Largely conjugated planar acceptor and rotatable donors to construct AIEgens with large molar extinction coefficients for the detection of metal ions

Abstract

To maintain high molar extinction coefficients when fabricating luminogens with aggregation-induced emission characteristics (AIEgens) is of great significance yet challenging. Herein, we utilize phenanthroline with high conjugation degree and electron-withdrawing ability as the electron acceptor and triphenylamine (TPA) or tetraphenylethylene (TPE) as the electron donor to fabricate new AIEgens with high molar extinction coefficients. Accordingly, DTPAP and DTPEP with D–A–D structure were obtained. Photophysical data indicated that the introduction of phenanthroline can enhance the donor–acceptor interactions to result in high molar extinction coefficients with a value of 2.90 × 10⁴ L mol⁻¹ cm⁻¹ at 400 nm for DTPEP. Moreover, with more rotors in the donor moiety, DTPEP exhibited the AIE feature. In contrast, with less rotors, DTPAP displayed aggregation-caused quenching (ACQ) property. Both DTPEP and DTPAP can be used for the fluorescence sensing of metal ions in aqueous solution. A facile and portable platform for smartphones capable of detection of Hg²⁺ was also fabricated using the AIEgen DTPEP. The device was applied for the rapid detection of Hg²⁺ with a wide range of 0–25 μM.