MC- contaminated food. New technologies for MC treatment are proposed in Chapter 2. The objective of Chapter 2 was to develop sustainable and non-chemical-based methods for controlling MCs: 1) ultraviolet with TiO2, which is a common food additive as well as a photocatalyst; and 2) cold plasma, which is a non-thermal treatment using ionized gas. Natural MCs were extracted from Microcystis aeruginosa and treated with several combinations: 1) UV at intensity of 1470 µW/cm2 [high] or 180 µW/cm2 [low]; 2) cold plasma; and 3) no treatment in a dark room (control). To determine synergistic effects, nanoparticles (TiO2) were coated on the outside of the UV treatment chamber prior to irradiation. The MC degradation efficiency was enhanced by the reusable TiO2 coating at lower UV intensity by 10 percent, but no significant difference was observed at higher intensity of UV. Cold plasma removed MCs rapidly (80% and 92% in 1 and 2 hours, respectively) under experimental conditions, indicating that it can be easily and practically used in household and industrial setting. In environmental settings, controlling CHABs formation is a better and effective way to reduce toxin production. Many previous studies have focused on environmental factors on blooms, but the role of cyanophage (viruses whose hosts are cyanobacteria) in the ecology of toxin production is much less understood, especially in freshwater. Cyanophage are known to contribute to biological controlling of CHABs by influencing the metabolism and evolution of cyanobacteria. Therefore, the information on the characteristics of cyanophage infection is crucial in potential bloom control. In Chapter 3, findings about cyanophage isolated from Lake Erie during bloom season were reported. The objectives of this study are to 1) isolate and characterize cyanophages from Lake Erie; and 2) examine the host-cyanophage interactions using multiple tools, especially atomic force microscopy (AFM). Cyanophage isolates were inoculated into toxin-producing Microcystis aeruginosa (host) originated from Lake Erie. The dynamic interactions between phages and hosts were monitored using spectrophotometer, fluorimeter, quantitative PCR and AFM. The structural and genetic characters of the cyanophages were identified by using transmission electron microscope (TEM) and PCR. The Podoviridae ~300 nm in size were infectious against the toxic strain of M. aeruginosa. The growth and photosynthesis capacity of hosts was significantly inhibited after cyanophage infection and cellular damages on membranes over time were clearly observed. We also found that UV irradiation with proper dose can induce the cyanophage shifting from their lysogenic stage to lytic stage. The psbA (photosynthesis core protein A) and the gp58 (special capsid protein) genes were identified, which showed high similarities of the same genes identified in marine cyanophages, indicating a close evolutionary root. In summary, this thesis reports comprehensive knowledge about CHABs and their toxins. In addition, emerging techniques were applied in this study to provide informative and essential basis to develop controlling strategies in various settings when toxins are present.

Committee:

Jiyoung Lee (Advisor); Ahmed Yousef (Committee Member); Luis Rodriguez-sonata (Committee Member)

Subjects:

Food Science

Keywords:

cyanobacteria, cyanotoxin, cyanophage, titanium dioxide, cold plasma

Mileyeva-Biebesheimer, OlgaAn Investigation into Metal Oxide Nanoparticle Toxicity to Bacteria in Environmental Systems Using Fluorescence Based Assays
Doctor of Philosophy in Engineering, University of Toledo, 2011, Civil Engineering
While photocatalytic bactericidal effect of titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles (NPs) is routinely studied, there is very limited information regarding the toxic properties of these NPs in the absence of light. This research was focused on the evaluation of possible toxic effect of TiO2 and ZnO NPs on pure planktonic cultures (Gram-Negative bacteria Escherichia coli and Gram-Positive bacteria Enterococcus faecium), single culture biofilm (E. coli), and anaerobic digester microorganisms in the absence of light. Fluorescent cell membrane integrity stain propidium iodide and dsDNA specific counter stain PicoGreen® were applied to distinguish damaged and intact cells. The pure culture and diluted sludge samples were incubated for 1 h with 0 – 500 mg⁄L of TiO2 and ZnO NPs. Biofilm was exposed to 0 – 100 mg⁄L of TiO2 and ZnO NPs for 24 h. Undiluted sludge samples were incubated for 144 h with 0 – 500 mg⁄L of TiO2 and ZnO NPs (0.31 – 15.43 μg NP⁄mg total suspended solids) or as titanium (Ti) in TiO2 calculated by weight: 375, 750, and 3752 μg⁄L or 0.01, 0.023, and 0.12 μg⁄mg TS. A statistically significant increase in the percentage of damaged cells was detected for pure culture of E. coli and diluted sludge samples at concentration 100 mg⁄L of TiO2 NPs. A pure culture of E. faecium and diluted sludge samples incubated with ZnO NPs did not exhibit an increase of damaged cells. The toxic effect was not significant for biofilm or undiluted sludge samples incubated with TiO2 NPs for 24 and 144 h respectively. Biofilm samples incubated with 100 mg⁄L of ZnO NPs demonstrated a statistically significant increase in the percent of damaged cells. Undiluted sludge samples incubated with 500 mg⁄L of ZnO NPs significantly reduced biogas production. This study demonstrated that fluorescent microscopy and cell membrane integrity stain propidium iodide may be utilized for evaluation of the toxic impact of NPs on microorganisms. This method enables evaluation of NPs impact on fastidious microorganisms and eliminates conventional plating techniques that strongly depend on culturability of the microorganisms.

