A fluorescent nanoprobe based on cellulose nanocrystals with porphyrin pendants for selective quantitative trace detection of Hg2+.

A well-dispersed chemosensor based on cellulose nanocrystals (CNCs) with porphyrin pendants (CNC-SA-COOC6TPP) was facilely synthesized by the combination of carboxylation, extended esterification and dicyclohexylcarbodiimide (DCC) reaction. The CNC-SA-COOC6TPP nanomaterials promoted the solubility of porphyrin groups in water and the nanomaterials could be easily separated from water by filtering. The structure of CNC-SA-COOC6TPP nanomaterials could be verified by FT-IR, 1H NMR and XPS characterization. The TEM images showed that CNC-SA-COOC6TPP nanomaterials presented needle-like morphologies. The unique properties of high sensitivity and selectivity for Hg2+ of porphyrin-modified CNCs were investigated separately via fluorescence emission spectroscopy under characteristic excitation wavelengths of porphyrin moieties. Further investigation revealed that CNC-SA-COOC6TPP nanomaterials (0.01 wt% in H2O) could specifically detect Hg2+ with a detection limit for Hg2+ of ca. 5.0 × 10−8 mol L−1 (50 nM). In addition, Hg2+ was specifically detected with interference from other metal ions, which was attributed to the specific formation of the Hg2+–porphyrin complex with an interaction stoichiometry of one Hg2+ per porphyrin moiety. The concentration of all other metal ions could be qualitatively detected based on the relationship between fluorescence intensity and concentration. As a result, the good dispersion of cellulose nanocrystals and the high selectively and sensitivity of porphyrin pendants resulted in the highly efficient detection of Hg2+ in water, which makes CNC-SA-COOC6TPP a promising fluorescence chemosensor. [ABSTRACT FROM AUTHOR]