Detection Of Metal Ions In Biological Environment Based On Functional Gold Or Silver Nanoparticles

In recent years, owing to the specific optical, magnetic, and catalytic properties, noble nanoparticles materials?especially AuNPs and AgNPs? have been widely used in the fileds of biology, material and medicine etc. The introduction of organic molecules onto the surface of the metal nanoparticles can improve not only its water solubility but also the sensing selectivity. In this thesis, based on different functionalized Au/Ag nanoparticles, we have successfully synthesized four kinds functionalized nanoparticles which were modified with different ligands and the quantitative methods of Cr³⁺, Hg²⁺, Cd²⁺ and Ni²⁺ were proposed here. The main contents are shown as follows:?1? The technique for monitoring Cr³⁺ concentration based on 4-amino hippuric acid?PAH? decorated Au nanoparticles?PAH-AuNPs?. Because of the co-ordination interaction between Cr³⁺ and PAH, it was found that modified AuNPs can easily aggregate in the presence of Cr³⁺, resulting in the color change from red to violet or blue. It is easily observed with the naked eye. There was a good linear relationship between ratio of the absorbance and the concentretion of Cr³⁺ in the range of 5.0 to 120 ?M with detection limit of 1.17 ?M. The confirmatory method is successfully applied to rapid determination of Cr³⁺ in water and milk products.?2? Colorimetric detection of Hg²⁺ based on anti-aggregation of gold nanoparticles in the prescence of 2-mercaptobenzothiazole. A simple, facile and sensitive colorimetric strategy for Hg²⁺ detection is proposed based on anti-aggregation of gold nanoparticles?AuNPs? which was induced by 2-mercaptobenzothiazole?MBT?. A certain concentration of aggregation agent MBT is responsible for a visible color change of AuNPs from wine red to blue. The aggregations of AuNPs decrease with increasing concentrations of Hg²⁺, which can be monitored by an ultraviolet-visible spectrophotometer or the naked eyes. The limit of the detection?LOD? is 0.1 ?M by the naked eyes and 6.0 nM by UV–vis spectroscopy with the linear range from 0.05 to 1.0 ?M.?3? Through a previously reported method ANS-AgNPs was prepared, which were stable and uniform in aqueous solution. A simple and lower-cost assay with high sensitivity for the Cd²⁺ detection is introduced using 1-amino-2-naphthol-4-sulfonic acid-modified silver nanoparticles?ANS-AgNPs?. The interaction between Cd²⁺ and ANS induces rapid aggregation of ANS-AgNPs accompanied by a naked-eye visible color change, resulting in precise quantification of Cd²⁺ that can be monitored by a simple UV-visible spectrometer. There was a good linear relationship between ratio of the absorbance and the concentretion of Cd²⁺ in the range of 1.0 to 10 ?M with detection limit of 87 nM. The proposed method is simple and efficient, which has been applied to determination of Cd²⁺ in milk power, lake water and serum.?4? Visual test for Ni²⁺ using silver nanoparticles modified with Adenosine monophosphate?AMP? and sodium dodecyl sulfonate?SDS?. The cofunctionalized AgNPs showed obvious advantages over the ones functionalized only by AMP or SDS in terms of selectivity. Based on Ni²⁺ induced AMP-SDS-AgNPs aggregation, a new method was successfully applied to the determination of Ni²⁺. The limit of the detection?LOD? is 0.6 ?M by UV–vis spectroscopy with the linear range from 4.0 to 60 ?M. The confirmatory method is successfully applied to rapid determination of Cr³⁺ in lake and tap water products.