Amphiphilic Nanoparticles As Electromagnetically Responsive Surfactants

We describe the development of a class of field-responsive surfactants based on the amphiphilic surface functionalization of inorganic nanoparticles.  Such particles combined with two competing ligands – one hydrophobic, the other hydrophilic – organize spontaneously at the oil-water interface to form amphiphilic supramolecular surfactants.  By using different types of particle cores and surface chemistries, we prepare amphiphilic particles that respond to electromagnetic, magnetic, and electric fields.  Electromagnetically responsive surfactants based on plasmonic cores enable the light-induced modification of the interfacial tension and viscosity through plasmonic heating.  Magnetically responsive surfactants based on single domain, magnetic cores allow for dynamic control over the interfacial tension through the field-induced rotation of the amphiphic particles via their magnetic moments.  Finally, anionic and cationic particle surfactants are prepared using postive and negatively charged ligands and respond to both static and time-varying electric fields.