Scanning Bipolar Electrochemical Microscopy

Abstract

Electrochemical techniques offer high temporal resolution for studying the dynamics of electroactive species at samples of interest. To monitor fastest concentration changes, a micro- or nanoelectrode is accurately positioned in the vicinity of a sample surface. Using a microelectrode array, it is even possible to investigate several sites simultaneously and to obtain an instantaneous image of local dynamics. However, the spatial resolution is limited by the minimal electrode size required in order to contact the electrodes. To provide a remedy, we introduce the concept of scanning bipolar electrochemical microscopy and the corresponding experimental system. This technique allows precise positioning of a wireless scanning bipolar electrode to convert spatially heterogeneous concentrations of the analyte of interest into an electrochemiluminescence map of the sample reactivity. After elucidating the working principle by recording bipolar line and array scans, a bipolar electrode array is positioned at the site of interest to record an electrochemical image of the localized release of analyte molecules.

Enhancing Electrogenerated Chemiluminescence on Platinum Electrodes through Surface Modification

“…ECL starts already at a potential of 0.85 V concurrently with TPrA oxidation, which corresponds to the particular mechanism uncovered by Bard's group [28] and simulated by Sojic's group, [29,30] implying only heterogeneous TPrA oxidation at the electrode to obtain ECL emission [Eqs. (1), (2), (5), (7), (8), mechanism 3].…”

“…Organic solvents may replace water, however, e. g. in acetonitrile, electrode fouling is a drawback both using glassy carbon or Pt electrodes. On the other hand, Pt microelectrodes are easy to fabricate and were used in imaging techniques such as scanning electrochemical microscopy (SECM) as well as scanning bipolar electrochemical microscopy (SBECM) . In combination with ECL, SECM has been applied for imaging purposes and elucidation of reaction mechanisms using Pt microelectrodes …”

“…On the other hand, Pt microelectrodes are easy to fabricate and were used in imaging techniques such as scanning electrochemical microscopy (SECM) as well as scanning bipolar electrochemical microscopy (SBECM). [7,8] In combination with ECL, SECM has been applied for imaging purposes and elucidation of reaction mechanisms using Pt microelectrodes. [6,9,10] The enhancement of ECL emission by surface modification demonstrated the applicability of this method for increasing the emission at poor electrode materials, which exhibit sluggish electron transfer kinetics.…”

Light in Electrochemistry

“…In recent years, attempts have been made to extend the cBPE/ECL sensing system to a microscopic system for the two-dimensional imaging of molecule concentration distributions [112][113][114][115][116][117][118]. These microscopic systems are based on a cBPE array that consists of vertically arranged cBPEs.…”

“…In 2017, Zhai et al reported a sensing platform using ECL for the measurement of molecules, such as hydrogen peroxide, with a cBPE array made of a nanoporous membrane filled with gold [109]. As an early attempt at a microscopic system using a cBPE array and ECL signals, Eßmann et al developed scanning bipolar electrochemical microscopy (SBECM) using a cBPE array probe that incorporated seven cBPEs in a single probe, which enabled imaging at high spatial resolution (50 µm) in real time by probe scanning [112].…”