Adaptations of Electrical Field Flow Fractionation For Use With Nanoparticles

Open Access
Author:
Konarske, Alison Marie
Graduate Program:
Chemistry
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 08, 2013
Committee Members:
  • Mary Elizabeth Williams, Thesis Advisor
  • Raymond Edward Schaak, Thesis Advisor
  • Christine Dolan Keating, Thesis Advisor
Keywords:
  • ElFFF
  • Field Flow Fractionation
  • Nanoparticles
  • separation
Abstract:
In this work, electrical field flow fractionation (EFFF) was tested for the separation of as-synthesized samples and mixtures of nanoparticle samples. The goal of this research focused on adapting EFFF for the separation of particles less than 20 nm in diameter, a size range in which nanoparticles with biological, catalytic, and other applications are currently being synthesized and investigated for use in imaging, antimicrobial, and green energy applications. Two modifications of the traditional mode of EFFF demonstrated the retention of particles smaller than previously reported in literature. First, cyclical EFFF (CycEFFF) was used to separate populations of sub-20 nm diameter particles; secondly, modified electrode surfaces were used with constant applied electric fields for the separation of nanoparticles. CycEFFF was found to separate a mixture of 5 and 13 nm diameter citrate stabilized CoFe2O4 nanoparticles in H2O; fractions collected demonstrated that the larger particles which have a higher surface charge were retained longer than the smaller particles with a lower surface charge. However, baseline resolution was not achieved using this method. Further investigations using this technique demonstrated a significant aggregation problem that resulted from application of the electric field. Modifying the surface of the electrodes with covalently bonded silanes to prevent hydrolysis caused an increase in particle retention for larger diameter CoFe2O4 particles, however the smaller diameter particles with lower surface charges aggregated under an applied electric field. Adding citrate to the mobile phase did not provide additional stabilization to the particle system to prevent aggregation.