Dynamic Optical Physically Unclonable Functions From Spatiotemporal Fluorescence Blinking in Plasmonic Nanocavities

ABSTRACT

Dynamic optical physically unclonable functions (PUFs) are promising for anti‐counterfeiting, but many reported systems still rely on predictable stimulus‐response pathways that can be functionally emulated. Here, we develop a stochastic dynamic optical PUF based on Ag nanocube‐on‐film plasmonic nanocavities. Randomly adsorbed Ag nanocubes define a static scattering fingerprint, while the nanocube‐film gap concentrates the optical near field and amplifies localized silver‐cluster photochemistry on the partially oxidized Ag film. Under continuous blue‐light excitation, reversible photoreduction and re‐oxidation of surface Ag ₂ O generate transient emissive Ag nanoclusters, producing spatially heterogeneous fluorescence blinking and multicolor emission. These spatial, spectral, and temporal responses serve as dynamic authentication keys that are difficult to replicate structurally or functionally. A parallel computer‐vision workflow integrating hash‐based similarity evaluation with scale‐invariant feature transform (SIFT)‐based structural verification enables robust cross‐modal authentication under spatial misalignment, environmental contamination, and device‐dependent optical variation. The fingerprints show a broad authentication window, with intra‐ and inter‐label sparsity‐aware Hamming distances centered at 0.026 and 0.760, respectively. Their mean entropy reaches 0.694, near the sparsity‐limited ceiling, and a conservative degree‐of‐freedom analysis gives ≈1.9 × 10 ⁵ distinguishable states within one readout field. This work establishes plasmonically amplified stochastic photochemistry as a machine‐readable security platform for dynamic optical anti‐counterfeiting.