基礎講座 電気泳動(Electrophoresis)

The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

http://depa.fquim.unam.mx/amyd//archivero/FidelmarLechugaSanabria_4940.pdf

Recent advances in the liquid-phase syntheses of inorganic nanoparticles.

1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

Applied Numerical Analysis. By C.F. Gerald. Pp. xii, 340. £3·60. 1970. (Addison-Wesley.)

A theoretical analysis was conducted on a multilayer internal diffusion and surface evaporation (IDSE) coextrusion process for preparing gradient-index (GI) polymer optical fibers (POFs). The predicted refractive index distribution (RID) was in good agreement with the experimental data reported in the literature. The effects of the essential parameters, including the mass transfer coefficient of monomer across solid -gas interface, k, the diffusivities of monomers, and the radius ratio of each layer on RID were investigated. We show that if k is either very small or very large, then RID deviates significantly from a parabolic curve. The effect of the diffusivity of BzMA monomer on RID is more significant than that of MMA monomer. The results of numerical simulation reveal that both the radius ratio and the composition of each layer have significant effect on RID, and the greater the number of layers, the closer the RID is to a parabolic curve.

Theoretical Analysis on a Multilayer Coextrusion Process for Preparing Gradient-Index Polymer Optical Fibers

Considering its potential application in improving the performance of a single-molecule biosensing device, the diffusiophoresis of a polyelectrolyte sphere in a charged cylindrical nanochannel is studied taking account of the effect of diffusioosmosis flow. The interaction of the double layers in the present system is expected to influence significantly the relevant fields, yielding profound diffusiophoretic behaviors. Adopting a zwitterionic, pH-regulated polyelectrolyte in a silicon dioxide nanochannel as an example, these behaviors are simulated by varying the pH and the bulk salt concentration of the liquid phase, and the nanochannel radius. We show that the charged nanochannel could influence significantly both the quantitative and the qualitative behavior of the polyelectrolyte. The underlying mechanisms leading to this observation are discussed in detail.

Diffusiophoresis of a pH-regulated polyelectrolyte in a pH-regulated nanochannel

The electrophoretic behavior of a droplet in a spherical cavity subject to an alternating electric field is analyzed theoretically under the conditions of an arbitrary level of surface potential and double-layer thickness. The influences of the thickness of the double layer, the level of surface potential, the size of a droplet, the viscosity of the droplet fluid, and the frequency of the applied electric field on the electrophoretic behavior of a droplet are examined through numerical simulations. We show that, because of the effect of double-layer deformation, the magnitude of the electrophoretic mobility of a droplet could have a local maximum and the phase angle could have a negative (phase lead) local minimum as the frequency of the applied electric field varies. In general, the lower the surface potential, the thicker the double layer and the larger the viscosity of the droplet fluid, and the more significant the boundary effect, the smaller the magnitude of the electrophoretic mobility of a droplet.

Dynamic electrophoresis of a droplet in a spherical cavity.

Extending previous electrokinetic analyses based on a Newtonian fluid to power-law fluids, we investigate the behaviors of the ion current rectification (ICR) and the ion selectivity S of a conical nanopore having a pH-regulated surface. The bulk salt concentration Cbulk, the solution pH, and the power-law index n are examined in detail for their influences on these behaviors. We show that the ICR ratio for the case where pH is lower than the isoelectric point (IEP) of the nanopore surface is different both quantitatively and qualitatively from that for the case where pH > IEP. The relative magnitude of the ICR ratio as n varies depends largely on the level of Cbulk. In contrast, S (pH   IEP), where | S | decreases with increasing Cbulk and/or decreasing n. In addition, S is very sensitive to n, for example, a decrease of n from 1.0 (Newtonian fluid) to 0.9 (pseudoplastic fluid) can yield a 245% increase in S at Cbulk = 100 mM. Implying that the performance of ion separation can be improved by tuning the fluid viscosity. Mechanisms are proposed for explaining the observed behaviors in the ICR ratio.

Ion transport in a pH-regulated conical nanopore filled with a power-law fluid

The current efficiency η for the transport of ions through an ion-exchange membrane is analyzed theoretically. In particular, the effect of discretizing the fixed charges contained in the membrane into charged intervals on η is investigated. We show that if the applied current density I is low, a membrane with a continuous linear fixed charge distribution has a higher η than a membrane with evenly distributed charged intervals, and the larger the number of charged intervals the lower the η. If I is high, a membrane with randomly distributed charged intervals may have a higher η than that of a membrane with a continuous linear fixed charge distribution. It can be inferred that, as far as raising η is concerned, distributing fixed charges discretely and/or randomly in a membrane has no practical advantage.

Jyh-Ping Hsu

Papers

Theoretical Analysis on a Multilayer Coextrusion Process for Preparing Gradient-Index Polymer Optical Fibers

Diffusiophoresis of a pH-regulated polyelectrolyte in a pH-regulated nanochannel

Dynamic electrophoresis of a droplet in a spherical cavity.

Ion transport in a pH-regulated conical nanopore filled with a power-law fluid

Current Efficiency of an Ion-Exchange Membrane: Effect of Piecewise Continuous Fixed Charge Distribution