Flexible liquid crystal polymer-based electrochemical sensor for in-situ detection of zinc(II) in seawater

Abstract

The authors describe a liquid crystal polymer (LCP) based bismuth (Bi) film electrode that can be directly deployed for in-situ determination of zinc(II) ions. The use of an LCP warrants improved operational reliability, high durability, and flexibility of the sensor, allowing it to be mounted on any flat or shaped surface. Square wave anodic stripping voltammetry shows the sensor to be able to detect Zn(II) (−1.64 V vs. thin-film Ag/AgCl reference electrode) in concentrations as low as 1.22 nM at a deposition time of 180 s. Other figures of merit include (a) an analytical sensitivity of 1.55 nA∙nM−1∙mm−2, (b) a linear detection range extending from 4.59 to 1071 nM, (c) a repeatability with a relative standard deviation of 3.35% (for n = 10), (d) a reproducibility with a relative standard deviation of 1.64% (for n = 6). Real-time applicability of the sensor for in-situ detection was demonstrated by determination of Zn(II) in seawater. In an extension of the method, a flexible sensor array consisting of four LCP-based sensors was attached to the hull of an autonomous kayak, which was remotely operated. The response of the sensor array indicated a clear trace of Zn(II) concentrations in seawater. This was confirmed by ICP-MS analysis. The results suggest the potential usage of the flexible LCP electrochemical sensor for in-situ monitoring.