Simple Recycling of Ag⁺, Surfactant, and Solvent for Repeatable Synthesis of Silver Nanowires for Applications as Flexible Transparent Heaters

Silver nanowires (AgNWs) have shown great potential in various optical and electronic applications, especially in flexible and wearable devices. Polyol method is now a mainstream strategy to synthesize AgNWs. However, unreacted reagents including silver salt, surfactant, and solvent are usually discarded after the collection of products, resulting in a huge waste as well as a burden to the environment. In this work, we demonstrate a simple recycle method to reuse these reagents based on a two-step direct centrifugation protocol. Larger nanowires are separated, while remaining small nanowires and nanoparticles provide nucleation sites and likely function as catalysts to achieve a three-times faster nanowire growth. The cyclic synthesis can maintain at least five consecutive rounds to produce AgNWs with similar size and yield and more rounds under suitable adjustment of Ag⁺ supply. Transparent conductive films based on AgNWs grown from recycled reagents show excellent and consistent optoelectronic performance, namely, a sheet resistance of 141.3 Ω/sq at a transmittance of 99.7% and 9.48 Ω/sq at 92.9%. A transparent heater with a PDMS/AgNWs/PET structure exhibits a resistance of 8.6 Ω at a total transmittance of 76.5% and is heated to 75.8 °C at a 3.5 V power supply. A fast-defrosting process is demonstrated. The recycling method significantly reduces the cost of AgNW production and may widen their application in high-performance flexible devices.