Synthesis Of Fluorescent Tetraphenylethylene-Based Porous Polymer For Pesticide Detection

With the attention to public health and safety increasing,it is important to find the more sensitive and rapid method to monitor toxic pesticide residues in the food and the environment.Porous organic polymers possess many desirable properties such as the high physical/chemical stability,large specific surface area and adjustable function and,as a result,it could be widely used in gas adsorption and separation,reaction catalyzing and detection.Tetraphenylethylene is a typical aggregation-induced luminescence（AIE）fluorescent chromophore.When the four phenyl groups are fixed in the polymer backbone,the polymer will show fluorescence enhancement.Because of its unique optical properties,it could be widely used in the fields of optoelectronic materials,fluorescent probes,etc.Therefore,the aim of this work is to introduce tetraphenylethylene and its derivatives in the porous polymer using the aminal reaction,developing a new type of fluorescent porous material to detect pesticide residues quickly and sensitively.In this paper,two fluorescent porous polyaminals with strong fluorescence emission are designed and synthesized.Their specific surface areas,pore size distributions and detection sensitivity to the pesticides were examined.At the same time,the influences of polymer-pesticide orbital energy level difference（?E）,the overlap between polymer fluorescence excitation and pesticide ultraviolet absorption,and the interaction between polymer backbone and pesticide molecules on the pesticide detection are studied.The contents are as below:Firstly,two aldehyde-based tetraphenylethylene monomers were obtained by Suzuki coupling reaction.Then the monomers were utilized to react with melamine,respectively,to yield two microporous polymer with strong fluorescence emission,named as PAN-TPE-1,PAN-TPE-2.Their BET surface areas are 257 m²/g,310 m²/g,respectively,with the micropores at 1.43 nm～1.93 nm,mesopores at 4.22 nm～7.07 nm,and some macropores.Additionally,the microporous surface areas are 52 cm²/g～57 cm²/g,whereas the micropore volumes and total pore volumes are 0.024 cm³/g～0.047 cm³/g and 0.29 cm³/g～0.35 cm³/g,respectively.For the fluorescent detection of fluconazole,the Stern-Volmer coefficients of PAN-TPE-1 and PAN-TPE-2 are 9.24×10³ M^-1 and 6.11×10³ M^-1,respectively.For trifluralin,PAN-TPE-1 is the most sensitive with K_svof 1.72×10⁴ M^-1,followed by PAN-TPE-2 at 1.07×10⁴ M^-1.The different sensitives to the pesticides are mainly caused by photoinduced electron transfer,competitive absorption,and electrostatic interaction.In the visualization experiment,PAN-TPE-1 can detect10^-4 M^-1 trifluralin residues sensitively by hand-held UV lamp irradiation.At the same time,PAN-TPE-1 has good selectivity in the fluorescent response to trifluralin,but has no response to common water ions,which proves that these porous materials modified by the group of AIE have potential application in pesticide detection in water.