Committee:

Cyndee Gruden, PhD (Committee Chair); Ashok Kumar, PhD (Committee Member); Isabel Escobar, PhD (Committee Member); Defne Apul, PhD (Committee Member); Youngwoo Seo, PhD (Committee Member)

Subjects:

Civil Engineering; Engineering; Environmental Engineering

Keywords:

nanoparticles; zinc oxide; titanium dioxide; bacteria; E. coli; viability; sludge

Arellano, MartinEffect of surfactant treatment on the dispersibility of titanium dioxide powders in various media
Doctor of Philosophy, Case Western Reserve University, 1995, Macromolecular Science
The purposes of this study were (1) to develop a strategy to modify the surface characteristics of titanium dioxide powders by surfactant treatment in order to improve dispersibility in non-polar media and (2) to investigate the effect of surfactant treatment on titania dispersion behavior in polyethylene melt. In order to facilitate the dispersion of titanium dioxide powders into non-polar media, a strategy involving the use of anionic surfactants to compatibilize the powder with the matrix media has been investigated. The methodology first involves the adsorption of surfactant onto the powder within highly stable aqueous dispersions. Surfactant-coated powders are then removed from the aqueous dispersion and dried. The treated powders obtained this way were used in further experiments. The surface-modified powders were characterized in terms of cohesivity, moisture adsorption, as well as dispersibility and sedimentation behavior in different low molecular weight liquids. Surfactant treated powders showed an enhanced dispersibility in non-polar liquids. From the sedimentation studies the solubility parameters of the powders were calculated. The surfactant treatment shifted the powder partial solubility components closer to the values for non-polar med ia making the powders more compatible with these media, including polymeric melts. Dispersion experiments of titania in polyethylene were performed in a rotating cone-and-plate device, set in a temperature controlled oven. In high viscosity media, the titanium dioxide agglomerates dispersed by an erosion mechanism in which small fragments detached from the surface. The erosion rate was higher for the surfactant treated powders. The increment was explained in terms of better wetting and more efficient transfer of stress. Surfactant treated powders showed better interactions with the polymeric material as measured also by the amount of bound polymer

Committee:

Ica Manas-Zloczower (Advisor)

Subjects:

Plastics Technology

Keywords:

Titanium dioxide powders, dispersion; Surfactant treatment

Hong, William SungilOxidation-reduction kinetics of porous titanium dioxide /
Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Titanium dioxide;Ceramics;Oxidation-reduction reaction

BALASUBRAMANIAN, GANESHEVALUATING THE EFFECT OF SELECTED PROCESS PARAMETERS ON THE PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS
MS, University of Cincinnati, 2002, Engineering : Environmental Engineering
TiO2 assisted photocatalysis for degradation of 4-chlorobenzoic acid has been the focus of this investigation. A quartz batch reactor was designed and built. This reactor was characterized and used to study the reaction kinetics of the degradation reaction. The effects of different process parameters like pH, UV intensity, UV wavelength, mixing, ionic strength, and size and shape of catalyst on the reaction kinetics were also examined. Several methods of immobilizing TiO2 on supports were studied and sol gel methods were investigated in detail. A modified sol gel method was found to be the most effective in preparing a stable and active supported catalyst The objective of the research was to evaluate the effect of selected process parameters on the photocatalytic oxidation of 4-chlorobenzoic acid (4-CBA) and modify existing TiO2 immobilization techniques to develop a more active and attrition resistant coating.

Committee:

Dr. Makram T. Suidan (Advisor)

Keywords:

titanium dioxide; photocatalysis; sol gel; immobilized powder; titania powder

Groves, Warren OlleyVapor-solid equilibria in the titanium-oxygen system /
Doctor of Philosophy, The Ohio State University, 1954, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Titanium dioxide;Phase rule and equilibrium

Shell, James AllenBehavior of iron and titanium oxides in the glassy phase /
Doctor of Philosophy, The Ohio State University, 1969, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Iron oxides;Titanium dioxide

Kumar, SachinGas Phase Oxidation of Dimethyl Sulfide by Titanium Dioxide Based Catalysts
Master of Science, Miami University, 2004, Paper Science and Engineering
In this study, a low temperature catalytic oxidation process was investigated for the oxidation of dimethyl sulfide using titania-based catalysts. TiO2 catalysts doped with vanadia were made using a wet incipient method and a flame synthesis method. The catalysts were characterized using XRD, Raman spectroscopy and BET surface area analysis to study the TiO2 phase transition as functions of calcination temperature and V/Ti mass ratio. A flow reactor was used to investigate the performance of the catalysts, and the exit gases were analyzed using gas chromatography. It was found that low concentrations of vanadia (V/Ti mass ratio ≤ 2%) inhibited phase transformation and sintering, which resulted in more activity per unit mass of the catalysts, and the catalysts having a V/Ti mass ratio of 2% were able to degrade dimethyl sulfide most efficiently.

