1. Schematic diagram for synthesizing CDs-Cu-TiO₂ nanocomposite

2. XRD patterns of TiO₂, CDs-TiO₂ and CDs-Cu-TiO₂ composite

3. TEM images of (A) TiO₂ , (B) CDs, (C, D) CDs-Cu-TiO₂; (E) SAED image of CDs-Cu-TiO₂ composite; (F) EDS patterns of CDs-TiO₂ and CDs-Cu-TiO₂ composite

4. (A) XPS survey spectra of different materials; XPS spectra of (B) C1s, (C) N1s, and (D) Cu2p for the CDs-Cu-TiO₂ composite

5. (A)FT-IR spectra and (B) UV-Vis diffuse reflectance spectra of TiO₂, CDs-TiO₂ and CDs-Cu-TiO₂ composite with inset showing the Tauc’s plots

6. (A) UV-Vis absorption spectrum and FL spectrum (λ_ex= 380 nm) of CDs; (B) Photoluminescence emission spectra of CDs at different near infrared excitation wavelengths; (C) FL spectra (λ_ex=320 nm) of TiO₂, CDs-TiO₂ and CDs-Cu-TiO₂ composite

7. RhB degradation under visible light irradiation using CDs-TiO₂ (A) or CDs-Cu-TiO₂ (B) as the photocatalyst; (C) the first order kinetics of RhB degradation in the presence of various photocatalysts; (D) recycling runs of the photocatalytic activity of CDs-Cu-TiO₂ toward RhB degradation

8. Photocatalytic mechanism of CDs-Cu-TiO₂ composite