SERS spectroscopy of nanocomposite porous films containing silver nanoparticles

It is demonstrated that surface-enhanced Raman scattering spectroscopy allows detecting 10−10 M Rhodamine 6G (Rh 6G) on nanocomposite films containing silver nanoparticles with an amplification factor of 3 × 107. The films used for SERS, which exhibit gradients of thickness and have silver particles and pores of different size, were obtained by pulse laser deposition from the low-energy backward erosion flux. To activate the SERS signal, the films were treated in solutions of metal chlorides and hydrogen chloride to achieve formation of anions of [AgCl2]− complexes. The composition of shells of silver nanoparticles, in particular, replacement of silver compounds preventing Rh 6G adsorption by anions of [AgCl2]− complexes enabling adsorption of Rh 6G cation between them, has been monitored by means of SERS spectroscopy. The obtained SERS spectra of Rh 6G in several locations on the film surface allowed determining the area with an optimal size of silver nanoparticles that gives rise to highest SERS signal intensity. The transmission spectra of the films revealed narrowing of the band corresponding to the local surface plasmon absorption, its shift toward the blue spectral region, and enhancement of plasmon resonance upon introduction of chlorine anion. The changes in absorption spectra of the films correlate with the activation of the Rh 6G SERS spectra.