Committee:

Catherine Almquist (Advisor)

Keywords:

VOC Oxidation; Titanium Dioxide based Catalysts; Vanadium Doping; Nanostructured Vanadia/Titania Catalysts

Song, InhoDefect structure and DC electrical conductivity of titanium dioxide-niobium dioxide solid solution
Doctor of Philosophy, Case Western Reserve University, 1990, Materials Science and Engineering
The defect structure and the dc electrical conductivity of TiO2-NbO2 solid solution have been studied by using time-of-flight neutron diffraction, Nb K-edge x-ray absorption spectroscopy, and dc electrical conductivity measurement as a function of composition. The oxygen content in the solid solutions was determined using thermogravimetric analysis, and the results of other experiments were analyzed and correlated to establish a defect structure that controls the dc electrical conductivity. The lattice parameters and the interstitial defect occupancy were determined using the Rietveld method applied to neutron diffraction results. The valence and the coordination state of Nb ions were determined through XANES and EXAFS analyses of Nb K-edge x-ray absorption data. The formation of Nb-Nb pairs postulated by other researchers was directly observed by Nb K-edge EXAFS analysis. The formation of Nb-Nb pairs was also noticed in the results of neutron diffraction analysis and dc electrical conductivity measurement. A conductivity maximum was observed at Nb0.1Ti0.9O2, after which the conductivity decreases with increasing Nb concentration. The decreasing conductivity with increasing Nb concentration is attributed to the pair formation, by which charge car riers are localized between the two Nb ions.

Committee:

Hisao Yamada (Advisor)

Keywords:

Defect structure DC electrical conductivity titanium dioxide-niobium dioxide solid solution

Beard, William ClarencePhase relations in the systems titania and titania--boric oxide /
Doctor of Philosophy, The Ohio State University, 1965, Graduate School

Committee:

Not Provided (Other)

Subjects:

Mineralogy

Keywords:

Titanium dioxide;Boric oxide

Han, ChangseokMonitoring and Removal of Water Contaminants of Emerging Concern: Development of A Multi-Walled Carbon Nanotube Based-Biosensor and Highly Tailor-Designed Titanium Dioxide Photocatalysts
PhD, University of Cincinnati, 2014, Engineering and Applied Science: Environmental Engineering
In this dissertation, as a monitoring technology for cyanotoxins, a multiwalled carbon nanotube (MWCNT)-based electrochemical biosensor was developed to determine microcystin-LR (MC-LR), a potent cyanobacterial toxin, in sources of drinking water supplies. The performance of the MWCNT array biosensor is evaluated using micro-Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, optical microscopy, and Faradaic electrochemical impedance spectroscopy. A linear dependence of the electron-transfer resistance on the MC-LR concentration is observed in the range of 0.05 to 20 µg L-1, which enables cyanotoxin monitoring well below the World Health Organization provisional concentration limit of 1 µg L-1 for MC-LR in drinking water. In addition to the development of monitoring tools for cyanotoxins, visible light-activated (VLA) TiO2 and monodisperse TiO2 were developed and evaluated for treatment of water contaminants of emerging concern. These materials were synthesized using modified sol-gel methods (i.e., wet chemistry-based methods) such as self-assembly-based and ionic strength-assisted techniques. For this study, first, VLA-sulfur-doped TiO2 (S-TiO2) nanocrystalline films were synthesized by a self-assembly-based sol-gel method using nonionic surfactant to control nanostructure and an inorganic sulfur source for decomposing MC-LR under visible light illumination. Second, the effects of solvent on the synthesis of VLA-S-TiO2 films were scrutinized. Four different polar, protic solvents, isopropanol, 1-butanol, ethanol, and methanol, were chosen as the solvent in four titania sol-gel preparations. Third, monodisperse anatase titania nanoparticles with controllable sizes (typically 10–300 nm) were synthesized using an efficient and straightforward protocol via fine tuning of the ionic strength in the devised sol–gel methodology. Finally, noble metal Ag-decorated, monodisperse TiO2 (TiO2-Ag) aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the pharmaceutical oxytetracycline (OTC) under both UV and visible light irradiation. With a self-assembly-based sol-gel method, nanostructured anatase S-TiO2 with high surface area (> 100 m2 g-1) and porosity (> 30 %) was synthesized and the sample calcined at 350 oC demonstrated the highest visible light absorption and visible light-induced photocatalytic activity in the decomposition of MC-LR. The structural and morphological properties of S-TiO2 could be also tailor-designed using different solvents in the sol-gel synthesis, while inducing negligible effects on the sulfur doping and the visible light activation of TiO2. Thus, it can be concluded that the enhancement of photocatalytic activity of S-TiO2 films can be achieved by judicious choice of the main solvent for the sol-gel method. With an ionic strength-assisted sol-gel method, monodisperse spherical anatase TiO2 (10-300 nm in diameter) as well as monodisperse TiO2-Ag aggregates with 350 nm of diameter were synthesized. For TiO2-Ag, its visible light absorption increased due to the presence of Ag on the surface of monodisperse TiO2, which resulted in the enhancement of the photocatalytic degradation of OTC under both UV-visible light and visible light irradiation compared to pure TiO2. There was an optimal Ag content to obtain the highest photocatalytic degradation of OTC. These newly developed materials demonstrated the efficient decomposition of water contaminants of emerging concern, especially MC-LR and OTC, under UV-visible light and visible light illumination.

