Detection And Mechanism Of Phosphonates By Fluorescence Probe Combined With Iron Ion

As a kind of scale inhibitors and metal ion chelators,organic phosphonates are widely used in industrial water treatment.However,on the one hand,due to the special physical and chemical properties of organic phosphonates,such as the high polarity,strong water solubility,strong complexation performance,no chromophore and so on,the detection process is very fussy with a long time,and it is easy to be disturbed by external factors,resulting in large error of the detection results.On the other hand,fluorescence analysis has attracted much attention because of its outstanding advantages such as high cost performance,high sensitivity,strong practicability and good selectivity.Based on fluorescence analysis,a series of fluorescent probes were constructed with iron ion as coordination metal for the detection of organic phosphonates.The quenching mechanism is determined by UV spectroscopy and fluorescence lifetime,and the recovery of the probe in actual water samples was calculated.The major research content of this study contains three parts,as follows:（1）Using natural salicylic acid（SA）as raw material and iron ion(Fe³⁺)as coordination metal,an iron-based salicylic acid fluorescence probe（Fe-SA）was constructed in absolute ethanol for the quantitative determination of 1-Hydroxyethylidene-1,1-Diphosphonic acid（HEDP）.In terms of optical properties,Fe-SA showed significantly different fluorescence intensity from SA.Under the optimum experimental conditions,the detection limit of HEDP was 2.7μM.The fluorescence quenching of SA can be attributed to static quenching.In addition,the electron hole analysis in Multiwfn wave function program was used to calculate the contribution of different fragments to holes and electrons in molecules and the amount of electron transfer between fragments,and the determine the electron excitation types and electron excitation characteristics of SA or Fe-SA complexes.In the actual sample detection,the recovery of HEDP detected by Fe-SA was 97%-107%.（2）Nitrogen doped carbon nanomaterials（NCMs）with good light stability were prepared by hydrothermal synthesis from melamine and citric acid.Fe-nitrogen doped carbon quantum dot complexes（Fe-NCMs）were formed with iron ion as modifier,showing weak fluorescence.In the solution containing amino trimethylene phosphonic acid（ATMP）and diethylenetriamine pentamethylene phosphonic acid（DTPMP）,Fe³⁺forms a more stable complex with organic phosphonic to release NCMs,and the fluorescence intensity was restored.Based on this principle,Fe-NCMs can be used as fluorescent probes for detecting ATMP and DTPMP.In the linear range,the detection limit of the fluorescence probe for ATMP and DTPMP were 0.479μM、0.254μM,respectively.（3）3,5-dimethylpyrazole（DP）was used as raw material and iron ion(Fe³⁺)as coordination metal,an iron-based 3,5-dimethylpyrazole fluorescent probe（Fe-DP）was constructed in water by direct synthesis method for the quantitative determination of diethylenetriamine pentamethylene phosphonic acid（DTPMP）.Under the optimum experimental conditions,the fluorescent probe showed a good linear relationship in the range of 0-55μM,and the limit of detection（LOD）was 0.105μM.In the detection process,the constructed Fe-DP fluorescent probe had good selectivity.This showed that it was expected to be used as a specific fluorescent probe for DTPMP detection in actual water samples.