A dual reversible-mode near-infrared AIE fluorescent probe: naked-eye identification and removal of CN- and HSO3-/SO32- anions from food and environmental samples.

We report a novel near-infrared AIE fluorescence probe TPA-S-Cy3. Fluorescence spectra showed that TPA-S-Cy3 specifically recognized CN- with a detection limit of 122.00 nM. In terms of UV colourimetric discrimination, both HSO3-/SO32- and CN- anions could discolour TPA-S-Cy3, with HSO3-/SO32- fading better and the detection limit for HSO3-/SO32- was found to be 791.00 nM. Meanwhile, the HSO3-/SO32- complex can produce hydroxyl radical oxidative addition under UV irradiation, and this restores the TPA-S-Cy3 structure and colour. TPA-S-Cy3 upon complexation with CN- do not undergo this change, and thus HSO3-/SO32- and CN- can be identified by simple UV irradiation with the 'naked eye'. In view of the low detection limits of TPA-S-Cy3 for HSO3-/SO32- and CN- anions, the spiked recoveries of TPA-S-Cy3 for both environmental and food testing were in accordance with the requirements. In addition, the detection of SO2 and HCN gases was achieved by loading TPA-S-Cy3 onto a hydrogel.