Committee:

Dionysios Dionysiou, Ph.D. (Committee Chair); Mallikarjuna Nadagouda, Ph.D. (Committee Member); Margaret Kupferle, Ph.D. P.E. (Committee Member); George Sorial, Ph.D. (Committee Member)

Subjects:

Environmental Engineering

Keywords:

Advanced Oxidation Process;Biosensor;Contaminants of emerging concern;Cyanotoxins;Titanium dioxide;Visible Light Activation

Gassama, EdrissaA Model of the Dye-Sensitized Solar Cell: Solution Via Matched Asymptotic Expansion
Master of Science, University of Akron, 2014, Applied Mathematics
The distribution of the components in the dye-sensitized titanium dioxide solar cell (DSC) is investigated in the thesis. The transport and drift of the ions (iodide, triiodide and cathion) in the electrolyte and the electrons in the nanocrystalline titanium dioxide semiconductor were modeled in the operation of the cell. Homogenization is used to reduce the three dimensional solar cell into a one dimensional system along the thickness of the cell. The model includes both the porous semiconductor and the bulk electrolyte layer between the semiconductor and the cathode. The influence of the parameters of the cell on electron concentration profile is investigated. In particular, the influence of the electron lifetime and the thickness of the nanocrytalline semiconductor are investigated. We applied boundary layer techniques in the solution of the resulting system.

Committee:

Dmitry Golovaty, Dr. (Advisor); Gerald Young, Dr. (Committee Member); Curtis Clemens, Dr. (Committee Member)

Subjects:

Alternative Energy; Applied Mathematics; Energy

Keywords:

solar cell ; dye sensitized titanium dioxide; solar cell ; semiconductor; boundary layer techniques; matched asymptotic expansion;

Kumar, VipulAn Investigation of Nanostructured Tungsta/Vanadia/Titania Catalysts for the Oxidation of Methanol
Master of Science, Miami University, 2004, Paper Science and Engineering
The use of nanostructured V2O5 / TiO2 and WO3 / V2O5 / TiO2 catalysts was investigated for the low temperature oxidation of methanol. A wet incipient method was used to dope WO3 and V2O5 on the Ishihara ST-01 TiO2 support. The V/Ti mass ratios varied from 0 to 0.10 for the V2O5 / TiO2 catalysts, and the W/Ti mass ratios varied from 0 to 0.10 with constant V/Ti mass ratio = 0.02 for the WO3 / V2O5 / TiO2 catalysts. Characterization of the catalysts using X-ray Diffraction, BET surface area and Raman Spectroscopy showed that the thermal stability of catalysts decreased with increasing V/Ti mass ratio over 0.02 but increased with increasing W/Ti mass ratio. The catalytic activity for methanol oxidation increased with W/Ti mass ratio up to W/Ti = 0.05. The catalyst having 0.05 V/Ti mass ratio and calcined at 400 °C showed the highest catalytic activity.

Committee:

Catherine Almquist (Advisor)

Subjects:

Engineering, Environmental

Keywords:

Methanol Oxidation; Titanium Dioxide Catalyst; Vanadia Tungsta Catalyst

Lee, Young-JinStudy on the dispersion of surface treated titanium dioxide in various media
Doctor of Philosophy, Case Western Reserve University, 1993, Macromolecular Science
The purposes of this study were (1) to develop the tools to characterize surface treated titanium dioxide powders, (2) to elucidate the dispersion mechanism in low viscosity solvents and high viscosity polymeric melts, and (3) to investigate the dispersion-compound property relationships. Characterization of various grades of surface treated titanium dioxide powders was performed using Inverse Gas Chromatography, electrophoretic mobility measurements, and cohesivity measurements. These measurements quantified various components of the overall interaction, namely dispersive interactions, acid/base interactions and electrostatic interactions. To quantify cohesivity, tensile strength and compression stress were measured using a split cell and a penetrating cone respectively. Dispersibility in low viscosity solvents was studied using a sedimentation test. Here, dispersibility was interpreted in terms of the wetting properties (quantified in terms of heat of mixing) and by the colloidal stability as governed by van der Waals attractive and electrostatic repulsive forces. Maps of the dispersibility of titanium dioxide powders in donor number and acceptor number coordinates were found to be useful. In high viscosity media, the titanium dioxide agglomerates primarily dispersed by an erosion mechanism in which small fragments detached from the surface. The kinetics of the process was found to be dependent on agglomerate porosity, the cohesive strength of agglomerate, the magnitude of applied shear stress and agglomerate-medium interactions. In this work, dispersion was performed in a rotating cone-and-plate device equipped for in situ observation of the dispersion process in polydimethylsiloxane, a liquid polymer at room temperature. Also the device was set in a temperature controlled oven for dispersion studies into low density polyethylene melt. Studies of the medium penetration were performed in order to gauge the influence of the medium on the effective cohesivity of the agglomerates. A model linking together all of these results was proposed. The degree of dispersion was found to affect the properties of resulting compounds. Optical properties (light transmittance and gloss) and mechanical properties (yield stress and elongation at break) were correlated with dispersion time, filler loading and interfacial interactions. Dynamic mechanical properties such as storage modulus and mechanical damping were also investigated and analyzed in terms of quality of dispersion and interfacial interactions

