Detection of dissolved Ammonia and trinitrophenol using hydrogel tags doped with pyridine-functionalized AIEgens: A strategy for mitigating ammonium picrate hazards in explosive disposal.

Dissolved ammonia and trinitrophenol (TNP) in water represent a critical environmental and safety challenge. Under slightly acidic conditions, these two compounds spontaneously react to form crystalline ammonium picrate-a highly shock-sensitive explosive compound. This poses explosion risks during wastewater transport, treatment, and sludge handling processes. Existing detection methods rely on complex laboratory instrumentation and cannot provide simultaneous, real-time on-site monitoring. Therefore, there is an urgent need for on-site and simultaneous monitoring of these two hazardous substances. Here, we developed an aggregation-induced emission (AIE) active molecule, DVA-4P, functionalized with four pyridine groups. Its highly twisted molecular conformation effectively suppresses π-π stacking and restricts intramolecular motions, resulting in intense solid-state fluorescence with a quantum yield of 41.87 %. This molecular design can fully leverage the dual functionality of pyridine: the protonated form (DVA-4P-H) enables "turn-on" fluorescence detection of ammonia, while the neutral form (DVA-4P) facilitates "turn-off" detection of TNP through electron donor-acceptor interactions. Two separate hydrogel tags are therefore prepared: one encapsulated in a PTFE membrane for selective dissolved ammonia detection, and one left unshielded for selective TNP detection. The tags can achieve high sensitivity and selectivity, with detection limits of 0.70 μg/L for ammonia and 66.2 nM for TNP. The recovery rates of both hydrogel tags in lake water exhibited excellent performance with deviations from the standard within 5 %, providing a practical, dual-mode analytical platform for the environmental monitoring and wastewater treatment.