Antimicrobial agents as photostabilizers for rigid poly(vinyl chloride)

Some amide derivatives of ethylene glycol‐bis(2‐aminoethylether)‐N,N,N^′,N^′‐tetraacetic acid (EGTA) have been prepared via their coupling with different aniline derivatives: amino, methyl, chloro, and hydroxy aniline. The EGTA amide derivatives were characterized, and their antimicrobial activities were evaluated. These antimicrobial agents have been investigated as photostabilizers for rigid poly(vinyl chloride) (PVC), suspension PVC, with a K value of 70. Their stabilizing efficiencies were evaluated by determining the percentage of weight loss, the intrinsic viscosities, as well as the amount of formed gel of the photodegraded PVC. The extent of discoloration and the change in the mechanical properties of the photodegraded polymer were also evaluated. The applied materials reduced the loss in weight that resulted from HCl evolution during photodegradation. Both viscosity and gel content measurements showed also a decrease in their values during the degradation process. The decrease in the percentage of gel formation upon applying the investigated photostabilizers reflects the lowering in extent of cross‐linking of the polymer, which implies preserving the mechanical properties of PVC. The extent of discoloration was also improved in the presence of the investigated compounds. The results have proved a greater stabilizing efficiencies of the antimicrobial EGTA amide derivatives than that of the phenyl salicylate ultraviolet (UV) absorber, which is commonly used as an industrial stabilizer. A radical mechanism was proposed to account for the stabilizing action of the investigated products. Copyright © 2011 John Wiley & Sons, Ltd.     

Fitting-free curve resolution of spectroscopic data: Chemometric and physical chemical viewpoints

In this paper the authors have investigated spectroscopic data analysis according to a recent development, i.e. the Direct Inversion in the Spectral Subspace (DISS) procedure.     

Hidden electrochemistry in the thermal grafting of silicon surfaces from grignard reagents

Covalent grafting of alkyl chains on silicon can be obtained by thermal treatment in Grignard reagents. Alkyl halide present in the Grignard solution as an impurity appears to play a key role in the grafting process. Grafting efficiency is improved when the alkyl halide concentration is increased. It is also enhanced on n-type substrates as compared to p-type substrates and when alkyl bromides are present in solution rather than alkyl chlorides. The grafting reaction involves a zero-current electrochemical step. A reaction model in which simultaneous Grignard oxidation and alkyl halide reduction take place at the silicon surface accounts for all these observations. Alkyl halide reduction is the rate-determining step. Negative charging of the silicon surface lowers the energetic barrier for this reaction, allowing for efficient grafting on n-Si.     

Green Synthesis of Ag Nanoparticles by Callicarpa Maingayi: Characterization and Its Application with Graphene Oxide for Enzymeless Hydrogen Peroxide Detection

A facile green synthesis of silver nanoparticles (AgNPs) was achieved using aqueous leaf extract of Callicarpa Maingayi as a reducing and stabilizing agent during the synthesis from its salt solutions. The synthesized silver nanoparticles were analyzed with transmission electron microscopy (TEM), X‐ray diffraction (XRD) and energy dispersive spectrometer (EDS). XRD study shows that the particles are crystalline in nature with face centered cubic geometry. The crystallite size obtained from XRD is about 15 nm which is in agreement well with the TEM results. A new nanostructure sensor was constructed by immobilizing silver nanoparticles and graphene oxide (AgNPs‐GO) composite film on a glassy carbon electrode (AgNPs‐GO/GCE). It was found that the AgNPs‐GO composite exhibits good catalytic activity toward the reduction of hydrogen peroxide (H₂O₂), leading to an enzymeless sensor with a fast amperometric response time of less than 5 s, high selectivity, good reproducibility and stability. The linear range was 5.0 μM to 700 μM with a detection limit of 0.6 μM (S/N = 3).     

Green,mild and efficient bromination of aromatic compounds by HBr promoted by trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane in water as a solvent

A combination of HBr and trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane as anew and powerful oxidant was found effective for facile brotnination of different aromatic compounds at room temperature in water as a green solvent.Mild reaction conditions,high selectivity and yield,high reaction rate and non-toxicity are some of the major advantages of this synthetic protocol.