An investigation of the catalytic abatement of emissions from the combustion of diesel/bioethanol blends

In this study, we investigated the activity of pre-sulfated 1%Pt–2%Sn/γ–Al₂O₃ on the catalytic abatement of the combustion emissions of three fuels: pure diesel E(0), pure bioethanol E(100) and bioethanol blended diesel containing 10% bioethanol E(10). The emissions generated, by each blend combustion, were conducted continuously to the catalyst sample. The catalytic activity was determined by following the evolution of the outflow emissions concentrations by FTIR gas spectroscopy as a function of the catalyst temperature. Results showed that the addition of bioethanol to diesel may be necessary to enhance the catalytic oxidation of diesel unburned hydrocarbons and particulate matter on pre-sulfated 1%Pt–2%Sn/γ–Al₂O₃.     

Waste‐Free Electrochemical Oxidation of Alcohols in Water

We describe a new sol‐gel molecular electrode made of a thin layer of organosilica doped with the nitroxyl radical TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl) electrodeposited on the surface of an ITO‐coated glass and its employment as a selective and versatile oxidation catalyst in the electrochemical conversion of different alcohols to carbonyl compounds. Environmentally friendly water or a water/acetonitrile mixture buffered with bicarbonate is used as solvent. The electrode is highly stable and it can be reused for a prolonged period of time allowing easy separation from the products.     

Fluorinated Polyphosphazenes: A Survey

A general survey of fluorinated phosphazene polymers starting from their synthesis in 1965 to recent times is presented. Various types of fluorinated phosphazenes are described depending on the way fluorine atoms are connected to the polyphosphazene skeleton. The characterization, properties and practical utilization of these compounds in different domains are critically discussed.     

Photo-polymerisation of composite resins measured by micro-Raman spectroscopy

The micro-Raman spectroscopy was used for measuring the photo-polymerisation of composite resins. The elevated spatial resolution of the technique revealed surface non-homogeneities via the intensity variations of a strong band at 1400 cm⁻¹ and the presence of weak bands around the CC and CO stretching frequencies. Values of the degree of monomer conversion (DC) were determined for samples of Z100 commercial composite irradiated with different wavelength laser beams. Two methods were used for obtaining DC values. The first one exploits band decompositions in the spectral region of interest around 1608 and 1637 cm⁻¹. The non-uniqueness of the decomposition introduces relevant uncertainties, which are amplified by unwanted weak bands. An alternative method, avoiding any fit procedure and exploiting the band shape conservation under irradiation, was found producing more reliable results. The 632 nm line of the He-Ne laser was used as an exciting source. The measurements of the DC versus time are reported for three different wavelengths of the irradiation light. Preliminary studies of the CO stretching bands are also reported. Their intensities decrease under irradiation and there are indications of a behaviour similar to that of the CC aliphatic band.     

Investigation of the properties of niobium pentoxide for use in dye-sensitized solar cells

This work demonstrates the obtention of Nb₂O₅ nanoparticles by the microwave-assisted hydrothermal synthesis method in a fast way and with the use of low temperatures. The heat treatment applied on the samples promotes the phase change in Nb₂O₅ from pseudohexagonal to orthorhombic as the temperature increases, with a particle size between 7.3 and 32.6 nm. The band gap of the samples decreases with increasing temperature, obtaining a minimum value of 3.04 eV at 800°C. Dye-sensitized solar cells (DSSC) were assembled using the Doctor Blade coating technique. The photovoltaic parameters of open-circuit voltage (Voc) and short-circuit current density (Jsc) were evaluated. The cells showed a photovoltaic response, demonstrating that Nb₂O₅ has a semiconductive potential. The DSSC have different characteristics regarding Jsc and Voc, showing that according to the temperature increase in the semiconductor sample, there is a decrease in the photovoltaic parameters of the cells.     

A PLS regression model using NIR spectroscopy for on-line monitoring of the biodiesel production reaction

In this work, a Partial Least Squares (PLS) regression model using Near-Infrared (NIR) spectroscopy was developed to monitor the progress of the catalyzed transesterification reactions of soybean oil that produce biodiesel. The NIR spectra were collected during the transesterification reaction with a lab made spectrophotometric flow cell. Proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy was employed for determining the conversion percentage of glycerides to methyl esters during the transesterification reaction and used as reference to build the PLS calibration model employing NIR spectroscopy data. The model, constructed with selected spectral range has not been tried before and allows the monitoring of the transesterification reaction in terms of conversion ratio for different temperatures. The model was validated and the values of Root Mean Square Error of Prediction (RMSEP) found for two different temperatures were 0.74% and 1.27% (of conversion) for reactions carried out at 20 ± 0.2 °C and 55 ± 0.2 °C, respectively.     

