Tunable Self-Assembly of YF Nanoparticles by Citrate-Mediated Ionic Bridges
Martínez-Esaín, Jordi (Universitat Autònoma de Barcelona. Departament de Química)
Faraudo, Jordi (Institut de Ciència de Materials de Barcelona)
Puig i Molina, Mª Teresa (Institut de Ciència de Materials de Barcelona)
Obradors, Xavier (Institut de Ciència de Materials de Barcelona)
Ros i Badosa, Josep (Universitat Autònoma de Barcelona. Departament de Química)
Ricart, Susagna (Institut de Ciència de Materials de Barcelona)
Yáñez López, Ramón (Universitat Autònoma de Barcelona. Departament de Química)
Institut de Ciència de Materials de Barcelona

Date:	2018
Abstract:	Ligand-to-surface interactions are critical factors in surface and interface chemistry to control the mechanisms governing nanostructured colloidal suspensions. In particular, molecules containing carboxylate moieties (such as citrate anions) have been extensively investigated to stabilize metal, metal oxide, and metal fluoride nanoparticles. Using YF nanoparticles as a model system, we show here the self-assembly of citrate-stabilized nanostructures (supraparticles) with a size tunable by temperature. Results from several experimental techniques and molecular dynamics simulations show that the self-assembly of nanoparticles into supraparticles is due to ionic bridges between different nanoparticles. These interactions were caused by cations (e. g. , ammonium) strongly adsorbed onto the nanoparticle surface that also interact strongly with nonbonded citrate anions, creating ionic bridges in solution between nanoparticles. Experimentally, we observe self-assembly of nanoparticles into supraparticles at 25 and 100 °C. Interestingly, at high temperatures (100 °C), this citrate-bridge self-assembly mechanism is more efficient, giving rise to larger supraparticles. At low temperatures (5 °C), this mechanism is not observed, and nanoparticles remain stable. Molecular dynamics simulations show that the free energy of a single citrate bridge between nanoparticles in solution is much larger than the thermal energy and in fact is much larger than typical adsorption free energies of ions on colloids. Summarizing our experiments and simulations, we identify as key aspects of the self-assembly mechanism the requirement of NPs with a surface able to adsorb anions and cations and the presence of multidentate ions in solution. This indicates that this new ion-mediated self-assembly mechanism is not specific of YF and citrate anions, as supported by preliminary experimental results in other systems.
Grants:	Ministerio de Economía y Competitividad SEV-2015-0496 Ministerio de Economía y Competitividad MAT2015-68994-REDC Ministerio de Economía y Competitividad MAT2014-51778-C2-1-R Ministerio de Economía y Competitividad RTC-2015-3640-3 European Commission 280432 European Commission 669504 Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-753
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Published in:	Journal of the American Chemical Society, Vol. 140, Issue 6 (February 2018) , p. 2127-2134, ISSN 1520-5126

DOI: 10.1021/jacs.7b09821
PMID: 29308645

8 p, 6.0 MB

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