SERS-active substrates for investigating ultrathin spin-crossover films

• Two different nanofabrication processes of SERS substrates are proposed.
• Both fabrication pathways permit to enhance Raman scattering of spin-crossover ultrathin films.
• The two approaches probe the molecules at the close vicinity of the SERS substrate.
• Thermal study of SERS spectrum indicates that the thin films remain in the high spin state regardless of the temperature.

The detection and characterization of extremely small quantities of material (e.g. ultrathin films) are still a big challenge in order to study the change of physical properties when reducing the size of the system. Surface Enhanced Raman Scattering (SERS) is known as a sensitive technique for detecting even isolated molecules of a given material. When the sample is deposited on Au or Ag nanostructures the Raman signal intensity of the studied compound is exalted. In this paper are presented two different approaches to obtain SERS spectra of ultrathin films of the spin-crossover compound Fe(pz)[Pt(CN)4]. Using both strategies we were able to record SERS spectra of continuous thin films and nanometric patterns (down to 200 nm). Moreover, by comparing the two methods, we suggest that the resulting SERS spectrum is attributed to the molecules located at the vicinity of the SERS-active substrate. Thermal study of the SERS spectrum in the spin-crossover temperature range is also discussed.

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