Abstract
The use of insoluble bismuth salts, typically BiPO4, is known to be a viable alternative to classical Bi3+ ion electrochemical reduction for the preparation of bismuth film electrodes (BiFE) on screen-printed electrodes. The freshly prepared electrodes are indefinitely stable, and the active bismuth film is simply formed by in situ reduction. Two aspects are still to be investigated, namely the bismuth distribution on the working electrode and the possible residual presence of the counteranion, namely phosphate. High-vacuum techniques such as electron microscopy or spectroscopy, which are commonly employed for this purpose, cannot be safely used: the bismuth surface is well-known to reconstruct and recrystallize under the electron beam in vacuum. Here, we demonstrate the suitability and the effectiveness of laser ablation ICP-MS (LA-ICP-MS, a technique that vaporizes and analyzes the surface material under flowing helium at atmospheric pressure) for the characterization of BiFE. Fast and stable measurements of bismuth and phosphorous distribution are achieved with the advantage of a minimum alteration of the sample surface, avoiding possible interferences. This investigation evidenced how, upon reductive activation, the bismuth film is distributed with a radial symmetry and the phosphate counteranion is completely absent on the working electrode surface.
Highlights
The pioneering works by Wang and Hocevar on bismuth [1,2] had the merit to draw considerable interest in this “green” element to prepare electroactive surface films as a low-toxicity alternative to conventional mercury films
Bi00 metal in screen-printed electrodes is known to have atoprofound on analytical metalphase phase in screen-printed electrodes is known have aeffect profound effect performances
Anan important role role hashas shown how ICP-MSmay mayplay play important in the characterization of electrochemical surfaces
Summary
The pioneering works by Wang and Hocevar on bismuth [1,2] had the merit to draw considerable interest in this “green” element to prepare electroactive surface films as a low-toxicity alternative to conventional mercury films. Bismuth shows evident analogies with mercury in forming alloys and adsorptive complexes with many metals [3]. Increased interest to “green” metal modifiers other than bismuth is observed [4,5,6,7]. Biosensors 2020, 10, 119 its very low toxicity, will play a definite role for the electroanalytical studies of organic as well as biological molecules [8,9,10]. The preparation of an active bismuth film on a screen-printed electrode (BiFE-SPE) is generally carried out under the conventional electrochemical reduction of Bi3+ ion in aqueous electrolytes
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