Electrochemical and surface enhanced infrared absorption spectroscopy studies of TEMPO self-assembled monolayers

Monitoring SEIRAS on a Graphitic Electrode for Surface-Sensitive Electrochemistry: Real-Time Electrografting

“…Both the anodic and cathodic peak currents correlate linearly with increasing scan rates, indicating that the TEMPO redox process arises from a surface-bound species (Figure d). The maximum average surface coverage obtained on our electrodes was 3.27 × 10 –11 mol/cm 2 , which is a reasonable coverage compared to the 1.33 × 10 –11 mol/cm 2 reported by Barman on glassy carbon, and the 48 × 10 –11 mol/cm 2 theoretical maximum for an undiluted TEMPO self-assembled monolayer on gold reported by Unni (eq S1). Cyclic voltammetry demonstrated clear attachment of 4-amino-TEMPO on the graphene surface.…”

“…An isotherm-like trend can be seen in both cases. This is perplexing as this peak should diminish as more aminoxyl radical species oxidize into the oxoammonium cation . In Figure b, we show the comparison of the pregraft electrode to the postgraft electrode before and after copious rinsing; these spectra clearly show the retention of new features on the grafted electrode.…”

“…Interpretation of ATR data is based on previously reported IR assignments for graphene, graphene oxide, and 4-amino-TEMPO (Table S1). ,,− Figure a shows the time-resolved spectra acquired while maintaining a 1.1 V potential for 10 min in a 1 mM 4-amino-TEMPO PBS solution. The main IR bands during the graft are positive 1574 cm –1 and negative 1592 cm –1 attributed to the aromatic CC bonds of the graphene .…”

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

“…Tafel slopes and reaction intermediates, which together can provide useful insight into reaction mechanisms, can be spectroscopically determined and identified, respectively, with time resolutions that barely go below 1 s. However, determination of some other important kinetic parameters, like rate constants of electron transfer, requires increasing the time resolution well beyond that limit, which requires resorting to more sophisticated techniques like step-scan FTIR spectroscopy. A recent exception is the use of normal FTIR to determine the rate constant of electron transfer to a monolayer of 2,2,6,6-tetramethylpiperidine-1-oxyl [9].…”

Surface sensitive infrared spectroelectrochemistry using palladium electrodeposited on ITO-modified internal reflection elements

“…Recently, the advantages of using a buffer layer of conductive metal oxide (CMO) for electrochemical ATR-SEIRAS have been reported. [26][27][28] Thin films of indium zinc oxide (IZO) 27 or indium tin oxide (ITO) 26,29,30 were shown to have the free charge carrier density and mobility to be sufficiently conductive to allow electrodeposition of gold island films from solutions of gold salt precursor. Gold films on CMO (Au@CMO) give strong ATR-SEIRAS (and SERS) signals 31 and are remarkably robust compared to metal films directly deposited on IRE surfaces, which are highly susceptible to film delamination under electrochemical conditions.…”