title: Increasing the Collision Rate of Particle Impact Electroanalysis with Magnetically Guided Pt-Decorated Iron Oxide Nanoparticles.
abstract: An integrated microfluidic/magnetophoretic methodology was developed for improving signal response time and detection limits for the chronoamperometric observation of discrete nanoparticle/electrode interactions by electrocatalytic amplification. The strategy relied on Pt-decorated iron oxide nanoparticles which exhibit both superparamagnetism and electrocatalytic activity for the oxidation of hydrazine. A wet chemical synthetic approach succeeded in the controlled growth of Pt on the surface of FeO/Fe3O4 core/shell nanocubes, resulting in highly uniform Pt-decorated iron oxide hybrid nanoparticles with good dispersibility in water. The unique mechanism of hybrid nanoparticle formation was investigated by electron microscopy and spectroscopic analysis of isolated nanoparticle intermediates and final products. Discrete hybrid nanoparticle collision events were detected in the presence of hydrazine, an electrochemical indicator probe, using a gold microband electrode integrated into a microfluidic channel. In contrast with related systems, the experimental nanoparticle/electrode collision rate correlates more closely with simple theoretical approximations, primarily due to the accuracy of the nanoparticle tracking analysis method used to quantify nanoparticle concentrations and diffusion coefficients. Further modification of the microfluidic device was made by applying a tightly focused magnetic field to the detection volume to attract the magnetic nanoprobes to the microband working electrode, thereby resulting in a 6-fold increase to the relative frequency of chronoamperometric signals corresponding to discrete nanoparticle impact events.
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, and Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Robinson
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, and Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Yoo
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, and Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Alma D
authors.initials: AD
authors.lastname: Castañeda
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, and Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Brett
authors.initials: B
authors.lastname: Gu
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, and Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Radhika
authors.initials: R
authors.lastname: Dasari
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, and Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Crooks
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, and Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Stevenson
keywords: electrocatalytic amplification; hybrid nanoparticles; magnetophoresis; microfluidics; multifunctional nanoparticles; nanoparticle collisions