ABSTRACT
Fluorescence-based detection is one of the most efficient and cost-effective methods for detecting hazardous, aqueous Hg2+. We designed a fluorescent porous organic polymer (TPA-POP-TSC), with a "fluorophore" backbone and a thiosemicarbazide "receptor" for Hg2+-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 (Ksv = 1.01 × 106 M-1) and outstanding selectivity for Hg2+ 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 Hg2+-detecting test strips that are convenient, inexpensive, fast, highly sensitive, and reusable. Our design takes advantage of the efficient and selective capture of Hg2+ by thiosemicarbazides (binding energy = -29.84 kJ mol-1), which facilitates electron transfer from fluorophore to bound receptor, quenching the sensor's fluorescence.
ABSTRACT
A new turn-on fluorescent chemosensor, DPPL1, was rationally designed and synthesized based on diketopyrrolopyrrole (DPP), which presented high sensitivity and selectivity for Zn(2+). Specifically, DPPL1 presented a large emission enhancement and a 70 nm blue-shift upon Zn(2+) binding. (1)H NMR titrations, studies into the pH effects and DFT calculations further proved that this phenomenon was due to both photo-induced electron transfer (PET) and intra-molecular charge transfer (ICT) processes. More importantly, DPPL1 was successfully used for imaging Zn(2+) in living HeLa cells. To the best of our knowledge, this is the first DPP-based fluorescent chemosensor to recognize Zn(2+) ions in living cells with a large blue-shift and a fluorescent enhancement based on both photo-induced electron-transfer (PET) and intramolecular charge-transfer (ICT) effects. Meanwhile, we have also provided a new effective platform for the development of fluorescent chemosensors for other analytes.
