We have investigated the nanoscale structural and vibrational properties of polyvinylpyrrolidone (PVP)-covered silver nanocubes (AgNCs) array. The ordered AgNCs array fabricated on Au(111) by the Langmuir–Blodgett method was utilized for a surface-enhanced Raman scattering (SERS) platform. The local arrangements and the facet structure of AgNCs were observed by various types of microscopies, which revealed that AgNCs form an ordered monolayer and exhibit an atomically flat facet. The vibrational peaks associated with PVP were clearly observed in the Raman spectra owing to the SERS effect by AgNCs. We found that two types of C=O stretching peaks appear in the Raman spectra, of which the appearance patterns depend on the excitation energy of the incident laser. The simulations based on the finite-difference time domain method imply that highly ordered 2D AgNCs enable us to excite localized surface plasmon modes, such as a single particle mode and a gap mode, of AgNCs selectively, leading to vibrational excitation of PVP existed at the surface and the gap of AgNCs.

We have investigated the thermally and photoinduced structural and chemical changes of a polyvinylpyrrolidone (PVP)-covered silver nanocube (AgNC) array on Au(111).