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The combination of two well-known analytical techniques, electrochemistry and spectroscopy, gives rise to spectroelectrochemistry (SEC), an established scientific methodology. This hybrid technology combines the advantages of each technique, offering the best of both worlds [1]. The word «spectroelectrochemistry» is the result of combining these two terms as two pieces of a puzzle that fit perfectly together.

In this article, written for both beginners in the field as well as more experienced readers, we focus on introducing this technique from its beginnings to its advantages in research, and then discuss new systems and solutions that will make it easier to work on the multitude of applications that spectroelectrochemistry can offer. 

Shedding light, in the literal sense of the phrase, on electrochemical knowledge and procedures. Spectroelectrochemistry offers analysts more information by being able to record both an optical and an electrochemical signal at the same time to obtain new data.

This is a multi-response method—it studies the process of electrochemical reactions with simultaneous optical monitoring. Spectroelectrochemistry provides two individual signals from a single experiment, which is a very powerful feature to obtain critical information about the studied system. Moreover, the autovalidated character of spectroelectrochemistry confirms the results obtained by two different routes. Find out more about this topic by downloading our free Application Note below.

Spectroelectrochemistry allows researchers to collect molecular, kinetic, and thermodynamic information from the reactants, intermediates, and/or products involved in electron transfer processes. Thus, it is possible to perform spectroelectrochemical studies on a broad range of molecules and different processes including: biological complexes, polymerization reactions, nanomaterial characterization, analyte detection, corrosion mechanisms, electrocatalysis, environmental processes, characterization of memory devices, and much more!

Ultimately, different kinds of information is obtained depending on the spectral range used. UV-VIS spectroscopy provides molecular information related to the electronic levels of the molecules, the NIR region provides data associated with the vibrational levels, and the Raman spectrum provides very specific information about the structure and composition of the sample due to the fingerprinting characteristics of this technique.

Electromagnetic Spectrum
Diagram of the electromagnetic spectrum.

The beginnings of spectroelectrochemistry

Theodore Kuwana, Ph.D. in chemistry and specialist in spectroelectrochemistry, bioelectroanalytical chemistry and modified electrodes.

This analytical technique was developed in the 1960’s, and became popularized by Professor Theodore Kuwana and other researchers [2]. They had begun to work with transparent electrodes to study a simultaneous process—measuring the charge and absorbance (at the same time) when a beam of light passes through the electrode. As a result, they developed transparent electrodes and this marked the beginning of concurrent electrochemical and UV-VIS absorption measurements.

These so-called «optically transparent electrodes» (OTEs) were developed to carry out the combination of optical and electrochemical experiments. Some of the most commonly used OTEs began as oxide doped with antimony on glass, then developed into different thin films of gold or platinum on quartz, followed by germanium electrodes for IR wavelengths, as well as pure gold and platinum micromeshes (where the holes provide the required transparency to light). However, not all spectroelectrochemical configurations require transparent electrodes. For more information, download the electrode reference flyers from Metrohm DropSens to properly work with the different spectroelectrochemical techniques.

A selection of Metrohm DropSens references. Left: C013 for in-situ surface Raman spectroscopy. Right: P10 optically transparent and specially designed for spectroelectrochemical applications.

Download the free flyers for these electrodes below for further information.

The first published paper on spectroelectrochemistry [2], in which Dr. Kuwana participated, describes the use of tin oxide-coated glass surfaces (optically transparent electrodes) for following the absorbance changes of different electroactive species during electrolysis. Since then, the number of works and investigations based on this technique have grown steadily.

Spectroelectrochemistry publications have increased significantly since its discovery in the 1960’s (results of searching «Spectroelectrochem*» as a term in Scopus as of June 2021).

Take a look for yourself to see how things have changed in the last several decades!

An array of spectroelectrochemical techniques to choose from

The following graphic is classified according to the combination of different electrochemical and spectroscopic methods. The general classification is based on the spectroscopic technique: ultraviolet (UV), visible (Vis), photoluminescence (PL), infrared (IR), Raman, X-ray, nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR).

Spectroelectrochemistry (SEC) is the combination of spectroscopy and electrochemistry.

