Synthesis and characterization of TiO₂-CQDs nanocomposites and testing of their anticancer potential

This work used a green approach to produce carbon quantum dots (CQDs). TiO₂ nanoparticles (NPs) and TiO₂–CQDs nanocomposites with different weight ratios of CQDs were organized through a facile sol-gel method. XRD showed that the anatase and rutile phases of TiO₂ were polycrystalline with a tetragonal structure and that the CQDs exhibited a broad peak at (002) and a hexagonal structure. High resolution-transmission-electron microscopy revealed that the TiO₂ NPs agglomerated in mostly spherical shapes and that the anatase and rutile phases of TiO₂ had sizes of less than 15 and 25 nm, respectively. The CQDs had a relatively uniform diameter, a spherical shape with a highly crystalline structure, and a size below 2 nm. UV–visible spectroscopy revealed that the absorbance of the TiO₂-CQDs nanocomposites increased with the increase in CQD ratio. The energy band gaps of the anatase and rutile phases were 3.07 and 2.7 eV, respectively, whereas that of CQDs was 3.14 eV. Meanwhile, the energy band gaps of the TiO₂–CQDs nanocomposites decreased with the increase in CQDs ratio. The growth inhibition rates of the liver cancer HepG2 cell line and the normal cell line RD were measured after 24 hours of experience to the two TiO₂ phases and TiO₂–CQDs nanocomposites. The cytotoxicity test presented that the tested substances were extremely harmful to cells in cancer. Inhibition rates increased with the increase in CQDs ratio. The inhibition rate of growth in cancer cells, including the liver cancer HepG2 cell line and the normal cell line (RD), was measured for 24 hours after they were exposed to TiO₂ (two phases) and TiO₂-CQDs nanocomposites. The samples showed a slight effect on the normal line (RD) compared to HepG2 cancer. The highest inhibition rate was 12.11% for the CQD 0.7 sample.