Ultra-long silver nanowires prepared via hydrothermal synthesis enable efficient transparent heaters

Ultra-long silver nanowires (AgNWs) with an aspect ratio of >2000 were prepared by the hydrothermal synthesis method. The influence of reaction time (4–32 h), reaction temperature (150–180 °C), polyvinylpyrrolidone (PVP) molecular weight (10 000–1 300 000 g mol(−1)), PVP concentration (50–125 mM), glucose concentration (5.6–22.4 mM) and CuCl(2) concentration (2–20 μM) on the AgNW length was investigated systematically. The optimum conditions provided nanowires with an average diameter of 207 nm, an average length of 234 μm and a maximum length of 397 μm. Finally, a AgNW electrode was prepared on a glass substrate and used in transparent heater application. The transparent heater enabled outstanding heat-generating properties, reaching >200 °C within 70 s with an applied voltage of 5 V. Our results demonstrate how increasing the aspect ratio of ultra-long AgNWs is beneficial for both optical and electronic applications in terms of increased transmission and a more efficient Joule effect in the heater application. In addition, our results show that AgNWs with different lengths can be simply obtained by tuning synthesis parameters.