A functional micro-needle sensor for voltammetric determination of iron in coastal waters

Abstract A novel micro-needle sensor based on gold nanoclusters (AuNCs) immobilized with conducting polymer film poly(3,4-ethylenedioxythiophene)-poly(sodium 4-styrenesulfonate) (PEDOT-PSS) was fabricated for determination of iron in coastal waters. The unique aciform structure of the micro-needle electrode (MNE) provided larger specific surface area than common electrodes. The surface modification of MNE with PEDOT-PSS improved the conductivity of the electrode and increased the active sites for combination and immobilization of AuNCs. The cluster-like structure of AuNCs was formed as a result of the regulation of PEDOT-PSS, which showed excellent electrocatalytic activity for the reduction of Fe3+. The so-fabricated AuNCs/PEDOT-PSS/MNE showed excellent sensitivity, selectivity, reproducibility, and repeatability for iron determination with the linear range of 0.01 to 5 μM and detection limit of 3.1 nM, respectively. Furthermore, the micro-needle sensor was successfully used for the determination of acidified dissolved iron in a coastal river from the source to the estuary with satisfactory results.