Spectroscopic characterization and in silico modelling of polyvinylpyrrolidone as an anion-responsive fluorescent polymer in aqueous media

ABSTRACT

Aqueous anion recognition has been a long-standing challenge in molecular recognition. The use of synthetic polymers is an emerging area of interest due to their conformational flexibility, creating microdomains that favor the desolvation and binding of anions in water. Here, we report that the fluorescence of off-the-shelf polyvinylpyrrolidone (PVP) can be used to detect the presence of not only nitrate, as previously reported, but also nitrite, iodide, and thiocyanate in aqueous media. The extent of quenching and anion affinity is dependent on the solution pH and the molecular weight of PVP, while showing close correlation with the Hofmeister series. Moreover, molecular dynamics simulations support our experimental findings, suggesting that anions associating closest to the surface of PVP quench its fluorescence to the greatest extent. Combined with the versatility of PVP, this fundamental study provides a starting point to confer anion binding properties with a fluorescence output in new materials.

Graphical abstract

KEYWORDS:

• Aqueous anion recognition
• Hofmeister series
• fluorescent polymer
• polyvinylpyrrolidone
• molecular dynamics

Acknowledgments

We thank Professor Gabriele Meloni, Dr. Koushambi Mitra, Ms. Whitney Ong, and Ms. Jasmine Tutol for helpful discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Welch Foundation [AT-1918-20170325].