Versatile electrochemical approaches

Electrochemistry is everywhere, from the batteries in ubiquitous portable electronic devices to the humble pH meter found in many experimental labs around the world. It is an incredibly versatile discipline with impact across many areas of society. Analytical aspects of electrochemistry enable a multitude of healthcare measurements daily, based on principles described by Nernst more than 100 years ago (e.g. ion-selective electrodes for blood electrolyte measurements), while environmental conditions are often assessed by employing electrochemical measurements of conductivity, pH and dissolved oxygen (Clarke's oxygen electrode). Analyst has always been an outlet for publication of important advances in electroanalytical chemistry, illustrated, for example, by the 1952 publication of Barker and Jenkins’¹ seminal work on square wave polarography, which evolved into the ubiquitous square wave voltammetry used in myriad trace analytical investigations, and, relatively more recently, the introduction of PVC to stabilise liquid membrane electrodes described in these pages by Moody, Oke and Thomas in 1970² and now a widely used platform in the evaluation of new sensor materials.†

This themed collection in Analyst focuses on versatile electrochemical approaches for sensing, biology, and energy. Today's challenges in these fields are beyond those of Nernst's time, and require immense creativity, skill, and ingenuity to develop enabling tools and strategies that unearth solutions to pressing issues in ultra-sensitive detection, in the understanding of charge transfer in energy materials, and in the observation of biological processes at ever smaller scales. Thus, we set out to bring together a collection of papers, including reviews, communications and primary articles, that cover the broad range of cutting-edge electrochemical approaches, encompassing nanoscale electrochemistry, rational electrode design, biomolecular analysis, and interface-sensitive methods amongst other fascinating topics. Accordingly, this collection now features new electroanalytical strategies in bioanalytical and biomarker diagnostics, in characterising energy storage and energy harvesting systems, and in biological and chemical measurement sciences that together illustrate the versatile ways in which electrochemistry is used in the characterisation of matter and the realisation of new analytical processes.

All together, this collection presents reviews and primary reports across the following themes:

Health-related electrochemical measurements, including bioanalytical and sensor strategies, in which Puthongkham and Venton (DOI: 10.1039/C9AN01925A) present a minireview on fast scan cyclic voltammetry for real-time neurotransmitter detection, emphasising new waveform, electrode and data analysis developments, coupled also with a critical review by Venton and Cao (DOI: 10.1039/C9AN01586H) on the fundamentals of fast scan cyclic voltammetry exemplified with dopamine detection at carbon fibre microelectrodes, while the minireview by Simoska and Stevenson (DOI: 10.1039/C9AN01747J) discusses recent advances in the rapid electrochemical detection of bacterial pathogens and direct comparison to conventional methods. The mini review by Mahmudunnabi, Farhana, Kashaninejad, Firoz, Shim and Shiddiky (DOI: 10.1039/D0AN00558D) discusses recent advances in the use of nanozymes in the sensing of disease biomarkers.

Primary papers from a number of groups deal with detection of small molecules of biological importance, whereby Casanova, Cuartero, Alacid, Almagro, García-Cánovas, García and Ortuño (DOI: 10.1039/C9AN02523E) present a biosensor for the detection of ascorbic, benzoic, gallic and kojic acids, emphasising enzymatic generation of quinone from catechol and electrochemical reduction of the quinone, with particular attention to signal processing for applications in beverage and cosmetic analyses; Zhuang and Chen (DOI: 10.1039/C9AN01947B) present atomically precise nickel nanoclusters in thin films for the electrocatalytic oxidation of ascorbic acid, attributing the activity to the high fraction of surface nickel atoms with low coordination; Si, Park, Lee and Lee (DOI: 10.1039/C9AN02638J) introduce a biosensor based on a polymethionine/graphene/carbon nanotube nanocomposite for direct detection of dopamine and uric acid in urine. Detection of macromolecular biomarkers features in the work of Wang, Liu, Qin, Nie, Dong, Liang, Zhu, Yang and Shao (DOI: 10.1039/C9AN01904A) who employ gold–silver nanourchins for the electrochemiluminescent detection of the biomarker cardiac troponin I, using the luminol–hydrogen peroxide system. The cancer biomarker CD44 is determined in serum by Zhou, Cheng, Chen, Yang, Lu, Ming, Chen, Lin and Chen (DOI: 10.1039/C9AN01764J) using an impedance-based aptasensor and the cancer biomarker prostate-specific antigen is determined in human serum by Wang, Zhou, Guo, Qiu and Lin (DOI: 10.1039/C9AN01935A) using an immunosensing approach based on surface-enhanced electrochemiluminesence from gold–silica nanocomposites. The biomarker procalcitonin, an indicator of sepsis, is detected in whole blood by Alshawawreh, Lisi, Ariotti, Bakthavathsalam, Benedetti, Tilley and Gooding (DOI: 10.1039/C9AN01519A) using liposome labels and personal glucose meters in conjunction with sandwich immunosensing.

