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High-photoluminescence (PL) graphene quantum dots (GQDs) were synthesized by a simple one-pot hydrothermal process, then separated by dialysis bags of different molecular weights. Four separated GQDs of varying sizes were obtained and displayed different PL intensities. With the decreasing size of separated GQDs, the intensity of the emission peak becomes much stronger. Finally, the GQDs of the smallest size revealed the most energetic PL intensity in four separated GQDs. The PL energy of all the separated GQDs shifted slightly, supported by density functional theory calculations. [ABSTRACT FROM AUTHOR]

Sulfur-doped graphene quantum dots (S-GQDs) decorated with high-quantum-yield titanium dioxide (TiO 2 ) nanocomposite are synthesized by a simple hydrothermal method. Photoluminescence characterization shows that S-GQDs exhibit stronger absorption peaks at ultraviolet (UV) region than GQDs. Photocatalytic activity of the obtained S-GQD/TiO 2 nanocomposite reaches 70% in 8 min; this activity is significantly enhanced compared with those of GQDs/TiO 2 and pure TiO 2 . Improved UV light absorption and effective transfer of photogenerated electrons can be attributed to integration of S-GQDs with TiO 2 in a cladding manner. The present work provides a new approach for development of attractive GQD-based nanocomposites with controllable structures and photocatalytic performance. [ABSTRACT FROM AUTHOR]