Nanomolar detection of hypochlorite in ground water samples by a norbornene-based polymeric sensor via unusual fluorescence turn-on response

Abstract

Hypochlorite anion has been widely used as a bleaching and disinfecting agent in daily life. Selective and sensitive identification ofOCl^-ions from water is very important for researchers. For this purpose, monomeric (NPh), and polymeric (PNPh-Peg) novel fluorescent sensors have been established for the specific and excellently unique sensors that exhibit selective characteristics like excellent resistance to bleaching and a high fluorescence brightness. A multi-functional random polymer (PNPh-Peg) with ICT (intramolecular charge transfer) active para–amino phenol functionality and reactive oxygen species (ROS) responsive, PEG attached are readily prepared via ROMP (ring-opening metathesis polymerization).: An ICT-active random polymer (PNPh-Peg) exhibited an unexpectedly strong cyan blue emission in a water medium compared to that in other common organic solvents, which was dramatically increased by adding a trace amount of NaOCl.: Incorporating PEG moiety in the polymeric backbone increases the water solubility of a copolymer, and the ROS-responsive groups make the polymer a good ROS scavenger. Upon oxidation of the phenol group into carbonyl, both the monomeric (NPh) and polymeric (Norp-PEG oh) sensors showed a selective, noticeable, unusual fluorescence turn-on response towardsanalyteOCl^-ions with a very fast response (within three minutes). The detection limit (59.14 nM) and (126.93 nM) were calculated for monomeric and polymeric sensors, respectively. This was a selective, specific oxidation reaction of the completely water-soluble random polymeric sensor (PNPh-Peg) for hypochlorite anions and can be applicable for quantitative measurement of aqueous OCl^-. This ICT-active random polymeric molecule (PNPh-Peg) can also be used as a fluorescent sensor for unique OCl^- detection from contaminated water by preparing a sensor-coated paper strip. Thus, these multi-functional monomeric (NPh) and polymeric (PNPh-Peg) sensors are anticipated to apply to the environment.

Graphical Abstract

Keywords:

• Bio-imaging
• bleaching property
• hygroscopic
• multi-functional
• polymeric sensor

Acknowledgments

J. S. thanks DBT for a research fellowship. R. S. thanks IISER-K, DBT, DST, and DRDO for funding. The authors thank IISER-K for the use of infrastructure and facilities.

Authors’ contributions

J.S. did all the reactions and wrote the manuscript. N.D. helps to do the reactions and write the manuscript. R.S. supervised every step of this project.

Disclosure statement

No potential conflict of interest was reported by the author(s).