Synthesis, Characterization and Applications of Modified TiO2 Systems

This thesis is divided in to 9 chapters and deals with the modification of TiO2 for various applications include photocatalysis, thermal reaction, photovoltaics and non-linear optics. Chapter 1 involves a brief introduction of the topic of study. An introduction to the applications of modified titania systems in various fields are discussed concisely. Scope and objectives of the present work are also discussed in this chapter. Chapter 2 explains the strategy adopted for the synthesis of metal, nonmetal co-doped TiO2 systems. Hydrothermal technique was employed for the preparation of the co-doped TiO2 system, where Ti[OCH(CH3)2]4, urea and metal nitrates were used as the sources for TiO2, N and metals respectively. In all the co-doped systems, urea to Ti[OCH(CH3)2]4 was taken in a 1:1 molar ratio and varied the concentration of metals. Five different co-doped catalytic systems and for each catalysts, three versions were prepared by varying the concentration of metals. A brief explanation of physico-chemical techniques used for the characterization of the material was also presented in this chapter. This includes X-ray Diffraction (XRD), Raman Spectroscopy, FTIR analysis, Thermo Gravimetric Analysis, Energy Dispersive X-ray Analysis (EDX), Scanning Electron Microscopy(SEM), UV-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), Transmission Electron Microscopy (TEM), BET Surface Area Measurements and X-ray Photoelectron Spectroscopy (XPS). Chapter 3 contains the results and discussion of characterization techniques used for analyzing the prepared systems. Characterization is an inevitable part of materials research. Determination of physico-chemical properties of the prepared materials using suitable characterization techniques is very crucial to find its exact field of application. It is clear from the XRD pattern that photocatalytically active anatase phase dominates in the calcined samples with peaks at 2θ values around 25.4°, 38°, 48.1°, 55.2° and 62.7° corresponding to (101), (004), (200), (211) and (204) crystal planes (JCPDS 21-1272) respectively. But in the case of Pr-N-Ti sample, a new peak was observed at 2θ = 30.8° corresponding to the (121) plane of the polymorph brookite. There are no visible peaks corresponding to dopants, which may be due to their low concentration or it is an indication of the better dispersion of impurities in the TiO2. Crystallite size of the sample was calculated from Scherrer equation byusing full width at half maximum (FWHM) of the (101) peak of the anatase phase. Crystallite size of all the co-doped TiO2 was found to be lower than that of bare TiO2 which indicates that the doping of metal ions having higher ionic radius into the lattice of TiO2 causes some lattice distortion which suppress the growth of TiO2 nanoparticles. The structural identity of the prepared system obtained from XRD pattern is further confirmed by Raman spectra measurements. Anatase has six Raman active modes. Band gap of the co-doped system was calculated using Kubelka-Munk equation and that was found to be lower than pure TiO2. Stability of the prepared systems was understood from thermo gravimetric analysis. FT-IR was performed to understand the functional groups as well as to study the surface changes occurred during modification. EDX was used to determine the impurities present in the system. The EDX spectra of all the co-doped samples show signals directly related to the dopants. Spectra of all the co-doped systems contain O and Ti as the main components with low concentrations of doped elements. Morphologies of the prepared systems were obtained from SEM and TEM analysis. Average particle size of the systems was drawn from histogram data. Electronic structures of the samples were identified perfectly from XPS measurements. Chapter 4 describes the photocatalytic degradation of herbicides Atrazine and Metolachlor using metal, non-metal co-doped titania systems. The percentage of degradation was analyzed by HPLC technique. Parameters such as effect of different catalysts, effect of time, effect of catalysts amount and reusability studies were discussed. Chapter 5 deals with the photo-oxidation of some anthracene derivatives by co-doped catalytic systems. These anthracene derivatives come underthe category of polycyclic aromatic hydrocarbons (PAH). Due to the presence of stable benzene rings, most of the PAH show strong inhibition towards biological degradation and the common methods employed for their removal. According to environmental protection agency, most of the PAH are highly toxic in nature. TiO2 photochemistry has been extensively investigated as a method for the catalytic conversion of such organic compounds, highlighting the potential of thereof in the green chemistry. There are actually two methods for the removal of pollutants from the ecosystem. Complete mineralization is the one way to remove pollutants. Conversion of toxic compounds to another compound having toxicity less than the initial starting compound is the second way. Here in this chapter, we are concentrating on the second aspect. The catalysts used were Gd(1wt%)-N-Ti, Pd(1wt%)-N-Ti and Ag(1wt%)-N-Ti. Here we were very successfully converted all the PAH to anthraquinone, a compound having diverse applications in industrial as well as medical fields. Substitution of 10th position of desired PAH by phenyl ring reduces the feasibility of photo reaction and produced 9-hydroxy 9-phenyl anthrone (9H9PA) as an intermediate species. The products were separated and purified by column chromatography using 70:30 hexane/DCM mixtures as the mobile phase and the resultant products were characterized thoroughly by 1H NMR, IR spectroscopy and GCMS analysis. Chapter 6 elucidates the heterogeneous Suzuki coupling reaction by Cu/Pd bimetallic supported on TiO2. Sol-Gel followed by impregnation method was adopted for the synthesis of Cu/Pd-TiO2. The prepared system was characterized by XRD, TG-DTG, SEM, EDX, BET Surface area and XPS. The product was separated and purified by column chromatography using hexane as the mobile phase. Maximum isolated yield of biphenyl of around72% was obtained in DMF using Cu(2wt%)-Pd(4wt%)-Ti as the catalyst. In this reaction, effective solvent, base and catalyst were found to be DMF, K2CO3 and Cu(2wt%)-Pd(4wt%)-Ti respectively. Chapter 7 gives an idea about the photovoltaic (PV) applications of TiO2 based thin films. Due to energy crisis, the whole world is looking for a new sustainable energy source. Harnessing solar energy is one of the most promising ways to tackle this issue. The present dominant photovoltaic (PV) technologies are based on inorganic materials. But the high material, low power conversion efficiency and manufacturing cost limits its popularization. A lot of research has been conducted towards the development of low-cost PV technologies, of which organic photovoltaic (OPV) devices are one of the promising. Here two TiO2 thin films having different thickness were prepared by spin coating technique. The prepared films were characterized by XRD, AFM and conductivity measurements. The thickness of the films was measured by Stylus Profiler. This chapter mainly concentrated on the fabrication of an inverted hetero junction solar cell using conducting polymer MEH-PPV as photo active layer. Here TiO2 was used as the electron transport layer. Thin films of MEH-PPV were also prepared using spin coating technique. Two fullerene derivatives such as PCBM and ICBA were introduced into the device in order to improve the power conversion efficiency. Effective charge transfer between the conducting polymer and ICBA were understood from fluorescence quenching studies. The fabricated Inverted hetero junction exhibited maximum power conversion efficiency of 0.22% with ICBA as the acceptor molecule. Chapter 8 narrates the third order order nonlinear optical properties of bare and noble metal modified TiO2 thin films. Thin films were fabricatedby spray pyrolysis technique. Sol-Gel derived Ti[OCH(CH3)2]4 in CH3CH2OH/CH3COOH was used as the precursor for TiO2. The precursors used for Au, Ag and Pd were the aqueous solutions of HAuCl4, AgNO3 and Pd(NO3)2 respectively. The prepared films were characterized by XRD, SEM and EDX. The nonlinear optical properties of the prepared materials were investigated by Z-Scan technique comprising of Nd-YAG laser (532 nm,7 ns and10 Hz). The non-linear coefficients were obtained by fitting the experimental Z-Scan plot with the theoretical plots. Nonlinear absorption is a phenomenon defined as a nonlinear change (increase or decrease) in absorption with increasing of intensity. This can be mainly divided into two types: saturable absorption (SA) and reverse saturable absorption (RSA). Depending on the pump intensity and on the absorption cross- section at the excitation wavelength, most molecules show non- linear absorption. With increasing intensity, if the excited states show saturation owing to their long lifetimes, the transmission will show SA characteristics. Here absorption decreases with increase of intensity. If, however, the excited state has strong absorption compared with that of the ground state, the transmission will show RSA characteristics. Here in our work most of the materials show SA behavior and some materials exhibited RSA behavior. Both these properties purely depend on the nature of the materials and alignment of energy states within them. Both these SA and RSA have got immense applications in electronic devices. The important results obtained from various studies are presented in chapter 9.

