Separation of Nanoparticles in Different Sizes and Compositions by Capillary Electrophoresis

Abstract

Nano-sized particles have received considerable interest in the past two decades.1 Due to the quantum confinement effect, the nanoparticles show distinct physical and chemical properties depending on the sizes and shapes, particularly when the sizes are close to or smaller than the dimensions of exciton of the corresponding bulk materials.2 However, their wide distributions of sizes always give rise to the major limitations for precise investigation of their unique physical and chemical characteristics. Therefore, the separation of the nano-sized particles has brought considerable attention in many scientific areas recently. 3-8Many methods such as transmission electron microscopy (TEM) and size-exclusion chromatography were introduced so far for identifying and separating nanoparticles. These methods, however, have some inherent problems in the detection processes involving the degradation of sample, irreversible adsorption, etc. [9][10][11][12] Recently, several attempts to use capillary electrophoresis (CE) as a novel separation method for nanoparticles of inorganic and polymer materials have been made. [11][12][13][14][15][16][17][18] The principle of electrophoretic separation is based on the fact that when an external electric field is applied to a solution of charged species, each ion moves toward the electrode of opposite charge.The electrophoretic mobility (µp) of ionic species is expressed as (1) where q is the charge of the ion, η is the coefficient of viscosity of the fluid, and r is the hydrodynamic radius of the ion. The apparent mobility (µa), which gives rise to the net driving force for the separation in CE, is given by the sum of electroosmotic mobility (µo) and electrophoretic mobility (µp). Overall, the migration time t of ionic species can be expressed by (2) where I and L are the effective and total lengths of capillary, respectively, E is the electric field strength, and V is the applied potential. Thus the separation in CE can be achieved by the mobility of the species depending on not only the solvent medium, but also the charges, sizes, and shapes of nanoparticles.

Rapid Purification and Size Separation of Gold Nanoparticles via Diafiltration

“…Particle size and size dispersity can be controlled to a certain extent by synthetic methods, such as deliberate variation of the gold-to-ligand ratio 19 and dendrimer encapsulation; − however, these methods are often sensitive to minute changes in reaction conditions. Centrifugation, electrophoresis, , fractional crystallization, chromatography, ,− stirred-cell ultrafiltration, and size-dependent solubility , have been reported for size-based separation. Unfortunately, the fractionation of nanoparticle samples by these methods is often dependent upon specific core or ligand shell properties, time-consuming, difficult, and expensive.…”

Ultra-broadband Optical Gain Engineering in Solution-processed QD-SOA Based on Superimposed Quantum Structure

“…Also, Hwang et al . claimed that particles of 5 nm size can be separated by this method 51 . Generally, the practical synthesis methods in this area are going to progress and obtain very high-resolution case.…”