Committee:

Ica Manas-Zloczower (Advisor)

Subjects:

Plastics Technology

Keywords:

Titanium dioxide, surface treated; Dispersion

Irick, VirgilEffects of impurities on phase development and crystal growth in bauxite-based refractories /
Doctor of Philosophy, The Ohio State University, 1970, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Bauxite;Titanium dioxide;Silica

Tilly, TrevorDISPERSION OF GEOMETRIC TITANIUM DIOXIDE NANOMATERIALS AND THEIR BIOLOGIC EFFECT
Master of Science, Miami University, 2013, Chemical, Paper & Biomedical Engineering
Tunable chemical and physical properties of engineered nanomaterials are achievable by changing their geometry and morphology. Titanium dioxide (TiO2) based nanofilaments-nanotube, nanowire, nanorod-have gained interest in industrial, energy, and as of recent, medical applications due to their superior performance over TiO2 nanoparticles. Safety assessment of these nanomaterials is critical to protect workers, patients, and bystanders as these technologies become widely implemented. Additionally, TiO2 based nanofilaments can easily be inhaled by humans and their high aspect ratio may make them toxic in the air passageway, like asbestos fibers. The tendency of TiO2 nanofilaments to aggregate makes their nanotoxicity assessment difficult and the results controversial because incomplete dispersion results in larger particle size exposure that is no longer at the nanoscale. In this study, a microfluidic device was utilized to produce stable dosing solutions necessary to evaluate the toxicity of TiO2 nanomaterials by eliminating any toxicity caused by aggregated TiO2 nanomaterials. The toxicity results could then be directly correlated to the TiO2 nanostructure itself. Well dispersed TiO2 based nanomaterials were nontoxic to cells. Whereas, aggregated 100 ug/ml concentrations of nanowires and nanotubes reduced viability up to 27%, indicating that in vitro toxicity results may be controlled by the dispersion of dosing solutions.

Committee:

Lei Kerr, PhD (Advisor); Saber Hussain, PhD (Advisor); Catherine Almquist, PhD (Committee Member); Justin Saul, PhD (Committee Member)

Subjects:

Biology; Chemical Engineering; Toxicology

Keywords:

Titanium Dioxide; TiO2; Nanotube; Nanofilament; toxicity; nanotoxicity

Hessler, Christopher MarkThe Influence of Capsular Extracellular Polymeric Substances on the Toxicological Interaction Between Titanium Dioxide Nanoparticles and Planktonic Bacteria
Master of Science in Chemical Engineering, University of Toledo, 2011, College of Engineering
The role of capsular extracellular polymeric substances (EPS) at the surface of planktonic microorganisms was investigated for possible toxicity mitigation from titanium dioxide (TiO2) nanoparticles, using variable EPS producing wild-type and isogenic mutant strains of Pseudomonas aeruginosa. Membrane integrity assays revealed that increased capsular EPS reduced cell membrane damage. Additionally, variability in EPS production provided a means to assess mechanisms of TiO2 microbial toxicity. Acting as a barrier to the cell membrane, capsular EPS permitted attachment of nanoparticles to the cell, while simultaneously delaying cellular damage caused by the production of reactive oxygen species (ROS). Modulations in ROS production were monitored in situ; while changes in the chemical composition of the microorganisms before and after exposure were examined with Fourier transform infrared spectroscopy (FTIR). The addition of methanol, a known radical scavenger, was shown to vastly reduce ROS production and membrane integrity losses, while not affecting physical interactions of nanoparticles with the microorganism. The results support that EPS provides an attachment site for nanoparticles, but more importantly act as a barrier to cell membrane oxidation from ROS. These observations provide better understanding of the overall importance of ROS in TiO2 microbial toxicity

Committee:

Youngwoo Seo (Committee Chair); Dong-Shik Kim (Committee Member); Cyndee Gruden (Committee Member)

Subjects:

