Design And Application Of Fluorescence Probe For Visual Detection Of Pesticide Residue

Human survival is inseparable from the development of agriculture,the use of pesticides is still an important means to protect agricultural production,economic benefits and people’s livelihood.With the extensive abuse of pesticides,some pesticide residues are difficult to degrade after entering the nature,which leads to many serious problems through the transfer and enrichment of the food chain.Pesticide residue detection is a long-term challenge in the field of environmental and food safety detection.However,most of the traditional pesticide residue detection methods rely on expensive large-scale analytical instruments.The sample pretreatment steps are cumbersome and time-consuming,which can’t meet the rapid,simple and real-time detection requirements of actual environmental samples.In view of the above problems,two paper-based fluorescent sensors were constructed to achieve high selectivity,high sensitivity and rapid real-time visual detection of pesticide residues and pesticide raw materials hydrazine,which provided an effective sensing strategy for pesticide residue supervision,environmental monitoring and food safety.The contents are as follow:1.Visual detection of pesticide thiram based on a novel nano-fluorescent probe.Quantum dots（QDs）were first adsorbed into the pore of dendrimer-like silica nanoparticles（d Si O₂）synthesized by anion-assisted method to form fluorescence beads.Gold nanoparticles（Au NPs）were then adsorbed on the surface of the beads to efficiently quench their fluorescence through fluorescence resonance energy transfer（FRET）pathway to obtain thiram-responsive probe.FRET pathway would be shut down due to the strong coordination between thiol in thiram and gold atom,leading to the fluorescence turn on of the probe,when thiram was present.In addition to detection limit of as low as 7 nmol/L for thiram assay,fluorescent test paper was developed for the detection of thiram in real samples,demonstrating the practicability of the fluorescence sensing platform.2.Hydrazine and viscosity dual-responsive organic small molecule fluorescent probes with molecular rotor characteristics was designed and synthesized for the first time.When hydrazine was present,recognition group cyanovinyl group in probe molecule could react with hydrazine to form hydrazone,resulting in the reduction of conjugated structure in probe molecule and thus affecting the electron density distribution.As a result,green fluorescent of the probe was recovered with the detection limit of as low as 135 nmol/L for hydrazine detection.Moreover,in solution with high viscosity,the free rotation of the probe is inhibited,leading to distorting of the intramolecular charge transfer and thus opening the red fluorescence of the probe.For application,the hydrazine vapor fluorescence test paper was developed to realize visual detection of hydrazine vapor.In addition,because their different biological structure,the probe could be used for the discriminating of living and dead cells.