title: Short-time dynamics of monomers and dimers in quasi-two-dimensional colloidal mixtures.
abstract: We report on the short-time dynamics in colloidal mixtures made up of monomers and dimers highly confined between two glass plates. At low concentrations, the experimental measurements of colloidal motion agree well with the solution of the Navier-Stokes equation at low Reynolds numbers; the latter takes into account the increase in the drag force on a colloidal particle due to wall-particle hydrodynamic forces. More importantly, we find that the ratio of the short-time diffusion coefficient of the monomer and that of the center of mass of the dimmer is almost independent of both the dimer molar fraction, x_{d}, and the total packing fraction, ϕ, up to ϕ≈0.5. At higher concentrations, this ratio displays a small but systematic increase. A similar physical scenario is observed for the ratio between the parallel and the perpendicular components of the short-time diffusion coefficients of the dimer. This dynamical behavior is corroborated by means of molecular dynamics computer simulations that include explicitly the particle-particle hydrodynamic forces induced by the solvent. Our results suggest that the effects of colloid-colloid hydrodynamic interactions on the short-time diffusion coefficients are almost identical and factorable in both species.
authors: Instituto de Física "Manuel Sandoval Vallarta," Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, 78000 San Luis Potosí, SLP, México.
authors: Erick
authors: E
authors: Sarmiento-Gómez
authors: División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, México.
authors: José Ramón
authors: JR
authors: Villanueva-Valencia
authors: Subdirección de Postgrado e Investigación, Instituto Tecnológico Superior de Xalapa, Sección 5A Reserva Territorial s/n, 91096 Xalapa, Veracruz, México.
authors: Salvador
authors: S
authors: Herrera-Velarde
authors: División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, México.
authors: José Arturo
authors: JA
authors: Ruiz-Santoyo
authors: Cinvestav Unidad Monterrey, Parque de Investigación e Innovación Tecnológica, Apodaca, 66629 Nuevo León, México.
authors: Jesús
authors: J
authors: Santana-Solano
authors: Instituto de Física "Manuel Sandoval Vallarta," Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, 78000 San Luis Potosí, SLP, México.
authors: José Luis
authors: JL
authors: Arauz-Lara
authors: División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, México.
authors: Ramón
authors: R
authors: Castañeda-Priego