Synthesis And Application Of Naphthalimide Fluorescent Probes For Detecting And Adsorbing Heavy Metal Ions

Metal ions are a kind of cations formed by the loss of electrons of metal elements,which play a vital role in human health.Many physiological and pathological processes require the participation of metal ions.Heavy metal ions refer to metal ions with a density greater than4.5 g/cm³.With the rapid development of modern industry,factory wastewater is discharged without treatment,which leads to the problem of excessive heavy metals.If the water polluted by heavy metal ions enters farmland without treatment,in which the growth of agricultural products will be rich in heavy metal ions,these agricultural products by human consumption,will seriously affect life and health.At present,most heavy metal ions are detected by atomic absorption spectroscopy,High-performance liquid chromatography and electrochemical methods,with the disadvantages of expensive equipment,complex pre-treatment and professional operation.In this thesis,we designed a probe with naphthalimide as a fluorophore,which can specifically detect copper,silver and chromium,and combine the fluorescence probe with the gel material,which can not only realize the visual detection of heavy metals,but also provide a new method for the detection of copper,silver and chromium,it can also contribute to the adsorption of heavy metal ions.The specific tasks are as follows:1.A fluorescence probe（PPNAP）for the specific detection of Cu²⁺and Ag⁺was designed and synthesized based on the structure of naphthalimide and dimethylpyridine amine（BPA）.The probe can exhibit different optical properties when Cu²⁺and Ag⁺are added.When Cu²⁺is added,the yellow-green fluorescence of the probe is quenched to be colorless,the yellow-green fluorescence of the probe itself can be converted to blue fluorescence,which can be used to detect Cu²⁺and Ag⁺.The detection limits of PPNAP probe for Cu²⁺and Ag⁺were 2.68μM and 2.23μM,respectively,the complex ratios of PPNAP,Cu²⁺and Ag⁺were 1:1 by Job’s-plot curves.In conclusion,PPNAP can be used as a sensitive and efficient probe for the detection of Cu²⁺and Ag⁺.In addition,we combined the fluorescence probe with sodium alginate to form a composite gel sphere（PPNAP-SA）,which showed a good adsorption effect on Cu²⁺.With the obvious fluorescence change,the maximum adsorption amount of Cu²⁺was about 42.49 mg/g,and the recycling of PPNAP-SA composite gel sphere could be realized after the treatment of hydrochloric acid.These excellent properties make PPNAP-SA composite gel sphere hopeful to be a kind of water purification material combining detection and adsorption of heavy metal ions.2.A fluorescent probe（TTNAP）was designed and synthesized based on the structure of naphthalimide and dimethylthiophenamine to detect Cr³⁺in THF:H₂O（9:1,v/v）solution.After adding Cr³⁺to the probe solution,fluorescence color changed from yellow-green to light yellow,and quenched to a certain extent.The detection limit of probe TTNAP for Cr³⁺was1.34μM.The complex ratio of TTNAP and Cr³⁺is 1:1 by Job’s-plot curve.Moreover,the probe TTNAP is also very effective in the detection of Cr³⁺in actual water samples,with a recovery rate of 88.60%～97.50%.The standard deviation is 2.04%～9.18%.In conclusion,the probe TTNAP has good selectivity and sensitivity for the detection of Cr³⁺.