Involvement of the LSPR spectral overlap for energy transfer between a dye and Au nanoparticle.

Nanometal surface energy transfer (NSET) is a molecular ruler technique that has been utilized to optically probe long distances in biomolecular structures. We investigate the useful spectral range of donor dyes and the importance of overlap between the localized surface plasmon resonance (LSPR) and the donor photoluminescence (520-780 nm) and provide a comprehensive study of the R(0) values for the NSET processes from dyes to 2 nm Au NP (gold nanoparticle). The distance-dependent quenching results provide experimental evidence that the efficiency curve slope, R(0) value, and distance of quenching is best modeled as a surface-mediated NSET process analogous to the predictions of Persson-Lang and Chance-Prock-Silbey (CPS). The results show that the LSPR plays a very important role in the observed quenching of excited-state donors at the surface of the nanometal, and the correlation to the NSET model allows a compilation of the necessary biophysical constants for application within the toolbox of biophysics.