Abstract
Understanding interfacial interactions at the native oxide surface of Mg is important for catalytic and biomedical applications. Recent advancements in plasmonic Mg research led to its use for surface-enhanced Raman scattering (SERS), a vibrational spectroscopy particularly sensitive to molecules bound to the enhancing substrate. Here, novel Mg film-over-nanospheres (FONs) are fabricated and used as SERS substrates to study molecular binding on Mg surfaces, augmenting previous results on 4-mercaptobenzoic acid (4-MBA) and 4-nitrothiophenol (4-NTP) by revealing the binding of 4-nitrophenol (4-NP) and 5,5′-dithiobis (2-nitrobenzoic acid) (DTNB). Through a systematic study of a total of 17 molecules with various functional groups, a pK(a)-related trend is unravelled: binding on natively oxidised Mg requires the adsorbate to dissociate and have a pK(a) between ∼4.5 and 7.5, however diselenides and ditellurides do not appear to follow this trend. The results pave the way for chemical functionalisation of Mg surfaces for plasmonic and other applications.