Self-organization of mixtures of fluorocarbon and hydrocarbon amphiphilic thiolates on the surface of gold nanoparticles.
Self-assembled monolayers composed of a mixture of thiolate molecules, featuring hydrocarbon or perfluorocarbon chains (H- and F-chains) terminating with a short poly(oxoethylene) (PEG) moiety, are the most extreme example of surfactant immiscibility on gold nanoparticles reported so far. The phase segregation between H-chains and F-chains and the consequent, peculiar folding of PEG chains are responsible for the increased affinity of a selected radical probe for the fluorinated region, which increases as the size of the fluorinated domains decrease, independently of the shape of such domains. This feature has been revealed by ESR measurements and an in silico innovative multiscale molecular simulations approach in explicit water. Our results reveal an underlying mechanism of a transmission of the organization of the monolayer from the inner region close to the gold surface toward the external hydrophilic PEG region. Moreover, this study definitively proves that a mixed monolayer is a complex system with properties markedly different from those characterizing the parent homoligand monolayers.
Molecular Simulation Engineering Laboratory (MOSE), DI3, University of Trieste, 34127 Trieste, Italy.
Paola
P
Posocco
Cristina
C
Gentilini
Silvia
S
Bidoggia
Alice
A
Pace
Paola
P
Franchi
Marco
M
Lucarini
Maurizio
M
Fermeglia
Sabrina
S
Pricl
Lucia
L
Pasquato
D003460:Crystallization / Q000379:methods*; D005466:Fluorocarbons / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
D005466:Fluorocarbons; D046911:Macromolecular Substances; D013438:Sulfhydryl Compounds; D011092:Polyethylene Glycols; D006046:Gold