While H-GNR was found to be insoluble in all solvents, it can be solubilized in aqueous solutions using surfactants, such as sodium dodecyl benzene sulfonate (SDBS). The UV-vis absorption spectra of H-GQD and H-GNR in aqueous SDBS solutions are shown in Figure and consist of broad, structureless features that span a large portion of the UV and visible regions. H-GNR exhibits a lowest-energy absorption peak ( =600 nm) that is red-shifted relative to that of H-GQD (=360 nm), as expected based on the quantum confinement effect. To illustrate the effect of GNR length on the optical properties, we calculated electronic transition energies for GNR fragments with sizes in the monomer to pentamer range (Figure , computational details are available in Section S4, SI). The calculated monomer spectrum consists of two absorption bands centered at 280 and 360 nm. Geometry optimizations reveal substantial folding in the trimer and tetramer, such that the molecule is not entirely planar (Figure , SI). As the length of the model GNR increases from monomer to pentamer, both transitions undergo a red-shift and merge into one peak with absorption bands centered at 510