Monitoring Scanning Electrochemical Microscopy Approach Curves with Mid-Infrared Spectroscopy: Toward a Novel Current-Independent Positioning Mode

Abstract

Single-bounce attenuated total reflection infrared spectroscopy in the 3-20 µm range (MIR) has been combined with scanning electrochemical microscopy (SECM) for in situ spectroscopic detection of electrochemically induced localized surface modifications using an ultramicroelectrode (UME). In this study, a novel current-independent approach for positioning the UME in aqueous electrolyte solution is presented using either changes of IR absorption intensity associated with borosilicate glass (BSG), which is used as shielding material of the UME wire, or by monitoring IR changes of the water spectrum within the penetration depth of the evanescent field due to displacement of water molecules in the volume between the sample surface and the UME within the evanescent field. The experimental results show that the UME penetrates into the exponentially decaying evanescent field in close vicinity (a few µm) to the ATR crystal surface. Hence, the resulting intensity changes of the IR absorption spectra for borosilicate glass (increase) and for water (decrease), can be used to determine the position of the UME relative to the ATR crystal surface independent of the current measured at the UME.

Invited Review Article: Combining scanning probe microscopy with optical spectroscopy for applications in biology and materials science

“…36,40 Scanning electrochemical microscopy has provided valuable insight in charge transfer mechanism at surfaces and electrochemical reactions. 37,43,44 For a more exhaustive list of feedback mechanisms recently developed to study individual atoms and molecules, the readers are encouraged to consult Ref. 45.…”

“…280 Using the same illumination geometry, a scanning electrochemical microscope (SECM) was combined with ATR-FTIR. 43,44 ATR-FTIR spectroscopy relies on the generation of an evanescent field on the waveguide surface, so it is extremely surfacesensitive and reduces the interferences with strong absorbers and water. The ATR crystal was an integral part of an electrochemical cell.…”

Scanning electrochemical microscopy in the 21st century. Update 1: five years after

“…59b Wang et al proposed novel current-independent method of microelectrode positioning within a separation distance of a few micrometres. 60 Their approach relies on the use of attenuated total reflection infrared spectroscopy to monitor the distance between the tip and the sample surface within the penetration depth of the evanescent field. One should notice that this setup requires an IR transparent substrate.…”

Dual microelectrodes decorated with nanotip arrays: Fabrication, characterization and spectroelectrochemical sensing

“…SECM has shown to be a very versatile technique pushing its limits towards new horizons: mapping the reactivity of various samples with better resolution, or with highly parallelized probes, or coupling the local electrochemical information with additional topographic and spectroscopic measurements [11][12][13][14][15][16][17]. This latter strategy has been pursued by several groups in recent years [18][19][20][21][22]. Indeed, the cross-correlation of spectroscopic information with local electrochemical measurements provides a powerful basis for increased selectivity and sensitivity.…”

“…The ability to merge intimately such techniques that are based on different physical principles offers the opportunity to acquire various and complementary information on complex micro-environments. For example, SECM has been associated with a variety of optical/spectroscopic techniques: optical microscopy [18,23], single-molecule fluorescence spectroscopy [24], infrared spectroscopy [21,22] and with surface plasmon resonance [25,26]. SECM has also been successfully combined with Raman spectrometry [27][28][29].…”