(316f) Optical Control of Nanoparticle Solvation and Mobility
AIChE Annual Meeting
2014
2014 AIChE Annual Meeting
Engineering Sciences and Fundamentals
Colloidal Hydrodynamics I: Soft and Active Systems
Tuesday, November 18, 2014 - 1:45pm to 2:00pm
The structuring of solvent about macromolecules and nanoparticles underlies a wide range of equilibrium and dynamic phenomena, including the hydrodynamic drag experienced when a colloidal species moves by Brownian diffusion through a solvent. We have measured the mobilities of surface-functionalized gold nanoparticles dispersed in an isotropic oil of 4-n-pentyl-4’-cyanobiphenyl to decrease upon illumination with white light when the temperature of the solvent is within 8¢ªC of a bulk phase transition from an isotropic oil to a nematic phase. Within this temperature interval, single-particle optical tracking using band-pass filters revealed that the hydrodynamic diameter of the nanoparticles in the oil increased by up to 40 nm in a wavelength-specific and nanoparticle size-dependent manner. Experiments designed to test several hypotheses regarding the origin of the effect, including the effects of optical pressures, surface plasmon resonances and hot electrons, support the proposal that an ordered solvent corona is induced by optically-excited interfacial electric fields. The change in solvation of the particles can be tuned reversibly by the choice of wavelength of the illuminating light. These results define new principles for optical manipulation of the mobility of nanoparticles.