Rapid and Reversible Plasmonic Coupling of Silver Nanoparticle Films on Arbitrary Solid Substrates for Information Encryption

Achieving solid-state plasmonic color switching with rapid and multimodal responses on arbitrary solid substrates remains a significant challenge. Herein, we report the design of dual-responsive plasmonic color-switching silver nanoparticle (AgNP) films on diverse solid substrates by integrating the reversible swelling of poly(vinyl alcohol) (PVA) film with the dynamic decoupling and coupling of AgNPs. In response to humidity, the swelling/deswelling of the PVA film expands/shrinks the AgNP interparticle distances and induces dynamic plasmonic decoupling/coupling, enabling solid-state plasmonic color switching on various substrates, including glass, paper, poly(vinyl chloride), aluminum foil, polypropylene, and ceramics. Specifically, the AgNP/PVA paper-based film demonstrates unprecedented performance, including fast plasmonic color switching within 400 ms and high stability beyond 1,000 cycles. Moreover, the plasmonic color switching can be simultaneously modulated by applying a low temperature due to the delayed deswelling rate of PVA molecules upon removing humidity. By combining humidity responsiveness with photolithographic patterning and a temperature-induced time-resolved color imaging technique, a sophisticated dual-modal encryption device is realized. This work provides strategies for designing solid-state plasmonic color switching with outstanding performance, holding great promise for applications in information encryption and smart optical devices.