Morphological, structural and ellipsometric investigations of Cr doped TiO2 thin films prepared by sol-gel and spin coating

International audiencePure and chromium doped titanium dioxide (TiO2) thin films at different atomic percentages (0.5%, 1.3% and 2.9%) have been elaborated on ITO/Glass substrates by sol-gel and spin-coating methods using titanium (IV) isopropoxide as a precursor. The surface morphology of films was investigated by scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM), the structure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission microscopy (HRTEM). SEM and HRTEM show homogenous and polycrystalline films. XRD patterns indicate a phase transition from anatase to anatase-rutile leading to expand the absorption band of TiO2 molecules around 520 cm(-1) in FTIR spectra. The optical constants such as the refractive index (n), the extinction coefficient (K) and the band gap (E-g) as well as the film thickness are determined using spectroscopic ellipsometry technique and Fourouhi-Blommer dispersion model. Results show three major changes; (i) the thickness of pure TiO2 layer is 54 nm, which linearly decreases when the layer is doped with chromium and reaches 33 nm for a doping concentration of 2.9%, (ii) the band gap energy (E-g) is also linearly reduced from 3.24 eV to 2.80 eV when the Cr-doping agent increases, and, (iii) a phase transition from anatase to anatase-rutile is observed causing an increase in values of n(lambda) for wavelength greater than 350 nm. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved

A Critical Review on Chagas Disease Chemotherapy

In this "Critical Review" we made a historical introduction of drugs assayed against Chagas disease beginning in 1912 with the works of Mayer and Rocha Lima up to the experimental use of nitrofurazone. In the beginning of the 70s, nifurtimox and benznidazole were introduced for clinical treatment, but results showed a great variability and there is still a controversy about their use for chronic cases. After the introduction of these nitroheterocycles only a few compounds were assayed in chagasic patients. The great advances in vector control in the South Cone countries, and the demonstration of parasite in chronic patients indicated the urgency to discuss the etiologic treatment during this phase, reinforcing the need to find drugs with more efficacy and less toxicity. We also review potential targets in the parasite and present a survey about new classes of synthetic and natural compounds studied after 1992/1993, with which we intend to give to the reader a general view about experimental studies in the area of the chemotherapy of Chagas disease, complementing the previous papers of Brener (1979) and De Castro (1993)