Dipole-Induced Raman Enhancement Using Noncovalent Azobenzene-Functionalized Self-Assembled Monolayers on Graphene Terraces
2021
Brill, Adam R. | Biswas, Santu | Caspary Toroker, Maytal | de Ruiter, Graham | Koren, Elad
Graphene is a promising material in the field of interface science, especially for noncovalent functionalization, sensing, and for applications in catalysis and nanoelectronics. The noncovalent self-assembly of aromatic molecules on graphene promotes electronic coupling through π–π interactions that allows for quenching of the fluorescence of adsorbent molecules and the enhancement of their Raman spectra via graphene-enhanced Raman spectroscopy (GERS). Although recent work has explored the Raman enhancement on mono- and bilayer graphene, the layer dependence of both electronic phenomena (i.e., fluorescence quenching and Raman enhancement) has largely remained underexplored. Similarly, the effect of near-surface molecular dipoles on GERS has sparsely been examined. In this work, we employ self-assembled monolayers of azobenzene-decorated triazatriangulene molecules (AzoTATA) on graphene terraces to examine the effect of switchable molecular dipoles on the GERS effect, which occurs as a function of azobenzene photoisomerization. Furthermore, using empirical and computational methods, we present a systematic study for deriving the mechanism of GERS enhancement and fluorescence quenching on graphene terraces.
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