Potassium ion determination via an ion-sensitive field effect transistor (ISFET) fabricated by electrodepositing copper hexacyanoferrate nanoparticles onto a commercial junction field effect transistor

This study introduces a simple, low-cost potassium sensor based on a commercial junction field effect transistor (JFET). The JFET was mechanically cut and electrically isolated, followed by electrodeposition of copper hexacyanoferrate nanoparticles (CuHCF-NPs) onto its copper gate using cyclic voltammetry from a solution containing only K₄Fe(CN)₆. The modified device served as an ion-selective field effect transistor (ISFET) for potassium detection. The sensor exhibited a near-Nernstian sensitivity of ۵۷.۲ mV per pK⁺ over a linear concentration range of ۱.۱۶۶ × ۱۰⁻⁵ to ۵.۴۳۲ × ۱۰⁻³ M, with a low drift of ۰.۲۳ mV h⁻¹ and a detection limit of ۷.۰۴ µM (S/N = ۳). The sensor also showed a fast response time of ۱۰.۳ s and a selectivity order of Cs⁺ > K⁺ > Na⁺ > Li⁺, consistent with the effective hydrated ionic radii of the cations. Scanning electron microscopy (SEM) revealed a uniform nanoparticle size distribution with an average diameter of ۴۰ nm. The sensor's practical applicability was confirmed by potassium determination in drinking water, tap water, orange juice, and human blood serum samples, with recovery values ranging from ۹۸.۶% to ۱۰۲.۰% and RSD values below ۳.۸%. Compared to previously reported metal hexacyanoferrate-based potassium sensors, the proposed CuHCF-NPs ISFET sensor offers a lower detection limit, faster response time, smaller size, and lower fabrication cost. The key novelty of this work is the successful combination of CuHCF-NPs with a mechanically modified commercial JFET—a strategy that has not been reported previously. To the best of our knowledge, this is the first report of a metal hexacyanoferrate compound on an ISFET electrode for potassium determination.

کلیدواژه ها:

ISFET ، copper hexacyanoferrate nanoparticles ، potassium determination ، ion sensitive field effect transistor