Due to the formation of a colorless side product, the dispersion was filtrated using a syringe filter (PTFE, 0.2 µm), yielding a dark-blue, clear solution. Caution: HF is formed as side product during the synthesis of TNPs using TiF 4 as the precursor. GO Synthesis. GO was synthesized following a modified Hummers method reported by Chen et al. with slight modifications in the purification process. For stopping the reaction, a stepwise addition of 20 mL of hydrogen peroxide solution (30 wt%) was added, until the color of the mixture changed from brown to yellow. After the reaction was completed, the mixture was centrifuged for 20 min (4000 g, 20 • C) and the supernatant was discarded. The precipitate was washed with ∼50 mL of a mixture of HCl/water (1/9, v/v) to remove metal ions and centrifuged for 1 hour (8000 g, 10 • C). This washing step was repeated twice. The solid was suspended in ∼300 mL DI water and purified via dialysis tubing (molecular cutoff: 3.5 kDa) to remove excess of acid and metal ions. After dialysis, the suspension was sonicated for 30 min. To remove un-exfoliated GO, the suspension was centrifuged for 30 min (3000 g, 20 • C). The precipitate was discarded, and the supernatant was filtered using a Büchner funnel. Finally, the GO was freeze-dried, and the aerogel was resuspended in DI water depending on the desired concentration, and sonicated for 5 min, yielding a clear, honey-colored solution.