Plasmonic Nanoparticles as a Physically Unclonable Function for Responsive Anti-Counterfeit Nanofingerprints

• Published in: Advanced functional materials 2016-03, Vol.26 (9), p.1315-1321
• Main Authors: Smith, Alison F., Patton, Paul, Skrabalak, Sara E.
• Format: Article
• Language: English
• Subjects: colloids; Deposition; Gold; gold and silver nanoparticles; Labels; metal nanostructures; Nanoparticles; Nanostructure; optically active materials; Refractive index; Refractivity; Scattering; stimuli-responsive materials
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201503989

Far‐field scattering of randomly deposited Au nanoparticles (NPs) is demonstrated as a physically unclonable optical function for anti‐counterfeit applications in which the scattering patterns are easily produced yet impractical to replicate. Colloidal metal NPs are superb components for nanoscale labels owing to their small dimensions and intense far‐field scattering visible at wavelengths that depend on colloidal size, shape, composition, and their local environment. The feasibility of Au NP depositions as nanofingerprints is presented using a simple pattern matching algorithm. These NPs offer extended functionality as environmental sensors. Taking advantage of the local refractive index dependent scattering wavelengths of metal NPs, a detectable color change is also demonstrated from a nanofingerprint comprised of Au and Ag NPs when placed in media with different refractive index. The facile deposition method coupled with the intense scattering and optical response of metal NPs provides physically unclonable tags (nanofingerprints) with the ability to serve as tamper‐evident and aging labels. An optical, physically unclonable function using a random distribution of Au nanoparticles is presented, with the additional functionality of refractive index based environmental sensing using both Au and Ag nanoparticles. This system provides facile fabrication of anti‐counterfeit labels, with total dimensions on the microscale for applications in pharmaceutical and electronic counterfeit prevention.