Síntese e caracterização textural do catalisador CeO2/TiO2 obtido via sol-gel: fotocatálise do composto modelo hidrogenoftalato de potássio

Este trabalho descreve um método de modificação do TiO2 obtido pelo processo sol-gel, através da adição de óxido de cério no momento da síntese. O material foi caracterizado por adsorção de N2 a 77K. A adição de CeO2 aumenta a área específica do catalisador em 135% e reduz o diâmetro de poros. A atividade catalítica desses materiais foi verificada frente à reação de foto-decomposição do hidrogenoftalato de potássio e comparada ao TiO2 comercial P25 da Degussa.

Photoelectrocatalytical degradation of basic blue 41 dye using nanoporous semiconductor of Ti/TiO2

O presente trabalho investiga a degradação fotoeletrocatalítica do corante Azul Básico 41 (AB 41) amplamente utilizado na tintura de fibras sintéticas, utilizando um semicondutor Ti/TiO2 como fotoanodo. 100% de degradação foi obtida após 60 min de tratamento de 8,33x10-5 mol L-1 do corante em 0,1 mol L−1 Na2SO4, pH 2 sob densidade de corrente de 0,40 mA cm−2 e irradiação UV. Ainda foi obtido 80% de remoção de carbono orgânico total, cuja oxidação segue uma reação de pseudo-primeira ordem com constante de velocidade inicial de -0,040 mim-1 e uma eficiência de corrente de 51%. Os resultados são superiores á fotocatálise convencional nas mesmas condições sem a polarização do fotoanodo que leva a 65% de mineralização sob constante de velocidade de -0,024 mim-1.

Influence of topography and surface chemistry on the wetting properties of TiO2-based ceramic coatings

Vätning av fasta ytor är ett viktigt fenomen i såväl naturen som i en lång rad av industriella tillämpningar. Det är allmänt känt att vätningen av en fast yta styrs av ytans kemi samt struktur. Målsättningen med avhandlingen var att studera hur kemisk heterogenitet och ytråhet på nanometernivå påverkar vätningsegenskaperna hos en fast yta. Ytorna som studerades var titandioxid-baserade kerama ytor som framställdes med hjälp av en sol-gel process. Vätningstudierna utfördes genom kontaktvinkelmätningar, vilket innebär att man mäter vinkeln som vätska/luft-gränsskiktet hos en vätskedroppe bildar mot en fast yta. Ytråheten hos materialen studerades främst genom atomkraftsmikroskopi (AFM). I AFM detekteras ytans struktur av en mycket skarp nål som skannar ytan. Resultaten i avhandlingen kunde framgångsrikt modelleras med existerande teorier för vätning av heterogena ytor.

System-level characterization of Th2 cell development and immune cell responses to ZnO and TiO2 nanoparticles

