Preparation Of Gold Nanoparticles And Its Application In Heavy Metal Analysis

The contamination of heavy metals is different from these of other pollutants since it is difficult to be eliminated and can be accumulated in biological organisms.Due to the unique optical properties of noble metal nanoparticles,the changes of state of the disaggregation/aggregation,size and morphology of nanoparticles have the influence on the surface plasmon resonance absorption.In this work,the unique optical properties of gold nanoparticles were employed to sensitively and rapidly detect Hg2+,Pb2+ and Cd2+ ions.The results were as follows:(1)The gold nanoparticles were prepared using the extract of grape skin.The structure of the functionalized gold nanoparticles are analyzed by the TEM and Uv-vis.(2)Gold nanoparticles cofunctionalized with ?-cyclodextrin used as selective colorimetric sensors for Hg2+,Pb2+ and Cd2+ detection.Due to the Hg2+,Pb2+ and Cd2+ binding with pyrimidine groups,the aggregation yield a red-to-bule color change,and could be monitored by naked eyes as well.?-CD-AuQDs shows high selectivity to Hg2+,Pb2+ and Cd2+ in comparison with other 8 metal ions(Mg2+?Ca2+?K+ etc.).Under optimum conditions,the absorbance ratio(A800/A500)was linear with the Hg2+,Pb2+ and Cd2+ concentration in the range of 0.01-2000?mol/L(R2=0.996),the detection limit of Hg2+,Pb2+ and Cd2+ could be as low as 6×10-6 mol/L.The results reveal the practicality of the developed method for the determination of heavy metal in environmental water samples.(3)A colorimetric method was developed for the detection of Hg2+ based on the specific thymine T-Hg2+-T structure and gold nanoparticles.A tweezers-like duplex DNA,containing T-T mismatches in the end,was designed.The mismatched thymines in the tweezers like dsDNA could not form helix structure,which could attach to AuNPs and effectively prevent AuNPs from salt induced aggregation.While in the presence of Hg2+ ions,the T-Hg2+-T coordinations would lead these thymines to form the structures of helix.The AuNPs were less well-protected thus aggregated at the same salt concentration,accompanied by color changing from red to blue.The results of fluorescence spectroscopy showed that when the mercury ions in the system,the gold nanoparticles to agglomerate based on the role of the aptamer,accompanied by the increase of the concentration of mercury ions,a strong agglomeration.With eight kinds of the composite ion system,the colorimetric results are not changed,indicating that colorimetric detection system has high detection selectivity and immunity.(4)AuNPs surface is modified by Glutathion(GSH).By TEM,uv-vis spectrophotometer,and infrared spectrum of GSH-AuNPs were characterized.The results show that the modified AuNPs appear a star-shaped and extend in the direction of different levels,which the average particle size is 60-70nm.Infrared spectrum analysis verify that the surface of AuNPs was successfully coated using GSH.we demonstrate a facile,sensitive and selective colorimetric probe for detection of Hg2+,Pb2+ and Cd2+based on the PGA functionalized AuNPs.The results show the absorbance ratio A800/A500 caused by heavy metal.The results reveal the practicality of the developed method for the determination of heavy metal in environmental water samples.