Plasmonic colloidal nanoparticles with open eccentric cavities via acid-induced chemical transformation

Plasmonic gold nanoparticles with open eccentric cavity are fabricated by selectively adapting the structure of non-plasmonic nanoparticles via acid-induced chemical transformation. Because of strong near-field enhancement occurring at the mouth of the open cavity and very rough surfaces resulting from uniformly covered hyperbranched sharp multi-tips as well as free access of SERS molecules inside the nanoparticles without diffusion limitation, adenine, one of four bases in DNA, in an extremely diluted aqueous solution (1.0 pM) was successfully detected with excellent reproducibility at a laser excitation with 785 nm wavelength.