Construction And Detection Of Cucurbit[8] Uril-based Supramolecular Fluorescent Probe For Ammonia And Hydrazine

As a low-cost,highly selective,and highly sensitive detection method,fluorescent probes have become an important means of identification and detection of pollutants in the environment.Ammonia and hydrazine are the homologous harmfully environmental pollutants.The detection of ammonia and hydrazine has always been research hotspots and difficulties.In order to solve the problem of fluorescence quenching due to the aggregation of traditional hydrazine fluorescent probes in water,and to solve the lack of AIE probes in the construction and application of solid sensors,while distinguishing ammonia and hydrazine gas,,the cucurbit[8]urea was selected as the host molecule to complex with fluorescent probe to prepare supramolecular fluorescent probes.The detection performance and mechanism for ammonia and hydrazine were studied,and the details were presented as the follows:（1）A novel fluorescent probe with coumarin skeleton was designed and synthesized,and to complex with cucurbit[8]urea to form a supramolecular fluorescent probe.The supramolecular fluorescent probe has excellent selective recognition ability for hydrazine in solution.After hydrazine is recognized,the fluorescence of the solution was changed from no to green.The response time is 5 min,the detection limit is 53 n M,and it is applicable within p H value of 6 to 10.This supramolecular probe has a more sensitive detection capability than some probes had been reported.A reasonable mechanism was suggested.The fluorescent probe has the properties of Aggregation-Caused Quenching（ACQ）,which was quenched due to the formation of aggregation in aqueous solution.When the fluorescenct probe molecule entered into the cavity of CB[8]to form supramolecular inclusion complex,theπ-πaccumulation between probe molecules was prevented and the ACQ mechanism would not take place.Moreover,the pores formed by the aggregation of supramolecules have a trapping effect on hydrazine molecules,which is conducive to the diffusion of hydrazine molecules and to increase the collision with the recognition group.The local concentration of hydrazine was increased,thus to enhance the sensitivity of fluorescent probe.（2）A novel fluorescent probe with triphenylamine skeleton was synthesized and to form inclusion complex with cucurbit[8]urea.This solid fluorescent material has excellent selective recognition ability for gaseous hydrazine and ammonia,and emits different fluorescent signals.The fluorescence of sensing material was changed from red to blue when to identify the hydrazine vapor.The response time is 12 min,and the detection limit is 0.41ppm.When identifying ammonia gas the fluorescence was changed from red to yellow,the the response time is 10 min,and the detection limit is 10 ppm.The sensing performance of this nove fluorescent material are superior to some probes,which had been reported.A possible mechanism was suggested.The fluorescent probe enter into the caivty of CB[8].The probe molucules are separated by CB[8]unit and to form macropores.The gaseous N₂H₄ and NH₃ was facile to diffuse.In addition,the ordered arrangement of inclusion complexes will increase the contact area with the gaseous analyte,thereby having excellent detection capabilities.