Spectrally Tailored Light‐Matter Interaction in Lithography‐Free Functional Nanomaterials

Functional materials with a tailored optical response are needed for applications including coloring, optical instrumentation, data encryption, thermal radiation shaping, energy harvesting, and environmental or biological sensing. A given application requires the material to absorb, transmit, reflect, or scatter light in a suitable way, in a specific, narrow, or broad spectral range selected in the visible or infrared. To achieve the optical response and functionality needed, it is appealing to design nanomaterials with a suitable composition and a properly engineered structure, and this should ideally be realized with high‐throughput and cost‐effective fabrication methods. Herein, the aim is to provide a view on some very recently reported functional nanomaterials showing an optical response tailored for applications by lithography‐free methods. It is illustrated how assembling tailor‐made nanostructures based on the expanding library of optical materials (and their specific wavelength‐dependent dielectric functions) enables harnessing a variety of optical resonances (plasmonic, epsilon near zero, high refractive index Mie, film interference) to tailor the nanomaterials' optical response. It is also shown that building the nanostructures from novel optical materials brings special functionalities, such as a switchable response. Examples of applications are put forward.