Dual mode detection of picric acid with fluorescence and smartphone colorimetry via AIE active tetraphenylethylene derivatives

In this study, six tetraphenylethene (TPE) derivatives had been designed and synthesized, named as TPEH, TPEOMe, TPEtBu, TPEOH, TPECN and TPEPy, which exhibited intramolecular charge transfer (ICT) character and aggregation-induced emission (AIE) performance. Based on the electron-donating ability originated from the highly localized pi electrons, electrons could be transferred from these TPE derivatives to electron-deficient nitroaromatic explosive picric acid (PA) resulting in quenched fluorescence emission. Thus, they had excellent sensitivity and selectivity for PA detection in aggregate states. The limits of detection (LOD) were 1.64, 0.50, 0.93, 1.48, 0.49 and 0.35 mu M for them, respectively, captured from fluorescence signal. Moreover, a semi-quantitative detection method based on smartphone digital image was developed to detect PA with LOD of 490, 26.6, 69.1, 74.1, 3.57 and 100 mu M, respectively. The dual-mode sensors had excellent detection character improving the accuracy of the detection result. The fluorescence quenching mechanism was explored as photoinduced electron transfer (PET) and energy transfer. This study provided a new strategy for the design of AIE active materials, expanded the application of smartphones in explosive detection which had practical potential in effective sensing.