Fluorescence detection of phosphonates in water by a naphthalimide-based receptor and its derived cryopolymers

Phosphonates have found broad commercial applications as scale inhibitors in reverse osmosis facilities, boilers, heat exchangers, evaporation plants, and oilfields. Irrespective of their long-term use, there is a cogent need to detect phosphonates in aqueous solution “online” to control their actual concentration in industrial water treatment. Towards this goal, a novel fluorescent-labeled monomer M containing a triamine subunit and 1,8-naphthalimide with an allyl group has been synthesized and found to exhibit a selective fluorescence enhancement with phosphonates in the presence of other anions. The absorption and fluorescence properties of M as well as its effective stability constants with various phosphonates have been studied in a wide pH range. M has been implemented in the synthesis of cryopolymers, which can detect phosphonates in aqueous solution. The presented results provide an important contribution to the future design of fluorescent polymer probes for antiscalants.