Single-molecule SERS detection of C60

Abstract

Single-molecule Surface-Enhanced Raman Scattering (SERS) detection of buckminsterfullerene (C₆₀) is achieved by using different isotopologues of the molecule with a distribution around an average isotopic substitution (¹²C → ¹³C) of ∼30%. The distribution of different isotopologues creates a broad (∼20 cm⁻¹) average SERS signal within which single-molecule SERS spectra of individual isotopic realizations of the molecule can be distinguished. The SERS enhancement factors for SM-SERS C₆₀ events are typically in the range of ∼10⁸, suggesting a limitation imposed by either photobleaching or surface interactions with the (Ag) metallic colloids to reach the highest SERS hot-spots (which can typically have larger maximum enhancements). SM-SERS signals of isotopically substituted C₆₀ also show broader peaks (FWHM ≈ 4 cm⁻¹) than equivalent signals in natural C₆₀. The latter feature suggests a contribution to the homogeneous broadening coming from isotopic disorder in the molecule; a feature that can only be observed with the ability to detect single-molecule spectra.