Novel porous titanium nitride microelectrode for selective detection of Zn2+ ion by electroanalytical method

Abstract

Reliable detection of heavy metal ions (HMIs) at trace levels is crucial for environmental and agricultural monitoring. Zinc (Zn²⁺) while essential for plant health, becomes phytotoxic at elevated levels as plants are prone to accumulate an excess rather than deficit. Excess Zn²⁺ in irrigation water, poses environmental risk and directly threatens plant health which plays a pivotal role in sustaining ecosystems stability and agricultural productivity. Since early and reliable monitoring of zinc levels is important in the ecosystem, developing a highly efficient, stable and low cost detection platform is a research priority. Existing Zn²⁺ ion detection platforms, face limitations in terms of stability and selectivity over prolonged use. Here, we present a porous transition metal nitride sensor that exhibits remarkable electrochemical stability and selectivity for Zn²⁺. This was attained without any modification, functionalization or reliance on precious metals. This notable performance was achieved using a novel material called porous titanium nitride thin film (p-TiN). The proposed sensor was characterized by Scanning electron microscopy (SEM), Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), Chronocoulometry (CC), and Linear sweep anodic stripping voltammetry (LSASV). Its electrochemical response was linear in the concentration range of 10-100µM, and the limit of detection (LOD) incorporating Bessel’s correction, was calculated as 2.65µM, a value well below the FAO’s permissible limit of 30.6µM for zinc in irrigation water. Additionally, the porous TiN microelectrode exhibit mixed control mechanism, high sensitivity (4µA/µM^. cm^-2) and a stable reproducible response to Zn²⁺ for a duration of over 45 days. By contrast, conventional TiN showed no HMI sensing activity. These findings suggest that HMI sensors based on such an inexpensive porous thin film material, can be leading candidates for sustainable environmental and agricultural technologies.