Evolving photonic authentication with sustainable luminescent smart e-tags

Counterfeiting remains a significant threat, causing economic and safety concerns. Addressing this, authentication technologies have gained traction. With the rise of the Internet of Things, authentication is crucial. Photonic Physical Unclonable Functions (PUFs) offer unique identifiers. We present low-cost and sustainable e-tags that may be printed virtually on any surface for authentication due to the bespoke texturization of sustainable inks of surface-modified carbon dots. A single e-tag provides randomized phosphorescence (or afterglow) patterns, which provide multiple layers of safety by exploiting different patterning, excitation energies, and temporal characteristics. A comprehensive case study employing photonic challenge-response pairs, involving a sample size of up to 2⁹ emission spectra in combination with 10² photographs taken with a smartphone, displays a low authentication probability of error (<10⁻¹¹), which supports the potential of our combined approach toward the development of more robust photonic PUF systems.