In recent years, significant advances have occurred regarding the design, development, and possibilities offered by instruments for working with spectroelectrochemical techniques. Also, the assemblies and the connections between products and accessories that facilitate the use of this equipment have improved in recent decades, contributing to make research and experiments in this field easier and more affordable.

The evolution of spectroelectrochemical instrumentation

Traditionally, the configuration for spectroelectrochemical analysis consists of two instruments: one spectroscopic instrument and the other for electrochemical analysis. Both instruments are connected independently to the same spectroelectrochemical cell and are generally not usually synchronized. In addition, each instrument is controlled by a different (and specific) software in each case, so two programs are also needed to interpret each signal and yet another external software for the processing and analysis of the data obtained by the first two programs. Finally, it must be considered that synchronization is not guaranteed, making the performance of experiments and tests with this configuration slow, complex, and costly.

This detached spectroelectrochemical setup displays the complexity of various software and programs used, showing that different systems are not able to obtain actual synchronized electrochemical measurements and data (click to enlarge).

Metrohm DropSens took this opportunity to create something that did not exist before—a revolution in the state-of-the-art of spectroelectrochemistry: the SPELEC line of instruments which are fully integrated, synchronized solutions that offer much more versatility to researchers. The devices include all of the components needed to work with spectroelectrochemical techniques in a simple way and in a single system with a (bi)potentiostat/galvanostat, the light source, and the spectrometer (depending on the selected spectral range).

Find out more about SPELEC, the next-generation tool for spectroelectrochemical research on our website.

The SPELEC systems from Metrohm DropSens consist of one device and one software—a fully integrated, easy to use, practical setup for researchers.

These designs and configurations simplify the work, processes, and spectroelectrochemical measurements as well because only a single system and a single software are needed. In the case of the SPELEC solution, its advanced dedicated software (DropView SPELEC) is a specific program that controls the instrument, obtains the electrochemical and spectroscopic signals simultaneously, and also allows users to process and analyze the data together in a single step. It’s really that simple!

The future of spectroelectrochemistry: SPELEC systems and software

One instrument and one software: Metrohm DropSens SPELEC has everything you need for your spectroelectrochemical experiments while saving laboratory space and valuable time. SPELEC instruments offer the combinations of electrochemistry and UV-Vis, Vis-NIR, or even Raman spectroscopy in a single measurement with several different instrument options available (see below). Everything is integrated which allows more tests in less time, multiple spectra, a full range of accessories, and research flexibility with the different configurations available.

Several options are available depending on the spectral range needed:

SPELEC: 200–900 nm (UV-VIS)
SPELEC NIR: 900–2200 nm
SPELEC RAMAN: 785 nm laser
(other wavelengths available upon request)
SPELEC 1050: 350–1050 nm (VIS-NIR)

DropView SPELEC is a dedicated and intuitive software that facilitates measurement, data handling, and processing. With this program, you can display electrochemical curves and spectra in real time and follow your experiments in counts, counts minus dark, absorbance, transmittance, reflectance, or Raman shift. As far as data processing is concerned, DropView SPELEC offers a wide variety of functions including graph overlay, peak integration and measurement, 3D plotting, spectral movie, and more.

Testimonial from the University of Burgos on the integrated SPELEC system from Metrohm DropSens.

SPELEC instruments are very versatile, and although they are dedicated spectroelectrochemical instruments, they can also be used for electrochemical and spectroscopic experiments. They can be used with any type of electrodes (e.g., screen-printed electrodes, conventional electrodes, etc.) and with different spectroelectrochemical cells. Optical and electrochemical information is obtained in real time/operando/dynamic configuration. The main advantages of spectroelectrochemical techniques can be summarized as follows:

  • they simultaneously provide information obtained by two different techniques (electrochemistry and spectroscopy) in a single experiment
  • qualitative studies and quantitative analyses can be performed
  • high selectivity and sensitivity
  • spectroelectrochemistry is used in a wide variety of different fields due to its great versatility
  • new configurations facilitate the performance of spectroelectrochemical experiments, saving time, samples, costs, etc.

