Controlling gold nanoparticle assemblies for efficient surface-enhanced Raman scattering and localized surface plasmon resonance sensors

Gold nanoparticle assemblies with different particle densities were immobilized upon functionalized glass substrates and their morphology and optical properties are analysed with TEM and UV - vis absorption spectroscopy. The efficiency of self-assembled gold colloidal nanoparticles as SERS-active substrates at 633 nm excitation line is evaluated by employing p-aminothiophenol. The average enhancements in the range of 10(5) - 10(7) are consistent with signals being dominated by molecules adsorbed at junctions inside nanoparticle assemblies. We employ an annealing treatment to induce changes in the initial morphology of gold assemblies and produce sensitive LSPR substrate. The sensitivity of the as-prepared substrate to transduce changes of the surrounding medium refractive index is further assessed.