Research Of Synthesis,Properties,and Application Of Uranyl Colorimetric Sensors Based On AZO Derivative

As a radioactive element extracted from ore,uranium has been widely used in the fields of energy production and military industry.With the higher energy calorific value and lower raw material costs,nuclear energy,natural gas and coal,the three tycoons in power field,will still have absolute dominance for a long time to come.However,with the rapid development of the nuclear industry,a series of pollution problems brought by uranium in the process of mining,production and reprocessing have become increasingly prominent.Once the uncontrolled uranium migrates into the environment,it will cause serious pollution to the surrounding natural environmental systems（such as soil and water）,thereby causing irreversible damage to organisms.It is an urgent need to develop a type of technology that can be used for radionuclide monitoring in actual environments to achieve rapid,sensitive and efficient monitoring of uranium in environmental samples.At present,most uranium sensors use fluorometry,voltammetry,surface-enhanced Raman spectroscopy and other methods to detect uranium.Although these techniques have high sensitivity and selectivity in the detection of uranyl ions,the high cost and complex instrument operation and sample preparation limit their application to on-line detection in the field.Colorimetry has caused great interest in the field of the detection of uranyl ions because its simple and fast to operate,unneed expensive instrument,and the phenomenon is easy to observe.However,the currently developed colorimetric uranyl colorimetric technology has relatively low sensitivity and selectivity,and does not meet the standards for detecting trace uranyl ions in the environment.How to designing a colorimetric sensor with highly selectivity and sensitivity are becaming an important direction for scholars.Based on the structure of azo derivatives,this thesis rationally designed and synthesized two types of colorimetric sensors with excellent response to uranyl ions and explored the related performance of sensor.At the same time,the mechanism of the interaction between the designed sensor and uranium was deeply explored from the mechanism and successfully applied to the on-line detection of uranium in actual environmental samples.Thereby establishing a method for real-time and online monitoring of environmental uranium samples.The specific work is as follows:In the 2rd chapter,we design and synthesize2-（5’-（p-（diphenylamino）phenyl）-2’-pyridylazo）-5-（diethylamino）phenol（abbr.S-LH）for the colorimetric detection of uranyl ions in mixed solvents.The rational introduced triphenylamine group by density functional theory（DFT）calculation enhances the chromaticity difference of the S-LH toward uranyl ions,making the detection limits of the uranyl ions approximately one order of magnitude lower than that of the present UV-vis and visual method.The species of S-LH and uranium at different pH are clarified and it well explains the reason of different color changes after adding uranyl ions.Stability constant experiments show that S-LH has excellent anti-interference to other metal ions during detecting uranium.The coordination structure of S-LH towards UO₂²⁺is further confirmed by HRMS,¹H NMR titration,and DFT calculation.Finally,colorimetric test strips with S-LH are prepared to detect uranium in Xiang River,providing an on-site and real-time method to detect uranyl ions in environment.In the 3rd chapter,with guiding by rational design method,a general and efficient screening strategy for the colorimetric uranium sensor based on PADAP derivatives has been developed using the rational design of DFT calculations.Based on four screening steps of theoretical caculation,we successfully confirm that the designed structure 2-(（3-bromo-5-（9,9-dioctyl-7-（4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl）-9H-fluoren-2-yl）-2-pyridylazo）-5-（diethylamino）phenol（abbr.W1）possess a significant red-shift（about 78 nm）compared with PADAP.For this reason,we designed and synthesized W1,which showed a significant color change from red to blue when it combined with uranium.The detection limit of W1 was as low as nanomolar,and it had excellent uranium selectivity,anti-anion and cation competitivity and recyclability.Importantly,the coordination mechanism of W1 toward uranium was investigated by experiment and theoretical calculation.Finally,ligand W1 and the colorimetric test strip prepared by W1 were successfully applied to the detection of low-concentration uranium in environmental samples around the uranium tailings,providing a promising direction for the detection of trace uranyl ions in the environment.