Pyrenyl-Functionalized Polysiloxane Based on Synergistic Effect for Highly Selective and Highly Sensitive Detection of 4-Nitrotoluene

4-Nitrotoluene (NT) is an important intermediate for the manufacture of dyes, agricultural chemicals, medicaments, and synthetic fibers. But its wide use has resulted in a series of ecological problems and health issues due to high toxicity, mutagenicity, and carcinogenicity. However, no fluorescent probes with high selectivity and high sensitivity to NT has been reported yet, and the current probes usually prefer to detect multi-nitrosubstituted nitroaromatic compounds (NACs) including 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol. Herein, we report a series of pyrene-functionalized polysiloxanes with high selectivity and high sensitivity to NT. Pyrene was introduced into polysiloxane through a carbon-carbon double bond, and the formed rigid side-chain fluorophore and flexible backbone structure of polysiloxane provide an ideal platform for the highly selective detection of NT. We further explored the possible response mechanism and speculated that the high selectivity and high sensitivity were derived from the synergistic effect between steric hindrance and dipolar interaction. In addition, paper sensors based on the obtained fluorescent materials were fabricated and change in their high sensitivity and visible fluorescence indicated that the paper sensor is a simple testing tool for portable and visual detection of NT. Furthermore, the design strategy in this work provides a novel synthetic route to synthesize other fluorescent probes with unique selectivity to NACs detection.