Smartphone-Compatible Electrospun Nanofiber Sensors for Fluorescent Detection of Picric Acid using Anthracene-Functionalized Halloysite Nanotubes

Abstract

Picric acid (PA, 2,4,6-trinitrophenol), which is highly soluble in water, seriously contaminates natural water sources and soil and causes significant health risks such as post-exposure sycosis, renal failure, abnormal liver function, and respiratory problems. This study aims to develop a novel nanosensing system based on halloysite nanotubes functionalized with anthracene groups (2) for the ultra-sensitive and selective detection of PA in complex real-world applications. Comprehensive characterization was performed using advanced microscopic (SEM, TEM), spectroscopic (FTIR, XRD, UV-Vis, fluorescence), and thermal (TGA) techniques. The hybrid nanosensor exhibited a robust turn-off fluorescence response driven by an electron transfer mechanism between PA's nitro groups and anthracene. Key sensing parameters were systematically optimized, including selectivity against competing compounds, photostability, and optimal sensor concentration. The system achieved remarkable detection and quantitation limits of 27.50 nM and 82.50 nM, respectively, with a linear range between 0.09 and 1.00 mu M. HPLC and spike recovery analysis were applied for validation and confirmed the method's reliability in detecting PA in lake water, food, and soil samples. The electrospinning technique was employed to fabricate portable nanofiber membranes by incorporating the nanosensor into a polycaprolactone polymer matrix, enabling the development of a practical test kit for real-world applications. The developed nanofiber membranes were successfully utilized as portable test kits, enabling rapid detection of PA through RGB analysis via a smartphone application. The results demonstrate the potential of this novel nanosensing platform for sensitive and reliable detection, offering promising applications in environmental and food safety monitoring.