PEGylation of Nanosubstrates (Titania) with Multifunctional Reagents: At the Crossroads between Nanoparticles and Nanocomposites

Titania (anatase) nanoparticles were successfully PEGylated through the use of catechol (dopamine)-terminated PEG derivatives. The resulting materials were characterized by excellent stability at neutral pH and extremely low toxicity (phagocytic and nonphagocytic cell lines). In particular, we focused on the comparison between mono- and bis-catechol PEGs. Due to the double terminal anchorage on the titania surface, bis-catechol ligands can produce chains differing from classical monoanchored PEG in conformation (horseshoe-shaped vs brush) and thus the possibility of interactions with biomolecules. At the same time, less than quantitative catechol binding may lead to the presence of dangling chains with unbound catechols which can polymerize and eventually produce PEG/titania nanocomposite colloids. Our results on double-functional PEG2000 show the latter to be the case. Pluronic F127 was also used as a bifunctional ligand, leading to nanocomposite aggregates with an even larger organic content.     

Spectral and thermal studies of thiobarbituric acid complexes

The complexes of 2-thiobarbituric acid with Fe(II), Fe(III), Co(II), Cu(II), Zn(II) and Cd(II) have been isolated and characterized on the basis of elemental analyses, molar conductance, magnetic moment and spectral studies. The thermal decomposition of the metal complexes was studied by TG and DTA techniques. The kinetic parameters namely, activation energy, entropy of activation and the reaction orders were estimated.     

Structural and morphological consequences of high-temperature treatments of hydroxyapatite in the absence or presence of HCl vapor

Hydroxyapatite [HAP; Ca5(PO4)3(OH)], a biocompatible, osteoconductive material, was perceived, in the present investigation, to mimic a healthy bone mineral. Structural and morphological properties of its bulk and surface were examined versus high-temperature (up to 900 degrees C) thermal treatments in air or wet HCl gas atmosphere, using thermogravimetry, X-ray powder diffractometry, N2 sorptiometry, scanning electron microscopy, X-ray energy dispersive spectroscopy, and ex- and in situ infrared spectroscopy. CO, CDCl3, and methylbutynol were used as infrared probe molecules. Results obtained revealed that, in the absence of HCl, the bulk crystalline structure and the chemical composition of HAP were stable during high-temperature treatments. The surface exposed isolated Lewis acid sites (Ca2+) and reactive base sites (O(x-) and/or OH-) that chemisorbed atmospheric CO2 molecules with the formation of surface carbonate species (CaCO3). It is assumed that surface OH groups may interact with atmospheric oxygen molecules, leading to the formation and incorporation of peroxide (O2(2-) species. In the atmosphere of wet HCl, HAP was shown to suffer loss of chemical integrity, facilitated by its carbonated domains, as well as disintegration (or erosion) of particle aggregates and creation of what appeared to be deep groves.     

Application of 8-hydroxyquinoline-5-sulfonic acid in the spectrophotometric determination of some lanthanides

A simple, sensitive, and selective spectrophotometric method for the determination of trivalent praseodymium, neodymium, samarium, gadolinium, dysprosium, and erbium ions with 8-hydroxyquinoline-5-sulfonic acid is described. The optimum conditions for determination of down to 10.0 μg/ml of lanthanide ion are reported. The proposed method shows an average recovery of 99.9% with standard deviation not exceeding 0.1%. The metal-ligand ratio and stability constant of the chelates are determined.     

Fluorinated hydrazonoyl chlorides as precursors for synthesis of antimicrobial azoles

Hydrazonoyl halides have been known for their ability to react with different reagents to afford wide range of bioactive heterocyclic systems as thiazoles and imidazopyrazoles. This research work focused on the synthesis of two new fluorinated hydrazonoyl chlorides and used them in synthesis of novel series of thiazole derivatives and two imidazopyrazole systems. The mechanistic pathways and the structures of all synthesized derivatives were discussed and assured based on the available spectral data. The results of antimicrobial activity of the tested thiazoles and imidazopyrazoles showed that some derivatives have moderate to no activity against tested fungi and bacteria strains. Only one derivative namely 2-(2-(3-fluoro-4-methylphenyl)hydrazono)-7-(2-oxoindolin-3-ylidene)-2,7-dihydro-3H-imidazo[1,2-b]pyrazole-3,6(5H)-dione is the most active against Candida albicans (CA) with IZD = 20 mm, which was equipotent to ketoconazole. Furthermore, docking simulation was carried out to predict the binding pattern of the new compounds in the ATP binding site of the DNA gyrase B enzyme. The results of the docking simulation revealed that compounds 9a-e , 12 , and 13a,b fit well in the ATP binding site of DNA gyrase B with docking score values ranging from −5.883 to −6.833 kcal/mol.     

Preparation and characterization of polyaniline/manganese dioxide composites and their catalytic activity

This paper is devoted to the preparation of polyaniline/MnO2 (PANI/MnO2) composites via chemical oxidation of aniline in H2SO4 medium using beta-MnO2 as an oxidant. The parameters affecting the polymerization reaction are considered. These parameters are [aniline], amount of beta-MnO2, stirring time, and polymerization temperature. SEM, FT-IR, XRD, and TGA techniques are used to characterize the resulting composites. XRD measurements reveal the distortion of the crystal structure of beta-MnO2 after the polymerization reaction. Thus, the XRD pattern of PANI is predominating. The crystalline composites are obtained using higher molar ratio of [Ox]/[ANI] and at higher temperature. Increasing the amount of beta-MnO2 led to an increase in the acidic character of the obtained composites due to adsorption of excess H+ on the oxide surface. The thermal stability of the composites decreased with increasing both [aniline] and stirring time, while it increased with increasing amount of beta-MnO2. The applications of the composites in the oxidative degradation of Direct Red 81, Acid Blue 92, and Indigo Carmine dyes exhibited good catalytic activity in the presence of H2O2 as an oxidant. The reactions followed first-order kinetics and the rate constants were determined. The degradation reaction involved the catalytic action of the PANI counterpart of the composite toward H2O2 decomposition, which can lead to the generation of HO radicals as a highly efficient oxidant attacking the target dyes. The detailed kinetic studies and the mechanism of these catalytic reactions are under consideration in our group.     

Development of a single-run liquid chromatography-mass spectrometry analysis for the detection of 11 multiclass contaminants of emerging concern using a direct filtration method

In toxicological analysis, the analytical validation method is important to assess the exact risk of contaminants of emerging concern in the environment. Syringe filters are mainly used to remove impurities from sample solutions. However, the loss of analyte to the syringe filter could be considerable, causing an underestimate of the analyte concentrations. The current study develops and validates simultaneous liquid chromatography-mass spectrometry analysis using a direct filtration method to detect four groups of contaminants of emerging concern. The adsorption of the analyte onto three different matrices and six types of syringe filters is reported. The lowest adsorption of analytes was observed in methanol (16.72%), followed by deionized water (48.19%) and filtered surface lake water (48.94%). Irrespective of the type of the matrices, the lowest average adsorption by the syringe filter was observed in the 0.45 μm polypropylene membrane (15.15%), followed by the 0.20 μm polypropylene membrane (16.10%), the 0.20 μm regenerated cellulose (16.15%), the 0.20 μm polytetrafluoroethylene membrane (47.38%), the 0.45 μm nylon membrane (64.87%) and the 0.20 μm nylon membrane (71.30%). In conclusion, the recommended syringe filter membranes for contaminants of emerging concern analysis are polypropylene membranes and regenerated cellulose, regardless of the matrix used.