Rational design of AIEE sensor: Ultrafast detection of methanol in liquid and gaseous states with highly sensitive and selective performance

The convenient and sensitive detection of methanol out of ethanol is still a great challenge due to their similar physical properties. We have designed a tetraphenylethene (TPE)-based AIEE fluorescence probe (TPEP4) with large steric hindrance composed of four large branches to overcome this challenge. Due to its four large branches, TPEP4 displayed substantially brighter fluorescence emission in aromatic solvents and a higher fluorescence quantum yield (12.67% in o-dichlorobenzene) compared to other TPE derivatives in dilute solution. Remarkably, TPEP4 exhibited a methanol-responsive fluorescence quenching in both liquid and film states. Therefore, methanol could be significantly distinguished from ethanol by the fluorescent change of TPEP4. Use of TPEP4 in biodiesel (B100) has multiple advantages, such as rapid response time (0.5 s), high selectivity to methanol, and ultralow limits of detection (LOD). In this case, the TPEP4 film remained its selectivity towards gaseous methanol with an ultralow LOD of 5.63 ppb. To the best of our knowledge, this is the first TPE-based AIEE fluorescence probe for methanol detection that shows significant potential for use in environmental monitoring. Thus, the present work provides a strategy for developing fluorescent sensing materials for volatile organic compound based on AIEE molecules.