Plasmonic color generation in silver nanocrystal‐over‐mirror films by thermal embedment into a polymer spacer

The production of colors by plasmonic nanostructures is an attractive prospect over dyes as they allow ultra‐high resolution, non‐fading colors. Typical techniques for producing plasmonic color patterns such as by electron beam or ion beam lithography are expensive, slow and not well scalable. This work demonstrates a simple, lithography‐free technique for producing plasmonic colors using a silver nanocube (AgNC) based nanoparticle‐over‐mirror (NPoM) system with thermally‐generated colors. AgNC's are deposited over a metal (Au or Ag) film with a polystyrene (PS) dielectric spacer. Upon heating the system past the glass‐transition temperature of PS, the AgNC embed into the polymer, reducing the AgNC/metal film distance. This results in a strong gap‐plasmon that can shift over 200 nm across the visible spectrum during the process. The thermal embedment of AgNC in NPoM systems is tunable across the visible range, producing wide, distinct color palettes depending on the metal film used. This technique can potentially be applied to plasmonic color‐patterning systems to produce high‐resolution microscale or nanoscale patterns over a large area. The work presents a simple technique for producing plasmonic colors. The color of the system is defined by the gap plasmon between silver nanocubes (AgNCs) and a gold or silver thin film. Upon heating the system past the glass‐transition temperature of polystyrene (PS), the nanocubes embed into the polymer, reducing the gap width. The gap plasmon can shift over 200 nm across the visible spectrum.