Integrated probe for electrochemical analysis of small volume droplets

• Published in: Sensors and actuators. B, Chemical Chemical, 2021-11, Vol.347, p.130542, Article 130542
• Main Authors: Dang, Ning, Djelidi, Nader, Echeveste Salazar, Gustavo Adrián, Walcarius, Alain, Liu, Liang, Etienne, Mathieu
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Anodic stripping voltammetry; Atmospheric corrosion; Chemical Sciences; Copper; Current distribution; Droplet analysis; Droplets; Electrochemical analysis; Electrochemical impedance spectroscopy; Microelectrode; Microelectrodes; Ohmic drop; Platinum; Potentiometry; Silver chloride; Substrates; Sulfuric acid; Three dimensional printing
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2021.130542

[Display omitted] •An easily renewable integrated probe is fabricated for in-situ analysis of droplets.•The integrated probe is used for potentiometric and voltammetric analysis.•Oxidation of steel plates by Fe3+ droplet is monitored by potentiometry.•Evolution of Cu2+ in a H2SO4 droplet is analysed by anodic stripping voltammetry.•Analysis results allow deriving kinetics of droplet/substrate interfacial reactions. Analysis of small volume droplets is increasingly important in biology, environment, and material science. In this work, an integrated probe consisting of a Pt microelectrode wrapped with an Ag/AgCl wire and inserted into an outer capillary filled with KCl is developed as sensor for electrochemical analysis of small volume droplets (20 μL). With a 3D-printed holder, the design allows easy fabrication, dismantling and re-assembly, which is important for renewing the probe. The integrated probe shows acceptable ohmic drop with electrochemical impedance spectroscopy, thus offers reliable and reproducible potentiometric and voltammetric measurements in bulk solutions. The ring-shaped opening between the inner microelectrode and the outer capillary also enables homogenous current distribution when applying potential between Pt and Ag/AgCl. Based on this, two droplet systems mimicking atmospheric corrosion are in-situ studied: (1) Fe3+ droplet on bare and silane-coated steel; (2) Cu2+ in a H2SO4 droplet on copper. The concentration of Fe3+/Fe2+ and Cu2+ in the droplet is monitored with time, allowing interfacial corrosion reactions between the droplet and the substrate to be studied.