Asthma and allergy are common diseases and their prevalence is increasing. One of the hypotheses that explains this trend is exposure to inhalable chemicals such as traffi c-related air pollution. Epidemiological research supports this theory, as a correlation between environmental chemicals and allergic respiratory diseases has been found. In addition to ambient airborne particles, one may be exposed to engineered nanosized materials that are actively produced due to their favorable physico-chemical properties compared to their bulk size counterparts. On the cellular level, improper activity of T helper (Th) cells has been connected to allergic reactions. Th cells can differentiate into functionally different effector subsets, which are identifi ed according to their characteristic cytokine profi les resulting in specifi c ability to communicate with other cells. Th2 cells activate humoral immunity and stimulate eradication of extracellular pathogens. However, persistent predominance of Th2 cells is involved in a development of number of allergic diseases. The cytokine environment at the time of antigen recognition is the major factor determining the polarization of a naïve Th cell. Th2 cell differentiation is initiated by IL4, which signals via transcription factor STAT6. Although the importance of this pathway has been evaluated in the mouse studies, the signaling components involved have been largely unknown. The aim of this thesis was to identify molecules, which are under the control of IL4 and STAT6 in Th cells. This was done by using system-level analysis of STAT6 target genes at genome, mRNA and protein level resulting in identifi cation of various genes previously not connected to Th2 cell phenotype acquisition. In the study, STAT6-mediated primary and secondary target genes were dissection from each other and a detailed transcriptional kinetics of Th2 cell polarization of naïve human CD4+ T cells was collected. Integration of these data revealed the hierarchy of molecular events that mediates the differentiation towards Th2 cell phenotype. In addition, the results highlighted the importance of exploiting proteomics tools to complement the studies on STAT6 target genes identifi ed through transcriptional profi ling. In the last subproject, the effects of the exposure with ZnO and TiO2 nanoparticles was analyzed in Jurkat T cell line and in primary human monocyte-derived macrophages and dendritic cells to evaluate their toxicity and potential to cause infl ammation. Identifi cation of ZnO-derived gene expression showed that the same nanoparticles may elicit markedly distinctive responses in different cell types, thus underscoring the need for unbiased profi ling of target genes and pathways affected. The results gave additional proof that the cellular response to nanosized ZnO is due to leached Zn2+ ions. The approach used in ZnO and TiO2 nanoparticle study demonstrated the value of assessing nanoparticle responses through a toxicogenomics approach. The increased knowledge of Th2 cell signaling will hopefully reveal new therapeutic nodes and eventually improve our possibilities to prevent and tackle allergic infl ammatory diseases.

Combination of pulsed corona discharge with TiO2 photocatalysis: verification of hypothesis

The oxidation potential of pulsed corona discharge concerning aqueous impurities is limited in respect to certain refractory compounds. This may be enhanced in combination of the discharge with catalysis/photocatalysis as developed in homogeneous gas-phase reactions. The objective of the work consists of testing the hypothesis of oxidation potential enhancement in combination of the discharge with TiO2 photocatalysis applied to aqueous solutions of refractory oxalate. Meglumine acridone acetate was included for meeting the practical needs. The experimental research was undertaken into oxidation of aqueous solutions under conditions of various target pollutant concentrations, pH and the pulse repetition rate with plain electrodes and the electrodes with TiO2 attached to their surface. The results showed no positive influence of the photocatalyst, the pollutants were oxidized with the rate identical within the accuracy of measurements. The possible explanation for the observed inefficiency may include low UV irradiance, screening effect of water and generally low oxidation rate in photocatalytic reactions. Further studies might include combination of electric discharge with ozone decomposition/radical formation catalysts.

Computational modeling of the properties of TiO2 nanoparticles

In this study we discuss the electronic, structural, and optical properties of titanium dioxide nanoparticles, and also the properties of Ni(II) diimine dithiolato complexes as dyes in dye-sensitized TiO2 based solar cells. The abovementioned properties have been modeled by using computational codes based on the density functional theory. The results achieved show slight evidence on the structure-dependent band gap broadening, and clear blue-shifts in absorption spectra and refractive index functions of ultra-small TiO2 particles. It is also shown that these properties are strongly dependent on the shape of the nanoparticles. Regarding the Ni(II) diimine dithiolato complexes as dyes in dye-sensitized TiO2 based solar cells, it is shown that based on the experimental electrochemical investigation and DFT studies all studied diimine derivatives could serve as potential candidates for the light harvesting, but the e ciencies of the dyes studied are not very promising.

The Combined treatment of UV Light and Titanium Dioxide (TiO2) in Grease Filtration Technique

The aim of this thesis was to identify the best grease removal technique with the application of low power of UV light to TiO2 coated grease filters. The treatment with various power series of ozone generating and ozone free lamps to normal grease filters and TiO2 coated grease filters were examined and the obtained results are compared to each other in this paper. The effect of ozone reaction was observed and compared with the effect of TiO2. The experiments were solely based on the photo oxidation and photo catalytic oxidation reactions. TiO2 is a green catalyst used in the photocatalytic reaction. Sunflower oil was used for grease production and tetracholoroethylene as a solvent. Grease samples were collected from the ventilation duct connected to the cooking hood system. Sample extraction was done in ultrasonic bath with the principle of sonication. The sample analysis was done by FTIR machine. The result determining the concentration of grease was the quantification of saturated C-H bonds in the chosen peak group of the spectrum. A very low power of UVC light functions perfectly with the Titanium dioxide. The experimental results have shown the combined treatment of titanium dioxide and UV light is an effective method in grease removal process. The photocatalytic reaction with titanium dioxide is better than photo oxidation reaction with ozone treatment. Photocatalytic reaction is environmentally friendly, energy efficient and economical.

