Thanks to their strongly enhanced surface plasmon resonance,
gold nanoparticles (GNPs) at optical frequencies are excellent
scatterers and absorbers of the visible light1 and, as a
consequence, make them visible at low concentrations using
optical microscopy.2−5 In addition to their optical properties,
GNPs are considered as biocompatible6−10 and can be
conjugated to a variety of biological molecules for different
medical applications