Electrochemistry relevant to energy storage and conversion technologies is featured in the work of Gossage, Hui, Sarbapalli and Rodríguez-López (DOI: 10.1039/C9AN02637A) who develop a strategy based on scanning electrochemical microscopy for mapping correlated ion and electron transfer processes during solid-electrolyte formation in lithium ion battery electrodes; Lee, Gruninger, Lodaya, Qadeer, Griffith and Dempsey (DOI: 10.1039/C9AN02192B) provide a comprehensive analysis via experiment and modelling of rotating disc electrode voltammetry in the evaluation of homogeneous catalysts for multi-electron transfer processes, relevant to electrocatalytic reactions for fuel cells. Bioelectrocatalysis features in the work of Lim, Sima, Stewart and Minteer (DOI: 10.1039/C9AN02168J), who introduce a single-step immobilisation strategy for enzymes employed in bioelectrocatalysis using an ionic strength-induced phase inversion of oppositely charged polyelectrolytes. Energy-relevant catalysis also underpins the work presented by Sconyers and Blakemore (DOI: 10.1039/C9AN01952A), who used an electrochemical quartz crystal microbalance to examine the electrodeposition and corrosion of first-row transition metal complexes with acetonitrile, which may be responsible for some ambiguities in molecular electrocatalysis for energy-related applications. The behaviour of gas diffusion electrodes based on nanoporous alumina membranes for hydrogen gas oxidation is presented by Fernandez, Tosello and Fernández (DOI: 10.1039/C9AN01882D), who elucidate regimes for high mass transport of reactants for potential use in fuel cells and/or sensors, while Agoston, Sayeed, Jones, de Jonge and O'Mullane (DOI: 10.1039/C9AN01905G) use synchrotron X-ray absorption near edge structure mapping, amongst other techniques, to unravel the heterogeneous distribution of nickel hydroxide catalyst centres during the oxygen evolution reaction, a key process in renewable energy technologies.

Many new approaches to underpinning platform tools or concepts are included in this collection. Reviews within this strand include that by Sachan and Mondal (DOI: 10.1039/C9AN01948K) who discuss the use of electrochemistry to create flexible molecular electronic junctions on various substrates including Au, H-terminated Si, and conductive carbon electrodes, that are suitable for the fabrication of reliable molecular electronics devices. In contrast, the minireview by Huang and Zhu (DOI: 10.1039/C9AN01562K) presents advances on rare earth nanomaterials and their electrochemical properties, and a range of applications including sensing of small biomolecules and DNA. In a tutorial review, Moazzenzade, Huskens and Lemay (DOI: 10.1039/C9AN01832H) introduce the concept of digital sensors based on large numbers of parallel, time-resolved measurements that detect, identify and count individual macromolecular events based on single-entity electrochemistry; while the critical review of ammonium potentiometric sensors provided by Cuartero, Colozza, Fernández-Pérez and Crespo (DOI: 10.1039/D0AN00327A), emphasises in particular the role of the ionophore in these devices and the on-going need for new approaches to overcome selectivity and detection issues. The critical review by Lozeman, Führer, Olthuis and Odijk (DOI: 10.1039/C9AN02105A) discusses the combination of electrochemistry with spectroscopy and spectrometry, i.e. spectroelectrochemistry, as a means of visualising electrode surface processes, and includes discussion of vibrational, NMR and mass spectrometric approaches in electrochemistry.

Primary reports dealing with new platforms or tools, e.g. electrodes, were contributed by a range of groups. In a communication, Li, Ying, Liu, Hu and Long (DOI: 10.1039/D0AN00041H) introduce the measurement of hydrogen nanobubble nucleation within a silicon nitride nanopore, as a method for understanding activation energies for nanobubble formation. Wahyuni, Putra and Marken (DOI: 10.1039/C9AN02186H) show that working electrode reactions can be used to both manipulate the local pH as well as detect a target analyte, in this case thiamine (vitamin B1), as a means to overcome sample conditions that are not ideal for the detection process. Lee, Hussain, López-Salas, MacFarlane and Silvester (DOI: 10.1039/C9AN02153A) show that a fluorinated porous polymer as a support for ionic liquid thin films on microfabricated electrodes enables sensitive and rapid detection of gases such as oxygen and ammonia, whereas Kalinke, Neumsteir, Aparecido, Ferraz, dos Santos, Janegitz and Bonacin (DOI: 10.1039/C9AN01926J) provide a comparative assessment of pretreatment methods for 3D-printed graphene electrodes, finding that hydroxide treatment is best amongst those investigated. Dual electrode systems for voltammetric characterisation in capillary electrophoresis are presented by Gunasekara, Wijesinghe, Pichetsurnthorn and Lunte (DOI: 10.1039/C9AN02112D), while Lan, Wang, Yuan, Fereja, Lou, Han, Li and Xu (DOI: 10.1039/C9AN00615J) presented the detection of tannic acid by quenching of the electrochemiluminescence of the 3,4,9,10-perylenetetracarboxylic acid/oxamic hydrazide system. Nguyen, McCreery and McDermott (DOI: 10.1039/D0AN00409J) studied carbon-on-gold films fabricated by electron-beam evaporation and found they exhibit many characteristics ideal for use in electroanalytical devices, such as fast electron transfer kinetics, low background current and minimal adsorption.

These papers show the diverse facets of the electrochemical analyst in the pursuit of solving big problems faced by society. We have enjoyed putting this collection together and thank the authors, the many reviewers and Analyst editorial staff for their valuable input. We hope this collection seeds new directions, and look forward to continuing to read accounts of versatile electrochemical approaches in Analyst in the coming years.

References

1. G. C. Barker I. L. Jenkins, Square-wave polarographyAnalyst, 1952, 776, 685–696; Republished Analyst 1992, 117, R1–R11.
2. G. J. Moody, R. B. Oke and J. D. R. Thomas, A calcium-sensitive electrode based on a liquid ion exchanger in a poly(vinyl chloride) matrix, Analyst, 1970, 95, 910–918.

Footnote

† Special thanks to Analyst Editorial Board member Prof. Sue Lunte for suggesting we highlight some of Analyst's important historical papers.

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