Tissue engineering is a technique that promotes healing by creating an ideal environment for endogenous cells to migrate and grow into the site of injury via a scaffold, improving regeneration and reducing the time required for in vitro cell culture. In this work, the effect of the addition of sonicated TiO2 in the soy protein isolate (SPI) matrix for tissue engineering applications was studied. In comparison to adding expensive nano TiO2, this method of incorporating sonicated TiO2 into the SPI matrix will aid in achieving improved properties at a lower cost. The effect of the addition of sonicated TiO2 on the morphological, UV transmittance, mechanical, thermal, surface energy, and hydrophilicity of SPI films was investigated. The result shows that the uniformly distributed TiO2 particles successfully blocked 95% of UV light. Scanning electron microscopy revealed a significant reduction in the TiO2 agglomerate size and homogeneous distribution of the same when sonication was applied instead of mechanical dispersion. A simultaneous increase of tensile strength (from 3.16 to 4.58 MPa) and elongation at break values (from 24.25% to 95.31%) with 0.5% TiO2 was observed. The addition of 0.25% TiO2 was found to significantly enhance the elongation at break value to 120.83%. Incorporation of micro-TiO2 particles could improve the surface roughness, surface energy, and wettability of SPI films. In vitro cell adhesion studies and in vivo subcutaneous implantation studies were performed to assess the cell growth and angiogenesis of the developed film membranes. An MTT assay showed that SPI-1%TiO2 film favored cell viability up to 118%, and in vivo subcutaneous implantation studies showed enhanced cell growth and angiogenesis for SPI-1% TiO2 films. This SPI-TiO2 film with enhanced surface properties can be used as an ideal candidate for tissue engineering applications.

Energy transfer reactions are the key for living open systems, biological chemical networking and development of life inspired nanoscale machineries. It is a challenge to find simple reliable synthetic chemical networks providing a localization of the time dependent flux of matter. In this paper we introduce a reliable, minimal reagent consuming, stable inorganic light promoted proton pump. Localized illumination was applied to a TiO2 surface in solution for reversible spatially controlled “inorganic photoproton” isometric cycling, the lateral separation of water splitting reactions. The proton flux is pumped during irradiation of the surface of TiO2 and dynamically maintained at the irradiated surface area in the absence of any membrane or predetermined material structure. Moreover we spatially predetermine a transient acidic pH on the TiO2 surface in the irradiated area with feedback-driven generation of a base as deactivator. Importantly we describe, how to effectively monitor the spatial localization of the process by in situ scanning ion selective electrode technique (SIET) measurements for pH and scanning vibrating electrode technique (SVET) for local photoelectrochemical studies. This work shows the great potential for time- and space-resolved water splitting reactions for following investigation of pH stimulated processes in open systems with their flexible localization on a surface.

This work was focused on designing the phase composition and microstructure of composite rutile – silicon carbide mixture by controlled redox reactions, aiming the preparation of multifunctional titania-based photocatalysts with inherent capabilities for thermal co-activation and stabilization of the anatase polymorph. The materials were processed using a conventional solid state route, involving a partial reduction of the rutile by SiC in inert Ar atmosphere, followed by the post-oxidation in air. The impacts of processing conditions on the phase composition of the oxidized samples and their photocatalytic activity were evaluated using Taguchi experimental planning. The XRD studies confirmed the presence of rutile/anatase mixtures in the oxidized samples. The results emphasized that the pre-reduction and post-oxidation temperatures are the most critical parameters in defining the phase composition, while the post-oxidation time appears to be relevant for the photocatalytic performance. Microstructural studies revealed the formation of core-shell particles in the pre-reduced and post-oxidized samples, which can suppress the photocatalytic activity. The highest apparent reaction rate (0.089 min-1) of the photodegradation of methylene blue was observed for the sample pre-reduced in Ar at 1300ºC for 5 h and then oxidized in air at 400ºC for 25 h, which is only 1.6-times lower than that for nanostructured industrial P25 photocatalyst, tested under the same conditions. The observed trends demonstrate good prospects for designing multifunctional titania-based photocatalysts based on the flexibility of the phase composition control

The sensitization activity of four zinc metalloporphyrin dyes: meso-tetrakis(4-pyridyl)porphyrinato Zn(II) (a), meso-triphenyl-(4-carboxyphenyl)porphyrinato Zn(II) (b), meso-tetrakis(4-carboxyphenyl)porphyrinato Zn(II) (c) and meso-tripyridyl(4-carboxyphenyl)porphyrinato Zn(II) (d) is reported here, in terms of current-potential curve, open-circuit potential, fill factor, and overall solar energy conversion efficiency which have been evaluated under 100 mW/cm2 light intensity and their performances compared to the benchmark N719 (di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato) ruthenium(II)). This work focus the structural aspects of dyes with anchoring groups using TiO2-based Dye Sensitized Solar Cells (DSSCs), which includes pyridyl and carboxyphenyl acid groups and argue how the combination of both anchoring groups, in the same structure, may allow relevant optimization of DSSCs performance in the near future. Also, a noticeable improvement in the photovoltaic performance of all dyes, reaching a maximum increase from 25% to 69% in the overall DSSC efficiency under short periods of white light illumination is discussed.

