Nanowire Probes for High Resolution Combined Scanning Electrochemical Microscopy − Atomic Force Microscopy

Abstract

We describe a method for the production of nanoelectrodes at the apex of atomic force microscopy (AFM) probes. The nanoelectrodes are formed from single-walled carbon nanotube AFM tips which act as the template for the formation of nanowire tips through sputter coating with metal. Subsequent deposition of a conformal insulating coating, and cutting of the probe end, yields a disk-shaped nanoelectrode at the AFM tip apex whose diameter is defined by the amount of metal deposited. We demonstrate that these probes are capable of high-resolution combined electrochemical and topographical imaging. The flexibility of this approach will allow the fabrication of nanoelectrodes of controllable size and composition, enabling the study of electrochemical activity at the nanoscale.

Carbon Nanotubes for Electronic and Electrochemical Detection of Biomolecules

“…[7,8] In particular, metallic (met-) nanotubes are highly suited for nanoscale circuits, [9] ultrathin, flexible, and transparent conductors, [10] supercapacitors, [11] field emitters, [12] actuators, [13] and nanosized electrochemical probes. [14] Semiconducting (sem-) CNTs on the other hand, are applicable for nanoscale sensors, [15,16] transistors, [17,18] and photovoltaic devices. [19] With diameters similar to or smaller than those of individual proteins, CNTs are expected to serve as high-performance electrical conduits for interfacing with biological systems.…”

Seeing Big with Scanning Electrochemical Microscopy

“…29 Metal nanowire AFM-SECM probes have been built by coating single wall carbon nanotubes with metal, insulating them with a polymer film, and exposing the final electrode surface with a focused ion beam. 30 Tilting the disk-shaped probe establishes a physical contact between one side of the insulating probe apex and the substrate while the active electrode area remains at a given distance from the sample. These nanowire AFM-SECM probes have been used in intermittent contact mode for high resolution imaging of both topographical and electrochemical surface information.…”

“…These nanowire AFM-SECM probes have been used in intermittent contact mode for high resolution imaging of both topographical and electrochemical surface information. 30 For rough surfaces and for sample areas larger than the typical scanning range of AFM instruments (e.g., 100 μm  100 μm  10 μm), a distance control has been achieved by shear-force detection in combination with a positional feedback system. 31,32 Since the shear forces must be measured in a viscous liquid, the signal change upon approach is rather small.…”

Simultaneous imaging of the topography and electrochemical activity of a 2D carbon nanotube network using a dual functional L-shaped nanoprobe

“…SECM-AFM has been used to study the local electrochemical activity of various substrates, enzyme activity, [20][21][22] and membrane ion transport. 8,23,24 Furthermore, SECM-AFM probes with nanoelectrodes have been developed to improve the electrochemical resolution; 12,13,15,[25][26][27][28][29][30] however, the application of high-resolution SECM-AFMs with disk-type nanoelectrodes is limited to the characterization of probes using the "lift-up" mode to avoid short circuiting. 27,30 In the lift-up mode, the probe tip is lifted from the substrate by a predefined distance to collect electrochemical data while tracing the surface topography recorded in the previous surface scan during which the probe was in contact with the surface.…”