Study On The Preparation And Chiral Properties Of The Ag Nanoparticles

As an advanced functional material, silver nanoparticles have extensive applications in civil and industrial areas. The properties of silver nanoparticles are dependent on their stru- cture, shape, size, and the environment. In this paper silver nanoparticles were prepared by photochemical reduction and chemical reduction, respectively. And the mechanism of the chirality of silver nanoparticles was studied.Silver nanoparticles were prepared by photochemical reduction method. By using deoxycholate sodium as stabilizer and chiral inducer, silver nitrate was reduced under the UV light irradiation. The prepared samples were characterized by UV-Vis spectrometer (UV-Vis), transission electron microscopy (TEM) and circular dichroism spectrometer (CD). The results show that silver nanoparticles have the optimal preparation condition. The monodispered Ag nanoparticles (10 nm in diameter) were obtained when the solution was adjusted to pH10 and aged for 24 hours. In addition, the initial obtained spherical silver nanoparticles can self-assemble into silver nanoflakes when aged at a low temperature for a long time (>1month). The circular dichroism spectra show that the prepared silver nanoparticles have optical properties, i.e. chirality.Using liquid-phase chemical reduction method, we prepared silver nanoparticles by the reduction of AgNO3 with NaBH4 in the presence of deoxycholate sodium as a stabilizer and chiral inducer. The results show that the monodispered Ag nanoparticles (10 nm in diameter) were obtained when the solution was adjusted to pH 7 and aged for 24 hours. The CD signal of the prepared silver nanoparticles is the strongest when the solution without aging treatment was adjusted to pH 7.We prepared silver nanoparticles in the presence of histidine as a stabilizer and chiral inducer by the reduction of AgNO3 with NaBH4. The optimal preparation condition was obtained when the pH value of solution was 10 and the molar ratio of Ag+/histidine was 1:5. On this condition the prepared silver nanoparticles has the average diameter of about 5 nm. The spherical nanoparticles can spontaneously assemble into nanoplates by increasing the initial concentration of Ag+ under the condition of maintaining the molar ratio of silver nitrate and histidine. And the histidine plays a role as a template in this process. The results of circular dichroism spectra show that the CD signal of the spherical silver nanoparticles prepared in the solution of pH10 was strong. In addition, we used a new seed-mediated growth method to prepare the anisotropic rod-shaped silver nanoparticles.In the presence of ascorbic acid as a stabilizer and chiral inducer we prepared silver nanoparticles by the reduction of AgNO3 with NaBH4. The results show that the silver nanoparticles obtained are about 10 nm in diameter. The results suggest that the generation of chirality of silver nanoparticles is reversible and the chirality of silver nanoparticles is caused by the distorted surface atoms.We prepared silver nanoparticles by the reduction of AgNO3 with NaBH4 in the presence of D-glucose sodium as a stabilizer and chiral inducer. The results show that the addition of PVP can effectively prevent the agglomeration of silver nanoparticles, and improve the stability of silver nanoparticles. The results of circular dichroism spectra show that the CD signal of the silver nanoparticles prepared is week in this system.