Thermodestruction in the surface layer of poly(vinyl chloride) during extrusion

Polymeric raw material passing through the extrusion machine and other forming devices undergoes the processes of destruction, which result in the formation of potentially harmful substances and their accumulation in the surface layers of the product directly contacting with heated parts of forming machines. The research of the top layer of a poly(vinyl chloride) profile has shown that the surface layer of polymer contains a number of chlorinated hydrocarbons. The following substances have been identified during the research of the hydrocarbons composition contained of the surface layer: hexachlorobenzene, hexachlorobutene, chloroform, acetyl chloride, biphenyl, anthracene, naphthalene, and other hydrocarbons. The difference of calculated activation energy of thermooxidizing destruction of surface and internal layers of a polymeric product reveals the process of partial destruction of a surface layer. Data about semivolatile substances, concentrating in polymer surface during processing will be used for development of stabilizers, ecology, and polymer‐manufacturing techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

Photo-electro-chemical properties of TiO2 mediated by the enzyme glucose oxidase

Electrochemical measurements show that the enzyme glucose oxidase (GO) is adsorbed on the surface of TiO₂ without apparently changing the flat band potential of the semiconductor, indicating that it does not cause a change of the energy of conduction band electrons. On the other hand, it is observed that GO markedly increases the efficiency of the two electron reduction of O₂ to H₂O₂ which is accumulated in the solution phase.

ESR spin trapping investigations indicate that GO favors the formation of OH radicals, due to either the inhibition of charge recombination processes or to H₂O₂ reduction by conduction band electrons. Accordingly, photo-oxidation of different alcohols to the corresponding radical species is also enhanced in the presence of GO.

The photo-oxidation of 1,2-propandiol on TiO₂/GO is regioselective in that (i) partial oxidation to hydroxyacetone is observed and (ii) no mineralization (full combustion to CO₂) of the substrate occurs. These facts are of particular interest in the field of studies concerning the design of new photocatalytic systems with enhanced activity and controllable oxidative power.     

Subwavelength focusing and guiding of surface plasmons

The constructive interference of surface plasmon polaritons (SPP) launched by nanometric holes allows us to focus SPP into a spot of high near-field intensity having subwavelength width. Near-field scanning optical microscopy is used to map the local SPP intensity. The resulting SPP patterns and their polarization dependence are accurately described in model calculations based on a dipolar model for the SPP emission at each hole. Furthermore, we show that the high SPP intensity in the focal spot can be launched and propagated on a Ag strip guide with a 250 x 50 nm2 cross section, thus overcoming the diffraction limit of conventional optics. The combination of focusing arrays and nano-waveguides may serve as a basic element in planar nano-photonic circuits.     

Multidimensional Raman spectroscopic signatures as a tool for forensic identification of body fluid traces: a review

The analysis of body fluid traces during forensic investigations is a critical step in determining the key details of a crime. Several confirmatory and presumptive biochemical tests are currently utilized. However, these tests are all destructive, and no single method can be used to analyze all body fluids. This review outlines recent progress in the development of a novel universal approach for the nondestructive, confirmatory identification of body fluid traces using Raman spectroscopy. The method is based on the use of multidimensional spectroscopic signatures of body fluids and accounts for the intrinsic heterogeneity of dry traces and donor variation. The results presented here demonstrate that Raman spectroscopy has potential for identifying traces of semen, blood, saliva, sweat, and vaginal fluid with high confidence.