Gap-enhanced Raman tags for physically unclonable anticounterfeiting labels

Anticounterfeiting labels based on physical unclonable functions (PUFs) are easy to generate but difficult to duplicate due to inherent randomness. Gap-enhanced Raman tags (GERTs) with embedded Raman reporters show strong intensity enhancement and ultrahigh photostability suitable for fast and repeated readout of PUF labels. This work demonstrates a PUF label fabricated by drop-casting aqueous GERTs, high-speed readout using a confocal Raman system, digitization through coarse-grained coding methods, and authentication via pixel-by-pixel comparison. A three-dimensional encoding capacity over 3 × 10^15051 is achieved for labels composed of ten types of GERTs with a mapping resolution of 2500 pixels and quaternary encoding of Raman intensity levels at each pixel. Authentication experiments show robust and secure performance, and practical viability is demonstrated. Such PUF labels provide a potential platform for unbreakable anticounterfeiting.