Synergism of Cl- and Br- on the controllable synthesis of flexible silver nanowires

Silver nanowires (AgNWs) exhibit excellent electrical conductivity and hold significant potential for usage in flexible electronics. AgNs can possess a suitable aspect ratio, uniformity, and flexibility that are essential for achieving high-performance flexible transparent conductive films. However, the synthesis of AgNWs presents a challenge in controlling its morphology, often resulting in varying lengths and aspect ratios that are difficult to regulate. Thus, the controlled preparation of AgNWs holds great significance. Herein, AgNWs were synthesized via a polyol method with FeCl3 and KBr composite metal salt as control agents, silver nitrate as a silver source, ethylene glycol as a reducing agent and solvent, and polyvinylpyrrolidone (PVP) as a growth director. By adjusting the ratio and dosage of FeCl3 and KBr, the morphology controllability of AgNWs was realized, and the obtained AgNWs can be straight or bendable. The surface morphology and microstructure of the AgNWs were analyzed by scanning electron microscopy (SEM). Due to the synergistic effect of FeCl3 and KBr, flexible AgNWs with an average diameter of 25-35 nm, an average length of 35-45 um, and an aspect ratio of over 1000 can be obtained. Mechanism studies have shown that through electrostatic interactions, AgCl, AgBr, NO3, and PVP in the reaction mixture can form binding sites for AgCl-PVP-NO3 and AgBr-PVP-NO3, thus causing the silver nanowires to become flexible. Meanwhile, the strong polarization effect caused by Br in the reaction causes the chain growth to become subject to the dual effects of electrostatic repulsion and external forces, resulting in the formation of flexible and soft silver nanowires.