Polysulfone membrane treated with NH3-O2 plasma and its property

The character of ammonia-oxygen (NH3-O2) plasma-treated polysulfone (PSF) membrane was studied in this work. The time effect of the plasma-treated PSF membrane was checked with energy-dispersive X-ray (EDX) detector, attenuated total reflection Fourier transform infrared (ATR-FTIR), membrane contact angle, and filtration property. EDX detector and ATR-FTIR spectra have shown that the surface oxygen content of the modified membrane increased in the form of peroxy, hydroxyl, and aromatic carboxide groups. However, nitrogen was not observed in the NH3-O2 plasma-treated membrane surface. The peroxy group disappeared and hydroxyl and aromatic carboxide groups were reduced 3 months later. However, the plasma-treated membrane still shown great hydrophilicity, and the contact angle decreased to 0 within 11 s despite the time effect. During the two rounds of 80 min of bovine serum albumin buffer solution filtration process, the fluxes of newly plasma-treated membrane and that of the membrane 3 months later decreased to 78 L m−2 h−1 and 54 L m−2 h−1, respectively, whereas the flux of the pristine membrane decreased to 12 L m−2 h−1.

The β-carotene dilemma: ESR study with coordinated peroxyl radicals

The apparently unpredictable behaviour of β-carotene in the supplementation of the diet of smokers is discussed in the light of the reactions of peroxyl radicals with β-carotene in the absence of oxygen. The decay of tert-butylperoxyl radicals in the presence of β-carotene was studied at ambient temperature in non-polar solvents by ESR spectroscopy. The primary reaction in the absence of oxygen is interpreted as a spin-trapping effect of a peroxyl radical by β-carotene producing an intermediate labile free radical, which disappears after recombination with a second tert-butylperoxyl radical. The result is the transformation of β-carotene to a diamagnetic compound with two peroxy bonds. In the presence of chelating transition metals with unpaired d-electrons as electron donors the peroxy group of the oxidized β-carotene can be split to alkoxyl free radicals. The primary attack of tert-butylperoxyl radicals is completely inhibited in the presence of vitamin E followed by production of free aryloxy radicals and the presence of oxygen has no significant effect on this reaction. Spin-trapping of peroxyl radicals by the double bond of vitamin A leads to its oxidation in the absence of vitamin E.Transition metal ions such as Co, Cr, Fe, and Mn, known to be present in the aerosol of cigarette smoke, homolyse the peroxyl bonds of peroxidised β-carotene, which results in cell damage.

Organometallic peroxy radicals. Part 5. Trialkylsilylperoxy and trialkylstannylperoxy radicals

A variety of organosilylperoxy and organostannylperoxy radicals, R3MO2•(R = Me, Et, n-Bu, t-Bu, and Ph and M = Si and Sn) have been prepared and studied by electron spin resonance spectroscopy. Trialkylsilylperoxy radicals exist in equilibrium with a tetroxide at temperatures below 233 K with ΔH0 = −11 ± 2 kcal mol−1 and ΔS0 < −30 cal deg−1 mol−1. Above 233 K these radicals decay either with first-order, one half-order, or zero-order kinetics depending on the radical and its concentration. Trialkylstannylperoxy radicals do not exist in reversible equilibrium with a dimer below ambient temperature and they undergo self-reaction with second-order kinetics. Tri-n-butylstannylperoxy radicals react with 2,6-di-tert-butyl-4-methylphenol and cobalt(II) acetylacetonate and Arrhenius parameters for these two reactions are reported. The structure of R3SiO2•resembles the structure of alkylperoxy radicals whereas the two oxygen nuclei of R3SnO2. are magnetically equivalent and the peroxy group becomes a bidentate ligand. This structural difference has a significant effect on radical reactivity.