Optical and morphological properties of N-doped TiO2 thin films

Nitrogen doped titanium dioxide (TiO₂) thin films were deposited by RF magnetron sputtering onto various substrates. The films were prepared in plasma of argon, oxygen, and nitrogen, with varying the nitrogen content, from 0% up to 70%. The resulting TiOx–Ny films were found to consist of cubic TiN osbornite and tetragonal TiO₂ rutile phases. Using optical spectroscopy with large spectral range from 350 to 1000 nm, the band gap width was determined and a narrowing of the optical gap from 2.76 to 2.32 eV was observed as a function of the N-content. It was found that the optical properties of the TiOx–Ny layers are influenced by the surface morphology, roughness, surface energy and phase content. The chemical composition, the crystalline structure, the surface morphology and the surface energy were thoroughly studied by the Rutherford backscattering spectrometry (RBS), grazing-angle XRD, atomic force microscopy (AFM) and contact angle measurements (wettability), respectively.     

A capillary electrophoresis method for free fatty acids screening and acidity determination in biodiesel

The advent of policies that incentivize or require alternative diesel fuels has increased the demand for the development of fast analytical methods aiming for the quality control of these fuels. This study approached an alternative method for the determination of biodiesel acidity employing capillary zone electrophoresis based on free fatty acids screening and quantification. Sample preparation comprised vortex-assisted liquid-liquid extraction of free fatty acids and was a crucial step for analysis. It was studied through a 3² full factorial design considering sample mass and the stirring time. Then, solvent suitability was evaluated univariately. The free fatty acid screening was carried out employing a capillary zone electrophoresis method able to separate C16:0, C18:0, C18:1 n-9, C18:2 n-6, and C18:3 n-3, major fatty acids in a variety of vegetable oils used for biodiesel synthesis. In addition to the straightforward sample preparation protocol, the running time of the developed method was only 12 min. Moreover, ultraviolet absorption indirect detection of analytes was approached to avoid analytes derivatization, considering the lack of chromophore groups in saturated fatty acids. Statistical tests did not evidence any significant differences in the biodiesel acidity determination expressed in percentage of free fatty acids when comparing the proposed capillary zone electrophoresis method and the traditional potentiometric titration approach within the 95% confidence interval, which demonstrates the suitability of this alternative method for the biodiesel quality control in routine.     

Distinguished People and Places Important in the History of Portuguese Analytical Chemistry

The people and places of importance in the history of chemistry in Portugal have been reviewed with particular reference to analytical chemistry.     

Potential of visible-near infrared spectroscopy combined with chemometrics for analysis of some constituents of coffee and banana residues

Banana (stalk, leaf, rhizome, rachis and stem) and coffee (leaf and husks) residues are promising feedstock for fuel and chemical production. In this work we show the potential of near-infrared spectroscopy (NIR) and multivariate analysis to replace reference methods in the characterization of some constituents of coffee and banana residues. The evaluated parameters were Klason lignin (KL), acid soluble lignin (ASL), total lignin (TL), extractives, moisture, ash and acid insoluble residue (AIR) contents of 104 banana residues (B) and102 coffee (C) residues from Brazil. PLS models were built for banana (B), coffee (C) and pooled samples (B + C). The precision of NIR methodology was better (p < 0.05) than the reference method for almost all the parameters, being worse for moisture. With the exception of ash (B and C) and ASL (C) content, which was predicted poorly (R² < 0.80), the models for all the analytes exhibited R² > 0.80. The range error ratios varied from 4.5 to 16.0. Based on the results of external validation, the statistical tests and figures of merit, NIR spectroscopy proved to be useful for chemical prediction of banana and coffee residues and can be used as a faster and more economical alternative to the standard methodologies.     

Validation of the mPW1PW Quantum chemical calculations for the vibrational study of organic molecules – re‐assignment of the isopropylamine vibrational spectra

The validity of the mPW1PW91 density functional theory (DFT) method coupled to the all‐electron basis set 6‐31G* (mPW1PW/6‐31G*) for the study of amines, using isopropylamine (iPram) as a case study, was evaluated. Validation was performed by comparing the calculated values with the corresponding experimental results obtained and/or reported in the literature. Moreover, the accuracy of that theoretical level was compared with that of other widely used theoretical levels, namely HF/6‐31G*, B3LYP/6‐31G* and MP2/6‐31G*. The effect of basis set improvement within the mPW1PW protocol was evaluated considering the widely used 6‐311G** basis set. On the whole, the results clearly show that the mPW1PW/6‐31G* calculations are a suitable tool for the prediction of the structural and vibrational features of iPram. The validation of the theoretical methodology allowed a complete revision of the vibrational assignments previously reported in the literature, being the result of several proposed re‐assignments. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of manganese in urine and whole blood samples by electrothermal atomic absorption spectrometry: comparison of chemical modifiers.

In this work, methodologies to determine manganese (Mn) in urine and whole blood by electrothermal atomic absorption spectrometry were developed. The use of Ru, Rh, and Zr as permanent modifiers, Pd as a modifier in solution, and the condition without modifier were investigated for the direct determination of Mn in urine and whole blood samples. The best results for Mn in urine and in whole blood were obtained without modifier use. The analytical characteristic, such as accuracy, precision and limit of detection of the proposed methodology were adequate.     

Superstrings with tensor degrees of freedom

We add antisymmetric tensor degrees of freedom to the usual superstring coordinates. We show that super and kappa symmetries are only achieved for the spacetime dimensionD=4. We also address problems related to the quantization of the model and discuss the influences of this extended spacetime in the usual quantum field theory.     

BFT formalism and first order systems

The Abelian conversion of a class of constraints characteristic of first order systems is implemented in a general way. The corresponding Wess-Zumino terms are obtained. We illustrate the procedure with an example of charged matter coupled via a pure Chern-Simons term.     

On the transversity condition for bosonicp-branes

We discuss on the transversity condition for tensionless and tensionfull bosonicp-branes.