Optimizations towards a nearly invariable WO3-functionalized electrochemical aptasensor for ultra-trace identification of arsenic in lake water

Abstract

Prolonged exposure to elevated levels of arsenic in water can lead to serious health problems and its efficient detection is vital for preventing acute arsenic poisoning incidents. The nanomaterial based electrochemical detection offers advantages in terms of high sensitivity, selectivity, and potential for compact, portable testing systems; albeit suffers from inter-device variability. This work presents a highly sensitive aptamer-based nano-biosensor for efficiently detecting arsenic in water through the electrochemical method using glassy carbon electrodes modified with tungsten trioxide (WO3) nanomaterial. The aptasensor in conjunction with electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) techniques is employed for detection of As(III) in de-ionised and lake water. To ensure reliability, rigorous optimization was conducted to achieve near uniformity in the adhesion of the nanomaterial dispersion. The designed sensor's detection limit is 1.12 nM and 0.76 nM for DPV and EIS methods respectively, well below the safe limit of 10 µg/L (∼133 nM). The sensitivity obtained using EIS is 22.5 µM-1 cm-2, and the sensor has a shelf life of 30 days. The proposed methodology can be applied to assess water toxicity without releasing any secondary toxins into the environment and can be coupled with a miniaturized sensing system for enhanced environmental monitoring.