A ortopedia permitiu uma grande melhoria na vida das pessoas, possibilitando a substituição ou reparação de diferentes tecidos, no entanto, ainda existem algumas limitações como a perda de qualidade das próteses com o passar do tempo. Um biomaterial, para ser utilizado em ortopedia deve possuir elevada biocompatibilidade e resistência mecânica e também boa capacidade adesiva. O uso de biomateriais baseados em polímeros e cerâmicas permitiu resolver alguns dos problemas relacionados com o uso dos biomateriais metálicos, como a baixa resistência à corrosão. Ainda assim, os polímeros possuem fraca adesão celular, baixa resistência mecânica e as cerâmicas possuem uma baixa resistência à tração e muita baixa tenacidade à fratura. Com o intuito de encontrar novos biomateriais para responder às limitações existentes, surgiu o presente trabalho que tem como objetivo alterar as propriedades superficiais dos polímeros poliéter éter cetona (PEEK) e polietileno de alta densidade (PEAD), com vista à sua aplicação em próteses ortopédicas. Estes polímeros apresentam boa biocompatibilidade e boa resistência mecânica, porém possuem baixa capacidade adesiva. De forma, a ultrapassar esta desvantagem os polímeros foram modificados através da pulverização catódica, por deposição de filmes de TiO2, que apresentam as características adequadas para a aplicação desejada. Após o revestimento com TiO2 os materiais obtidos foram caracterizados por difração de raios-X, microscopia eletrónica de varrimento e medidas do ângulo de contato, de modo a avaliar as características estruturais e morfológicas. Para avaliar a biocompatibilidade e as propriedades adesivas dos biomateriais desenvolvidos foram efetuados testes de citotoxicidade com células Vero e de adesão com células de osteoblastos, o que permitiu concluir que o revestimento com TiO2 aumenta a biocompatibilidade e adesão celular dos polímeros, podendo também aumentar a resistência mecânica.

The work achieved with this thesis consisted of the production and characterization of new low-cost upconversion nanoparticles based on a titanium dioxide (TiO2) host matrix. These nanoparticles were produced by solvothermal synthesis assisted by microwave irradiation. Two elements (europium and ytterbium) were used as dopant in the matrix to allow the upconversion process. Different parameters of synthesis were considered, to achieve an ideal process of synthesis. Also, different acids and solvents were considered and studied to achieve the most successful conditions. Three acids were tested: ( hydro-chloric acid (HCl), nitric acid (HNO3,), and oxalic acid (C2H2O4)). Besides acids, also 2 solvents were tested: ethanol (C2H6O) and water (H2O). The nanoparticles produced are going to be an essential part of a security marker ink to be used by INCM (Imprensa Nacional – Casa da Moeda). The goal of this thesis is to achieve the synthesis of nanoparticles to be mixed in an ink to be used as a low-cost security marker ink to replace the current ink used by INCM. According to studies realized on the different reagents, it was concluded that oxalic acid and ethanol produced particles with desired properties (good size uniformity, spherical particles, and small size) for the TiO2 matrix. The concentration of dopant was also considered and studied, in an initial test, 4 molar concentrations were considered: 2.5%; 5%; 7.5%; and 10%. The 7.5% concentration was decided due to particles size, shape, and uniformity. The upscaling of the process was successful, when converting 50ml solutions to 600 ml. The nanoparticles produced in both solutions presented similar properties when analyzed. The ink formulation was achieved with good results, the nanoparticles were easily mixed without the need to add dispersants. The detection of the dopant in the nanoparticles was successful in both powder and when mixed as ink.

TiO2 fibres grown by the laser floating zone technique show the rutile crystalline phase as identified by X-ray diffraction and Raman spectroscopy. Scanning electron microscopy evidences a uniform surface, free of inclusions and without low-angle grain boundaries and bubbles. At low temperatures, the fibres luminescence is dominated by a richly structured optical centre with two well-defined zero-phonon lines at 1.579 eV and 1.574 eV followed by an intense vibronic sideband with a maximum close to 1.47 eV. Electron paramagnetic resonance revealed that substitutional chromium and iron ions are present as contaminants in the grown fibres, alongside with Ti3+ interstitials and other structural defects. The chemical nature of the defect responsible for the structured near-infrared luminescence is discussed.

Titanium oxide nanocrystals synthesized by the Pechini method were calcinated at temperatures between 300 and 1000 C. The crystalline structure was analysed by X-ray diffraction, scanning electron microscopy (SEM) and Raman spectroscopy. A phase transition from the anatase to rutile crystalline phase was found to occur at temperatures near 500 C. The samples were characterized by photoluminescence (PL) and dielectric spectroscopy. The influence of the calcination temperature on the visible and near infrared luminescence is discussed. A correlation between the structural properties, luminescence and dielectric properties are discussed.

In this work TiO2 layers have been deposited by screen-printing in common glazed ceramic tiles. These TiO2 layers were evaluated for the photocatalytic degradation of Orange II in aqueous solutions, in a batch photoreactor under visible light, and compared with TiO2 (anatase) suspensions. The photocatalytic behaviour of the TiO2 was evaluated by taking into account experimental variables which include (i) firing temperature of the TiO2 printed layer; (ii) layer thickness; (iii) operation time. Optimal processed layers showed an interesting decolourisation performance (over 90% efficiency after 7–8 h). The maximum decolourisation rate, assuming an apparent first order reaction, is over 0.050 min−1 and is close to values reported in the literature for supported TiO2 photocatalysis under UV irradiation. We anticipate that these new ceramic materials might be developed as an interesting alternative to TiO2 suspensions, for example in photocatalytic applications excusing the removal of the particles at the end of the process.