title: Electrophoretic Separation of Single Particles Using Nanoscale Thermoplastic Columns.
abstract: Phenomena associated with microscale electrophoresis separations cannot, in many cases, be applied to the nanoscale. Thus, understanding the electrophoretic characteristics associated with the nanoscale will help formulate relevant strategies that can optimize the performance of separations carried out on columns with at least one dimension below 150 nm. Electric double layer (EDL) overlap, diffusion, and adsorption/desorption properties and/or dielectrophoretic effects giving rise to stick/slip motion are some of the processes that can play a role in determining the efficiency of nanoscale electrophoretic separations. We investigated the performance characteristics of electrophoretic separations carried out in nanoslits fabricated in poly(methyl methacrylate), PMMA, devices. Silver nanoparticles (AgNPs) were used as the model system with tracking of their transport via dark field microscopy and localized surface plasmon resonance. AgNPs capped with citrate groups and the negatively charged PMMA walls (induced by O2 plasma modification of the nanoslit walls) enabled separations that were not apparent when these particles were electrophoresed in microscale columns. The separation of AgNPs based on their size without the need for buffer additives using PMMA nanoslit devices is demonstrated herein. Operational parameters such as the electric field strength, nanoslit dimensions, and buffer composition were evaluated as to their effects on the electrophoretic performance, both in terms of efficiency (plate numbers) and resolution. Electrophoretic separations performed at high electric field strengths (>200 V/cm) resulted in higher plate numbers compared to lower fields due to the absence of stick/slip motion at the higher electric field strengths. Indeed, 60 nm AgNPs could be separated from 100 nm particles in free solution using nanoscale electrophoresis with 100 μm long columns.
authors.affiliation: Department of Chemistry, Louisiana State University , Baton Rouge, Lousiana 70803, United States.|Department of Biomedical Engineering, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Kumuditha M
authors.initials: KM
authors.lastname: Weerakoon-Ratnayake
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Franklin I
authors.initials: FI
authors.lastname: Uba
authors.affiliation: Department of Chemistry, Louisiana State University , Baton Rouge, Lousiana 70803, United States.|Department of Biomedical Engineering, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Nyoté J
authors.initials: NJ
authors.lastname: Oliver-Calixte
authors.affiliation: Department of Chemistry, Louisiana State University , Baton Rouge, Lousiana 70803, United States.|Department of Biomedical Engineering, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.|Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.|Center of Biomodular Multiscale Systems for Precision Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.|Ulsan National Institute of Science and Technology , Ulsan 44919, South Korea.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Soper
mesh_terms: D000327:Adsorption; D004586:Electrophoresis / Q000295:instrumentation*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D019904:Polymethyl Methacrylate; D012834:Silver / Q000737:chemistry / Q000302:isolation & purification*; D020349:Surface Plasmon Resonance; D013499:Surface Properties; D013696:Temperature
chemical_list: D012834:Silver; D019904:Polymethyl Methacrylate