Cathodic Electropaint Insulated Tips for Electrochemical Scanning Tunneling Microscopy

Abstract

A method of preparing tungsten tips insulated for in situ scanning tunneling microscopy (STM) work is presented. Tips were electrocoated at low applied voltages using an organic solution of the cathodic electropaint rather than the more frequently utilized electropaint emulsions. The insulated tips were then characterized using cyclic voltammetry and electrochemical STM (EC-STM). They displayed low Faradaic leakage currents under electrochemical conditions and provided for high-resolution STM imaging in electrolyte solution. Flat terraces on a monocrystalline Au surface and adlayers of 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) were imaged under potential control in dilute HClO4 using the fabricated tips, and atomic or molecular resolution images were obtained in both cases. The developed procedure allows for the fast, reproducible generation of large numbers of electrically insulated tungsten tips suitable for EC-STM imaging experiments.

Applications of Scanning Electrochemical Microscopy (SECM) Coupled to Atomic Force Microscopy with Sub-Micrometer Spatial Resolution to the Development and Discovery of Electrocatalysts

“…In order to achieve nanometer resolution in SECM analyses, the AFM technique was recently combined with SECM. Thus, the combined AFM-SECM technique using an AFM cantilever with a conductive coating as the tip electrode for SECM has led to recent progress [55][56][57][58][59][60][61][62][63]. A number of approaches have been attempted in order to use the conductive cantilever as the tip electrode, with the objective to confine the active tip area of the AFM cantilever.…”

“…employing various techniques, e.g., physical insulation by polymer films or electrophoretic deposition of chemicals, followed by mechanical abrasion or electric discharge methods to expose the end of the tip as the active electrode [56,57,59,60]. For example, electropaint concentrated in an organic solvent (Clearclad HSR, Harvey, IL) was used to cover most of the conducting area of the AFM cantilever by an electrochemical anodic/cathodic deposition method [59]. Prior to electrodeposition of the electropaint on the cantilever, the electrical contact should be prepared on the body of the cantilever to connect the conducting cantilever to the potentiostat.…”

Applications of Scanning Electrochemical Microscopy (SECM) Coupled to Atomic Force Microscopy with Sub-Micrometer Spatial Resolution to the Development and Discovery of Electrocatalysts

“…Thus, the combined AFM-SECM technique using an AFM cantilever with a conductive coating as the tip electrode for SECM has led to recent progress [55][56][57][58][59][60][61][62][63]. A number of approaches have been attempted in order to use the conductive cantilever as the tip electrode, with the objective to confine the active tip area of the AFM cantilever.…”

“…In these methods, most of the conducting area of the cantilever was covered by employing various techniques, e.g., physical insulation by polymer films or electrophoretic deposition of chemicals, followed by mechanical abrasion or electric discharge methods to expose the end of the tip as the active electrode [56,57,59,60]. For example, electropaint concentrated in an organic solvent (Clearclad HSR, Harvey, IL) was used to cover most of the conducting area of the AFM cantilever by an electrochemical anodic/cathodic deposition method [59]. Prior to electrodeposition of the electropaint on the cantilever, the electrical contact should be prepared on the body of the cantilever to connect the conducting cantilever to the potentiostat.…”

Self-assembled monolayers formed by 5,10,15,20-tetra(4-pyridyl)porphyrin and cobalt 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine on iodine-passivated Au(111) as observed using electrochemical scanning tunneling microscopy and cyclic voltammetry

“…W tips were prepared by mechanically cutting W wire (0.25 mm diameter, 99.95% purity, Alfa Aesar, Ward Hill, MA, USA). To minimize the electrochemical contribution to the tip current during EC-STM imaging, tips were coated with an electrophoretic paint (Clearclad HSR, Clearclad, Harvey, IL, USA) using a procedure described previously [25]. STM images were recorded in constant-current mode using tunneling setpoints between 0.5 and 2.0 nA, and are shown without any filtering.…”