Silver nanoflowers with SERS activity and unclonable morphology

This manuscript presents surface-growth of silver nanoflowers with high surface-enhanced Raman scattering (SERS) activity and unique morphology. The nanoflower morphology is mediated by the seed-mediated growth of silver nanostructures over gold nanoparticles immobilized on hemispherical polymer features. Randomly positioned hemispherical polymer features are self-assembled via surface dewetting of a nanoscopic film of poly (2-vinylpyiridine) (P2VP) film on the polystyrene-grafted substrate. The time-dependent growth study shows that the silver nanoflowers evolve from the circular contact lines separating the P2VP features and underlying substrate. The three-dimensional nature of the underlying feature facilitates growth in a flower like morphology. The silver nanoflowers exhibit high levels of SERS activity allowing for detection of rhodamine 6G at a 100 pM level under 532 nm laser excitation. A feature matching algorithm-based image analysis confirms the unique morphology of every single silver nanoflower. The direct fabrication of silver nanoflowers at random positions with unclonable morphology and high SERS activity is particularly promising for anti-counterfeiting applications.