title: Visualizing and Calculating Tip-Substrate Distance in Nanoscale Scanning Electrochemical Microscopy Using 3-Dimensional Super-Resolution Optical Imaging.
abstract: We report a strategy for the optical determination of tip-substrate distance in nanoscale scanning electrochemical microscopy (SECM) using three-dimensional super-resolution fluorescence imaging. A phase mask is placed in the emission path of our dual SECM/optical microscope, generating a double helix point spread function at the image plane, which allows us to measure the height of emitting objects relative to the focus of the microscope. By exciting both a fluorogenic reaction at the nanoscale electrode tip as well as fluorescent nanoparticles at the substrate, we are able to calculate the tip-substrate distance as the tip approaches the surface with precision better than 25 nm. Attachment of a fluorescent particle to the insulating sheath of the SECM tip extends this technique to nonfluorogenic electrochemical reactions. Correlated electrochemical and optical determination of tip-substrate distance yielded excellent agreement between the two techniques. Not only does super-resolution imaging offer a secondary feedback mechanism for measuring the tip-sample gap during SECM experiments, it also enables facile tip alignment and a strategy for accounting for electrode tilt relative to the substrate.
authors.affiliation: Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Vignesh
authors.initials: V
authors.lastname: Sundaresan
authors.affiliation: Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Kyle
authors.initials: K
authors.lastname: Marchuk
authors.affiliation: Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Yun
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Titus
authors.affiliation: Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wilson
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States.
authors.forename: Chadd M
authors.initials: CM
authors.lastname: Armstrong
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States.
authors.forename: Bo
authors.identifier: 0000-0002-1737-1241
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Katherine A
authors.identifier: 0000-0002-1417-4656
authors.initials: KA
authors.lastname: Willets