Study On The Analytical Application Of Cesium-lead Bromide-lead Perovskite Luminescent Nanocrystals To Mercury And Silver Ions

All-inorganic cesium-lead perovskite halide(ILHPs)is a new type of nano-optical material which has widely used in light-emitting diodes(LEDs)and various optoelectronic devices due to the excellent optical and electrical properties such as adjustable band gap,wide absorption range,high extinction coefficient,and low exciton binding Energy,ultra-high photoluminescence quantum yield(?100%),and long carrier diffusion length,etc.,Due to the inherent instability and flexibility,the all-inorganic cesium-lead perovskite nanocomposite material can be synthesized in various sizes,shapes and compositions by various methods.At present,many researches are devoted to synthesizing all-inorganic cesium-lead perovskite nanomaterials with high stability and high photoluminescence quantum yield(PLQY),and applying them in various fields.However,the stability of the all-inorganic cesium lead perovskite nanomaterials against water,oxygen and light treatment is still a major challenge.Its low stability and water insolubility limit its application in analysis and detection.Compared with other cesium halogen lead perovskite nanocrystals,all-inorganic cesium lead bromide perovskite nanocrystals(CsPbBr₃ PNCs)has received extensive attention from scientists due to its better stability and better optical controllability.Aiming at the problem of luminescent cesium-lead bromide perovskite nanocrystals that are poor in stability to water and air and are difficult to dissolve in water,this thesis mainly studied the stability,water solubility,optical properties of the CsPbBr₃ PNCs,and tried to improve their stability in water.Different kinds of CsPbBr₃ PNCs were finally used as fluorescent probes for heavy metal ions detection such as mercury ion(Hg²⁺)and silver ion(Ag⁺)in water.The details of the research contents are as follows:1.In order to solve the problem that the cesium lead perovskite nanocrystals(CsPbBr₃PNCs)synthesized by the traditional high-temperature thermal injection synthesis method cannot exist stably in aqueous solution and cannot be used for the analysis of target samples in water,a liquid-liquid extraction method is used to realize the extraction and selective and visual detection of mercury ions in water by CsPbBr₃ PNCs.The results indicated that by using liquid-liquid extraction method,mercury ions in the water phase can be extracted into the organic phase containing CsPbBr₃ PNCs under the condition of p H 6.0,and the fluorescence of the CsPbBr₃ PNCs in the organic phase can be quenched by the extracted mercary ions.Mercury ions have good selectivity for the fluorescence quenching of CsPbBr₃PNCs and the fluorescence intensity of CsPbBr₃ PNCs decreases linearly with the increase of Hg²⁺in the concentration range of 50.0 n M-10.0?M.Based on this phenomenon,a liquid-liquid extraction fluorescence detection method for mercury ions was established with a detection limit of 35.65 n M.2.Because the traditional high-temperature thermal injection method which used to synthesize CsPbBr₃ PNCs has a complex operation process and a high-risk,the method of synthesizing CsPbBr₃ PNCs at room temperature was studied,and the liquid-liquid extraction method was used to apply the selective and visual detection of mercury ions in water.The experimental results show that the CsPbBr₃ PNCs synthesized from lead bromide,cesium bromide,oleic acid and oleylamine as raw materials have green emission and the maximum emission wavelength is at 522 nm.It has good stability and is relatively stable compared to traditional high-temperature thermal injection synthesis.The method has simple operation process,short synthesis time and good reproducibility.The CsPbBr₃ PNCs was used for liquid-liquid extraction and detection of Hg²⁺ions.The results showed that with the increase of Hg²⁺ion concentration,the fluorescence intensity of CsPbBr₃ PNCs would be quenched.By detecting the fluorescence intensity change of CsPbBr₃ PNCs,the selective detection of Hg²⁺can be achieved.The detected Hg²⁺The linear concentration range is 1.0?M-85.0?M,and the detection limit is 0.15?M.3.In order to solve the problem that CsPbBr₃ PNCs are insoluble in water and cannot be directly used for the detection of heavy metal ions in water,a ligand-assisted synthesis method by using lead bromide,cesium bromide,arginine,tert-butoxycarbonylarginine and lysine as raw materials was used to synthesize water-soluble CsPbBr₃ PNCs.The synthesized CsPbBr₃ PNCs has good stability and green emission at room temperature,and can also be partially miscible with water.The optical properties of CsPbBr₃ PNCs synthesized by three amino acids,arginine,tert-butoxycarbonyl arginine and lysine,were experimentally studied.The synthesized CsPbBr₃ PNCs were dispersed in chloroform and ethyl acetate.The results showed that CsPbBr₃ PNCs synthesized with arginine,tert-butoxycarbonylarginine and lysine were dispersed in chloroform and ethyl acetate.Their emission peaks are located at 528 nm and 525 nm,530 nm and 525 nm,528 nm and 515 nm,respectively.Among them,CsPbBr₃PNCs synthesized with arginine have the best stability and the highest fluorescence intensity when dispersed in chloroform.Thus,the CsPbBr₃ PNCs synthesized with arginine was used as a fluorescent probe for the detection of silver ions in water.The results show that the fluorescence of this CsPbBr₃ PNCs will be significantly enhanced after Ag⁺is introduced.Ag⁺can be selectively detected by detecting changes in the fluorescence intensity of CsPbBr₃PNCs,with a linear range of 0.1-4.0?M,the detection limit is 0.28?M.