Learn more about the next-generation tool for spectroelectrochemical research on our website!

SEC analysis techniques: suitable for multiple applications

The characteristics of spectroelectrochemistry allow the constant development of new and broad applications in several different fields. Read on below to discover the capabilities of this technique.

Materials science: characterization of specific properties of carbon materials, quantum dots, composites, nanoparticles, Janus materials, polymers, as well as stability studies, determination of photochemical properties, development of new materials, etc.

For more information, download our free related Application Note below.

Sensing: selective and sensitive detection, rapid quantification of a huge variety of analytes, diagnostic tool, development of new methodologies and sensors, etc. [3].

Organic and inorganic chemistry: study of the properties and structure of different compounds, analysis of kinetic reactions, determination of electron transfer capacity, etc. [4].

Corrosion: evaluation of protective films as corrosion inhibitors, determination of electrode stability and reversibility, monitoring of layer and sublattice generation, improvement of protective properties of coating materials, etc.

Energy storage: monitoring of exchange and discharge cycles, determination of oxidation/reduction levels, characterization of new electrolytes for batteries, understanding of doping and splitting processes in solar cells, etc.

Electrocatalysis: characterization and comparison of the electrocatalytic activity of different catalysts, identification of intermediate species and their structural changes, elucidation of the reaction mechanism, etc. [5].

Life sciences: study of biological processes, characterization of molecules used in biotechnology, biochemistry or medicine, determination of antioxidant activity, etc.

Environment: identification and quantification of pesticides, dyes, and pollutants, monitoring of degradation and filtration processes, etc. [6]

Download our free related Application Note for more information.

Others: characterization of new materials for memory devices, comparison of minerals, identification of pigments, oils, and pastes, etc.

Learn even more about spectroelectrochemistry (SEC) and what it can do for your research by downloading our free brochure.

Contact us

to discuss how spectroelectrochemistry can boost your research.

References

[1] Kaim, W.; Fiedler, J. Spectroelectrochemistry: The Best of Two Worlds. Chem. Soc. Rev. 2009, 38 (12), 3373. doi:10.1039/b504286k

[2] Kuwana, T.; Darlington, R. K.; Leedy, D. W. Electrochemical Studies Using Conducting Glass Indicator Electrodes. Anal. Chem. 1964, 36 (10), 2023–2025. doi:10.1021/ac60216a003

[3] Martín-Yerga, D.; Pérez-Junquera, A.; González-García, M. B.; Perales-Rondon, J. V.; Heras, A.; Colina, A.; Hernández-Santos, D.; Fanjul-Bolado, P. Quantitative Raman Spectroelectrochemistry Using Silver Screen-Printed Electrodes. Electrochimica Acta 2018, 264, 183–190. doi:10.1016/j.electacta.2018.01.060

[4] Perez-Estebanez, M.; Cheuquepan, W.; Cuevas-Vicario, J. V.; Hernandez, S.; Heras, A.; Colina, A. Double Fingerprint Characterization of Uracil and 5-Fluorouracil. Electrochimica Acta 2021, 388, 138615. doi:10.1016/j.electacta.2021.138615

[5] Rivera-Gavidia, L. M.; Luis-Sunga, M.; Bousa, M.; Vales, V.; Kalbac, M.; Arévalo, M. C.; Pastor, E.; García, G. S- and N-Doped Graphene-Based Catalysts for the Oxygen Evolution Reaction. Electrochimica Acta 2020, 340, 135975. doi:10.1016/j.electacta.2020.135975

[6] Ibáñez, D.; González-García, M. B.; Hernández-Santos, D.; Fanjul-Bolado, P. Detection of Dithiocarbamate, Chloronicotinyl and Organophosphate Pesticides by Electrochemical Activation of SERS Features of Screen-Printed Electrodes. Spectrochim. Acta. A. Mol. Biomol. Spectrosc. 2021, 248, 119174. doi:10.1016/j.saa.2020.119174

Post written by Dr. David Ibáñez Martínez (Product Specialist Spectroelectrochemistry) and Belén Castedo González (Marketing and Communication) at Metrohm DropSens, Oviedo, Spain.

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