Hyperfine structure and isotopic shift of the n^2 P_J levels (n = 7-10) of ^203,205 TI measured by Doppler-free two-photon spectroscopy

Using Doppler-free two-photon absorption spectroscopy, we have measured hyperfine splitting constants as well as isotopic level shifts of the 6s^2 np ^2 P_l/2,3/2 states in (n=7-10) in ^203 TI and ^205 TI. Calculations for hyperfine constants and electron density at the nucleus have been performed by the Dirac-Fock method. The experimental results are compared with these calculations as well as with the predictions of the semiempirical theory.

Para ti : proyecto de acercamiento a la realidad del alumno-a mediante tutorías individuales.

Este proyecto de tutoría se ha dirigido a alumnos y alumnas del centro que cursan Educación Secundaria Obligatoria y carecen de modelos de conducta adulta positiva o que están expuestos a otros factores de riesgo relacionados con comportamientos negativos y bajo rendimiento académico. El objetivo fundamental ha sido desarrollar relaciones exitosas entre los tutores-ayudantes y sus tutorizados, influir positivamente en el desarrollo personal del adolescente. En muchos casos, esto ha requerido la estimulación de la autoestima, desarrollo de valores positivos, perfeccionamiento de las destrezas de resolución de conflictos, incremento de las destrezas sociales o mejora de las relaciones con la familia y los iguales. Entre estos objetivos conseguidos están el fomentar la responsabilidad social y el rendimiento académico, las actitudes y mejora del comportamiento en el instituto. Los tutores han trabajado con los tutorizados y sus familias, sus profesores y primeros tutores para determinar los logros que se deseaban obtener, y los pasos necesarios para alcanzarlos. Se ha mejorado la convivencia en el centro, se han adelantado a las conductas negativas antes de llegar a medidas extremas, reduciendo partes de sanción, comisiones de convivencia y expulsiones.

