Fig. 4

a, b SERS spectra of 10⁻⁹ M 1,4-BDT adsorbed on dendritic Ag nanostructures and Au/Ag bimetallic nanostructures excited at 488 nm and 785 nm, respectively. c SERS spectra of 10⁻⁹ M 1,4-BDT detected at the freshly prepared and 90-day-old substrates, respectively. Curves are shifted vertically for clear presentation