Investigation Of Functionalized Au/Ag Nanoparticles For Colormeric Detection Of Heavy Metal Ions In Aqueous Solutions

Among the environmental pollutants, the heavy metal pollutions are very difficult to beeliminated, and would accumulate in biological body via the enrichment of the organism, so itseriously damages the health of living bodies in the polluted environment. In view of that, it issignificant to realize the real-time rapid and sensitive detection for heavy metal ions.At present, various methods have been reported for heavy metal ions detection, which weremostly with the aid of the insrtument. However, these methods were inconvenient andtime-consuming. For the unique optical properties, the change of the concentration, morphology,particle size change in noble metal nanoparticles will cause the surface plasmon resonanceabsorption and color changes, has been widely used on the analysis of the testing field. In thisthesis, we utilize its unique properties and realize the rapid colorimetric detection for Mn2+、Cu2+、Hg2+in aqueous solutions as follows:1) Visual and colorimetric detection of Hg2+based on8-hydroxyquinoline and oxalate modifiedgold nanoparticles. The AuNPs are prepared stabilized by polyvinylpyrrolidone (PVP). When8-hydroxyquinoline is added, it can adsorb to the surface of AuNPs through the hydrogen bondwith PVP. In the presence of Hg2+the modified AuNPs aggregate quickly, which leads to colorchange of the nanoparticles dispersion from wine red to gray, the surface plasmon absorption peakand intensity are also changed. The limit of detection by naked eyes was0.4μM and10nM byUV-vis. The real water samples including Hg2+were also detected by this method.2) A new rapid colorimetric detection method of Mn2+based on tripolyphosphate modified silvernanoparticles (P3O105-_AgNPs). The monodispersed AgNPs were prepared by Na5P3O10protectedwith a diameter of10nm. For Mn2+could form a six-coordinated structure with P3O105-coating onthe AgNPs, which leads to formation of large particles aggregation, the SPR absorption peak andthe color of P3O105-_AgNPs also changed, then realized the detection of Mn2+by naked eyes andUV-vis. The limit of detection by naked eyes was0.1μM and50nM by UV-vis. The real watersamples including Mn2+were also detected by this method.3) A new rapid colorimetric detection method of Cu2+based on catalytic etching silver nanoparticles circularly with the assistance of Cl-. The AgNPs were synthesized in the presence ofTween20. With the assistance of Cl-, the Tween20_AgNPs are etched quickly in the presence ofCu2+in acidic environment, which leads to color change of the nanoparticle dispersion from yellowto colorless and decrease of the surface plasmon absorption intensity. Based on this mechanism, thelimit of detection by naked eyes was0.4μM and10nM by UV-vis. The real water samplesincluding Cu2+were also detected by this method.