Hydrogel-filled micropipette contact systems for solid state electrochemical measurements
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ORIGINAL PAPER
Hydrogel-filled micropipette contact systems for solid state electrochemical measurements Margherita Donnici 1 & Salvatore Daniele 1 Received: 30 April 2020 / Revised: 11 May 2020 / Accepted: 11 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This paper reports on the use of a novel microcapillary system for solid contact electrochemical measurements. The probe is made of moveable micropipettes, with orifice of 1–30-μm radii, filled with a conducting hydrogel, which forms a thin-gelled meniscus at the pipette end. The hydrogel is made of 2 % (w/v) agarose and water solutions, containing KCl or KNO3 as supporting electrolytes. The micropipette can be brought in contact with a conducting substrate to form a microcell, which allows performing voltammetric measurements confined within limited contact regions. The suitability of the proposed probe for local electrochemical measurements are tested using two electroactive species, dissolved in the hydrogel, namely [Fe (CN6)]4- and Ag+ ions. Mass transport characteristics of the two species, in bulk hydrogel and at micropipette meniscuses of different radii, are examined in detail in the frame of existing theory. For comparison, voltammetric measurements are also performed with micropipettes filled with the corresponding aqueous solutions. It is shown that the gel-filled micropipette, at variance with the aqueous one, prevents the spreading and leakage of solution on the sample surface. The microprobe developed here can be useful to perform electrochemical measurements on surfaces, which suffer from direct contact with liquid electrolytes. A proof-of-concept hydrogelcapillary measurement is performed to distinguish the presence of metallic silver deposited on a graphite-on-paper–based material, realized through simple pencil strokes. Keywords Microcapillary . Agarose . Hydrogel . Voltammetry . Silver deposits . Graphite-on-paper
Introduction Polymeric gels (PGs) prepared by biopolymers (BPs), such as starch, pectin, or agar, have been extensively used in different areas including biology [1] and food industry [2, 3]. PGs have also been frequently used in electrochemical devices such as batteries, accumulators [4, 5], solar cells [6], and sensors [7]. In the latter field, biopolymeric gels (BPGs) have been used to avoid adverse effects arising from organic matter, which can adsorb onto the electrode surface [8], to minimize contribution due to natural convection in the mass transport [9], and to accommodate nanomaterials within its matrix for sensor Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10008-020-04651-w) contains supplementary material, which is available to authorized users. * Salvatore Daniele [email protected] 1
Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30137 Venice, Italy
applications [7]. Recently, BPGs have found applications to construct contact electrochemical cells for solid surface analysis by using elect
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