NOPR Collection:

Sodium polystyrene sulfonate template assisted hydrothermal synthesis of hydroxyapatite nanorods

Thu, 01 Sep 2016 00:00:00 GMT

Title: Sodium polystyrene sulfonate template assisted hydrothermal synthesis of hydroxyapatite nanorods Authors: Chaopanich, Pakvipar; Siriphannon, Punnama Abstract: Hydroxyapatite nanoparticles (nHAp) have been synthesized by benign hydrothermal reaction from the aqueous mixture of Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄ solutions in the presence of non-toxic sodium polystyrene sulfonate (PSS) template. The pH of starting precursors has been adjusted to 10.5 before hydrothermal treatment at 100°C for 1, 2 and 3 h. The added PSS template generates the largely negative surface of dicalcium phosphate dihydrate (DCPD) precursor, resulting in minimization of precursor agglomeration and promoting the hydrothermal growth of nHAp along preferential c-axis as rod-shaped crystals. The crystallite sizes along 002-plane of nHAp synthesized with and without PSS template are 47.1 and 29.5 nm, respectively. With longer hydrothermal treatment time, larger crystallite size of nHAp is obtained. In vitro cytotoxicity of the synthesized nHAp has been evaluated by MTT assay using African green monkey kidney fibroblast cells, in which the nHAp exhibits low cytotoxicity. Antibacterial activities of the synthesized nHAp against S.aureus and E.coli have been tested. Due to the presence of largely negative surface, the nHAp could inhibit only the gram-positive S.aureus, creating a clear zone of about 9.5 mm. Page(s): 1084-1089

Intermolecular interactions in sulfuric acid-water system

Thu, 01 Sep 2016 00:00:00 GMT

Title: Intermolecular interactions in sulfuric acid-water system Authors: Loshali, Renu; Kandpal, Narain D Abstract: Viscosity (ƞ) and density (ρ) of aqueous concentrated sulfuric acid (1.0–9.0) mol dm⁻³ have been measured at 297.65 K and the values of A and B- coefficients of Jones-Dole equation have been calculated from the viscosity data. The value of B-coefficient is positive which suggests a strong ion-solvent interaction in aqueous sulfuric acid. It is assumed that in concentrated aqueous sulfuric acid, HSO₅^3- acts as structure maker. Three concentration regions of sulfuric acid having value of B-coefficient (measure of ion-solvent interaction or structure making capacity) in the order 1.0–4.0 mol dm⁻³ < 4.0–7.0 mol dm⁻³ < 7.0–9.0 mol dm⁻³ have been proposed. Page(s): 1080-1083

Kinetics and mechanism of electron transfer reaction: Oxidation of sulfanilic acid by hexachloroiridate(IV) in acid medium

Thu, 01 Sep 2016 00:00:00 GMT

Title: Kinetics and mechanism of electron transfer reaction: Oxidation of sulfanilic acid by hexachloroiridate(IV) in acid medium Authors: Sailani, Riya; Pareek, Deepmala; Meena, Anita; Jangid, Kritika; Khandelwal, Chandra L Abstract: The kinetics of oxidation of sulfanilic acid by [IrCl₆]^2- in acid medium has been studied. The reaction is overall second order being first order with respect to each reactant. However, rate is retarded by hydrogen ion concentration. Various proposals have been suggested on the basis of reactivity of Ir(IV) species. The activation parameters such as energy and entropy of activation calculated by Eyring equation are found to be 59.99±0.93 kJ mol^-1 and -106.44±2.2 J K^-1 mol^-1 respectively. The oxidation product, 2-keto-azoxy- benzene-4,4′-disulfonic acid has been confirmed spectrally. Page(s): 1074-1079

Kinetics and mechanism of oxidation of thiourea by Waugh-type enneamolybdomanganate(IV) in aqueous perchloric acid

Thu, 01 Sep 2016 00:00:00 GMT

Title: Kinetics and mechanism of oxidation of thiourea by Waugh-type enneamolybdomanganate(IV) in aqueous perchloric acid Authors: More, Shekhar S; Gokavi, Gavisiddappa S Abstract: The Waugh-type polyoxometalate, enneamolybdomanganate (IV), oxidizes thiourea in aqueous perchloric acid, to give formamidine disulphide as confirmed by HRMS spectra. The rate of reaction increases linearly as hydrogen ion and thiourea concentrations increase, while it remains constant as the concentration of oxidant, enneamolybdomanganate(IV), is varied. The protonated form of the oxidant and the unprotonated form of thiourea were found to be active species of the reaction. The protonation and the interaction of thiourea with the oxidant have been supported by UV-vis spectral studies. The reaction is found to be initiated by nucleophilic attack of unprotonated thiourea on the protons attached to the oxygen atoms directly bound to the Mn(IV) centre. The interaction between the thiourea and the oxidant to form a precursor complex has been verified spectrophotometrically. The proposed mechanism, in accordance with the kinetic results obtained, involves formation of a precursor complex between thiourea and oxidant which decomposes in a slow step. The corresponding sulfenic acid is the intermediate formed due to the decomposition of the complex which reacts with another thiourea molecule giving the final product. The rate law derived as per the proposed mechanism is also verified kinetically. The results of effects of ionic strength, solvent polarity and the temperature also support the proposed mechanism. Page(s): 1068-1073