Visualization And Recognition Of Heavy Metal Ions By Phthalimide Functionalized Gold/silver Nanoparticles

Heavy metal ions are serious pollutants for the ecological environment,whether air,water or soil.Furthermore,heavy metal ions can not be degraded,transformed in nature,and it's very difficult to be eliminated.Therefore,it is significant toestablish a quick and accurate method for detecting heavy metal ions.Now,the main methods of detecting heavy metal ions are mostly with the aid of the instrumentation.These methods have advantages in terms of the accuracy.However,they are often complicated,expensive,and longer period of detection,which are unable to meet the increasing demands of people to environmental governance.Recent research found that the color of nanoparticles is dependent on itssize,morphology and aggregation state,which can be used as visualization reagents for detecting heavy metal ions.Based on this new strategy,in this thesis,Au/Ag nanoparticles were studied as the colorimetric regent for detecting heavy metal ions by the combination of experiment and computational simulationo This thesis mainly includes the following three aspects;1)Lysine-functionalized perylene(LPL)was used to modify sliver nano-particles(AgNPs)at different pH values(12.6,12.0,11.0,10.0).The diameter of AgNP is about 7nm.At pH=12.6,Cr6+ with a concentration of 100 nM could be detected by a color change from deep yellow to orange.After decreasing the pH value to 12.0,the detection limit decreased to 2?M.After further decreasing the pH to 11.0,another kind of metal ion(Cd2+)could be recognized with a detection concentration of 10?M.At pH=10.0,Pb2+ with a concentration of 2?M could be detected.2)The gold nanoparticles with size of 2-3 nm were prepared at pH = 10 with lysine modified perylene imide(LPL-AuNPs).The gold nanoparticles prepared under these conditions have uniform particle size and disperse well.The experience results shows that LPL-AuNPs hasselect detection effect on Pb2+,and the lowest detection concentration was 3?M.The transmission electron microscopy(TEM)shows that gold nanoparticles were aggregation linearly orirregular,which is depengent on the Pb2+ concentration.3)The optimized structures of LPL and three heavy metal ions(Cr2+,Cd2+,Pb2+)complexes wereobtained by density functional theory(DFT)method.Bond structural parameters and energeticswere discussed in detal to compare the stability of these complexes.The result shows that LPL-Cr3+ was the most stable one under alkaline condition.The selectivity of chromium to LPL-AgNPs at pH=12.6 and 12.0 was verified.The adsorptions of LPL on gold and silver surfaces werethen simulated by molecular dynamics simulations,and the recognition processes of heavy metal ions on LPL surface were finally studied.The results show that LPL and heavy metal ions(Cd2+)can bridge nanoparticles,which confirms the experimental predication ofheavy metal ions detection mechanism with nano-particles.