Patchy and Janus Nanoparticles by Self-Organization of Mixtures of Fluorinated and Hydrogenated Alkanethiolates on the Surface of a Gold Core

Abstract

The spontaneous self-organization of dissimilar ligands on the surface of metal nanoparticles is a very appealing approach to obtain anisotropic "spherical" systems. In addition to differences in ligand length and end groups, a further thermodynamic driving force to control the self-assembled monolayer organization may become available if the ligands are inherently immiscible, as is the case of hydrogenated (H-) and fluorinated (F-) species. Here, we validate the viability of this approach by combining F NMR experiments and multiscale molecular simulations on large sets of mixed-monolayer-protected gold nanoparticles (NPs). The phase segregation of blends of F- and H-thiolates grafted on the surface of gold NPs allows a straightforward approach to patterned mixed monolayers, with the shapes of the monolayer domains being encoded in the structure of the F/H-thiolate ligands. The results obtained from this comprehensive study offer molecular design rules to achieve a precise control of inorganic nanoparticles protected by specifically patterned monolayers.

Fluorinated and Charged Hydrogenated Alkanethiolates Grafted on Gold: Expanding the Diversity of Mixed-Monolayer Nanoparticles for Biological Applications

“…15,38 A synoptic view of the solubility properties of NP-MDDS/ F6-b, NP-MDA/F6-c, and NP-TMDA/F6-c is presented in Figure 2A. The relation between the composition of the H-and F-ligands used in the NPs synthesis and the composition of the resulting mixed monolayer can be conveniently analyzed by plotting the final molar fraction of the F-component in the monolayer against the molar fraction of the fluorinated ligand in the reaction mixture ( Figure 2B).…”

“…In particular, in order to favor the solubility in aqueous media the F-thiol length has to be shorter than that of H-thiols but presenting at least six Fmethylene groups in order to exploit the lipophobicity properties for the monolayer organization. 15 These NPs systems display good solubility in polar media, including water. Their toxicity and internalization pathway were preliminarily assessed on HeLa cells.…”

Quantified Binding Scale of Competing Ligands at the Surface of Gold Nanoparticles: The Role of Entropy and Intermolecular Forces

“…Various methods can unveil the composition of biligand shells, such as mass spectrometries, [20,21] electron paramagnetic resonance, [22] fluorescence, [4,23] and surface enhanced Raman spectroscopies. [24] Liquid state Nuclear Magnetic Resonance (NMR) is also a versatile tool to quantify the ligand shell composition for a range of molecules and inorganic cores, [25][26][27][28][29] to study the ligand surface distribution, [25,[29][30][31][32] and the exchange dynamics. [33][34][35][36] Among these state-of-the art studies, only a few correlate together the shell and medium compositions at the steady state [24,26,37] or during the exchange process.…”

Mixed Fluorinated/Hydrogenated Self‐Assembled Monolayer‐Protected Gold Nanoparticles: In Silico and In Vitro Behavior

“…Scanning tunneling microscopy (STM) is only applicable to relatively short ligands (<14 atoms) . NMR could be employed in principle to probe surface domains but depends on the availability of signals sensible to changes in the monolayer composition/morphology and suitable for NMR analysis that are lacking. Matrix‐assisted laser desorption/ionization mass analysis (MALDI‐MS) could also distinguish different surface organizations of immiscible thiolate ligands, but only if they desorb with equal probability, which is not necessarily the case, particularly in presence of fluorinated ligands, as we have also observed .…”

“…Finally, another alternative, small angle neutron scattering (SANS), is limited to nanoparticle samples with very narrow size dispersity, not achievable for C8TEG/F8PEG‐modified AuNPs with our current synthetic methodologies. This left an in silico approach as the only viable method currently available to directly characterize this type of monolayer self‐organization, given also it has already been successful in predicting phase segregation of several mixtures of immiscible thiols at molecular level …”