Combined forces: Raman and UV

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  • Published: Aug 1, 2016
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Combined forces: Raman and UV

Working together

A first in a spectroelectrochemistry device sees both the UV-Vis and Raman responses being observed at the same time. The demonstration opens up high-quality data from a single experiment and expands the versatility of such devices. (Credit: American Chemical Society/Ibañez et al)

A first in a spectroelectrochemistry device sees both the UV-Vis and Raman responses being observed at the same time. The demonstration opens up high-quality data from a single experiment and expands the versatility of such devices.

David Ibañez, Jesus Garoz-Ruiz, Aranzazu Heras, and Alvaro Colina of the Department of Chemistry, at the University of Burgos, in Spain, explain how versatile spectroscopy can be. It has been used in reaction mechanism studies, the investigation of diffusive and adsorptive processes, analysis of substances of biological interest, the characterization of many different types of compounds, in optical and electrical studies of the properties of materials, and in the evaluation of parameters of electron-transfer reactions. The application of statistical methods provides suitable information for quantitative analysis using UV-Vis spectroscopy. Perpendicular (normal) and parallel modes of operation are commonly used, including by the current researchers who perform experiments using the two configurations at the same time, so-called Bidimensional Spectroelectrochemistry.

Likewise, Raman spectroscopy has been used in a wide range of applications and is particularly useful for characterizing steady-state systems and also in situ studies of different evolving processes. The development of new devices for time-resolved Raman spectroscopy has allowed scientists to study systems of a completely different nature.

Together is better

Intriguingly, several devices that can carry out both UV-Vis and Raman experiments separately have been developed and these take advantage of the complementarity of UV−Vis absorption and Raman spectroelectrochemistry. But, despite these devices incorporating both technologies, the techniques must be applied separately to the sample.

Now, Ibañez and colleagues have extended this form of spectroelectrochemistry to incorporate simultaneous UV-Vis and Raman spectroscopy in the same electrochemical experiment, which they suggest allows two different perspectives to be taken on the same sample. The team has built a new device in which the bare optical fibres can be used for UV−Vis spectroscopy in long optical path length configuration. But, at the same time, the Raman response can be measured in the "normal" arrangement. This, the team says, "further expands the versatility of spectroelectrochemistry techniques and enables us to obtain much more high-quality information in a single experiment."

They have demonstrated proof of principle with three different types of electrochemical systems: the well-defined, one-electron ferricyanide/ferrocyanide system, oxidation of the neurotransmitter dopamine involved in the brain's reward systems and behaviour and associated with schizophrenia and Parkinson's disease, and the electropolymerization of 3,4-ethylenedioxythiophene (EDOT) to PEDOT, one of the most widely used conducting polymers. They have used these to show that their multitasking device operates as expected. The researchers found that processes that occur in solution can be readily distinguished from processes that occur at the electrode surface during the electrochemical experiment, providing a whole picture of reactions taking place at the interface to between solution and electrode. In their experiments, the team used a glassy carbon foil or a single-walled carbon nanotube (SWCNT) film for the working electrode.

Clarity with multitasking

"This device allows us to study a larger number of complex electrochemical processes from different points of view taking into account not only the UV−Vis spectral changes in the solution adjacent to the electrode but also the Raman signal at any location," the team reports in the journal Analytical Chemistry. Moreover, they suggest that information that would otherwise be ambiguous can also be obtained with greater clarity than before.

Related Links

Anal Chem 2016, online: "Simultaneous UV-Vis Absorption and Raman Spectroelectrochemistry"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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