Plasmonic colors are structural colors generated by the resonant interaction of light with metallic nanostructures through surface plasmons. [13] In recent years, plasmonic colors have drawn considerable attention due to their super-high printing resolution, tunable color properties, excellent chemical stability, scalable manufacturability, and environment-friendly recyclability. [13] The potentials of applying plasmonic colors in active displays have been increasingly recognized and various novel device configurations implementing plasmonic colors have been demonstrated, such as metal-nanostructures-array-based color filters for imaging devices, [14][15][16] metal-insulator-metal resonators tuned by modulating refractive index, [17,18] plasmonic color substrates controlled by liquid crystals, [19][20][21] electrochromically switchable plasmonic color devices, [22][23][24] plasmonic colors operated via reversible electrodeposition, [25,26] and aluminum nano-antenna arrays for high-chromaticity color filters in displays. [20] Recently, integrating EC polymers onto plasmonic color substrates has emerged as a very promising direction for developing ECD-based full-color flexible electronic papers. [22,24,27] From technological points of view, such device configurations offer several distinctive advantages. First, the colors are generated from the plasmonic color substrates rather than from the EC polymers, which straightforwardly breakthroughs the limited available colors of the latter. Second, through surface plasmons, plasmonic color substrates can establish strong nanoscale confinement of optical fields and thus require ultra-thin EC poly mer layer (<100 nm thick) for attaining high-contrast control of colors. The flux of material (dopant) to and from the EC polymer film during the doping/dedoping processes, upon the application of a voltage, can be significantly boosted in the ultra-thin film, which can enable unprecedented fast switching speed to display videos. [22,24] Third, plasmonic color substrates can potentially be manufactured on flexible substrates, which opens up an avenue to new applications such as next-generation wearable display devices. Promising up-scalable manufacturing techniques of plasmonic colors or structural colors include roll-to-roll (R2R) nanoimprint, [28] laser-induced photothermal reshaping, [29,30] and inkjet printing. [31,32] Out of these techniques, high-speed R2R nanoimprint has the best overall throughput and allows largearea generic plasmonic color patterns to be replicated onto flexible thin foils. [28] It is noteworthy that plasmonic color pixels manufacturable through R2R process must have surface-relief nanostructures, which are defined on a master stamp surface during its origination procedure.Combining electrochromic (EC) polymers with plasmonic colors is a very promising configuration for realizing full-color, low-power, flexible, reflective displays. From materials perspectives, the polymer material growth and its electrochemical properties, and the plasmonic color subst...

Control of the surface plasmon resonance (SPR) enhanced light transmission through array of nanoholes on gold films was achieved by modifying the metal surface with a thin layer of electroconductive polymer film. The electrochromic properties of the polymer were then triggered by tuning the electrochemical potential. Conducting polymer-modified nanohole array electrodes were prepared by electrodeposition of polypyrrole (PPy) using cyclic voltammetry. Only the gold surfaces inside the holes were accessible for film formation. The doping level of the PPy film was tuned by the electrochemical potential allowing fine control for the amount of light transmitted through the arrays. The concept demonstrated here paves the way for the fabrication of a new type of controllable nanometric optoelectronic devices based on polymeric materials.

The electrochemical responses from periodic 6 × 6 arrays of recessed gold nanorings were compared to the 6 × 6 recessed gold nanodiscs arrays. The nanostructured arrays were fabricated by focused ion beam milling and their electrochemical response from a reversible redox pair was obtained. Three-dimensional cyclic voltammetry simulations using COMSOL were performed on 6 × 6 periodic arrays of both recessed nanodiscs and nanorings to elucidate the differences in mass transport between these geometries. Specific mass transport properties near the electroactive surface of the electrodes were elucidated by analyzing the calculated concentration profiles of the redox species. Relative contributions from radial diffusion regimes inside the nanoholes play an important role on the electrochemical response of the recessed nanorings. Arrays of nanodiscs are common in different types of applications, particularly in biosensors. The results presented here suggest that the performance and sensitivity of electrochemical nanosensors can be simply improved by implementing electrodes with a geometry which offer greater current density while keeping the overall footprint of the sensor element constant.

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A 6 × 6 recessed Au nanoring-ring electrodes microarray was fabricated over a glass substrate using focused ion beam milling. The electrochemical responses of this device to a reversible redox pair were examined. In redox-cycling mode, the lower ring acts as a generator and the upper ring as a collector. High collection efficiencies (close to 100%) and amplification factors (∼3.5) were achieved with this configuration. The redox-cycling behavior of this device was modeled using COMSOL Multiphysics. The effects of scaling the geometric parameters of the electrodes (ring height and radius), potential sweep rates, and inter-electrode gap distance were evaluated through simulations. The computational models showed that the attainable limiting current depends strongly on the ring radius, while it is almost independent of the ring height variations (for a particular inter-electrode gap). The effects of the scan rate and inter-electrode gap distance on the electrochemical characteristics of the device are also discussed. This study provides insights on the influence of the geometry on the performance of these arrays, which should guide the development of future applications.