1212.3856 (Dmitry V. Matyushov)

Electrophoretic mobility without charge driven by quadrupolar
polarization of the nanoparticle/water interface    [PDF]

Dmitry V. Matyushov

Quadrupolar polarization of the interfacial water layer, typically found for water at contact with hydrophobic solutes, couples with the uniform external field to produce the force acting on a suspended particle. This force exists even in the absence of a net particle charge and its direction is consistent with an effectively negative surface charge. The surface charge density scales as $R^{-2}$ with the particle radius $R$, and the corresponding contribution to the $\zeta$-potential scales as $R^{-1}$. The charge density and $\zeta$-potential are consistent with the values typically reported for oil drops and bubbles in water at $R\simeq 3-10$ nm, but decay below those values for larger particles. The study indicates that electrophoretic mobility without charge is possible, but is limited to relatively small particles a few nanometers in size.

View original: http://arxiv.org/abs/1212.3856