Nanostructures for Infrared Imaging: Enhanced Detection

Advanced detection systems increasingly rely on infrared (IR) imaging to overcome the limitations of visible light cameras in adverse environments such as fog, rain, and low-light conditions. However, the effectiveness of IR detection remains fundamentally constrained by the low emissivity contrast between targets and their backgrounds. Here, we present a plasmonic metal-dielectric-metal nanostructure comprising a porous anodic aluminum oxide (AAO) dielectric layer sandwiched between an aluminum substrate and a surface Au nanoparticle layer that enables near-independent modulation of visible reflectance (400-800 nm) and long-wave infrared emissivity (8-14 μm). The decoupling mechanism exploits the distinct characteristic length scales governing each spectral band: visible reflectance is controlled by Fabry-Pérot cavity interference and plasmonic absorption of the Au nanoparticle layer, while infrared emissivity is governed by the intrinsic phonon absorption of the AAO layer and is insensitive to Au coverage. Using scalable anodic oxidation and screen-printing fabrication, we achieve tunable visible reflectance (R = 0.2-0.9) and infrared emissivity (ε = 0.1-0.87). Applied to infrared-enhanced license plate detection, our patterned plates achieve an average recognition rate of ∼45% under adverse environmental conditions, compared to ∼5% for conventional plates. This work offers a scalable route to multispectral patterned surfaces for infrared imaging, thermal sensing, and anticounterfeiting applications.