Environmental Engineering

Keywords:

titanium dioxide; nanoparticles; microbial toxicity; reactive oxygen

DAVYDOV, LEVPHOTOCATALYTIC DEGRADATION OF ORGANIC CONTAMINANTS: NOVEL CATALYSTS AND PROCESS
PhD, University of Cincinnati, 2001, Engineering : Chemical Engineering
Photocatalysis has recently emerged as an advanced oxidation process. The present dissertation aims at the practical increase of the energy efficiency of photocatalysis using fundamental tools. A comprehensive kinetic model was developed to describe primary photocatalytic processes taking place on the surface of semiconductors. The steady-state assumption for all the intermediate species in the system allowed to find the lumped kinetic parameters and elucidate the relative extent of electron-hole and recombination reactions. It is important to utilize single-stage oxidation reactions to test this kinetci model and obtain kinetic parameters. This simple method also allowed to determine experimentally the rates of radical generation as well as the rate of electron-hole recombination for a number of commercial titania photocatalysts. When interfaced with the continuous flow reactor design, the model allowed to predict the optimal radiation profiles in photoreactors, which would significantly increase the reactor output. Such profiles are represented by a combination of exponential functions, and they prescribe more radiation at the beginning of the reactor in comparison with that at the end. Furthermore, it was found that when a continuous-flow reactor with recycle, the use of the optimal profile can produce a major enhancement of the output in comparison with the uniformly illuminated photoreactor. The expansion of the working range of photocatalysts to enable them to utilize visible light was also undertaken. To achieve this, a combination of doping and sensitization properties was needed. It was found that titania-loaded transition metal MCM-41 materials can allow for such combination. The heterojunction with the transition metal substituted MCM-41 works as a "sensitizer" for the titania deposit, while the extraframework transtion metal inclusion can diffuse inside the titania loading and work as a dopant. The latter allows to effectively utilize visible light to perform photocatalytic reactions. Similar effect of sensitization was found for Cd-MCM-41, which enhances the photoactivity of titania in ultraviolet light. Conclusively, it has been shown that the use of optimal reactor design as well as novel catalysts containing active supports can significantly increase the reaction rates and exclude the dependence of the process on the artificial sources of energy.

Committee:

Dr. P.G. Smirniotis (Advisor)

Subjects:

Engineering, Chemical

Keywords:

CATALYSIS; PHOTOCATALYSIS; TITANIUM DIOXIDE; ZEOLITE; SEMICONDUCTOR

Schmall, Nicholas EdwardFabrication of Binary Quantum Solids From Colloidal Semiconductor Quantum Dots
Master of Science (MS), Bowling Green State University, 2009, Physics
In this thesis I report on an attempted colloidal synthesis of heterostructured quantum solids comprising of a staggered heterojunction of nearly lattice matched cadmium sulfide and zinc selenide semiconductor quantum dots. I present compelling evidence of photoinduced charge separation between zinc selenide and cadmium sulfide domains, via absorption and photoluminescence spectra, but can not provide conclusive evidence via transmission electron microscopy of the merging of the quantum dots. Also in this thesis I report on a colloidal synthesis of lead selenide, titanium dioxide heterostructures, comprising of small diameter lead selenide nanocrystals, grown onto the surface of titanium dioxide nanorods. The deposition of lead sulfide on titanium dioxide proceeds via formation of sub-2 nm lead selenide islands that can be controllably grown to 5 nm by introducing secondary precursor injections. Evidence of the formation of lead selenide nanocrystal islands on the titanium dioxide rods was determined via the acquisition of transmission electron microscopy images that confirm the statistically distributed formation of lead selenide islands.

Committee:

Mikhail Zamkov, PhD (Advisor); Robert Boughton, PhD (Committee Member); Eric Mandell, PhD (Committee Member)

Subjects:

Physics

Keywords:

Quantum Dots; Nanocrystals; Cadmium Sulfide Quantum Dots; Zinc Selenide Quantum Dots; Titanium Dioxide Nanorods.

Douglass, D. L.The kinetics and mechanism of the conversion of titanium dioxide to titanium nitride /
Doctor of Philosophy, The Ohio State University, 1958, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Titanium dioxide;Titanium nitride

DIONYSIOU, DIONYSIOS DENGINEERED PROCESS FOR THE PHOTOCATALYTIC TREATMENT OF ORGANIC CONTAMINANTS IN WATER
PhD, University of Cincinnati, 2001, Engineering : Environmental Engineering
A novel thin-film rotating-disk TiO2 photocatalytic reactor (RDPR) was developed and evaluated for the complete elimination of traces of recalcitrant halogenated aromatic and other organic contaminants in drinking water and industrial wastewater. The RDPR incorporates important features including immobilization of the catalyst on the rotating disk and the degradation and mineralization of organic impurities in a thin film of contaminated water using only TiO2 catalyst, UV radiation, and oxygen from the atmosphere. The study included detailed investigation of the hydrodynamics of flow in the RDPR, determination of the liquid carrying capacity of the disk, immobilization and characterization of the catalyst, and quantification of the light intensity distribution. Detailed experimental work accompanied by mathematical modeling investigated the effects of disk angular velocity, incident light irradiance, type and concentration of electron acceptors including hydrogen peroxide and oxygen, initial contaminant concentration, and solution matrix characteristics. The effects of these parameters were evaluated considering initial rates of degradation and extent of mineralization of the parent contaminant, reaction rate constants in the thin liquid film exposed to TiO2 and UV, and efficiencies of light utilization. Determination of the dimensionless Damköhler number (Da), which accounts for the influence of mass transfer on the photocatalytic process, revealed that degradation reactions were not mass transfer limited when the disk angular velocity surpassed a critical value. The latter was mainly due to the increase of mass transfer coefficient for the transport of the contaminant from the bulk of the thin liquid film carried by the disk to the surface of the catalyst. On the other hand, photocatalytic reactions were limited by the intensity of UV radiation. The influence of initial contaminant concentration on the degradation reactions follow Langmuir-Hinshelwood kinetics. Similarly, the effect of oxygen concentration on the degradation reactions was found to obeyed the Langmuir-Hinshelwood model. The effect of hydrogen peroxide in the feed solution during the continuous-mode operation of the RDPR revealed the existence of an optimum concentration of hydrogen peroxide and that high concentrations of this electron acceptor inhibited the photocatalytic reactions mainly due to the predominance of other reactions involving scavenging of hydroxyl radicals, the major oxidizing species in the photocatalytic process.

