Development of BODIPY-based dyes with ICT and AIE characteristics for dual-channel CO2 detection in ionic liquid optical sensors

Abstract

Ionic liquids increase in polarity and viscosity through chemical bonding with CO₂, making them ideal for portable CO₂ optical sensors that incorporate organic dyes sensitive to these changes. Research on dyes capable of efficient dual-channel (colorimetric and fluorescent) CO₂ detection remains limited. This study synthesized four BODIPY-based dyes—TPABDP, PTPABDP, TBTPABDP, and MTPABDP—by introducing triphenylamine (TPA) moieties to form donor–acceptor (ED–EA) structures with aggregation-induced emission (AIE) characteristics. The dyes showed strong intramolecular charge transfer (ICT) behavior, with optical properties responding to changes in polarity and viscosity. Computational analysis verified the separation of hole and electron orbitals, confirming their CT transition properties. Sensors created by dissolving these dyes in ionic liquids demonstrated significant optical changes when exposed to CO₂. In the colorimetric channel, the color shifted from pale yellow to deep red. The fluorescence channel exhibited emission changes from blue to bright green or cyan. MTPABDP exhibited the most significant color shift in the visual channel, while TBTPABDP and TPABDP displayed greater fluorescence enhancement. These results highlight how dyes with rotatable structures and electron push–pull effects enable efficient dual-channel CO₂ detection. This study provides valuable insights for developing dual-mode CO₂ sensors for environmental and industrial applications.