Cationic fluorene-thiophene diblock copolymers: Aggregation behaviour in methanol/water and its relation to thin film structures

Optical spectroscopy and photophysical measurements on cationic fluorene-thiophene diblock copolymers in solution show distinct properties for the two blocks, with clear indications of singlet exciton migration from the polyfluorene to polythiophene blocks. Electrical conductivity measurements and small angle X-ray scattering studies show that different aggregates are formed in water and methanol. This may be associated both with different solubilities of the two blocks and with the effect of solvent on the degree of dissociation of the ionic part. Atomic force microscopy (AFM) shows that different nanostructures are deposited from the two solvents, with large, vesicular structures deposited on mica from methanolic solution. Aggregation behavior is also found to be modulated, and to lead to more rigid thiophene blocks, by addition of the oppositely charged surfactant sodium dodecylsulfate.     

Fabrication of polyoxometallate-modified gold nanoparticles and their utilization as supports for dispersed platinum in electrocatalysis

The usefulness of Keggin-type anions (PMo₁₂O₄₀³⁻) as both reducing, capping and activating agents during synthesis of polyoxometallate-modified gold nanoparticles is demonstrated here. Fabrication of gold nanoparticles stabilized with monolayer-type films of inorganic polyoxometallates (e.g. phosphododecamolybdates), Au-PMo₁₂, was achieved by treating an aqueous solution of gold precursor (HAuCl₄) with a solution of the partially reduced heteropolyblue molybdate. The choice of temperature strongly affected morphology and size of the resulting Au nanoparticles. The presence of strongly adsorbed molybdate-agents on surfaces of gold nanoparticles was evident from the independent infrared (FTIR by reflectance) and voltammetric experiments. Interfacial polymolybdate anions on Au prevent the particle agglomeration and support formation of the stable colloidal Au-PMo₁₂ solutions. They are colored due to existence of the plasmonic effect. The Au-PMo₁₂ nanoparticles typically had 30–40 nm diameters, and they were used as supports or carriers for dispersed catalytic platinum nanoparticles (of ca. 7–8 nm diameters). Polyoxometallates (PMo₁₂O₄₀³⁻) existing on gold surfaces could also interact with neighboring platinum centers thus acting as “linking” agents facilitating dispersion of Pt nanoparticles. Further, the phosphomolybdate adsorbates (on Au supports) are also likely to activate Pt sites (e.g. by providing reactive hydroxy groups) towards more efficient electrocatalytic oxidation of ethanol both under voltammetric and chronoamperometric conditions.     

Electrochemical synthesis of polymers with alternate phenothiazine and bithiophene units

An electrochemical and spectroelectrochemical study of a new monomer—N-alkyl-bis(thiophene)phenotiazine have been presented. Electrochemical polymerization of the monomer leads to a polymer with alternate phenothiazine and bithiophene units. Polymerization proceeds after bielectronic oxidation of the molecule. Monoelectronic oxidation gives a stable radical cation with spin located on phenothiazine. Electrochemical properties of the polymer depend on the thickness of the film deposited on the electrode. For thin layers one can observe a characteristic redox couple of phenothiazine oxidation to a radical cation. Analysis of the polymer behaviour and the results of spectroelectrochemical measurements indicate a mixed-type of polymer conductivity.     

The use of electronic and human nose for monitoring rapeseed oil autoxidation

This work was aimed at assessing the effectiveness of the electronic nose to monitor off‐flavor associated with lipid oxidation as a supplementary tool to human sensory panel assessment. Therefore, correlations between electronic nose and sensory analysis were determined. Also GC analyses and chemical analyses of oil samples were run to characterize the analyzed samples with well‐described parameters. Refined rapeseed oil was subjected to an accelerated storage test for 12 days at 60 °C and to an ambient temperature storage test in which it was stored in retail plastic bottles for up to 6 months. PCA of electronic nose data samples stored at an elevated temperature was related to PCA of sensory analysis, and similarities in sample clustering were observed. For samples stored at room temperature, the human panel showed greater sensitivity than the electronic nose. Prediction models based on PLS of electronic nose data were able to predict the sensory quality changes during storage at elevated and room temperature, ranging from 0.721 to 0.989 and from 0.849 to 0.881 (p <0.05), respectively. PV and p‐AV were well predicted on the basis of both electronic nose (0.989, 0.998 for elevated temperature; 0.907, 0.881 for room temperature) and sensory analysis data (0.973, 0.993 for elevated temperature; 0.939, 0.886 for room temperature). Applicability of the electronic nose technology to verify sensory and rancidity changes during storage showed to be promising in quality control of oils.     

Critical Heat Flux of R134a and R245fa Inside Small-Diameter Tubes

This article presents new experimental critical heat flux results under saturated flow boiling conditions for a macro-/microscale tube. The data were obtained in a horizontal 2.20-mm inside diameter stainless-steel tube with heating lengths of 361 and 154 mm, R134a and R245fa as working fluids, mass velocities ranging from 100 to 1500 kg/m²-s, critical heat flux from 25 to 300 kW/m², exit saturation temperatures of 25, 31, and 35°C, and critical vapor qualities ranging from 0.55 to 1. The experimental results show that critical heat flux (CHF) increases with increasing mass velocity and inlet subcooling but decreases with increasing saturation temperature and heated length. The data also indicated a higher CHF for R245fa when compared with R134a at similar conditions. The experimental data were compared against four CHF predictive methods and the results of the comparisons are reported.     

White grape pomace as a source of dietary fibre and polyphenols and its effect on physical and nutraceutical characteristics of wheat biscuits

BACKGROUND: Grapes are one of the world's staple fruit crops, with about 80% of the yield being utilised for winemaking. Since grape by‐products still contain large amounts of secondary metabolites, uses other than as fertilisers might be appropriate. In this study, white grape pomace (WGP) was incorporated in wheat flour at levels of 10, 20 and 30% (w/w) to investigate its influence on rheological, nutraceutical, physical and sensory properties. RESULTS: Farinograph characteristics of dough with different levels of WGP showed a decrease in water absorption from 56.4% (0% WGP) to 45.9% (30% WGP). Addition of WGP reduced hardness and caused a deterioration in brightness and yellowness of all enriched samples. The smallest addition of WGP (10%) caused an approximately 88% increase in total dietary fibre content as compared with the control. The content of phenolic compounds increased from 0.11 mg g^?1 with 0% WGP to 1.07 mg g^?1 with 30% WGP. The most stable phenols were as follows: γ‐resorcylic acid < gallic acid < tyrosol < catechin < isovanilic acid. An assay of radical‐scavenging activity showed that WGP addition greatly enhanced the antioxidant properties of biscuits. Acceptable biscuits were obtained when incorporating 10% WGP. CONCLUSION: WGP might be utilised for the novel formulation of biscuits as an alternative source of dietary fibre and phenols. Copyright © 2012 Society of Chemical Industry     

Comparison of ZnO:Al,ITO and carbon nanotube transparent conductive layers in flexible solar cells applications

In the paper the mechanical, optical and electrical parameters of transparent conductive layers (TCLs) made of carbon nanotubes and metal conductive oxides are explored and compared. All investigated materials are deposited on transparent, flexible polymer foils used for solar cell applications. Obtained results are compared with available parameters of rigid transparent conductive oxides (TCOs) as well as literature reports about Indium–Tin Oxide (ITO) on flexible substrates. Presented paper is a report from the preliminary stage of a new flexible solar cell construction.