Ultrasensitive polysiloxane-based fluorescent probes for selectively detecting of 4-nitrophenol and their application in paper sensors

4-nitrophenol (4-NP) is widely used in dyes, pesticide and pharmaceutical industries. The water-solubility of 4NP makes it be a dangerous toxic pollutant. To detect 4-NP effectively, triphenylamine was introduced into the polysiloxane through Heck reaction with a carbon-carbon double bond as the bridge. In this work, two kinds of polysiloxane-based fluorescent probes (BpaD and BpaP) to detect 4-NP were designed and synthesized for the first time. Due to the electron-rich triphenylamine side-chain and the flexible and bendy polysiloxane mainchain, the fluorescent probes bearing a unique structure with triphenylamine as the fluorophore. The electron transfer from triphenylamine groups to 4-NP, leading to the fluorescence quenching. The obtained fluorescent probes exhibited high efficiency and high selectivity to 4-NP detection. Moreover, the high-efficiency fluorescent materials were coated on the filter paper to fabricate paper sensors, which provide a simple, portable, and visual method to 4-NP with high efficiency. This work also represented a new approach for the design of fluorescent probes for detecting NACs.