A cost-effective purification strategy of ultra-long AgNWs for enhancing stability and durability of AgNWs/PU sensor

A large amount of silver nanoparticles (AgNPs) and short-sized silver nanowires (AgNWs) were produced in the reaction of AgNW synthesis by the polyol method. These impurities immensely affected the practical application of AgNWs dispersion. To promote the electrical property of AgNWs, it is necessary to develop a cost-effective method to separate impurities in AgNWs dispersion. Herein, we developed a new purification strategy called centrifugation-sedimentation separation-centrifugation to purify the ultra-long AgNWs (average length of 98.26 μm and the aspect ratio of 1240) synthesized by an improved polyol method. The yield of sedimentation separation was up to 78.1 % in this strategy. Based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the sedimentation mechanism of the ultra-long AgNWs and impurities was systematically investigated. The AgNWs/polyurethane (PU) composite foam prepared by the impregnation method with purified ultra-long AgNWs demonstrated a superior conductivity of 13227 S/m, which was twice than that of the composite foam with unpurified ultra-long AgNWs. The resistance variation of the purified ultra-long AgNWs-5/PU sensor was only elevating 11 % after 100 cycles of 100 % strain compression at 1 Hz frequency, while the AgNWs-5/PU sensor prepared from commercial 20 μm AgNWs showed a resistance change of up to 492 %. Our study provides a low-cost, highly selective, and efficient purification strategy for ultra-long AgNWs dispersions, and also demonstrates that ultra-long AgNWs can enhance the sensing stability and durability of AgNWs/PU foam sensors. [Display omitted] •A centrifugation-sedimentation separation-centrifugation novel strategy was developed for purifying ultra-long silver nanowires (AgNWs).•The purification strategy maintains the separation yield of AgNWs at 78.1 % on average.•The AgNWs-5/PU sensor prepared by ultra-long AgNWs has excellent conductivity (13227 S/m), good sensing stability and durability.