Cost-effective and highly selective paper-based potentiometric thiocyanate nanosensor employing nanocomposite for substrate preparation

Abstract

This study represents the first investigation into the fabrication of paper-based thiocyanate-selective potentiometric nanosensor, employing a palladium(II) complex as an ionophore. The construction of a new disposable, environmentally friendly and cost-effective sensing platform and the optimization of both nanocomposite ink suspension containing multi-walled carbon nanotubes (MWCNTs) and NiO nanoparticles (NiONPs) used to achieve conductive paper and thiocyanate-selective membrane cocktail deposited onto the paper substrate using a drop-casting technique were described. Electrochemical impedance spectroscopy (EIS) and potentiometric measurements were examined to identify the appropriate ink and selective membrane compositions resulting in best analytical performances such as Nernstian slope of 59.0 ± 0.8 mV/pSCN with 6.7 nM limit of detection (LOD) in linear range of 1.0 × 10⁻⁶- 1.0 × 10⁻¹ M at pH = 2.0. EIS was also used for characterization of membrane-solution interface to confirm interaction between analyte and the ionophore in the organic membrane phase. Water-layer test was performed to evaluate membrane adherence to the conductive paper substrate by chronopotentiometric method. Assessment of the selectivity coefficients determined through the separate solution methodology indicated that the developed nanosensor displayed a highly selective interaction with thiocyanate in comparison to the other anions that were tested. Finally, the repeatability, reproducibility and analytical applicability of the proposed sensor were studied. Artificial saliva, mustard seed and veterinary drug were selected as real sample examples to prove its successful use as an indicator electrode.