Study On The Synthesis And Chiral Properties Of The Ag Nanoparticles

Considerable attention has been directed towards silver nanoparticles which exhibitinteresting optical properties due to their unique surface plasmon resonance (SPR). Asconfirmed by various studies, surface modification by chiral functional molecules caninduce a chiral perturbation in the surface of metal nanoparticles. Chiral nanomaterials hasattracted great interest because of their potential applications in chiral catalysis, chiraldiscrimination and chiral functional optical and electrical devices. In this paper, silvernanoparticles were prepared by chemical reduction method in aqueous solution. Themechanisms of the chirality of the prepared silver nanoparticles were discussed.Silver nanoparticles were synthesized by the reduction of AgNO3with NaBH4in thepresence of glycyl-L-glutamic Acid as stabilizer and chiral inducer. The prepared Agnanoparticles were characterized by UV-Vis spectrometer (UV-Vis), transmission electronmicroscopy (TEM) and circular dichroism spectrometer (CD). Monodispered spherical Agnanoparticles (15nm in diameter) were obtained when the pH value of the solution wasadjusted to10and the molar ratio of Ag+to glycyl-L-glutamic acid was1:2. The preparedsilver nanoparticles show stronger CD signal under the above experimental condition. By atwo-step approach, silver nanoparticles were prepared by the reduction of AgI sol, and thestability of the prepared Ag nanoparticles was studied.In the presence of sodium glycocholate hydrate as stabilizer and chiral inducer, silvernanoparticles were prepared by the reduction of Ag+with NaBH4. The optimum preparationcondition was obtained when the pH value of the solution was7.5, the molar ratio of Ag+tosodium glycocholate hydrate was1:2, and concentration of Ag+was0.25mmol·L-1. Underthis condition the prepared silver nanoparticles were uniform in the size with the averagediameter of about10nm. The pH value of the solution has an important influence on the CDsignals of the prepared Ag nanoparticles. The CD signals enhance gradually with thedecrease of the pH value of the solution.Inosine capped-silver nanoparticles were synthesized by the reduction of Ag+in thepresence of inosine as stabilizer and chiral inducer. The synthesized Ag nanoparticles were10nm in diameter and spherical in shape. Chiroptical properties of the prepared silvernanoparticles were investigated by circular dichroism. The prepared PVP-capped silvernanoparticles did not exhibit any CD signal in the wavelength region of300-500nm.However, inosine capped-silver nanoparticles exhibit a negative Cotton effect in the regionof the surface plasmon resonance (SPR) of the silver nanoparticles.Deoxycholate sodium capped-silver nanoparticles were prepared by the chemical reduction of AgNO3in the presence of deoxycholate sodium as stabilizer and chiral inducer.The optimum pH value for the preparation of silver nanoparticles was7.0. The obtainedsilver nanoparticles with8nm in diameter were mono-dispersed. The Ag nanoparticlesprepared at pH value of7.0exhibited a strong positive Cotton effect in the CD spectrum.