Highly sensitive, selective and reliable detection of picric acid in aqueous media based on conjugated porous polymer nanoparticles

Conjugated porous polymer is known as a promising sensing material for detecting nitroaromatic compounds, however, the sensing application in aqueous media is restricted, due to their poor solubility/dispersity in water. Herein, two novel conjugated porous polymer nanoparticles (PTPA-TPE1 and PTPA-TPE2) containing triphenylamine in the backbone and tri/tetraphenylethene as side groups were designed and synthesized. PTPA-TPE1 and PTPA-TPE2 were fully characterized by FT-IR, 1H NMR, TEM, N2 sorption isotherms, UV–vis absorption spectra, photoluminescence (PL) spectra and cyclic voltammetry. The electron-rich triphenylamine backbones benefit the interaction with nitroaromatics and the porosity could promote the adsorption/diffusion of the analytes. The PL sensing properties of the polymers were evaluated in aqueous dispersion, and the detection limits of PTPA-TPE1 and PTPA-TPE2 towards picric acid (PA) are 72 ppb and 111 ppb, respectively. Importantly, the PL quenching effect towards PA exhibits no noticeable change upon the addition of other nitroaromatic compounds, indicating the anti-interference characteristic and selective detection of PA. Furthermore, at 95 % confidence level, there was no significant difference between the results of our sensing method and HPLC analysis for detecting PA in real environmental water samples by the t-test.