The development of a silica nanoparticle-based label-free DNA biosensor

A silica nanoparticle-based DNA biosensor capable of detecting Bacillus anthracis bacteria through the use of unlabelled ss-oligonucleotides has been developed. The biosensor makes use of the optical changes that accompany a nanoparticle-immobilized cationic conjugated polymer (polythiophene) interacting with single-stranded vs. hybridized oligonucleotides, where a fluorescence signal appears only when hybridized DNA is present (i.e. only when the ss-oligonucleotide interacting with the polymer has hybridized with its complement). In order to enhance the sensitivity of the biosensor, two different nanoparticle architectures were developed and used to elucidate how the presence of neighboring fluorophores on the nanoparticle surface affects F?rster-resonant energy transfer (FRET) between the polythiophene/oligonucleotide complex (FRET donor) and the fluorophores (FRET acceptors). We demonstrate that the silica nanoparticle-based FRET platform lowers the limit of detection at least 10-fold in comparison to the polythiophene itself, and allows the detection of ～2 × 10(-12) moles of ss-oligonucleotide in a 100 μL sample with a standard fluorimeter (i.e. has a limit of detection of ～2 nM ssDNA). Such nanoparticle-based biosensor platforms are beneficial because of the robustness and stability inherent to their covalent assembly and they provide a valuable new tool that may allow for the sensitive, label-free detection (the target DNA that produces the fluorescence signal is unlabelled) without the use of polymerase chain reaction.     

Molecular quantum spintronics: supramolecular spin valves based on single-molecule magnets and carbon nanotubes

We built new hybrid devices consisting of chemical vapor deposition (CVD) grown carbon nanotube (CNT) transistors, decorated with TbPc(2) (Pc = phthalocyanine) rare-earth based single-molecule magnets (SMMs). The drafting was achieved by tailoring supramolecular π-π interactions between CNTs and SMMs. The magnetoresistance hysteresis loop measurements revealed steep steps, which we can relate to the magnetization reversal of individual SMMs. Indeed, we established that the electronic transport properties of these devices depend strongly on the relative magnetization orientations of the grafted SMMs. The SMMs are playing the role of localized spin polarizer and analyzer on the CNT electronic conducting channel. As a result, we measured magneto-resistance ratios up to several hundred percent. We used this spin valve effect to confirm the strong uniaxial anisotropy and the superparamagnetic blocking temperature (T(B) ~ 1 K) of isolated TbPc(2) SMMs. For the first time, the strength of exchange interaction between the different SMMs of the molecular spin valve geometry could be determined. Our results introduce a new design for operable molecular spintronic devices using the quantum effects of individual SMMs.     

Microstructural and phase transformations during sintering of a phillipsite rich zeolitic tuff

Microstructural and phase transformations during sintering of a Phillipsite rich zeolitic tuff, from Tenerife, Canary Islands, was investigated in order to their utilization in ceramic manufacturing industries. Green samples were obtained from powders and pressed at 150 MPa and heat-treated for 1 hour in the temperature range between 900-1080 °C. The zeolitic tuffs show endothermic peaks at about 100 °C and 200 °C, corresponding to dehydration of zeolitic water observed in the thermo- gravimetric curves and at ∼700 °C a small endothermic peak was identified corresponding to the structural breakdown of Phillipsite. According to the dilatometric traces, at about 870 °C, sintering of solid particles starts and a linear shrinkage of about 6% is reached at about 1050 °C. The maximum absolute and apparent densities were obtained after sintering at 1040 °C (absolute density = 2.59 g/cm³; apparent density = 2.33 g/cm³). Over this temperature, the sample heat-treated at 1060 °C, density results show a decreasing trend. The chemical composition of studied zeolitic tuffs make possible the liquid phase formation during heat-treatment, through the supplement of alkaline oxides. SEM image of the sample obtained at 1040 °C shows a zone with micro-crystallinity around the boundary of Sanidine grain highlighting the beginning of the phase transition from Sanidine, to Microcline. Heat-treatment effect of zeolitic tuff leads to the decomposition of Phillipsite and Sanidine and the formation of a new crystal phase of Hematite.