An efficient way to prepare silver nanorods in high concentration by polyol method without adding other metal or salt

Using ethylene glycol as solvent and reductant, polyvinyl pyrrolidone(PVP) as capping agent under the action of appropriately preformed silver crystal seeds and controlled addition rates of silver nitrate and PVP solution, silver nanorods with length of 2–15 μm and diameter of 200–880 nm can be obtained in high concentration of AgNO3 as 0.50 M. In the absence of the preformed seeds, nanorods cannot be obtained as the main product, if the AgNO3 concentration is over 0.10 M. It is necessary to use the appropriately preformed silver crystal seeds for the high concentration preparation of silver nanorods. Transmission Electron Microscopy images showed that Ag seeds preformed at appropriate silver nitrate concentrations exhibited the multiply twinned particles of decahedral shape(MTPs), which formed Ag nanorods in the presence of PVP. Through study of the effects of various factors on the nanostructure of silver, the favorable conditions are: appropriately preformed seeds concentration at 6.54–9.81 mM, addition rate of AgNO3 solution at 0.30–0.43 mL min−1 and molar ratio of PVP/AgNO3 at 1.1–1.4, in order to control the crystal growth rate of silver matching the reduction rate of AgNO3 by ethylene glycol. The nanorods obtained were characterized by Scanning Electron Microscopy, EDX, XRD, Raman spectrometry, Infrared Spectrophotometry and Ultraviolet Spectrophotometry. On the base of the above results, the mechanism of rates matching for obtaining silver nanorods was briefly discussed. This method is a simple, facile and economical method using high concentration with high yield without using other metal or salt to massively synthesize silver nanorods through adding preformed silver seeds to control the reduction rate of silver nitrate and the crystal growth rate of silver nanorods. As compared to the conventional polyol method using lower silver nitrate concentration, this method can save ethylene glycol used and time of operation and the as-prepared Ag nanorods are suitable to wide application for electromagnetic shielding materials, conductive adhesive, conductive plastic composites and flexible conductors, etc.

► Ag nanorods can be prepared in high AgNO3 concentration without adding metal or salt.
► Preformed Ag seeds are necessary for preparation of silver nanorods at high [AgNO3].
► Rate of reducing Ag+ matching that of crystal growth yields Ag nanorods.
► This is a convenient and economical method for massive production of Ag nanorods.