Carbon-dot-modified TiO2−x mesoporous single crystals with enhanced photocatalytic activity for degradation of phenol

We introduce a facile method to synthesize carbon quantum dots/titanium dioxide mesoporous single crystals (CQDs–MSCs). CQDs were synthesized using a pyrolysis method with citric acid as carbon precursor. V-CQDs–MSCs composite was prepared using a vacuum activation method and exhibited enhanced photocatalytic activity. The composites were characterized by diffuse reflectance spectroscopy (DRS), electron paramagnetic resonance (EPR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) analysis, and thermogravimetry (TG) analysis. XPS results indicated that CQDs were bonded on the surface of MSCs by formation of Ti–O–C bonds, which played an important role in transfer of photogenerated electrons from Ti3+–TiO2 to CQDs. V-CQDs–MSCs obtained using CQD loading content of 2% and vacuum activation temperature of 600 °C showed the highest photocatalytic activity for degradation of phenol under simulated solar light irradiation.