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Abstract  

The complex formation of uranium(VI) with salicylhydroxamic, benzohydroxamic, and benzoic acid was investigated by time-resolved laser-induced fluorescence spectroscopy (TRLFS). We observed in all three systems a decrease in the fluorescence intensity with increasing ligand concentration. All identified complexed uranyl species are of the type MpLqHr. In the uranium(VI)-salicylhydroxamate system a 1: 1 complex with a stability constant of log β 111 = 17.34±0.06 and a 1: 2 complex with a stability constant of log β 122 = 35.0±0.11 was identified. Also in the uranium(VI)-benzohydroxamate system the stability constants are determined to be log β 110 = 7.92±0.11 and log β 120 = 16.88±0.49. In the uranium(VI)-benzoate system only a 1: 1 complex is existent with a stability constant of log β 110 = 3.56±0.05.

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Journal of Thermal Analysis and Calorimetry
Authors: S. Papp, L. Kőrösi, B. Gool, T. Dederichs, P. Mela, M. Möller, and I. Dékány

Abstract  

Gold nanoparticles (Au NPs) were prepared by the reduction of HAuCl4 acid incorporated into the polar core of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer micelles dissolved in toluene. The formation of Au NPs was controlled using three reducing agents with different strengths: hydrazine (HA), triethylsilane (TES), and potassium triethylborohydride (PTB). The formation of Au NPs was followed by transmission electron microscopy, UV–Vis spectroscopy, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). It was found that the strength of the reducing agent determined both the size and the rate of formation of the Au NPs. The average diameters of the Au NPs prepared by reduction with HA, TES, and PTB were 1.7, 2.6, and 8 nm, respectively. The reduction of Au(III) was rapid with HA and PTB. TES proved to be a mild reducing agent for the synthesis of Au NPs. DLS measurements demonstrated swelling of the PS-b-P2VP micelles due to the incorporation of HAuCl4 and the reducing agents. The original micellar structure rearranged during the reduction with PTB. ITC measurements revealed that some chemical reactions besides Au NPs formation also occurred in the course of the reduction process. The enthalpy of formation of Au NPs in PS-b-P2VP micelles reduced by HA was determined.

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