Emission enhanced two-component gels for the detection of organic amine vapors

Abstract

Hydrogen bonds could help two compounds (C12Ph and SP) with weak emission to produce strong fluorescent complexes and give them the capability to form gels in organic solvents. The complexes exhibited very weak emission in the sol state but emitted strong blue fluorescence with more than a 100-fold increase in emissive intensity after the sols changed into gels. The results from UV-vis absorption, circular dichroism and FT-IR spectral observations suggest that gelation induces the formation of J-aggregates. The fluorescence spectra imply that J-aggregates are responsible for the enhanced emission during gelation. Moreover, a small amount of SP, for example 10% by mole, could help C12Ph to construct three-dimensional fibrous networks and prevent the solvent from flowing. More importantly, a two-component gel film could be used as a sensor to quantitatively detect and discriminate between aliphatic and aromatic organic amine vapors. Aromatic amine vapors might quench the fluorescence of gel film and fluorescence would recover after the quenched film was exposed to air, suggesting a reversible sensing behaviour. On the other hand, although the strong blue emission disappeared after the gel film was exposed to aliphatic amine vapour, blue fluorescence was not restored because the hydrogen-bonded complex was destroyed.