Surface enhanced infrared spectroelectrochemistry using a microband electrode

Abstract

The successful use of a microband electrode printed on a silicon internal reflection element to perform time resolved infrared spectroscopy is described. Decreasing the critical dimension of the microband electrode to several hundred micrometers provides a sub-microsecond time constant in a Kretschmann configured spectroelectrochemical cell. The high brilliance of synchrotron sourced infrared radiation has been combined with a specially designed horizontal attenuated total reflectance (ATR) microscope to focus the infrared beam on the microband electrode. The first use of a sub-microsecond time constant working electrode for ATR surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is reported. Measurements show that the advantage afforded by the high brilliance of the synchrotron source is at least partially offset by increased noise from the experimental floor. The test system was the potential induced desorption of an adsorbed monolayer of 4-methoxypyridine as measured using step-scan interferometry. Based on diffusion considerations alone, the expected time scale of the process was less than 10 microseconds but was experimentally measured to be three orders of magnitude slower. A defect-mediated dissolution of the condensed film is speculated to be the underlying cause of the unexpected slow kinetics.

ATR-SEIRAS for time-resolved studies of electrode–electrolyte interfaces

“…They monitored the potential-induced desorption of 4dimethylaminopyridine from a gold nanoparticle film electrode deposited on an ITO-modified Si prism and demonstrated the ability of dual-frequency comb IR spectroscopy to achieve time resolution in the microsecond regime (Figure 4(A)), requiring less time for data acquisition than step-scan spectroscopy. The level of noise (Figure 4(B)) was lower than in the experiments using synchrotron radiation [27] which, together with the high photon flux characteristic of laser pulses, opens interesting possibilities in terms of combining dualfrequency combs with microband electrodes. One drawback, however, is the narrow spectral window inherent to the frequency comb method.…”

“…This is evidence of the ability of step-scan ATR-SEIRAS to monitor the different stages through which the structure of interfacial water transits during double-layer charging after a potential step, a topic which, to the best of our knowledge, has not been explored at all. Very recently, Morhart et al' [27] have studied the desorption of a monolayer of 4-mehoxipyridine using a microband electrode. The microsecond time domain explored by Morhart et al [27] is particularly important because, due to limitations imposed by double-layer charging, as well as by the response time of potentiostats, it is the limit that can be achieved by potential step methods.…”

“…Very recently, Morhart et al' [27] have studied the desorption of a monolayer of 4-mehoxipyridine using a microband electrode. The microsecond time domain explored by Morhart et al [27] is particularly important because, due to limitations imposed by double-layer charging, as well as by the response time of potentiostats, it is the limit that can be achieved by potential step methods. Reaching this regime requires decreasing the electrochemical cell's time constant down to just a few microseconds, which Morhart et al achieved by depositing a gold microband electrode on an indium tin oxide (ITO) modified Si groove, which was used as the ATR substrate.…”

SpectIR-fluidics: completely customizable microfluidic cartridges for high sensitivity on-chip infrared spectroscopy with point-of-application studies on bacterial biofilms

“…16 The opportunity presented by these wafer-based ATR crystals includes implementation of surface-enhanced methods 18 and spectroelectrochemistry. 19 To reduce the system cost and expand applications, our group has demonstrated a simple method for generating linear maps or "x-scans" via a moving aperture that admits light into different locations of such multi-ridge ATR-coupled devices, with detection handled by a standard single-element detector. 20 Despite their potential, the trend in multi-ridge ATR crystals in lab-on-a-chip applications has largely remained the same: open microchannels are constructed using a pattered photoresist on top of the ATR sensing surface, with the latter forming the bottom wall.…”

“…16 The opportunity presented by these wafer-based ATR crystals includes implementation of surface-enhanced methods 18 and spectroelectrochemistry. 19…”