The Preparation, Characterization, Application In Spectrum Analysis Of Silver Nanoparticles

In this paper, we reported several new method of preparation silver nanoparticles, and the obtained nanoparticles were characted and applicated to detected DNA and BSA.First, silver nanoparticles were obtained by the aqueous-gaseous phase reaction of silver nitrate solution and ammonia gas. The method is simple and cheap. XRD and TEM were used to characterize the structure of the particles. The results indicated that the particles are almost about 10 nm average diameters and spherical shape. To our surprise, the silver nanoparticles have strong fluorescence. The fluorescence of silver nanoparticles was quenched, when calf thymus DNA (ct-DNA) was added into sliver nanoparticles solution. The fluorescence intensity was quenched linearly with the concentration of ct-DNA. The linear range concentration of ct-DNA was 0.5-5.0×104 ng/mL and the detection limit was 0.3 ng/mL.Sencondly, in the solution containing ammonia, silver nitrate was reduced by tartaric acid at boiling point, and nano-silver colloid was generated. The products were characterized by transmission electron microscope (TEM) and powder X-ray diffraction (XRD). Both TEM and XRD measurements show that the average size of silver colloid particles is 25-30 nm and near-spherical shape. Researches on the character of resonance light scattering (RLS) of nano-silver colloid indicates that the strongest RLS peak of nano-silver colloid appeares at 447 nm. When BSA adding into the nano-silver colloid solution, the RLS peaks intensity was quenched. Based on this, a novel and simple method of determination of BSA was developed. Under optimum conditions, decrease of the quenched intensity of RLS peaks is in proportion to the concentration of BSA. It has a linear response over the range 25-2.5×106 pg/mL. This method can be satisfactorily used for the determination of BSA.Thirdly, Fe3O4 magnetic nanoparticles being used as seeding materials, Ag+ ions on the Fe3O4 magnetic nanoparticles reduced to the metal form by tartaric acid using heated treatment. Thus, Fe3O4/Ag composite core-shell magnetic nanoparticles were synthesized. The products were characterized by transmission electron microscope (TEM) and X-ray diffraction (XRD). Both TEM and XRD results showed that the Ag nanoparticles were well distributed on the surface of Fe3O4 magnetic nanoparticles. The size for Fe3O4/Ag composite magnetic nanoparticles which were spherical shape was ~40 nm. Furthermore, the magnetic properties of samples were characterized on a vibrating sample magnetometer (VSM). Under optimal conditions, Fe3O4/Ag composite nanoparticles showed higher magnetism than pure Fe3O4 nanoparticles.