Molecular Modelling of Polychlorinated Dibenzo-p-Dioxins Non-Covalent Interactions with ß and γ-Cyclodextrins.

Polychlorinated dibenzo-p-dioxins (PCDD) are persistent organic pollutants which result as byproducts in industrial or combustion processes and induce toxicity in both wildlife and humans. In this study, all seven PCDD, tetrachlorinated dibenzo-p-dioxins (TCDD), pentachlorinated dibenzo-p-dioxins (P5CDD), hexachlorinated dibenzo-p-dioxins (H6CDD), heptachlorinated dibenzo-p-dioxins (H7CDD), and octachlorinated dibenzo-p-dioxins (OCDD) were studied in interaction with two cyclodextrins, ß-CD and γ-CD, resulting in a total of 40 host-guest complexes. The flexibility of the cyclodextrins was given by the number of glucose units, and the placement of the chlorine groups on the dioxins structure accounted for the different complex formed. Various geometries of interaction obtained by guided docking were studied, and the complexation and binding energy were calculated in the frame of MM+ and OPLS force fields. The results show that the recognition of the PCDD pollutants by the CD may be possible through the formation of PCDD:CD inclusion complexes. This recognition is based on the formation of Coulombic interactions between the chlorine atom of the PCDD and the primary and secondary hydroxyl groups of the CD and van der Waals interaction of the CD hydrophobic cavity with PCDD aromatic structures. Both MM+ and OPLS calculus resulted in close values for the complexation and binding energies. Molecular mechanics calculations offer a proper insight into the molecular recognition process between the PCDD compounds and CD molecules, proved by a good description of the C-H···O bonds formed between the guest and host molecules. It was shown for the first time that CD may efficiently trap PCCDs, opening the way for their tremendous potential use in environmental remediation.

Luminescence, Paramagnetic, and Electrochemical Properties of Copper Oxides-Decorated TiO2/Graphene Oxide Nanocomposites.

The properties of newly synthesized Cu2O/CuO-decorated TiO2/graphene oxide (GO) nanocomposites (NC) were analyzed aiming to obtain insight into their photocatalytic behavior and their various applications, including water remediation, self-cleaning surfaces, antibacterial materials, and electrochemical sensors. The physico-chemical methods of research were photoluminescence (PL), electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The solid samples evidenced an EPR signal that can be attributed to the oxygen-vacancy defects and copper ions in correlation with PL results. Free radicals generated before and after UV-Vis irradiation of powders and aqueous dispersions of Cu2O/CuO-decorated TiO2/GO nanocomposites were studied by EPR spectroscopy using two spin traps, DMPO (5,5-dimethyl-1-pyrroline-N-oxide) and CPH (1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine), to highlight the formation of hydroxyl and superoxide reactive oxygen species, respectively. The electrochemical characterization of the NC modified carbon-paste electrodes (CPE) was carried out by CV and DPV. As such, modified carbon-paste electrodes were prepared by mixing carbon paste with copper oxides-decorated TiO2/GO nanocomposites. We have shown that GO reduces the recombination process in TiO2 by immediate electron transfer from excited TiO2 to GO sheets. The results suggest that differences in the PL, respectively, EPR data and electrochemical behavior, are due to the different copper oxides and GO content, presenting new perspectives of materials functionalization.

Gamma Irradiation and Ag and ZnO Nanoparticles Combined Treatment of Cotton Textile Materials.

In this work, cotton textile materials were impregnated by immersion with three different nanocomposites: Ag/chitosan, Ag/polyvinylpyrrolidone, and ZnO/polyvinylpyrrolidone and irradiated with a 60Co gamma source. After the nanoparticles impregnation, the cotton materials were irradiated in a dry and wet state at 5 and 20 kGy radiation doses. The following methods were used for the characterization of the obtained cotton materials to reveal the modification of the textile materials: Fourier transform infrared-attenuated total reflection spectroscopy (FTIR-ATR) and thermogravimetry (TG). The obtained materials have good antibacterial properties. The microbiological tests have shown the best material results for the gamma irradition and Ag nanoparticles combined treatment. The objective was to create a more environmentally friendly approach for textile functionalization by eliminating toxic chemicals-based technology and replacing it with the eco-friendlier gamma technology.

Thermal desorption/gas chromatography/mass spectrometry approach for characterization of the volatile fraction from amber specimens: a possibility of tracking geological origins.

Research on the chemical composition of fossil resins has evolved during the last decades as a multidisciplinary field and is strongly oriented toward the correlation with their geological and botanical origin. Various extraction procedures and chromatographic techniques have been used together for identifying the volatile compounds contained in the fossil resin matrix. Hyphenation between thermal desorption (TD), gas chromatography (GC) and mass spectrometry detection (MS) has been chosen to investigate the volatile compounds fraction from ambers with a focus on Romanite (Romanian amber) and Baltic amber species. A data analysis procedure was developed for the main purpose of fingerprinting ambers based on the MS identity of the peaks generated by the volatile fraction, together with their relative percentual area within the chromatogram. Chromatographic data analysis was based entirely on Automated Mass Spectral Deconvolution &Identification System (AMDIS) software to produce deconvoluted mass spectra which were used to build-up a mixed mass spectra and relative retention scale library. Multivariate data analysis was further applied on AMDIS results with successful discrimination between Romanite and Baltic ambers. A special trial was conducted to generate pyrolysis "like" macromolecular structure breakdown to volatile compounds by gamma irradiation with a high absorbed dose of 500 kGy. Contrary to our expectations the volatile fraction fingerprints were not modified after irradiation experiments. A complementary non-destructive new approach by ESR spectroscopy was also proposed for discriminating between Romanite and Baltic ambers.