Design of Thermally Robust Plasmonic Nanocrystals for Surface Enhanced Raman Scattering and Anticounterfeit Applications

Counterfeit products are a global economic threat and include high-end parts in electronics and the automotive sector. Their counterfeit versions can lead to catastrophic failures, posing serious risks to human safety and security. Current anticounterfeiting technologies frequently degrade at the high operating temperatures of these technologies, reducing the efficacy of security features and leaving them vulnerable to tampering. Thermally stable nanocrystals are of interest for their ability to withstand extreme temperature conditions while retaining desirable size-dependent properties relevant to anticounterfeit tag creation, including their light scattering and Raman enhancement capabilities. This manuscript reports design principles for thermally stable nanocrystals capable of intense surface enhanced Raman scattering (SERS) through bimetallic nanocrystal creation. Specifically, the thermal stabilities of and SERS enhancements provided by core@shell Au@Pd nanorods of variable Pd-shell thicknesses were compared to Au nanorods, both functionalized with model Raman reporters. Notably, the thermal stability of the nanorods increased with Pd-shell thickness, while SERS enhancement was maintained at thin Pd shells. These results highlight the ability to balance thermal stability and SERS enhancement through integration of a high melting-point metal (Pd) with a strongly plasmonic metal (Au) through nanocrystal architecture.