title: Focused-Ion-Beam-Milled Carbon Nanoelectrodes for Scanning Electrochemical Microscopy.
abstract: Nanoscale scanning electrochemical microscopy (SECM) has emerged as a powerful electrochemical method that enables the study of interfacial reactions with unprecedentedly high spatial and kinetic resolution. In this work, we develop carbon nanoprobes with high electrochemical reactivity and well-controlled size and geometry based on chemical vapor deposition of carbon in quartz nanopipets. Carbon-filled nanopipets are milled by focused ion beam (FIB) technology to yield a flat disk tip with a thin quartz sheath as confirmed by transmission electron microscopy. The extremely high electroactivity of FIB-milled carbon nanotips is quantified by enormously high standard electron-transfer rate constants of ≥10 cm/s for Ru(NH3)63+. The tip size and geometry are characterized in electrolyte solutions by SECM approach curve measurements not only to determine inner and outer tip radii of down to ~27 and ~38 nm, respectively, but also to ensure the absence of a conductive carbon layer on the outer wall. In addition, FIB-milled carbon nanotips reveal the limited conductivity of ~100 nm-thick gold films under nanoscale mass-transport conditions. Importantly, carbon nanotips must be protected from electrostatic damage to enable reliable and quantitative nanoelectrochemical measurements.
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, USA.
authors.forename: Ran
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Chemistry and Biochemistry, Queens College-CUNY, Flushing, New York 11367, USA.
authors.forename: Keke
authors.initials: K
authors.lastname: Hu
authors.affiliation: Department of Chemistry and Biochemistry, Queens College-CUNY, Flushing, New York 11367, USA.
authors.forename: Yun
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Chemistry and Biochemistry, Queens College-CUNY, Flushing, New York 11367, USA.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Mirkin
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, USA.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Amemiya