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.