A porous β-cyclodextrin-based terpolymer fluorescence sensor for in situ trinitrophenol detection.

Permanent porosity plays a key role in fluorescent-based polymers with "on-off" emissive properties due to the role of guest adsorption at accessible fluorophore sites of the polymer framework. In particular, we report on the design of a porous fluorescent polymer (FL-PFP) composed of a covalently cross-linked ternary combination of β-cyclodextrin (β-CD), 4,4'-diisocyanato-3,3'-dimethyl biphenyl (DL) and tetrakis(4-hydoxyphenyl)ethene (TPE). The textural properties of FL-PFP were evaluated by the gas uptake properties using N 2 and CO 2 isotherms. The BET surface area estimates according to N 2 uptake ranged from 100-150 m 2 g -1 , while a lower range of values (20-30 m 2 g -1 ) was estimated for CO 2 uptake. Model nitroarenes such as trinitrophenol (TNP) and nitrobenzene (NB) were shown to induce turn-off of the fluorescence emission of the polymer framework at concentrations near 50 nM with ca. 50% fluorescence quenching upon TNP adsorption and detection. The strong donor-acceptor interaction between the nitroarenes and the TPE reporter unit led to fluorescence quenching of FL-PFP upon nitroarene adsorption. The fluorescence lifetime ( τ ) for FL-PFP ( τ = 3.82 ns) was obtained along with a quantum yield estimate of 0.399 relative to quinine sulphate. The β-CD terpolymer reported herein has significant potential for monitoring the rapid and controlled detection of nitroarenes (TNP and NB) in aquatic environments and other complex media.