We design and characterize spherical gold nanoparticles, which are covalently linked to and completely covered by
3(10)-helical peptides. These helices provide a scaffold to place C-13=O isotope labels at defined distances from the gold surface, which we employ as local thermometers. Probing
these reporter groups with transient infrared spectroscopy, we monitor the vibrational energy flow across the peptide capping layer following excitation of the nanoparticle plasmon resonance.