Committee:

Dr. Makram T. Suidan (Advisor)

Subjects:

Engineering, Environmental

Keywords:

photocatalysis; rotating disk reactor; organic contaminants in water; titanium dioxide; water treatment

Sand, Sara CatherineTiO2/CNT Composite Electrodes in Dye-Sensitized Solar Cell Electrodes
Bachelor of Science (BS), Ohio University, 2017, Physics
While greenhouse gasses continue to devastate our planet and our atmosphere, solar energy offers a possibility for clean and renewable energy. While many solar cells strive for high efficiency, dye-sensitized solar cells offer a solar cell with lower cost, but they are currently at much lower efficiency. Dye-sensitized solar cells have several layers including a light absorbing dye and an active electrode which is typically made of a porous titanium dioxide. This electrode must be both porous to allow electron transfer into the electrode and have continuous pathways in order to allow electrons move easily toward the load. We incorporated carbon nanotubes into a sintered titanium dioxide electrode in order to add continuous, conductive pathways through which the electrons could travel. These carbon nanotubes increased the electron lifetimes from 0.07497 seconds with titanium dioxide alone to 1.6632 seconds. Ultimately, this indicates that carbon nanotubes could be an effective structure to improve dye-sensitized solar cell efficiency.

Committee:

Martin Kordesch (Advisor)

Subjects:

Materials Science; Physics

Keywords:

Solar cell, carbon nanotubes, titanium dioxide, dye-sensitized, electron lifetimes

McCracken, Christie JoyToxicity of Food-Relevant Nanoparticles in Intestinal Epithelial Models
Doctor of Philosophy, The Ohio State University, 2015, Integrated Biomedical Science Graduate Program
Nanoparticles are increasingly being incorporated into common consumer products, including in foods and food packaging, for their unique properties at the nanoscale. Food-grade silica and titania are used as anti-caking and whitening agents, respectively, and these particle size distributions are composed of approximately one-third nanoparticles. Zinc oxide and silver nanoparticles can be used for their antimicrobial properties. However, little is known about the interactions of nanoparticles in the body upon ingestion. This study was performed to investigate the role of nanoparticle characteristics including surface chemistry, dissolution, and material type on toxicity to the intestinal epithelium. Only mild acute toxicity of zinc oxide nanoparticles was observed after 24-hour treatment of intestinal epithelial C2BBe1 cells based on the results of toxicity assays measuring necrosis, apoptosis, membrane damage, and mitochondrial activity. Silica and titanium dioxide nanoparticles were not observed to be toxic although all nanoparticles were internalized by cells. In vitro digestion of nanoparticles in solutions representing the stomach and intestines prior to treatment of cells did not alter nanoparticle toxicity. Long-term repeated treatment of cells weekly for 24 hours with nanoparticles did not change nanoparticle cytotoxicity or the growth rate of the treated cell populations. Thus, silica, titanium dioxide, and zinc oxide nanoparticles were found to induce little toxicity in intestinal epithelial cells. Fluorescent silica nanoparticles were synthesized as a model for silica used in foods that could be tracked in vitro and in vivo. To maintain an exterior of pure silica, a silica shell was hydrolyzed around a core particle of quantum dots or a fluorescent dye electrostatically associated with a commercial silica particle. The quantum dots used were optimized from a previously reported microwave quantum dot synthesis to a quantum yield of 40%. Characterization of the silica particles showed that the surface properties resembled pure silica. These particles were able to be detected in vitro as well as in vivo after oral administration of nanoparticles to mice by gavage. After four daily administrations, nanoparticles were detected by fluorescence confocal microscopy in intestines as well as liver, kidney, spleen, lung, and brain. Thus, silica nanoparticles were able to traverse the intestinal epithelium. Further investigation is needed to determine nanoparticle accumulation and potential functional consequences throughout the body. Silver nanoparticles were particularly toxic to proliferating (subconfluent) C2BBe1 cells plated at low density, inducing 15% necrosis and a 76% decrease in mitochondrial activity. Silver nanoparticle treatment induced oxidative stress in cells based on increased GSH/GSSG ratios. In addition, silver nanoparticles induced G2/M phase cell cycle arrest and inhibited cell proliferation at doses forty times lower than those at which silica, titanium dioxide, and zinc oxide nanoparticles had inhibitory effects. Silver nanoparticles subjected to in vitro digestion before cell exposure required higher doses to induce toxicity, likely due to slower dissolution because of greater surface species adsorption. Silver nanoparticles did not cause toxicity or oxidative stress in confluent (stationary) cells. Thus, upon ingestion, silver nanoparticles may be especially toxic to proliferating stem cells in intestinal crypts, particularly in disease states with a compromised epithelium.

