Emeraldine Salt Form of Polyaniline as a Probe Molecule for Surface Enhanced Raman Scattering Substrates Excited at 1064 nm

Associating polyaniline and metallic nanoparticles may result in the combination/synergism of properties, which have been attracting great attention. This paper describes an investigation that verified the effectiveness of several gold nanostructures acting as surface enhanced Raman scattering (SERS) substrates using the emeraldine salt form of PANI (PANI-ES) as a probe-molecule. The surface enhanced resonance Raman scattering (SERRS) spectra of PANI-ES at 1064 nm results from two enhancement effects: one from the PANI-ES resonance Raman and the other from localized surface plasmon resonance of the gold nanostructures when the plasmon wavelength approaches the NIR region. A considerable SERRS intensity for PANI-ES at the 10 nM level could be obtained using a gold nanoplates colloidal suspension as substrates. The SERRS spectra of PANI-ES and the high correlation between SERRS intensity and LSPR extinction of Au nanostructures at 1064 nm indicate that the enhancement was mostly due to the electromagnetic mechanism. These results indicate that PANI-ES can be employed as a general probe-molecule for the evaluation of SERRS substrates performance at 1064 nm excitation.