Español para ti : iniciación en ambientes educativos multiculturales.

Resumen basado en el de la publicación. Elaborado por el grupo de trabajo e investigación 'Educación intercultural, atención educativa al alumnado inmigrante' (Centro de Profesorado de El Ejido)

Aragón es para ti.

Seleccionado en la convocatoria: Ayudas para proyectos de temática educativa, Gobierno de Aragón 2008-09

Neuromarketing: qué sabe de ti, que los demás no

En este documento se describe la forma en la que el neuromarketing hace que la segmentación de género, sea una herramienta funcional para poder conocer al cliente y sus deseos. Se explorará el mercadeo desde sus inicios, mostrando cómo evoluciona hasta enfocarse en el cliente como su principal objetivo. Al llegar a este punto el mercadeo se encuentra con un nuevo aliado, la neurociencia, la cual le muestra que por medio de diversas técnicas tiene la capacidad de medir las reacciones de su consumidor, a los distintos estímulos que le envía para cautivarlo. En este proceso se dan a conocer las tecnologías más usadas por el neuromarketing para este fin; además se expondrá parte de la anatomía del consumidor con la que interactúa el mercadeo: sus sentidos y su cerebro. Posteriormente se explica cómo a través del entendimiento de las percepciones y comportamiento del cliente, puede beneficiarse el mercadeo en sus propósitos y su vez, satisfacer al mercado en lo que realmente quiere.

Por ti!

Lo propuesto en este plan de negocio, es el diseño de un restaurante de comida oriental, recibiendo como nombre de POR TI: COME SALUDABLE, COME RICO, COME POR TI., ubicado en la ciudad de Bogotá D.C, específicamente en el barrio de chico de la localidad de Chapinero, dirigido al 1% de la población flotante y habitantes del sector entre estratos 4 a 6. POR TI nace bajo una propuesta que busca entregar al consumidor salud y cuidado personal. Brindando un producto de excelente calidad, preparado con ingredientes frescos, naturales y basados en recetas caseras, a través del concepto slow food y take away, arraigados en la cocina oriental, buscando crear colores, texturas y sabores que cautiven al consumidor. Se implementaran estrategias claras y concisas que permitan penetrar el mercado de la forma se ajuste a las necesidades del mismo. Se espera y aspira iniciar operaciones para Mayo del 2016, con un incremento de las ventas prometedor superando así el punto de equilibrio para el segundo año.

Propuestas didácticas en base a los sistemas bodypercussion y ta ke ti na.

Resumen tomado de la revista. La publicación recoge resumen en Inglés

Las editoriales mueven ficha : ahora te toca a ti.

Se analiza la gran producción de cuadernos, fichas y materiales escolares por parte de las editoriales, dirigidos a niños de entre 2 y 6 años, y su uso masivo en los centros educativos, así como el proceso de enseñanza y aprendizaje que estos materiales desencadenan. Para ello, se hace una reflexión acerca de la idoneidad de estos materiales curriculares, con el fin de averiguar en qué medida y de qué manera contribuyen o dificultan el desarrollo infantil. Se exponen los puntos débiles y fuertes en la manera de saber y conocer de la primera infancia, destacando la naturaleza como fuente de vida y de conocimiento, y las relaciones sociales como fuente de construcción de la personalidad, frente a las situaciones educativas artificiales, en las que los niños son sometidos a los intereses y estructura de pensamiento del adulto educador.

Aquí no pasan de ti : nueve testimonios sobre diversificación y garantía social.

Resumen tomado de la revista

De ti depende, de nosotros depende, pero, ¿valoraste tu decisión adecuadamente?

Este proyecto, enmarcado en la Eduacación para la Salud, está dirigido a la prevención de drogodependencias, fundamentalmente las legales, alcohol y tabaco. Los objetivos son: desarrollar actividades de forma autónoma y equilibrada, valorar el esfuerzo y la superación de dificultades, participar en grupos y superar inhibiciones y perjuicios sin necesidad de consumir ningún tipo de sustancia. Describe los objetivos generales y contenidos de Secundaria para las áreas de Inglés, Química, Biología, Ciencias Sociales y Tutoría. De cada una aporta una unidad didáctica. En anexos, incluye encuestas sobre hábitos en el consumo de alcohol y tabaco, gráficos, estadísticas y fichas de seguimiento.

Yo, ti te, contigo.

Esta innovación obtuvo un premio de la Consejería de Educación de la Comunidad de Madrid en 2003

Reírme contigo, nunca de ti : campaña para la mejora de la convivencia en infantil y primaria (curso 2008-2009).

Resumen tomado de la web del Departamento de Educación