Reaction of oxygen plasma active species with polyethylene

The composition of the polyethylene surface upon treatment in an oxygen plasma and its afterglow was studied by attenuated total reflectance IR spectroscopy and X-ray photoelectron spectroscopy. The oxidation of the surface at the lowest destruction rates was attained upon simultaneous action of excited O₂(a¹Δ_g) and ground-state oxygen molecules. However, O(³ P) atoms are involved in both the formation of oxygen-containing groups and their destruction accompanied by polymer degradation.     

Oxidation and Degradation of Polypropylene in an Oxygen Plasma

The rates of the formation of gaseous products were measured and the chemical composition of surface was determined upon the surface treatment of polypropylene in an oxygen low-temperature dc discharge plasma. The mechanisms of modification and oxidative degradation were discussed.     

Mechanism of hydrogen peroxide formation in electrolytic-cathode atmospheric-pressure direct-current discharge

The kinetics of buildup of hydrogen peroxide in an atmospheric pressure direct-current discharge with a distilled-water cathode has been experimentally measured. A kinetic reaction scheme has been proposed and analyzed to calculate peroxide concentrations in accordance with experimental data.     

The Ability of Acid-Based Natural Deep Eutectic Solvents to Co-Extract Elements from the Roots of Glycyrrhiza glabra L. and Associated Health Risks

The roots of licorice (Glycyrrhiza glabra L.) have been widely used in traditional and officinal medicines for the treatment of different diseases. Natural deep eutectic solvents (NADES) have become popular for the extraction of active principles from medicinal plants. However, the ability of NADES to co-extract trace elements during the isolation of target active compounds is rarely investigated. The aim of this study was to analyze the content of trace elements in acid-based NADES extracts from the roots of G. glabra and the health risks associated with them. In this study, we have tested for the first time the ability of several acid-based NADES to co-extract glycyrrhizic acid (GA) and trace elements from the roots of G. glabra. GA has been identified as the dominant phytochemical in G. glabra NADES extracts (0.145–0.495 mg/g). Due to the close pKa of lactic acid and GA, the yield of GA in lactic acid-based NADES was higher in comparison with other tested NADES. The yield of GA in NADES3-NADES5 was statistically significant and surpassed the yield of GA in water. The recovery of all elements (except Li) by all tested NADES was low (less than 6%). According to an ANOVA test, the hydrogen bond donor type plays a decisive role in the extraction of elements. A strong positive correlation between the recovery of GA and MPI was noted. The metal pollution index, hazard quotient, hazard index, and chronic daily intake were calculated and suggest that all tested NADES extracts of G. glabra roots were nontoxic and possess no health risk for both ingestion and topical application.     

Immobilization of tetraphenylporphyn and its metallocomplexes on the surface of plasma-treated polypropylene

The immobilization of 5,10,15,20-tetraphenylporphyn and its zinc and manganese complexes on the surface of polypropylene modified by plasmachemical treatment and subsequent grafting copolymerization of acrylamide or 4-vinylpyridine has been studied by multiple attenuated total reflection FTIR spectroscopy, electronic absorption spectroscopy, and atomic force microscopy. It has been demonstrated that the immobilized molecules of tetraphenylporphyn and its metallocomplexes are active in the photosensitized generation of singlet oxygen to the gas phase.     

Surface oxidation of polyethylene using an atmospheric pressure glow discharge with liquid electrolyte cathode

This study investigated the action of an atmospheric pressure air glow discharge (APGD) with aqueous electrolyte cathode onto the surface of polyethylene (PE) films. Distilled water and aqueous solutions of KCl and HCl were utilized as a cathode. The surface properties of PE were characterized by contact angle measurement followed by surface free energy calculation, Fourier transform infrared by attenuated total reflectance (FTIR-ATR), and XPS. After treating the PE surface, we observed OH groups, CO groups in ester, ketone, and carboxyl groups, and CO groups in unsaturated ketones and aldehydes. For a treatment time of 20 min and a discharge current of 40 mA, atomic concentrations of O and N were 12% and 2%, respectively, under distilled water application. Modification processes were able to improve the surface free energy of PE.     

Modification and Degradation of Polyethylene under the Action of Oxygen Plasma

The results of measurements of the rates of formation of gaseous products and the composition of functional groups in the surface layer of polyethylene upon treatment in a low-temperature dc oxygen discharge plasma are presented. Based on these data, the mechanisms of polyethylene modification and oxidative degradation are discussed.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 5, 2005, pp. 386–391.Original Russian Text Copyright © 2005 by Shikova, Rybkin, Titov, Shutov, Kuvaldina.     

Effect of the Structure of the Macroheterocyclic Ligand on the Catalytic Properties of Tetraarenoporphyrazine Metal Complexes: II. Oxidation of Cysteine,Catalyzed by Cobalt Tetraarenoporphyrazines

The catalytic activity of cobalt tetraarenoporphyrazine complexes in heterogeneous oxidation of cysteine is much dependent on the macrocycle structure and is inversely related to the electron-acceptor power of the ligand.