title: Magnetically-responsive electrophoretic silica organosols.
abstract: OBJECTIVE
  Silica nanoparticles can be dispersed in organic solvents (organosols) using surfactants, such as didodecyldimethylammonium bromide (DDAB). DDAB analogs prepared with lathanide tetrahalide counterions, either a high-magnetic moment ion (HoCl3Br, DDAH) or low-magnetic moment one (NdCl3Br, DDAN), are expected to produce charged particles, but only DDAH-stabilized dispersions are expected to be magnetically responsive.
  
  
  METHODS
  Phase-analysis light scattering (PALS) measurements have been performed to determine the charge on DDAH- and DDAN-stabilized organosols. Magnetic sedimentation experiments have been performed to determine whether or not the silica dispersions are magnetically responsive. Sedimentation was monitored both by visual observations and UV-vis spectroscopy.
  
  
  RESULTS
  Both DDAH and DDAN organosols are negatively charged, the same as DDAB-stabilized nanoparticles. The DDAH-stabilized nanoparticles are found to respond to a magnetic field, whereas the DDAN-stabilized nanoparticles do not. This opens up possibilities for creating nanoparticle dispersions in nonpolar solvents which can be tailored to respond to desired external stimuli.
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Smith
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK. Electronic address: julian.eastoe@bristol.ac.uk.
authors.forename: Julian
authors.initials: J
authors.lastname: Eastoe
keywords: Electrophoresis; Magnetophoresis; Nanoparticle dispersions; Nonpolar solvents; Organosols