The investigation of the emission from metal nanoparticles is generally hampered by the strong influence of the local photonic mode density, ρ phot , on the PL spectrum, which governs the emission probability through the Purcell effect. The influence of ρ phot manifests itself most clearly in the mathematical expression for the emission rate, Γ em (λ em ), derived from Fermi's golden rule for a continuum of states: Γ em (λ em ) ∝ ρ phot (λ em )