Ultrasensitive and On‐Site Detection of Nitroaromatic Explosives Through a Dual‐Mode Hydrogel Sensor Utilizing Portable Devices

Abstract The development of straightforward and dependable explosive sensors for on‐site identification is essential to preserving public safety concerns and lowering the safety risks related to explosions. However, one of the main barriers to the advancement of on‐site explosives detection in the future is the complexity of detection process. Here, a flexible hydrogel‐based sensing platform based on 3,4‐bis (4‐(1,2,2‐triphenylvinyl) phenyl) thiophene (TPE‐Z) and a methyl red design concept is shown that simultaneously achieves all targeted properties, including being quick, portable, reliable, and resistant to external interference. This composite fluorescent probe demonstrates outstanding detection capabilities, including low detection limits (0.48 mg L⁻¹) and rapid response times (<5 s), which can be combined with smartphones for on‐site 2,4,6‐trinitrophenol (picric acid, PA) detection. Two independent fluorescence and colorimetric channels on the sensor showed selective response to PA under fluorescence and visible light irradiation, respectively. Meanwhile, the hydrogel sensor's distinct “turn on” and “turn off” response modes to PA can be utilized to construct “YES” and “NO” logic gates, which subsequently proves that they can be employed to differentiate PA on‐site. This sensing platform based on hydrogel is envisaged to offer in‐depth insights in advancing the on‐site detection of nitroaromatic explosives.