情報共有
selective and sensitive detection, rapid quantification of a huge variety of analytes, diagnostic tool, development of new methodologies and sensors, etc. [3].
よく知られた2つの分析技術、電気化学と分光法の組み合わせによって生まれたのが、分光電気化学（SEC）という科学的手法です。このハイブリッド技術は、光学信号と電気化学的信号の両方を同時に記録できるため、研究者にとって両分野の利点を活かして新たなデータを得ることができます［1］。本稿ではまず分光電気化学の定義を紹介し、研究におけるその利点を示した上で、さまざまな分光電気化学アプリケーションに取り組む際の利便性を高める新しいシステムやソリューションについて紹介します。
分光電気化学とは？
分光電気化学的手法は、マルチレスポンス手法に分類されます。これは、電気化学反応のプロセスを、光学的なモニタリングを同時に行いながら研究する方法です。分光電気化学は、1回の実験から2つの独立した信号を得ることができるため、対象とする系について重要な情報を得るための非常に強力な手法です。さらに、分光電気化学は自己検証的な性質を持ち、2つの異なる手段によって得られた結果の正当性を確認できます。
このトピックの詳細は、弊社のアプリケーションノートをご覧ください。
分光電気化学：自己検証型の分析手法 – 一つの実験で二つの異なる方法によって結果を確認
分光電気化学の原理は、電気化学反応に関与する化合物と電磁波のビームとの相互作用を解析することに基づいています。光学的および電気化学的信号の変化を通じて、電極反応の進行状況についての洞察が得られます。
この分析手法は、1960年代にセオドア・クワナ教授が、光を透過する電極を用いて、光ビームが電極を通過する際に同時に電荷と吸光度を測定するという手法で、同時進行するプロセスを研究したことにより開発されました［2］。このような電極は「光学的に透明な電極（optically transparent electrodes, OTEs）」と呼ばれ、光学的および電気化学的な実験を同時に行うために開発されました。ただし、すべての分光電気化学の構成が透明電極を必要とするわけではありません。
1964年に最初の分光電気化学に関する論文が発表されて以来［2］、この技術に基づく研究と論文の数は着実に増加しています（図1）。
図1.
分光電気化学法が1960年代に開発されて以来、この手法に関する論文の発表数は大幅に増加している（2025年1月時点で「Spectroelectrochem*」をScopusで検索した結果に基づく）。
分光電気化学法は、電子移動反応に関与する反応物、中間体、あるいは生成物から、分子的、速度論的、熱力学的な情報を収集することを可能にする手法です。そのため、生体複合体、重合反応、ナノ材料の特性評価、分析物の検出、腐食機構、電気触媒反応、環境プロセス、メモリデバイスの特性評価など、さまざまな分子や多様なプロセスに対して分光電気化学的研究を行うことが可能です。
選べる多様な分光電気化学的手法：SECの種類
使用するスペクトル領域によって得られる情報の種類は異なります。以下の図（図2）は、さまざまな電気化学法と分光法の組み合わせに基づいて分類されています。一般的な分類は分光法の種類に基づいており、紫外（UV）、可視（Vis）、フォトルミネッセンス（PL）、赤外（IR）、ラマン、X線、核磁気共鳴（NMR）、および電子スピン共鳴（EPR）が含まれます。
図2.
分光電気化学法（SEC）とは、分光法と電気化学法を組み合わせたものであり、ここではこの2つの手法が重なり合う部分として示されています。
たとえば、UV/VIS分光法は分子の電子準位に関する分子情報を取得し、近赤外（NIR）領域は振動準位に関連するデータを取得します。また、ラマン分光は、この手法のフィンガープリント特性により、試料の構造や組成に関する非常に特異的な情報を取得します（図3）。
図3.
電磁スペクトルの図
The main advantages of spectroelectrochemical techniques are summarized below:
- 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 several different fields due to its versatility
- new configurations facilitate the performance of spectroelectrochemical experiments, saving time, samples, costs, etc.
Significant advances have occurred in recent years 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, 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 (Figure 4). Both instruments are connected independently to the same spectroelectrochemical cell and are usually not synchronized. In addition, each instrument is controlled by a different (and specific) software, so two programs are needed to interpret each signal as well as yet another external software for processing and analyzing 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.
Figure 4.
This detached spectroelectrochemical setup displays the complexity of the software and programs used, showing that different systems are not able to obtain actual synchronized electrochemical measurements and data.
Metrohm DropSens took this opportunity to create something that did not exist before—revolutionizing state-of-the-art spectroelectrochemistry: the SPELEC line of instruments (Figure 5). These are fully integrated, synchronized solutions that offer researchers much more versatility. 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).
Figure 5.
The SPELEC systems from Metrohm DropSens consist of one device and one software—a fully integrated, easy-to-use, practical SEC 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 valuable time and laboratory space. 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 offered.
Multiple options are available depending on the spectral range needed:
SPELEC: 200–900 nm (UV-VIS)
SPELEC 1050: 350–1050 nm (VIS-NIR)
SPELEC NIR: 900–2200 nm (NIR)
SPELEC RAMAN: 785 nm, 638 nm, or 532 nm laser
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 array 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.
Find out more in our blog post.
Simplifying spectroelectrochemistry setups with intuitive and user-friendly cells
Multiple spectroelectrochemistry applications
The characteristics of spectroelectrochemistry allow constant development of new applications in several different fields. Read on below to discover the capabilities of this technique (click to expand each section).
study of the properties and structure of different compounds, analysis of kinetic reactions, determination of electron transfer capacity, etc. [4].
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.
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.
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].
study of biological processes, characterization of molecules used in biotechnology, biochemistry or medicine, determination of antioxidant activity, etc.
identification and quantification of pesticides, dyes, and pollutants, monitoring of degradation and filtration processes, etc. [6].
characterization of new materials for memory devices, comparison of minerals, identification of pigments, oils, and pastes, etc.
Learn even more about spectroelectrochemistry application possibilities by downloading our free Application Book.
Your knowledge take-aways
Catalog: SPELEC line portfolio
Blog post: Simplifying spectroelectrochemistry setups with intuitive and user-friendly cells
Spectroelectrochemistry Application Book
On-demand webinar: Spectroelectrochemistry in action: Live experiments
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.; et al. 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.; et al. 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.; et al. 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
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