Abstract: An overview of the chemical strategies developed in our laboratories to obtain welldefined
BiVO4 particles is presented. The methods rely on the thermal treatment (including
hydrothermal conditions) of aqueous solutions containing bismuth(III) cations, vanadium(V)
species and organic ligands. The use of distinct polyaminocarboxylates and cyclodextrins as
possible morphological modifiers was investigated. NMR spectroscopic techniques were applied to
the distinct chemical baths in order to have a better insight on the nature of the solute precursors.
Abstract: We have studied the synthesis and sintering of BaTiO3 (BTO) nanometric powders
produced by Pechini technique. A laser sintering procedure was applied to the BTO and its major
advantage was the quickness of the processing. We have used the radiation of a CO2 laser (CW –
100 W) as the heating source. A linear rate of irradiation was applied to avoid macroscopic defects.
The calcined powder at 800°C presented a single crystalline phase confirmed by the XRD and a
crystallite size of 20 nm. BTO ceramics sintered at Pmax = 7.0 W/mm2 for 10 min of irradiation
showed a high relative density (98 ± 1) % with an average grain size of 400 nm for a total time of
sintering of 40 minutes.
Abstract: Transparent hybrid organic-inorganic ureasil xerogels with embedded PbS nanoparticles
were prepared by exposing the xerogels doped with lead (II) nitrate to hydrogen sulphide
atmosphere. Absorbance spectrum of the nonocomposites showed well defined peaks at 560 nm and
370 nm attributed to 1s(v) - 1s(c) and 1s(v) - 2p(c) exciton transitions, respectively. After four days
of thermal treatment at 50 °C under argon atmosphere the obtained materials showed enhanced
photoluminescence response in the near infra-red region.
Abstract: In this work, mechanically alloyed Al-5AlN powders have been sintered by the Electrical
Resistance Sintering (E.R.S.) technique. A die of alumina-base refractory concrete has been employed.
Several electric intensity currents and passage times through the compact have been tested
during the consolidation process. Compacts have been mechanically characterized by their hardness
distribution and by an indirect tensile test. The obtained results are compared with the corresponding
values of compacts prepared with the same powders by the conventional route of cold pressing
and furnace sintering. Finally, for all the electrically consolidated compacts, the final porosity, as
well as the average hardness and the strength in the indirect tensile test are empirically related to the
electric energy supplied during the process. This energy is a function of the electric intensity current
and passage time. The aforementioned empirical relationships are useful to select the best process
Abstract: Time-resolved luminescence and Furje Transformation Infrared (FTIR) absorption
spectroscopy for ZnO nanocrystals prepared under different chemical reactions using microwave
driven hydrothermal process was studied. OH- group stretching vibration frequency is considerably
different in nanocrystals studied and in single ZnO crystal. It is shown that fractions of chemicals
used in synthesis process could be found in nanopowders. Luminescence at ~2.0 eV (due to defect
states in ZnO crystals and nanopowders) was suppressed in nanopowders obtained by urea method.
Abstract: Dispersions of colloidal particles of polycyclic aromatic hydrocarbons were obtained by
nanosecond laser ablation. Aqueous suspensions of micron-sized crystals were irradiated with the
second harmonic output of a Nd:YAG laser and converted into colloidal particles. Ionic and nonionic
surfactants were used in the ablation process to stabilise the particles. Dispersions with good
long term stability were obtained. A strong dependence of particle formation rate on laser fluence
was found and the particle formation process is discussed on the basis of UV-Vis spectra and
microscopic examination of the crystals.
Abstract: The synthesis and characterization of Co,Al Layered Double Hydroxides (LDHs)
containing carbonate is reported. The solids have been submitted to several thermal treatments,
hydrothermal and microwave-hydrothermal, modifying both the treatment time and temperature,
with the main aim of studying their influence on the crystallinity of the solids and on the
stabilization of divalent cobalt oxidation state. The results show that whichever the temperature and
time used the only phase detected was the hydrotalcite, and that the cobalt cations keep the divalent
Abstract: The encapsulation of Cu(II) purine derivative complex was carried out by ion exchange
of the complex from aqueous solutions into zeolite NaY. The entrapped complex was characterized
by spectroscopic methods (FTIR and ICP-AES) and surface analysis (XRD). The various
techniques of characterization used show that the Cu(II) complex was effectively encapsulated in
the zeolite and this process does not modify the morphology and structure of the NaY zeolite. These
materials have potential applications in heterogeneous catalysis in mild reaction conditions.
Abstract: Films produced by plasma polymerization of ethyl ether and methyl or ethyl acetate show
good adsorption characteristic for polar and non-polar organic compounds. These films when used
in microchannels machined in a 3D-structure present some preconcentration of organic compounds.
Therefore, the aim of this work is to investigate the physical-chemical preconcentration
mechanisms on this structure. The test molecules used were n-hexane and 2-propanol. Quartz
crystal microbalance and mass spectrometry were used to measure preconcentration. Two different
procedures for reactant injection on the structure were used: a continuous flow during several
minutes or a small amount injected on a single pulse and in a few seconds. The microchannels were
also modified by the introduction of small ceramic particles for enhancement of the flow dispersion.
It was possible to notice for all films a similar kinetic of retention. The main removal mechanism is
adsorption. Although all films can provide the removal of the adsorbents molecules, the most
important characteristic for the adsorption and/or retention is the surface condition. Thus, the
retention of polar compound can be troubled if a non-polar compound was used previously. The
most promising films for retention are ethyl ether and ethyl acetate when n-hexane and 2-propanol
are used as test molecules. The results using n-hexane or 2-propanol point out the use of low-cost
microchannels for preconcentration development.
Abstract: Melting-freezing dynamics of water confined in three MCM-41 materials with pore
diameters of 2.0 nm, 2.5 nm and 3.7 nm was analyzed using dielectric spectroscopy method.
Obtained results show, that reorientation of water molecules is strongly affected by confinement and
interaction with the pore surface, which leads to the formation of highly disordered hydrogen
bonded network. Defects of this network play the key role in the overall relaxation of confined