Application of gold nanoparticle self-assemblies to unclonable anti-counterfeiting technology

Counterfeits are now world-wide issue. An anti-counterfeit technology with high security level (unclonable), high through-put rate of authentication, and low cost is desirable. Nanotag of plasmonic nanostructure with surface enhanced Raman scattering (SERS) activity is promised for the ideal authentication. The gold nanoparticle (AuNP) self-assemblies were applied to SERS active “stealth nanobeacon” for authentication. Mild deposition of aqueous dispersion of self-assembled AuNP was used. 10 ng AuNP assemblies deposited on a commercial medicine tablet were almost invisible to the eye. Distinguishable SERS signals of reporting molecules was produced by 1s irradiation of 785 nm laser over the nanobeacon, while Raman spectrum of the ingredients was observed on the tablet without the nanobeacon. Rapid authentication of tablets stocked for 60 days was sufficiently carried out. It is considered that the presence of discrete AuNP assemblies allows excellent performances of stealth nanobeacon.