Gold Nanoclusters And Their Application In Fluorescence Detection Of Pb²⁺/Hg²⁺

With the rapid development of society,the pollution of Pb2+and Hg2+in the environment is becoming more and more serious,and their toxicity poses a great threat to the survival and development of human beings.Therefore,the detection and removal of Pb2+ and Hg2+in the environment has become an urgent problem in environmental protection.Fluorescent probe technology has attracted much attention from researchers because of its many advantages of easy operation and high sensitivity in detecting the target.In this paper,three fluorescent probe materials,gold nanoclusters,carbon quantum dots,and gold nanocluster hydrogels,were prepared and used to investigate the fluorescence intensity changes of Pb2+and Hg2+respectively,and a series of application studies were conducted.The second chapter experiments use gold nanoclusters to realize the highly selective and sensitive detection of Pb2+;the third chapter experiments use carbon quantum dots and gold nanoclusters to construct ratiometric fluorescent probes,based on the previous chapter,to optimize the detection limit and detection range for the detection of Pb2+;Based on the"detection" function of the fluorescent probe in the first two chapters,a new type of gold nanocluster hydrogel was synthesized for the first time in Chapter 4,which can achieve sensitive detection and adsorption of Hg2+ in the application.This material can be applied to the sensitive detection and adsorption of Hg2+,which enables the real-time,on-site detection and removal of Hg2+ions in the aqueous environment.The main work is as follows:(1)Gold nanoclusters(GSH-AuNCs)were synthesized using a one-pot method with chloroauric acid as precursor and glutathione as stabilizer and reducing agent.The average particle size was 1.65 nm,excitation wavelength was 350 nm,emission wavelength was 580 nm,and orange fluorescence was emitted under UV lamp(365 nm).In the presence of Pb2+,the GSH-AuNCs coμLd undergo aggregation-induced fluorescence enhancement effect(AIE)to produce bright aggregates.The fluorescence intensity of the generated aggregates has a good linear relationship with the Pb2+concentration,which enables the detection of Pb2+.The range of Pb2+detection was obtained as 1-9 μM.The linear equation was F580=62.81[Pb(Ⅱ)]+767.21(R2=0.9983),and the minimum detection limit was 0.26 μM.The probe was used for the detection of Pb2+ in real samples,and the spiked recoveries ranged from 93.9%to 113.0%with RSD was less than 5.0%.(2)Carbon quantum dots(CDs)were synthesized by hydrothermal method using citric acid as the carbon source and ethylenediamine as the nitrogen source.CDs have an average particle size of 2.8 nm,excitation wavelength of 350 nm and emission wavelength of 450 nm,and can emit bright blue fluorescence under the irradiation of UV lamp(365 nm).And a novel CDs/AuNCs ratiometric fluorescent probe was constructed by combining the synthesized CDs with the GSH-AuNCs synthesized in the previous section,and the mechanism of its construction was investigated.Based on the highly selective fluorescence enhancement effect of Pb2+on CDs/AuNCs fluorescent probe,CDs were used as the reference probe and GSH-AuNCs as the response probe,and a good linear relationship between the fluorescence intensity ratio(F=F580/F450)of GSH-AuNCs(580 nm)and CDs(450 nm)and Pb2+concentration was obtained.The range of Pb2+ detection was 20-700 nM,and the linear equation was F580/F450=0.0897[Pb(Ⅱ)]+2.7277(R2=0.9946),LOD=3.9 nM.The probe was used for the detection of Pb2+in real samples,and the spiked recoveries ranged from 90.5%to 117.1%with the RSD less than5.4%.(3)A new fluorescent nanocellμLose hydrogel based on AuNCs was prepared with an AQY of 4.5%,optimal excitation of 507 nm,optimal emission of 645 nm,bright red fluorescence under UV light(365 nm),and stable fluorescence emission properties.The new hydrogel was observed to have a three-dimensional pore-like structure by SEM.In summary,the BSA-AuNCs Hydrogel was applied to the sensitive detection and effective adsorption of Hg2+,and the linear range of Hg2+ detection was 5～150 mg g L-1,the linear equation was AQY/AQY0=-0.00812[Hg(Ⅱ)]+4.44445,and the minimum limit of detection(LOD)was 2.7 mg L-1.The recovery of BSA-AuNCs Hydrogel for the detection of Hg2+in real samples was between 93.7%and 110.30%with an RSD lower than 4.73%,indicating that BSA-AuNCs Hydrogel can be a safe biosorbent for real-time,in situ detection and removal of Hg2+ions in the aqueous environment.