A. Figueras

GC/MS, HPLC and FAB Mass Spectrometric Analysis of Organic Micropollutants in Barcelona's Water Supply

Water samples from Llobregat river entering two water work plants, Barcelona tap water and waste dumping samples taken along the river course were analyzed for trace organic contaminants by different procedures, liquid-liquid extraction, adsorption on granular activated carbon followed by GC/MS/DS. Ether insoluble organic fractions were analyzed and fractionated by HPLC with diode-array detection, followed by FAB and FAB-CID-MIKE characterisation. Results, after two years monitoring, proved that surfactants, plasticizers, ethyleneglycol derivatives, phosphates, hydrocarbons and other miscellaneous compounds can be considered as chronic pollutants of Llobregat river. Some of the identified compounds by GC/MS and FAB mass spectrometry have not been previously reported to occur in water.

Morphological properties of chemical vapour deposited AlN films

Abstract In this paper we analyse some results on AIN CVD film deposition, published in the literature, from a morphological point of view, and we propose a model to explain the observed preferential orientations based on the reactivity of the AIN crystal faces of the equilibrium form.

Characterization of polyethoxylated surfactants and their brominated derivatives formed at the water treatment plant of Barcelona by GC/MS and FAB mass spectrometry

Abstract Polyethoxylated C 12 -C 15 alcohols, nonylphenols and [(nonylphenoxy) polyethoxy] acetic acid and their brominated derivatives were identified in the River Llobregat and the tap water of Barcelona by GC/MS and FAB mass spectrometry. Whereas GC/MS is limited to those compounds with a low polyethoxylation degree, FAB mass spectrometry is a fast and simple technique to determine surfactants with a high range of oligomers present in the samples. We believe that both techniques are complementary. The source of these compounds is the discharge of effluent wastes of surfactant industries and dyeing and textile processes. Their brominated derivatives are formed in the chlorination stages in the water works plant due to a high content of bromide ions in the upper course of the river.

Identification of surfactants in water by fab mass spectrometry

Abstract An application of fast atom bombardment (FAB) for identification of some organic micro-pollutants was performed. A study of the most common surfactants, including non-ionic, cationic and anionic compounds was carried out and the results obtained used to build a table for rapid characterization of surfactants in real samples. Negative FAB and tandem mass spectrometry (CID-MIKE) were also occasionally employed, when two or more compounds gave the same series of peaks. Sensitivity limits for standards varied from low to upper nanogram range for cationic to anionic surfactants. Raw and drinking water extracts of Barcelona (N.E. Spain) were analysed and the most common surfactants and some brominated derivatives were identified.

Determination of texture by infrared spectroscopy in titanium oxide-anatase thin films

A theoretical model to determine the effective dielectric tensor of heterogeneous materials composed by anisotropic microcrystallites has been introduced to explain the infrared spectral features of textured thin films of uniaxial materials as the function of a textural parameter. This theoretical treatment is able to satisfactorily reproduce the experimental absorbance spectra of TiO2–anatase thin films chosen as a model system. Comparison of texture data obtained from infrared spectroscopy and x-ray diffraction are in good agreement which support the validity of the proposed model.

A morphological and structural study of SiC layers obtained by LPCVD using tetramethylsilane

Abstract -SiC polycrystalline layers were grown by LPCVD in a cold wall reactor using TMS (tetramethylsilane) diluted in hydrogen as precursor. TMS has the advantage of supplying Si and C from an individual molecule free from halogen. The dependence of the kinetics of deposition on substrate temperature, total pressure and TMS partial pressure was obtained. Structural and morphological analysis were performed using SEM and X-Ray diffraction.

Influence of the experimental conditions on the morphology of CVD AIN films

Abstract AIN crystalline thick films are obtained by LPCVD using trimethylaluminium and ammonia. A model is proposed to analyse the growth morphologies of these films. The equilibrium morphology of AIN, in a gas-solid system, is derived from the periodic bond chain analysis of the crystal structure and the application of the Bravais-Donnay-Harker law to the crystal lattice and space group. A morphological diagram, showing the habits produced by changing the relative rates of growth of the different crystal forms, has been constructed and used to describe the morphologies obtained in this work and a number of previous references. The influence of the reactant gas flows, the temperature, the total pressure and impurities (mainly hydrogen) on the morphology is analysed.

Preparation and characterization of conducting thin films of molecular organic conductors (TTF-TCNQ)

Abstract Tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) form a charge-transfer complex which exhibits a high electric conductivity. In this work TTF-TCNQ thin films were prepared by CVD (chemical vapour deposition) at low pressure and using TTF and TCNQ as precursors. Substrates were common glass. These layers exhibit preferential orientation in the crystallization along the [001] direction and have a room temperature conductivity ranged between 6–24 Ω −1 cm −1 . Whereas at low temperatures (smaller than a transition temperature T p ) they display a highly resistive semiconductor-like behaviour, above T p the conductivity exhibits a small effective activation energy. T p ≈ 50–60 K is interpreted as a signature of the Peierls transition. The evaluation of the stoichiometry was performed by UV-visible spectroscopy. The morphology and structure of the layers were also studied.

Biomolecular papain thin films grown by matrix assisted and conventional pulsed laser deposition: A comparative study

Biomolecular papain thin films were grown both by matrix assisted pulsed laser evaporation (MAPLE) and conventional pulsed laser deposition (PLD) techniques with the aid of an UV KrF∗ (λ=248 nm, τFWHM≅20 ns) excimer laser source. For the MAPLE experiments the targets submitted to laser radiation consisted on frozen composites obtained by dissolving the biomaterial powder in distilled water at 10 wt % concentration. Conventional pressed biomaterial powder targets were used in the PLD experiments. The surface morphology of the obtained thin films was studied by atomic force microscopy and their structure and composition were investigated by Fourier transform infrared spectroscopy. The possible physical mechanisms implied in the ablation processes of the two techniques, under comparable experimental conditions were identified. The results showed that the growth mode, surface morphology as well as structure of the deposited biomaterial thin films are determined both by the incident laser fluence value as well...

Growth of Au–TiO2 nanocomposite thin films by a dual-laser, dual-target system

Nanocomposite thin films formed by gold nanoparticles embedded in a titanium dioxide matrix have been synthesized by pulsed laser deposition. Two synchronized laser sources, an ArF* excimer (λ=193nm, τFWHM∼12ns) laser and a frequency tripled Nd:yttrium aluminium garnet (λ=355nm, τFWHM∼10ns) laser, were used for the simultaneous ablation of the titanium dioxide and gold targets. The optical absorption characteristics of the obtained nanocomposites were investigated as a function of laser parameters used for the ablation of the gold target. The obtained results proved the possibility of tuning the optical properties of gold–titanium dioxide nanocomposites with the proper choice of laser irradiation parameters. Band gap narrowing and absorption in the visible spectral region induced by the incorporation of gold enable the design of nanostructured thin films to be achieved for photocatalysts and solar energy converters.