UV–Vis absorption thin-layer spectroelectrochemistry greatly contributes to the assessment of parameters of electron-transfer reactions by providing electrochemical and spectroscopic information obtained simultaneously in a confined space around the working electrode. In this work we present an ingenious modification of a spectroelectrochemistry device based on carbon nanotubes and bare optical fibers to perform UV–Vis absorption thin-layer spectroelectrochemistry measurements. The working and counter electrodes are made of carbon nanotubes filtered and press-transferred onto a flat support where a painted silver line acts as pseudo-reference electrode. To perform high sensitivity measurements, two bare optical fibers are fixed to the support in a parallel arrangement. In a novel development, a quartz plate is placed on top of the bare optical fibers in order to create a thin layer whose thickness is reproducibly controlled by the diameter of the optical fibers. This methodology is also successfully applied using commercial screen-printed electrodes. Three different electroactive compounds, ferrocenemethanol, o-tolidine and [Ru(bpy)3]2 +, are studied and good results are obtained. As demonstrated below, these long optical path UV–Vis absorption thin-layer spectroelectrochemistry cells considerably reduce the complexity associated with this type of devices, eliminating one of the major disadvantages of this technique and making it much more accessible to the scientific community.
