Unprecedented high plasmonic sensitivity of substrates based on gold nanoparticles

This work focused on the plasmonic sensitivity of a substrate composed of gold nanoparticles (AuNp) and 3-aminopropyltriethoxysilane (APTES)-modified graphene oxide (GO-APTES). The multilayered system fabricated by dip-coating was analyzed by means of FTIR spectroscopy and scanning electron microscopy (SEM). The localized surface plasmon resonance (LSPR) band of AuNp was shifted from ca. 520 nm (monolayer of AuNp) to ca. 600 nm (multilayered with GO), which was a result of the agglomeration of AuNp. SEM micrographies revealed a system containing agglomerated grapheme oxide sheets on the substrate. An unprecedented sensitivity profile, determined in different refractive index (RI) media, was ca. 460 nm/RIU. The bio-sensitivity of the substrate was evaluated by immobilization of BSA on MUA-NHS-treated Au/GO, which presented a shift of 2.07 nm after binding to the protein.