BODIPY-derived multi-channel polymeric chemosensor with pH-tunable sensitivity: selective colorimetric and fluorimetric detection of Hg²⁺ and HSO₄^− in aqueous media

다국어 초록 (Multilingual Abstract)

<P>The development of water-soluble polymeric probes capable of recognizing more than one analyte is quite challenging and has attracted significant attention. A water-soluble random copolymer (P1) consisting of hydrophilic <I>N</I>,<I>N</I>′-dimethyl acrylamide (DMA) and aldehyde-terminated difluoroboron dipyrromethene (BODIPY) methacrylate segment was synthesized <I>via</I> the reversible addition-fragmentation chain transfer (RAFT) polymerization for the detection of Hg<SUP>2+</SUP> and HSO4<SUP>−</SUP> ions, respectively. The aldehyde terminal end of P1 was post-functionalized with 4-amino phenol through a Schiff-base condensation reaction, leading to a final polymeric probe (P2). P2 exhibited both colorimetric and fluorimetric responses according to the pH of the aqueous solution or bubbling the solution with CO2, manifesting itself as a pH indicator and CO2 sensor. Upon the addition of Hg<SUP>2+</SUP> ions, P2 showed apparent color changes from pink to light yellow under ambient light and colorless to bright green emission under 365 nm UV light with a very low limit of detection (LOD = 1.10 μM). At low pH, no change in the fluorescence enhancement was observed upon exposure to Hg<SUP>2+</SUP> ions, whereas the fluorescence intensity of P2 increased remarkably at high pH. Similar sensing behavior was observed for HSO4<SUP>−</SUP> ions with a LOD of 1.12 μM. P2 was quite selective toward Hg<SUP>2+</SUP> and HSO4<SUP>−</SUP> over the other metal cations and anions tested, respectively. The detection of both Hg<SUP>2+</SUP> and HSO4<SUP>−</SUP> ions originated from the direct hydrolysis of imine bonds of P2.</P>