Pulsed electric field assisted sol-gel preparation of TiO2 particles and their photocatalytic properties

The objective of this thesis was to study the effect of pulsed electric field on the preparation of TiO2 nanoparticles via sol-gel method. The literature part deals with properties of different TiO2 crystal forms, principles of photocatalysis, sol-gel method and pulsed electric field processing. It was expected that the pulsed electric field would have an influence on crystallite size, specific surface area, polymorphism and photocatalytic activity of produced particles. TiO2 samples were prepared by using different frequencies and treatment times of pulsed electric field. The properties of produced TiO2 particles were examined X-ray diffraction (XRD), Raman spectroscopy and BET surface area analysis. The photocatalytic activities of produced TiO2 particles were determined by using them as photocatalysts for the degradation of formic acid under UVA-light. The photocatalytic activities of samples produced with sol-gel method were also compared with the commercial TiO2 powder Aeroxide® (Evonic Degussa GmbH). Pulsed electric field did not have an effect on the morphology of particles. Results from XRD and Raman analysis showed that all produced TiO2 samples were pure anatase. However, pulsed electric field did have an effect on crystallite size, specific surface area and photocatalytic activity of TiO2 particles. Generally, the crystallite sizes were smaller, specific surface areas larger and initial formic acid degradation rates higher for samples that were produced by applying the pulsed electric field. The higher photocatalytic activities were attributed to larger surface areas and smaller crystallite sizes. Though, with all of the TiO2 samples produced by the sol-gel method the initial formic acid degradation rates were significantly slower than with the commercial TiO2 powder.

Photocatalysis Studies under Visible Light Irradiation with TiO2 Obtained by Pulsed Electric Field Assisted Sol-Gel Method

The objective of this thesis was to study the effect of pulsed electric field on the preparation of TiO2 nanoparticles via sol-gel method under the visible light irradiation. The literature part introduces properties of different TiO2 crystal forms and principle of photocatalysis. It was expected that pulsed electric field would have an influence on degradation for oxalic acid and formic acid. TiO2 samples were prepared by using three frequencies (50Hz, 294Hz, and 963Hz) and two treatment times (12 minutes and 24 minutes) of pulsed electric field. The photocatalytic activities of TiO2 samples produced with sol-gel method were also compared with the TiO2 particles made by previous study and with the commercial TiO2 powder Aeroxide® (Evonic Degussa GmbH) at the same condition. Results show that pulsed electric field does have an effect on degradation for oxalic acid and formic acid. Generally, higher photocatalytic activities for oxalic acid and formic acid were obtained with lower frequency and longer treatment time of pulsed electric field.

Síntesis y caracterización de oxidos ceramicos en el sistema SrO-Li2O-TiO2

Tesis (Maestría en Ciencias con Especialidad en Química Analítica) UANL

Estudio de nuevos compuestos en el sistema Cs2O-TiO2-SiO2

Tesis (Maestría en Ciencias con Especialidad en Ingeniería Cerámica) UANL

Envejecimiento artificial para el BAO-TIO2, utilizado como elemento dieléctrico en un capacitor

Tesis ( Maestro en Ciencias de la Ingeniería Mecánica, con Especialidad en Térmica y Fluidos) UANL, 2002

Síntesis de nanoestructuras bidimensionales de oro y plata depositadas sobre TiO2 por rocío pirolítico asistido por ultrasonido.

Tesis (Doctorado en Química de los Materiales) UANL, 2011.

