Ion-Unquenchable and Thermally “On–Off” Reversible Room Temperature Phosphorescence of 3-Bromoquinoline Induced by Supramolecular Gels

Ion-unquenchable and thermally on–off reversible room temperature phosphorescence (RTP) can be induced by entrapping 3-bromoquinoline (3-BrQ) into supramolecular gels formed by the self-assembly of a sorbitol derivative (DBS). In comparison with conventional substrates inducing RTP, the gel state 3-BrQ/DBS can produce strong RTP due to the efficient restriction of the vibration of 3-BrQ. Notably, the rather inconvenient deoxygenation is no longer necessary in the preparation of 3-BrQ/DBS gels. The produced RTP was found to be very fast to reach stable, not depending on the standing time. As a reference, in the liquid state of 3-BrQ/sodium deoxycholate (NaDC), stable RTP can be observed after standing for 5 h. The investigation of RTP quenching indicates that the mechanism of RTP induced by DBS gels mainly involves the microenvironment in which 3-BrQ is located. 3-BrQ was entrapped in the hydrophobic 3D network structure of DBS gels, thereby restricting the motion and collision of 3-BrQ and avoiding RTP quenching and additionally quenching by ions. Furthermore, the RTP of 3-BrQ/DBS gels show an excellent “on–off” effect at 10 or 80 °C. This indicates that the solid DBS gel is beneficial for the preparation of RTP sensor devices.