Photophysical Modulation of Rhodamine‐B via π‐π stacking with GQD and Its Further Tuning by Cucurbit[7]uril**

Abstract Herein, we report modulation of photophysical properties of a rhodamine B (RhB) upon interaction with a synthesized graphene quantum dot (GQD). The GQD nanomaterial was prepared through a facile top‐down liquid phase peeling technique, starting from synthesized graphene oxide (GO). The detailed characterization using FT‐IR, XPS, AFM and TEM revealed that the GQDs consisted of 2–3 graphene layers with about 5 nm size dots and major functional groups −COOH and −OH on the surface edges. The modulations in the absorption and emission spectra of RhB in ethanol and water with the addition of the prepared GQD were observed using UV‐vis absorption, steady‐state and time‐resolved fluorescence spectroscopy. Such photophysical modulations of RhB can be attributed to the synergistic effect of charge transfer and π‐π interactions between the electron rich GQDs and the cationic RhB molecules. Importantly, strong ability of the GQDs to quench the fluorescence of RhB, in addition to its modulated ground state absorption spectra, indicated the dynamic and static quenching mechanism. Further, the addition of the macrocyclic host cucurbit[7]uril (CB7) to the RhB@GQD composite in water caused anticipated recovery of fluorescence of the RhB dye, indicating a weak non‐covalent interaction between the GQDs and RhB. Hence, this study might provide a fresh outlook on the interactions of photoluminescent GQDs and organic dye molecules for making useful functional materials.