AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Evaluating the Mobility of Nanorods in Electric Fields
MINGDONG LI, Rian You, George Mulholland, Michael Zachariah, University of Maryland
Abstract Number: 60 Working Group: Aerosol Physics
Abstract The mobility of a nonspherical particle is a function of both particle shape and orientation. In turn the higher magnitude of electric field causes nonspherical particles to align more along the field direction, increasing their mobility or decreasing their mobility diameter. In our previous works, we developed a general theory for the orientation-averaged mobility and the dynamic shape factor applicable to any axially symmetric particles in an electric field, and applied it to the specific cases of nanowires and doublets of spheres. The experimental results of doublets of NIST traceable size standard PSL particles with primary spheres larger than 127nm were shown to be in excellent agreement with the expected values based on our theory. In this work, the theory for a nanowire is compared with experimental results of gold nanorods with known shape determined by TEM images. We compare the experimental measured mobility sizes with the theoretical predicted mobility in the continuum, free molecular, and the transition regime. The mobility size shift trends in the electric fields based on our model, expressed both in the free molecular regime and in the transition regime, show in good agreement with the experimental results. For rods of dimension: width dr=17 nm and length Lr=270 nm, where one length scale is smaller than the mean free path and one larger, the results clearly shows that the mobility of an object is most controlled by the smallest dimension. In this case the free molecule transport properties best represented our nanorod. The net charge effect on the particle alignment was also evaluated and indicated for a conducting particle, that while the electrophoretic velocity is net charge dependent, the actual orientation of the particle is not.