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Entropy‐Driven Reversible Agglomeration of Crown Ether Capped Gold Nanoparticles
Author(s) -
Hill Alexander P.,
KunstmannOlsen Casper,
Grzelczak Marcin P.,
Brust Mathias
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201705820
Subject(s) - endothermic process , crown ether , dynamic light scattering , zeta potential , aqueous solution , colloidal gold , chemistry , nanoparticle , moiety , economies of agglomeration , colloid , chemical physics , spectroscopy , agglomerate , adsorption , chemical engineering , materials science , nanotechnology , ion , organic chemistry , physics , quantum mechanics , engineering
It is shown that plasmonic gold nanoparticles functionalised with a thiolated 18‐crown‐6 ligand shell agglomerate spontaneously from aqueous dispersion at elevated temperatures. This process takes place over a narrow temperature range, is accompanied by a colour change from red to purple‐blue and is fully reversible. Moreover, the temperature at which it occurs can be adjusted by the degree of complexation of the crown ether moiety with appropriate cations. More complexation leads to higher transition temperatures. The process has been studied by UV/Vis spectroscopy, electron microscopy, dynamic light scattering and zeta potential measurements. A thermodynamic rationale is provided to suggest an entropy‐driven endothermic agglomeration process based on attractive hydrophobic interactions of the complexed crowns that are competing against electrostatic repulsion of the charged ligand shells.