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- Csendes, Z., et al.
(author)
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Synthesis, structural characterisation, and catalytic activity of Mn(II)-protected amino acid complexes covalently immobilised on chloropropylated silica gel
- 2015
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In: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 241, s. 264-269
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Journal article (peer-reviewed)abstract
- In this work the syntheses, structure, superoxide dismutase (SOD) activity and the catalytic use in the oxidative transformations of cyclohexene of covalently grafted Mn(II)-complexes formed with various C-protected amino acid (L-histidine, L-cysteine and L-cystine) ligands are presented. The structural features of the surface complexes were studied by EPR, X-ray absorption, and mid/far IR spectroscopies. The superoxide dismutase activities of the materials were determined in a biochemical test reaction. The obtained materials were used as catalysts for the oxidation of cyclohexene with peracetic acid in acetone. Covalent grafting and building the complex onto the surface of the chloropropylated silica gel were successful in all cases. It was found that in many instances the structures obtained and the coordinating groups substantially varied upon changing the conditions of the syntheses. All the covalently immobilised Mn(II)-complexes displayed superoxide dismutase activity and could catalyse the oxidation of cyclohexene. (C) 2014 Elsevier B.V. All rights reserved.
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| 4. |
- Kohut, A., et al.
(author)
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From plasma to nanoparticles : Optical and particle emission of a spark discharge generator
- 2017
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 28:47
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Journal article (peer-reviewed)abstract
- The increased demand for high purity nanoparticles (NPs) of defined geometry necessitates the continuous development of generation routes. One of the most promising physical techniques for producing metal, semiconductor or alloy NPs in the gas phase is spark discharge NP generation. The technique has a great potential for up-scaling without altering the particles. Despite the simplicity of the setup, the formation of NPs in a spark discharge takes place via complex multi-scale processes, which greatly hinders the investigation via conventional NP measurement techniques. In the present work, time-resolved optical emission spectroscopy (OES) was used to provide information on the species present in the spark from as early as approximately 100 ns after the initiation of the discharge. We demonstrate that operando emission spectroscopy can deliver valuable insights into NP formation. The emission spectra of the spark are used to identify, among others, the main stages of material erosion and to calculate the quenching rate of the generated metal vapour. We demonstrate that the alteration of key control parameters, that are typically used to optimize NP generation, clearly affect the emission spectra. We report for Cu and Au NPs that the intensity of spectral lines emitted by metal atoms levels off when spark energy is increased above an energy threshold, suggesting that the maximum concentration of metal vapour produced in the generator is limited. This explains the size variation of the generated NPs. We report a strong correlation between the optical and particle emission of the spark discharge generator, which demonstrate the suitability of OES as a valuable characterization tool that will allow for the more deliberate optimization of spark-based NP generation.
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