Analysis Of Phosphate By Selective Fluorescence/Ratio Fluorescence Based On Polydopamine Nanomaterials

In natural water,when the phosphorus content in water is too high(higher than 0.2mg/L),it can cause a large number of algae reproduction and consume a large amount of dissolved oxygen.When the number of algae reaches a harmful level(called eutrophication),it will lead to the decay and death of vegetation and aquatic organisms,and then the water quality will continue to deteriorate.The detection of phosphorus in water is an important topic for the environmental science community of all countries.Intensity fluorescent probes and ratio fluorescent probes are increasingly becoming important tools for water quality monitoring and related water resources management decisions.Due to its simplicity,repeatability and high biocompatibility,fluorescent nanoparticles have become one of the commonly used materials for the preparation of intensity fluorescent probes and ratio fluorescent probes.Therefore,two fluorescent probes,fluorescent PDA NPs and fluorescent PDA NPs/chlorophyll,were designed to recognize and detect the contents of pyrophosphate(PPi)and phosphate(Pi).The main contents are as follows:(1)Fluorescent polydopamine nanoparticles with excellent fluorescence properties were synthesized by simple alkaline oxidation at room temperature.The structure of PDA NPs was characterized using TEM,DLS and FTIR,respectively.We also explored the effect of different excitation wavelengths,different oxidation conditions,different oxidation times,and different p H conditions on the fluorescence of polydopamine nanoparticles to determine the optimal conditions for the synthesis of fluorescent PDA NPs,thus leading to their best fluorescence performance.In addition to explore the sensitivity of fluorescent PDA NPs to metal ions,we investigated the fluorescence response of fluorescent PDA NPs to different metal ions,among which Fe³⁺and Cu²⁺responded especially prominently to fluorescent PDA NPs with fluorescence quenching rates of 82%and 78%.Therefore,we took advantage of the sensitivity of fluorescent PDA NPs to Fe³⁺and Cu²⁺for further studies.(2)Through the quenching effect of Cu²⁺ions on the fluorescence of PDA NPs,and the strong complexation ability of Cu²⁺ions with PPI,we established an"Turn-off"type fluorescent probe that can detect Cu²⁺ions and a"Turn-on"type fluorescent probe that specifically detects PPi.First,Cu²⁺ions have a strong affinity with the catechol functional groups on the surface of fluorescent PDA NPs,so the fluorescence of PDA NPs is quenched.Then,Cu²⁺ions react with PPi,and Cu²⁺ions no longer combine with catechol on the surface of fluorescent PDA NPs,which promotes the recovery of solution fluorescence.We calculated that the PPi concentration has a good linear relationship with the fluorescence intensity in the range of 0?300?M.The linear correlation coefficient is R²=0.996.The limit of detection(LOD)is calculated to be 4.55?M.Based on the above,we successfully detected the concentration of PPi using the change in the fluorescence signal of the polydopamine nanoparticles.At the same time,the intensity-type fluorescent probe can be used to detect PPi in environmental water bodies,with simple operation,low cost,and no complicated synthesis and detection processes.(3)Using the fluorescence quenching effect of Fe³⁺ions on PDA NPs and chlorophyll,a novel ratiometric fluorescence analysis strategy was proposed.Based on fluorescent PDA NPs and chlorophyll,a fluorescent PDA NPs/chlorophyll composite probe with dual emission function was constructed.The probe has good fluorescence emission performance at 495 nm and 680 nm.Thus,a"green to red"type fluorescent probe that can detect Fe³⁺ions and a"red to green"type ratio fluorescent probe that can specifically detect Pi are established.The probe has a good linear relationship with Pi in the concentration range of0?260?M,the correlation coefficient R²=0.991,and limit of detection(LOD)is 1.25?M.In the experiment of interfering ions,the PDA NPs/chlorophyll-Fe³⁺composite system has a certain selectivity for the detection of Pi.At the same time,when the ratiometric fluorescent probe detects Pi in real water samples,the color evolution under the ultraviolet lamp has an excellent visual effect.Compared with the foregoing intensity fluorescent probe detection method,the ratiometric fluorescent probe method is not susceptible to external influences,has higher sensitivity,and the composite system uses sweet-scented osmanthus leaves to extract chlorophyll in a simple,rapid,and low cost.Figure[38]table[8]reference[94]...