Hot-SWV: Square Wave Voltammetry with Hot Microelectrodes

Abstract

A promising strategy to lowering detection limits in electrochemical analysis is the active modulation of the electrode temperature. Specifically, by tuning the electrode's surface temperature one can enhance detection limits due to improved electrode process kinetics and increased mass transfer rates, all without affecting the bulk solution. Motivated by this argument, here we report the development of a new electroanalytical technique based on electrode-temperature modulation, which we call hot square wave voltammetry (Hot-SWV). The technique utilizes the superposition of conventional SWV, already considered as one of the most sensitive voltammetric techniques, and a high frequency alternating current (ac) waveform to electrically polarize microelectrodes. By applying about 100 MHz ac frequencies (with varying V rms amplitudes), our method generates an electrothermal fluid flow (ETF) in the electrolyte surrounding the electrode, thereby increasing the sensitivity of the SWV-based detection. We demonstrate this by investigating the oxidation of ferrocyanide and iron(II) ions, as well as the reduction of the coordination compound ruthenium(III) hexamine under various experimental conditions. We validate our experimental results against a theoretical model built using finite element analysis and observe agreement within ≤15% error at temperatures ≤39 °C. Using Hot-SWV, we observe at least one-order-of-magnitude improvement in the limit of detection of ferrocyanide ions relative to conventional, mm-size electrodes at 25 °C. In addition, we anticipate that Hot-SWV will be particularly useful for electroanalytical measurements of ultralow (≤pM) concentrations of analytes in environmental and biomedical applications.

Using voltammetry augmented with physics-based modeling and Bayesian hypothesis testing to identify analytes in electrolyte solutions

“…amplifying Faradaic processes, 20,42,48 offering an advantage over CV. 4,49 For this reason, square wave (SW) voltammetry-that is, CSW voltammetry without the reverse sweep-has been employed in many studies involving qualitative analyses. 14,15,17 Further, CSW voltammetry can more readily discern various electron transfer mechanisms (e.g., an electron transfer followed by the homogeneous degradation of the product 50 ) than SW voltammetry by virtue of the reverse sweep.…”

“…Voltammetry is a foundational technique in electrochemical science that enables both qualitative and quantitative characterization of electroactive species-such as analytes (i.e., redoxactive compounds)-for a variety of applications. [1][2][3][4][5][6][7][8][9][10] Examples include tracking the transient behavior of solutions in electrochemical systems 8,[11][12][13] and labeling compounds within a sample. 14-species), along with the electrode surface morphology, are known prior to and remain constant throughout the experiment, established fundamental relationships can often be leveraged to discern both physical and electrochemical properties in the system of interest, 3,5,7,18 enabling mechanistic insights into electrochemical and chemical reactions of electroactive compounds.…”

Using Voltammetry Augmented with Physics-Based Modeling and Bayesian Hypothesis Testing to Estimate Electrolyte Composition

“…We elected to use CSW voltammetry to acquire the data for library construction because it can be more accurately modeled; its waveform minimizes background electrochemical signals while amplifying Faradaic processes, 20,42,46 offering an advantage over CV. 4,47 For this reason, SW (so by extension CSW) voltammetry have been employed in many studies involving qualitative (i.e., visual) analyses. 14,15,17 Further, CSW voltammetry can more readily discern various electron transfer mechanisms (e.g., an electron transfer followed by the homogeneous degradation of the product 48 ) than square wave (SW) voltammetry by virtue of the reverse sweep.…”

“…Voltammetry is a foundational technique in electrochemical science that enables both qualitative and quantitative characterization of electroactive species for a variety of applications, [1][2][3][4][5][6][7][8][9][10] including tracking the transient behavior of electrolytes 8,[11][12][13] and labeling compounds within a sample. [14][15][16][17] When electrolyte composition and electrode surface morphology are known prior to and remain constant throughout the experiment, established fundamental relationships can be leveraged to discern physical and electrochemical properties in the system of interest, 3,5,7,18 enabling mechanistic insights into electrochemical and chemical reactions of electroactive compounds.…”

Using Voltammetry Augmented with Physics-Based Modeling and Bayesian Hypothesis Testing to Estimate Electrolyte Composition

“…Voltammetry is a foundational technique in electrochemical science that enables both qualitative and quantitative characterization of electroactive species for a variety of applications, [1][2][3][4][5][6][7][8][9][10] including tracking the transient behavior of electrolytes 8,[11][12][13] and labeling compounds within a sample. [14][15][16][17] When electrolyte composition and electrode surface morphology are known prior to and remain constant throughout the experiment, established fundamental relationships can be leveraged to discern physical and electrochemical properties in the system of interest, 3,5,7,18 enabling mechanistic insights into electrochemical and chemical reactions of electroactive compounds.…”