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Issue 122, 2015
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Morphological evolution of noble metal nanoparticles in chloroform: mechanism of switching on/off by protic species

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Abstract

The morphological stability/morphological reshaping of noble metal nanoparticles are studied experimentally in order to unravel the chemical mechanisms lying beneath. Gold and silver nanoparticles (AuNPs and AgNPs, respectively) formed in a chloroformic environment are used, as model synthetic systems, to study the phenomena of morphological change. The morphological evolution of NPs that follows their formation, is characterized by spectroscopy (UV-visible, Raman and FTIR) and TEM (Transmission Electron Microscopy). The change of NP morphology involves the increase of the average NP size and the broadening of size distribution, in a close resemblance with the effect characteristically obtained from the Ostwald ripening. The effect of the poor solvating properties of chloroform in stabilizing small charged species (H+, Ag+, Au+) as well as the principle of electroneutrality of matter are analyzed in order to formulate a feasible reaction scheme consisting of a three-step process: the generation of soluble intermediary species by corrosion of nanoparticles, the diffusion of intermediary species from one nanoparticle to another, and the re-deposition process involving the reduction of intermediary species. This basic reaction scheme is used as a hypothesis to plan and perform experiments, which reveal that molecular oxygen dissolved in the dispersive medium can drive NP corrosion, however, protic species are also required as co-reactants. The polarity of the hydrogen bond and the ligand properties of the anions produced by de-protonation are features of the protic species that enable/disable corrosion and, in turn, the NP morphological evolution.

Graphical abstract: Morphological evolution of noble metal nanoparticles in chloroform: mechanism of switching on/off by protic species

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Publication details

The article was received on 29 Aug 2015, accepted on 11 Nov 2015 and first published on 13 Nov 2015


Article type: Paper
DOI: 10.1039/C5RA17529A
Citation: RSC Adv., 2015,5, 100488-100497
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    Morphological evolution of noble metal nanoparticles in chloroform: mechanism of switching on/off by protic species

    O. A. Douglas-Gallardo, C. G. Gomez, M. A. Macchione, F. P. Cometto, E. A. Coronado, V. A. Macagno and M. A. Pérez, RSC Adv., 2015, 5, 100488
    DOI: 10.1039/C5RA17529A

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