BackgroundTitanium (Ti) and its alloys possess high biocompatibility and corrosion resistance due to Ti ability to form a passive oxide film, i.e. TiO2, immediately after contact with oxygen. This passive layer is considered stable during function in the oral cavity, however, emerging information associate inflammatory peri-implantitis to vast increases in Ti corrosion products around diseased implants as compared to healthy ones. Thus, it is imperative to identify which factors in the peri-implant micro-environment may reduce Ti corrosion resistance.MethodsThe aim of this work is to simulate peri-implant inflammatory conditions in vitro to determine which factors affect corrosion susceptibility of Ti-6Al-4V dental implants. The effects of hydrogen peroxide (surrogate for reactive oxygen species, ROS, found during inflammation), albumin (a protein typical of physiological fluids), deaeration (to simulate reduced pO2 conditions during inflammation), in an acidic environment (pH 3), which is typical of inflammation condition, were investigated. Corrosion resistance of Ti-6Al-4V clinically-relevant acid etched surfaces was investigated by electrochemical techniques: Open Circuit Potential; Electrochemical Impedance Spectroscopy; and Anodic Polarization.ResultsElectrochemical tests confirmed that most aggressive conditions to the Ti-6Al-4V alloy were those typical of occluded cells, i.e. oxidizing conditions (H2O2), in the presence of protein and deaeration of the physiological medium.ConclusionsOur results provide evidence that titanium’s corrosion resistance can be reduced by intense inflammatory conditions. This observation indicates that the micro-environment to which the implant is exposed during peri-implant inflammation is highly aggressive and may lead to TiO2 passive layer attack. Further investigation of the effect of these aggressive conditions on titanium dissolution is warranted.

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Dye-sensitized solar cells (DSSC's) are devices that can convert sunlight to energy and have in composition a semiconductor oxide and a suitable photosensitizer. Due to the high cost, the research for new materials applied in solar cells arouses great interest. This work aims to study hybrid solar cells of FTO/TiO2/dye interface, produced with different low cost natural photosensitizers, extracted in acidified ethanoic solution of different natural products: plum, grape, urucum and eggplant. The techniques of characterization used were: UV-VIS Spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Open Circuit Potential as function of time (Voc), Photocronoamperometry curves (PCA) and Photocurrent Density Curves as function of Potential (j-V). The dyes tested in the DSSC presented the character of photosensitivity, with the adsorption in TiO2 films and the maximum absorption on the visible region. The DSSC with the best photovoltaic parameters was using the dye extracted from the plum, generating a solar cell with ƞ = 0.12±0.03%, Voc = 572±12 mV, FF = 0.57±0.01 and jsc = 0.40±0.09 mA cm-2 .

Dye-sensitized solar cells (DSSC) have received much attention as an alternative to silicon-based solar cells, due to various advantages. Zinc oxide (ZnO) is an n-type semiconductor employed as photoanode on DSSC. The decrease of charge recombination is an efficient strategy capable of improving the photovoltaic performance of the device. In this perspective, Nb 2 O 5 was added on ZnO solar cells. The oxides were characterized by the X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and X-ray fluorescence (XRF). The photovoltaic parameters were obtained through J-V plots and photocronoamperometry. The results showed that the niobium oxide obtained presented orthorhombic crystal structure and DSSC with the addition of niobium oxide showed better efficiency, of 1.42% when compared the device with only ZnO.

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