Gold nanoparticles protected by mixed hydrogenated/fluorinated monolayers: controlling and exploring the surface features
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Harnessing the reciprocal phobicity of hydrogenated and fluorinated thiolates proved to be a valuable strategy in preparing gold nanoparticles displaying mixed monolayers with a well-defined and pre-determined morphology. Our studies display that the organisation of the fluorinated ligands in phase-separated domains takes place even when these represent a small fraction of the ligands grafted on the gold surface. Using simple model ligands and by combining 19F NMR or ESR spectroscopies, and multiscale molecular simulations, we could demonstrate how the monolayer morphology responds in a predictable manner to structural differences between the thiolates. This enables a straightforward preparation of gold nanoparticles with monolayers displaying stripe-like, Janus, patchy, and random morphologies. Additionally, solubility properties may be tuned as function of the nature of the ligands and of the monolayer morphology obtaining gold nanoparticles soluble in organic solvents or in aqueous solutions. Most importantly, this rich diversity can be achieved not by resorting to ad hoc developed fabrication techniques, but rather relying on the spontaneous self-sorting of the ligands upon assembly on the nanoparticle surface. Besides enabling control over the monolayer morphology, fluorinated ligands endow the nanoparticles with several properties that can be exploited in the development of novel materials with applications, for instance in drug delivery and diagnostic imaging.
KeywordsGold nanoparticles Self-assembly Fluorinated thiolates Monolayer morphology Phase segregation Janus nanoparticles
We also wish to thank all the collaborators of our group that with their enthusiasm and hard research work contributed to the results cited here: Paolo Ronchese, Elena Pellizzoni and Stefano Valente and the collaborators of other research groups/institutions; Marco Lucarini and his research group at the University of Bologna; Maurizio Fermeglia, Sabrina Pricl and Paola Posocco of the MOSE lab at the University of Trieste; Francesco Stellacci and Silke Krol and their research groups in Milano; Stefano Polizzi and the electron microscopy group of the University of Venezia; Petra Rudolf and her group of the University of Gröningen; Paolo Scrimin of the University of Padova for the support and the very helpful discussions and Fabrizio Mancin, University of Padova, for several analyses and the continuous fruitful discussions. We are very grateful to Claudio Gamboz and Paolo Bertoncin of the Electron Microscopy facilities lab of the University of Trieste for TEM images and Chiara Schmid, DIA, University of Trieste for TGA measurements.
This research received support from the University of Trieste (FRA 2015, FRA 2016).
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Conflict of interest
The authors declare that they have no conflict of interest.
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