Committee:

W. James Waldman, PhD (Advisor); Prabir Dutta, PhD (Committee Chair); Narasimham Parinandi, PhD (Committee Member); Estelle Cormet-Boyaka, PhD (Committee Member)

Subjects:

Biomedical Research; Nanotechnology; Toxicology

Keywords:

intestinal epithelial cells, C2BBe1 cells, nanoparticles, food-relevant nanoparticles, nanoparticle toxicity, silica, titanium dioxide, zinc oxide, silver, toxicity, fluorescent nanoparticles

Lindstrom, Mathias E.V.Generation Of A Novel TiO 2 - Composite – A Feasibility Study
Master of Science, Miami University, 2002, Paper Science and Engineering
The objective of this work was to explore the feasibility of generating a fiber-latex-TiO 2 -composite material that could be used as an additive in the papermachine wet end. By initially binding a cationic latex and subsequently anionic TiO 2 to the fiber surface and then curing the latex, it was envisioned that the pigment would be strongly retained in a latex film on the fiber surface. This novel additive could be utilized in papermaking operations achieving high TiO 2 retention and substantial cost-savings. Dispersion turbidity and microscopy were used to monitor experiments. Data were generated on the interaction between fiber and cationic latex, and a fiber-latex intermediate and TiO 2 . Retention levels of TiO 2 in the range of the target value were achieved, and stability tests proved the material resistant to normal pH and shear stresses. However, the cured composite proved difficult to redisperse and a different approach for curing must be explored.

Committee:

William Scott (Advisor)

Subjects:

Engineering, Materials Science

Keywords:

paper making; titanium dioxide; TiO 2 ; latex; cationic latex; composite; retention; retention aid; additive; opacity; turbidity; Britt Jar; fiber surface

Choi, HyeokNovel Preparation of Nanostructured Titanium Dioxide Photocatalytic Particles, Films, Membranes, and Devices for Environmental Applications
PhD, University of Cincinnati, 2007, Engineering : Environmental Engineering

Precise manipulation of matter at the nanoscale will enhance our potential to synthesize materials with tailor-designed properties and functionalities for their environmental applications. This dissertation explores the development of innovative nanotechnological procedures for the preparation of highly efficient visible light-activated nanostructured TiO2 photocatalytic particles, films, membranes, and devices for environmental applications.

Nanocrystalline TiO2 particles and immobilized films and membranes with mesoporous inorganic network were prepared via a sol-gel method modified with surfactants as pore-directing agents. Not only did we manipulate the physicochemical properties of TiO2 such as crystallographic structure, particle size, and defect structure but also tailor-design its structural properties such as surface area, pore volume, and pore size distribution. Asymmetric mesoporous multilayer TiO2 photocatalytic membranes exhibiting hierarchical changes in pore diameter and materials porosity were also fabricated. These TiO2 films and membranes inherently possessed multiple and simultaneous functions including photocatalytic decomposition of organic pollutants, inactivation of pathogenic microorganisms, physical separation of contaminants, and anti-biofouling action.

In addition, for the design of solar-driven treatment technologies, highly efficient visible light-activated TiO2 photocatalysts with mesoporous structure and narrowed band gap energy were synthesized by introducing nitrogen-containing surfactant as a pore templating material as well as a nitrogen dopant in the sol-gel method of TiO2 For the development of highly sensitive and stable electrochemical sensors to detect a neurotransmitter, catechol, sonogel carbon electrodes were modified with the nanostructured TiO2 acting as an adsorbent for catechol and a redox mediator for electron transfer.

We also elucidated the formation of nanocrystalline TiO2 particles at ambient synthesis conditions via sol-gel method employing water immiscible room temperature ionic liquid as reaction medium and modified with surfactant as pore template. Detail information on the preparative method, synthesis route and mechanism, crystallographic and structural properties, and photocatalytic activity of the nanocrystalline TiO2 particles with thermal stability was investigated.

From a scientific point of view, this study will provide new nanotechnological and materials chemistry procedures to synthesize highly efficient photocatalytic TiO2 particles, films, and membranes that can be used for the treatment and disinfection of water and wastewater under even visible light irradiation, and highly sensitive TiO2-based devices for the development of new type of sensors.

Committee:

Dr. Dionysios Dionysiou (Advisor)

Subjects:

Engineering, Environmental

Keywords:

Titanium Dioxide; Photocatalysis; Advanced Oxidation Technologies; Water and Wastewater Treatment and Water Quality; Environmental Application; Nanoscience and Nanotechnology; Green Engineering and Sustainability; Nanostructured and Functional Materials

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