Development And Application Of Planar Optode Technology In Micro-interface Research

Rhizosphere research is of great significance for exploring the biogeochemical cycling process of elements.Root microinterface researches can explore the migration and transformation mechanism of heavy metals or nutrients(N,P)in soil or sediment system contributing to clarifying the pollution characteristics and migration rules,and providing a basis for large-scale research.However,soil and sediment systems are highly heterogeneous due to root growth,biological disturbance and other activities.These processes cause hot spots in the environment.The traditional rhizosphere research methods often use chemical extraction method,which can not reflect the characteristics of heterogeneity of environmental media and may cause damage to the samples,thus limiting the accuracy of the analysis.Recently,various high resolution rhizosphere research methods have been developed in a non-invasive way,which can provide information on the distribution of substances on two-dimensional scale.Planar optode technology is one of the fluorescence sensing methods with high spatial and temporal resolution.As O2 and pH are the main factors affecting the environmental behavior of heavy metals and other pollutants,this paper mainly focuses on the development of O2 and pH planar optode system and its application in rhizosphere research.In this study,five new HPTS derivatives were synthesized and embedded in hydrogels as pH-sensitive fluorescent dyes to prepare sensing films,and PtTFPP dyes were used as O2sensitive dyes to prepare O2sensing films.In this experiment,the pH and O2planar optode films have good response in the range of6.5-9.5 and 0-saturated dissolved oxygen,respectively.The results of laboratory study showed that the HPTS derivatives modified by alkylamine were slightly affected by ionic strength,exhibiting excellent light stability,and fluorescence intensity was not affected by oxygen concentration.The carbon number of derivatives with more than6 substituents could be used for long-term experiments in neutral and alkaline environments.The carbon number of derivatives with more than 2 substituents could be used for long-term experiments in acidic environments.Owing to the fact that the internal standard can not be corrected,the temperature of the O2planar optode system should be kept stable during the experiment.This technique has been successfully applied to the study of oxygen radical loss effect and acidification in the rhizosphere of sediment and soil interface.Our research team has also combined optode planar with high resolution DGT technique to observe the geochemical cycling process of heavy metals in rice rhizosphere.In the future,planar optode for different objects can be developed,and multi-parameters can be integrated into the same sensing film to realize simultaneous monitoring of multi-parameters.