Influence de la taille de départ, de l’état d’agglomération et de la dose de nanoparticules de dioxyde de titane (TiO2) inhalées sur la réponse pulmonaire chez le rat

En raison de leur petite taille, les nanoparticules (NP) (< 100 nm) peuvent coaguler très rapidement ce qui favorise leur pénétration dans l’organisme sous forme d’agglomérats. L’objectif de cette recherche est d’étudier l’influence de l’état d’agglomération de NP de dioxyde de titane (TiO2) de trois tailles de départ différentes, 5, 10-30 ou 50 nm sur la toxicité pulmonaire chez le rat mâle (F344) exposé à des aérosols de 2, 7 ou 20 mg/m3 pendant 6 heures. Dans une chambre d’inhalation, six groupes de rats (n = 6 par groupe) ont été exposés par inhalation aiguë nez-seulement à des aérosols ayant une taille primaire de 5 nm, mais produits sous forme faiblement (< 100 nm) ou fortement (> 100 nm) agglomérée à 2, 7 et 20 mg/m3. De façon similaire, quatre autres groupes de rats ont été exposés à 20 mg/m3 à des aérosols ayant une taille primaire de 10-30 et 50 nm. Les différents aérosols ont été générés par nébulisation à partir de suspensions ou par dispersion à sec. Pour chaque concentration massique, un groupe de rats témoins (n = 6 par groupe) a été exposé à de l’air comprimé dans les mêmes conditions. Les animaux ont été sacrifiés 16 heures après la fin de l’exposition et les lavages broncho-alvéolaires ont permis de doser des marqueurs d’effets inflammatoires, cytotoxiques et de stress oxydant. Des coupes histologiques de poumons ont également été analysées. L’influence de l’état d’agglomération des NP de TiO2 n’a pu être discriminée à 2 mg/m3. Aux concentrations massiques de 7 et 20 mg/m3, nos résultats montrent qu’une réponse inflammatoire aiguë est induite suite à l'exposition aux aérosols fortement agglomérés. En plus de cette réponse, l’exposition aux aérosols faiblement agglomérés à 20 mg/m3 s’est traduite par une augmentation significative de la 8-isoprostane et de la lactate déshydrogénase. À 20 mg/m3, les effets cytotoxiques étaient plus importants suite à l’exposition aux NP de 5 nm faiblement agglomérées. Ces travaux ont montré dans l'ensemble que différents mécanismes de toxicité pulmonaire peuvent être empruntés par les NP de TiO2 en fonction de la taille de départ et de l’état d’agglomération.

Spectrum simulation of rough and nanostructured targets from their 2D and 3D image by Monte Carlo methods

Corteo is a program that implements Monte Carlo (MC) method to simulate ion beam analysis (IBA) spectra of several techniques by following the ions trajectory until a sufficiently large fraction of them reach the detector to generate a spectrum. Hence, it fully accounts for effects such as multiple scattering (MS). Here, a version of Corteo is presented where the target can be a 2D or 3D image. This image can be derived from micrographs where the different compounds are identified, therefore bringing extra information into the solution of an IBA spectrum, and potentially significantly constraining the solution. The image intrinsically includes many details such as the actual surface or interfacial roughness, or actual nanostructures shape and distribution. This can for example lead to the unambiguous identification of structures stoichiometry in a layer, or at least to better constraints on their composition. Because MC computes in details the trajectory of the ions, it simulates accurately many of its aspects such as ions coming back into the target after leaving it (re-entry), as well as going through a variety of nanostructures shapes and orientations. We show how, for example, as the ions angle of incidence becomes shallower than the inclination distribution of a rough surface, this process tends to make the effective roughness smaller in a comparable 1D simulation (i.e. narrower thickness distribution in a comparable slab simulation). Also, in ordered nanostructures, target re-entry can lead to replications of a peak in a spectrum. In addition, bitmap description of the target can be used to simulate depth profiles such as those resulting from ion implantation, diffusion, and intermixing. Other improvements to Corteo include the possibility to interpolate the cross-section in angle-energy tables, and the generation of energy-depth maps.