Silver nanowires for anti-counterfeiting

Silver nanowire (AgNW) films have been widely used as flexible transparent electrodes due to the high electrical conductance and high transmittance in the visible range. The infrared (IR) properties of AgNW films, however, are seldom discussed. Here, we show that ultrathin AgNWs present high transmittance in the visible range (∼95%) and high reflectance (60–70%) in the IR range of 8–14 μm. Such a significant difference makes AgNW films invisible to naked eyes but visible under an IR camera, being an ideal selection for anti-counterfeit technologies, while no excitation is required. We have demonstrated that AgNW films can be spray-coated on either flat or microstructured surfaces with high conformability and high scratch-resistance, and thus these anti-counterfeiting materials can be applied to a variety of applications. The AgNW-based anti-counterfeiting may be helpful for combating counterfeiting crimes in the fields of medicines, artwork, banknotes, brand luxuries, industrial parts, and so on.