Bolaamphiphile Surfactants as Nanoparticle Stabilizers: Application to Reversible Aggregation of Gold Nanoparticles

摘要

Development of processes to render inorganic nanoparticles (NPs) dispersible and stable in water has received considerable attention in the past decade, the final nanoma-terial having many applications in catalysis, material science, biology, and so forth. Surface chemical modification of the NPs is a popular example of such processes. For metal NPs, bifunctional molecules bearing a polar group and an anchoring function (e.g., thiol) on the NPs are highly used to get water-soluble NPs. But this chemical modification often modifies the properties or even totally passivates the final material. Adsorption of polymers on the NPs surface is another interesting way to stabilize NPs. However, the slow dynamics of polymers can strongly increase the time of its organization at the surface of the particle and makes it sometimes irreversible. The thick final polymer layer around the NPs could also be a strong limitation for many applications. Adsorption of surfactants on NPs is a third simple strategy which avoids the previous difficulties and is often used in organic solvent to get well-defined but hydrophobic NPs. In water, a few examples of stabilization have been also described. In that case, the surfactant adopts interdigi-tated or vesicle-like structures on the NP surface. This last architecture is maintained by alkyl tail interactions and is therefore relatively weak and quite difficult to obtain. To Figure 1. Chemical structure of the bolaamphiphiles used in this work (with n = 10, 12, 14, 16, and 20).