The synthesis of GQDs and GNRs is summarized in Scheme S1 and involves Diels-Alder chemistry, Yamamoto coupling polymerization and chlorination reactions that have been reported previously for similar substrates. The Diels-Alder reaction between cyclopentadienones 1 and acetylide 2, followed by a loss of CO, resulted in the formation of polyphenylenes 3. The oxidative dehydrogenation of 3H using FeCl3 yielded H-GQD, while the subsequent chlorination using iodine-monochloride resulted in the formation of Cl-GQD. The NMR and MS analysis of Cl-GQD indicates that C-H group between two N-center of bipyrimidine unit are not chlorinated, while the remaining C-H groups are mostly chlorinated (~80%). The polymerization of 3-Br via Yamamoto coupling yields polymer-3, which is then oxidized to H-GNR using FeCl3. The MS characterization of polymer-3 indicates that ribbons up to ~20 nm in length (~16 3H units) are formed, while longer polymer-3 units, which may exist in the H-GNR sample, are not expected to get ionized and detected in the mass spectrometry. The ICl chlorination methods yield Cl-GNR, which have been characterized using XPS and NMR (Section S1, SI).