2012/12/16 by Dmitry V. Matyushov, Matyushov, Dmitry V.
Chemistry · Engineering · #Electrostatics and Colloid Interactions #Microfluidic and Bio-sensing Technologies #Nanopore and Nanochannel Transport Studies
paper · pdf · doi:10.48550/arxiv.1212.3856
Polarization of the interface, spontaneously occurring when water is in\ncontact with hydrophobic solutes or air, couples with the uniform external\nfield to produce a non-zero force acting on a suspended particle. This force\nexists even in the absence of a net particle charge, and its direction is\naffected by the first-order, dipolar and the second-order, qudrupolar\norientational order parameters of the interfacial water. The quadrupolar\npolarization gives rise to an effectively negative charge. The corresponding\nsurface charge density is inversely proportional to the area of the shear\nsurface. As a result, the overall contribution from the quadrupolar\npolarization to the particle mobility becomes negligible compared to\nexperimentally reported values for particles exceeding a few nanometers in\nsize. The dipolar order of the interface dominates the zero-charge mobility of\nsub-micron particles. The corresponding electrokinetic charge is determined by\nthe preferential orientation of interfacial dipoles relative to the surface\nnormal.\n