Silver Nanoparticle Rings of Controllable Size: Multi-Wavelength SERS Response and High Enhancement of Three Pyridine Derivatives
The preparation method of nanoporous poly(methyl methacrylate) (PMMA) containing silver nanoparticles self-organized in rings is highly adaptable, yielding a variety of materials of controllable pore size (ranging from 200 nm to over 5 mm), nanoparticle size (20 to 200 nm), surface coverage and silver precursor concentration. In this article, it is optimized aiming at a best performance as enhancers for Surface Enhanced Raman Spectroscopy. The versatility of these sensors is shown by a multi-wavelength excitation experiment at 457, 488, 514 and 633 nm. Finally, the efficiency of 2,2’-bipyridine, 4,4’-bipyridine and trans-bis-(4,4’-bipyridyl)ethylene as SERS probe molecules is compared using PMMA/Ag-rings. Ag+ ions are shown to play an important role in the adsorption of the target molecules on these surfaces leading to a SERS enhancement factor of 3.783 10^8 at 488 nm for trans-bis-(4,4’-bipyridyl)ethylene.