Hydrothermal Synthesis of High-Purity, Ultralong Silver Nanowires by Heterogeneous Nucleation

This study presents the synthesis of ultralong silver nanowires (AgNWs) with high purity via a hydrothermal approach. AgCl hydrosol is first converted into polyhedral particles, which serve as heterogeneous nucleation sites and a source of Ag precursor for subsequent reduction by maltose to yield AgNWs. The presence of sufficient poly(vinylpyrrolidone) (PVP) helps to suppress the growth of Ag nanoparticles formed on the Ag(100)/AgCl(100) interface. The low concentration of Ag⁺ limited by the solubility product of AgCl hinders the secondary nucleation and growth of AgNPs in the bulk solution. A relatively high reduction rate, which is conducive to the self-catalyzed longitudinal growth of AgNWs along the ⟨110⟩ direction, can be achieved through the synergy among the low portion of AgNPs with pentagonal twinnings formed on the Ag(111)/AgCl(100) interface, stable concentration of maltose, and steady release of Ag⁺ from AgCl. Experimental parameters including temperature, the concentration of maltose, the concentration of metal chlorides, and so on exert their influence on the formation of AgNWs via altering the reduction rate of Ag⁺ in the reaction system. Optimal conditions result in AgNWs > 200 μm, 30 nm dia., with simplified NH₄OH purification. This study provides a scalable method for high-purity AgNW production.