Preparation and characterization of size and morphology controllable silver nanoparticles by citrate and tannic acid combined reduction at a low temperature

In this paper, Ag nanoparticles (NPs) were prepared by using the citrate and tannic acid combined reduction of silver nitrate at 60 °C. Tannic acid is employed as both auxiliary reductant and surface modification agent. The size of Ag NPs can be well under controlled by varying the concentration of tannic acid. The size of Ag NPs decreases from 30 to 10 nm with the decrease of the concentration of tannic acid. The minimum average particle size, 10 nm, could be obtained with the 6 μM of tannic acid under the reaction condition of 60 °C. The products are rod-like, triangle, polygon NPs when the concentration of tannic acid turns to 24 μM. The results show that the obtained Ag NPs at 60 °C are smaller than that of boiling. Moreover, the morphology of the obtained Ag NPs is controllable under the condition of 60 °C. A SERS experiment was conducted for RhB in the presence of Ag NPs prepared at 60 °C, and a clear surface enhanced Raman spectroscopy was recorded.