| Environmental pollution threatens the health of human life,leading many people suffering from disease and even death.Industry and agriculture,which are vital to human survival,have caused much pollution to the environment,with heavy metals and pesticides being the main environmental pollutants.Although traditional methods of environmental detection and analysis are well established,they have drawbacks such as time-consuming and cumbersome processing steps,which cannot meet the requirements of rapid on-site detecting.Ratiometric fluorescence sensors have many advantages such as good repeatability,high sensitivity,and strong stability,and have been applied in the analysis and detection of environmental pollutants and fluorescence imaging.As their simple operation and short time-consuming,they have great potential in real-time detection in the field.In this thesis,a sensing system for the detection of Cu2+and the pesticide thiram was constructed using a synthetic ratiometric fluorescent sensor,as follows:1.Blue fluorescent silica spheres（CDs@Si O2@PEI）were successfully synthesized by doping carbon dots（CDs）and polyethyleneimine（PEI）into silica via a reversed-phase microemulsion method,and showed strong stability at high salt concentrations and in buffer solutions of different p H values.Rhodamine B fluorescent spheres（Rh B@Si O2）were successfully synthesized by doping the fluorescent dye rhodamine B into silica by sol-gel method.The two fluorescent silica spheres were mixed in a certain ratio to finally obtain a novel ratiometric fluorescent sensor（designed as CSP/RBS）.Two separate fluorescence emission peaks appeared at 433 nm and 578 nm at an excitation wavelength of 355 nm.After adding Cu2+,Cu2+combined with the amino groups on the surface of CDs@Si O2@PEI,quenching the fluorescence at 433 nm,while the fluorescence intensity at 578 nm remained almost unchanged.Based on this sensing principle,a ratiometric fluorescence sensor（CSP/RBS）was developed for the detection of Cu2+with a detection time of only 10 min and a detection limit of 0.04μmol/L.This can be used in achieving sensitive and rapid detection of Cu2+and applied to the detection of Cu2+in real samples such as lake water and tap water.2.A ratiometric fluorescent and visual probe（designed as d SQSQ）was developed for on-site visualization of thiram.First,the fluorescence intensity of d SQSQ probe at 541 nm was quenched in the presence of Au NPs due to fluorescence inner filter effect,while the635 nm emission of d SQSQ probe almost kept constant.Then,the fluorescence intensity at541 nm was selectively recovered with adding thiram due to strong chelation between thiram and Au NPs,achieving ratiometric fluorescence(F541/F635)sensing of thiram.Simultaneously,the fluorescent color of d SQSQ/Au NPs system changed from orange to green,achieving colorimetric thiram sensing.Furthermore,this d SQSQ/Au NPs system was integrated with a smartphone by taking pictures and analyzing RGB values to achieve fluorometric and colorimetric output without fluorescent spectrometer,and the limit detection was 0.06μM.Finally,this smartphone sensing platform was successfully applied in thiram analysis in soil,lake water and apple,demonstrating its promising capability for on-site visually monitoring thiram residues in real samples without elaborate equipment. |
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