As the excitation wavelength move to lower energy, the relative intensity of the 625 nm feature increases. Quite similar emission profiles consisting of intense and skinny bands in the higher energy range and broad emission features at lower energies were observed by us and others concentration-dependent emission spectra of analogous GQDs. Based on this similarity, we assign the 500 nm band to the emission from monomeric Cl-GQD, while the emission at 625 nm is assigned to the -stacked aggregate of Cl-GQD. The absorption profiles of monomeric and aggregated Cl-GQD can be derived from the excitation spectra collected at monomer emission (490 nm) and aggregate emission (625 nm) wavelengths. The excitation spectrum assigned to the monomeric species exhibits an absorption maximum at 375 nm. The excitation spectrum assigned to the aggregate exhibits a much broader, featureless signature that ranges from 300-475 nm. Again, these excitation profiles are similar to the electronic transitions observed in the variable-concentration absorption spectra reported previously for analogous GQDs, 8,51-53 further confirming our assignment.