Light Extinction by Agglomerates of Gold Nanoparticles: A Plasmon Ruler for Sub-10 nm Interparticle Distances

Plasmon rulers relate the shift of resonance wavelength,lambda l, of goldagglomerates to the average distance,s, between their constituent nanoparticles. These rulers are essential for monitoring the dynamics of biomolecules (e.g.,proteinsand DNA) by determining their small (<10 nm) coating thickness. However, existing rulers for dimers and chains estimate coating thicknesses smaller than 10 nm with rather large errors (more than 200%). Here, the light extinction of dimers, 7- and 15-mers of gold nanoparticles with diameterdp=20-80 nm ands=1-50 nm issimulated. Such agglomerates shift lambda lup to 680 nm due to plasmonic coupling, inexcellent agreement with experimental data by microscopy, dynamic light scattering, analytical centrifugation, and UV-visible spectroscopy. Subsequently, a new plasmonruler is derived for gold nanoagglomerates that enables the accurate determination ofsub-10 nm coating thicknesses, in excellent agreement also with tedious microscopy measurements.

Automated summary

Plasmon rulers are used to relate the shift in resonance wavelength of gold agglomerates to the average distance between their constituent nanoparticles. They are essential for accurately monitoring the dynamics of biomolecules. A new plasmon ruler for gold nanoagglomerates has been derived that enables the accurate determination of sub-10 nm coating thicknesses.