NanoPOP: Solution-Processable Fluorescent Porous Organic Polymer for Highly Sensitive, Selective, and Fast Naked Eye Detection of Mercury

Fluorescence-based detection is one of the most efficient and cost-effective methods for detecting hazardous, aqueous Hg 2+ . We designed a fluorescent porous organic polymer (TPA-POP-TSC), with a “fluorophore” backbone and a thiosemicarbazide “receptor” for Hg 2+ -targeted sensing. Nanometer-sized TPA-POP-TSC spheres (nanoPOP) were synthesized under mini-emulsion conditions and showed excellent solution processability and dispersity in aqueous solution. The nanoPOP sensor exhibits exceptional sensitivity ( K sv = 1.01 × 10 6 M –1 ) and outstanding selectivity for Hg 2+ over other ions with rapid response and full recyclability. Furthermore, the nanoPOP material can be easily coated onto a paper substrate to afford naked eye-based Hg 2+ -detecting test strips that are convenient, inexpensive, fast, highly sensitive, and reusable. Our design takes advantage of the efficient and selective capture of Hg 2+ by thiosemicarbazides (binding energy = −29.84 kJ mol –1 ), which facilitates electron transfer from fluorophore to bound receptor, quenching the sensor’s fluorescence.