Size Control and Surface Modification of Colloidal Semiconductor Particles

Several methods for the control of semiconductor particle sizes, in particular in the quantum size regime, are surveyed. Rational choice of solvent polarity, reaction temperature, concentration of reactants, solution pH, and counterions will determine the size and size distribution of the particles. Sizes of colloidal particles formed in microheterogeneous environments will often be predetermined by the dimensions of the micropores and cavities within the network of the medium. This is the situation in zeolite and clay cavities, and in polymer networks. Self-aggregation of amphiphillic molecules often generates microdomains which may be utilized to direct the particle precursors or the particles themselves into these domains and thus limit their growth. Finally, complexation at the surface of the particles may limit and control the growth processes of the particles. The latter approach also allows functional modification of the particles' surface.     

A white emitting poly(phenylenevinylene)

A white emitting copolymer with the polyphenylenevinylene (PPV) structure is obtained via the Stille cross-coupling reaction. Substitution of hydrogen atoms with fluorine atoms on the vinylene units of poly(1,4-dialkoxyphenylenevinylene) shifts the emission from orange-red to blue. White emission is obtained by combining dialkoxyphenylenedifluorovinylene and dialkoxyphenylenevinylene units in proper ratio. The two complementary emitters are obtained separately by Stille polymerization reaction. Then, the two reaction mixtures are combined without purification in different ratios and further reacted in similar experimental conditions. A white luminescent material is obtained using 99/1 mixing ratio. OLED devices fabricated with this copolymer shows near-white emission with CIE (0.30, 0.40) and excellent stability in the range 10–200 cd/m².     

Gravure printing for thin film ceramics manufacturing from nanoparticles

Printing technologies can offer high potential for the thin film deposition of functional materials. Among the printing techniques, the gravure is considered one of the most promising, although to date it is still little employed, especially for the inorganic functional materials. In this work, the study of the gravure printing process for the metal oxides thin film production on flexible polymer substrate is reported. For this purpose, zinc oxide (ZnO) was chosen due to its versatile properties and nanosize effects, which make it suitable for many high technology areas. The gravure printing was made using low viscosity inks of ZnO nanoparticles. The characteristics of the printed thin films were examined and discussed. Thanks to the understanding of the physics underlying the film forming during the printing process combined to the knowledge on such specific material, uniform, compact, very transparent and smooth films were obtained in different nanometric thicknesses. Moreover, the possibility of fabricating ceramic nanocomposite films directly through this printing technique is also presented. Thanks to its scientific approach, this work makes available to the world of ceramics an industrial versatile and low-cost production technique which can allow to study and develop high-quality thin film ceramics with technologically interesting properties as well as nanoparticles behavior and their treatments in order to develop and use their fascinating nanosize properties.     

Effect of the addition of air-classified barley flours on the lipid stability of bakery products

Whole grains are a potential source of dietary antioxidants, and their phenolic compounds play a potential role in the prevention of lipid oxidation. In the present study, the barley coarse fraction was tested as a source of phenolic compounds to minimize lipid oxidation in bakery products (tarallini) during storage. The content of phenolic compounds in wheat and barley flours and in their mixtures was evaluated by capillary electrophoresis. Three recipes of tarallini were formulated containing different levels of barley coarse fraction (0, 20, 50%, w/w) and either extravirgin olive oil or sunflower oil. Samples were stored for 6 months and analysed every 3 months. The peroxide value was used to establish the primary oxidation state; secondary oxidation products were also evaluated (oxidized fatty acid and diene and triene conjugated by UV). All samples showed an increase in lipid oxidation during storage. The increase in peroxide values after 6 months was in the range of 183–574%. Tarallini prepared with sunflower oil showed the highest lipid oxidation. Antioxidant effects were not observed with the coarse fraction phenolic compounds.     

Large-scale production of high-quality multi-walled carbon nanotubes: Role of precursor gas and of Fe-catalyst support

The crucial role of precursor gas (PG) and of catalyst support (CS) in the growth of multi-walled C nanotubes (MWCNTs) by iron-catalysed chemical vapour deposition (CVD) is evidenced. This is accomplished by comparing structural and morphological properties of MWCNTs synthesised by the use of different PGs (ethane and isobutane) and CSs (silica and alumina). The results of analyses, carried out on catalysts and C deposits by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), thermo-gravimetry (TG) and X-ray diffraction (XRD), demonstrate that Al₂O₃-supported catalysts are more efficient than SiO₂-supported ones in decomposing hydrocarbons. The use of i-C₄H₁₀ as PG allows reducing Fe-encapsulation and improving yield (Y_C) and selectivity, so as the large-scale production (Y_C > 900 wt.%) of high-quality nanotubes can be operated even at moderate reaction temperature (600 °C) after proper calibration of Fe-load (29 wt.%) and catalyst reduction temperature (500 °C).     

Improved Time-Resolved Measurements of Inorganic Ions in Particulate Matter by PILS-IC Integrated with a Sample Pre-Concentration System

A particle-into-liquid sampler coupled with ion chromatograph (PILS-IC) for the on-line measurement of inorganic ions has been modified by the insertion of two ion-exchange pre-concentration cartridges that enrich the sample during the period of the IC analysis. The limits of detection of the modified instrument were 10-15 times lower and the time coverage 24 times higher (from 2 to 48 min per hour) than those of the original PILS-IC setup. The instrumental performance in terms of recovery and break-through volume from the cartridges was satisfactory. The modified PILS-IC was operated in comparison with a diffusion denuder line and with a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) during a short intensive measurement period organized in the framework of the European Monitoring and Evaluation Programme (EMEP), a co-operative program for monitoring and evaluation of the long-range transmission of the air pollutants in Europe. The instrument showed a quantitative response in agreement with the results of the diffusion lines, and an ability to trace fine concentration variations not so different from the performance of the much more complex HR-TOF-AMS. From the time patterns of the ion concentrations measured by the modified PILS-IC, it was possible to obtain useful information about the variations in the air quality and in the strength of the particulate matter sources.

Copyright 2015 American Association for Aerosol Research     

Recovery of phenolic compounds from orange press liquor by nanofiltration

This research was undertaken in order to evaluate the potential of a nanofiltration (NF) process for the separation and concentration of phenolic compounds from press liquors obtained by pigmented orange peels. Four different spiral-wound NF membranes, characterised by different molecular weight cut-off (MWCO) (250, 300, 400 and 1000 Da) and polymeric material (polyamide, polypiperazine amide and polyethersulphone), were investigated. The rejection of the investigated membranes towards anthocyanins, flavonoids and sugars was evaluated in order to identify a suitable membrane to separate phenolic compounds from sugars. The performance of the investigated NF membranes was also evaluated in terms of permeate flux and antifouling performance.The obtained results indicated a reduction of the average rejection towards sugars by increasing the MWCO of the selected membranes, while the rejection towards anthocyanins remained higher than 89% for all the NF membranes investigated. The NFPES10 membrane showed the lowest average rejection towards sugar compounds and high rejections towards anthocyanins (89.2%) and flavonoids (70%). Permeate flux values at lower transmembrane pressures were also favourably high compared to the other NF membranes.