Stability and morphology of Ag nanoplatelets probed by Depolarized Dynamic Light Scattering

The stability of silver nanoplatelet suspensions prepared with different concentrations of Trisodium Citrate (TSC) was studied by depolarized dynamic light scattering and UV-vis spectrometry. The morphology of the nanoparticles, as well as the color and stability of the sols, are tuned by the concentration of the capping agent. The nanoparticles prepared with high TSC concentration (> 10-4 M) are blue triangular nanoplatelets showing a slight truncation of the tips with aging. When low TSC concentrations are used, the color of the sols changes from blue to yellow with aging time and a strong modification of the morphology occurs: the nanoparticle shape changes from triangular to spherical. Remarkably, they show a high degree of anisotropy. The aging process was followed by the UV-vis spectra and by measuring the rotational diffusion coefficient by depolarized dynamic light scattering, providing information on the nanoparticle size and shape evolution. The high intensity of depolarized signal and the high value of rotational diffusion coefficient suggest that the aging process increases the thickness and the roughness of the nanoparticles.