## 4 Conclusions  
The presented TiO\({}_{2}\)@rGO nanocomposites were successfully synthesized with appropriate structural features for the possible application on the photodegradation of MB and RhD dyes under natural sunlight. Graphene-based TiO\({}_{2}\) nanocomposites, prepared using an optimized two-step method that combined hydrothermal treatment and calcination, presented a significantly improved photocatalytic activity under solar-like irradiation. The chemical bonding of particles was closely associated with the amount of rGO, time of hydrothermal synthesis, and calcination temperature. Importantly, the obtained value of the bandgap energy (\(E_{\text{g}}\) = 2.71 eV and 3.03 eV) of nanocomposites indicate that the wavelength value shifted to visible light when compared with pure TiO\({}_{2}\) (\(E_{\text{g}}\)\(\leq\) 3.15 eV). The application of prepared TiO\({}_{2}\)@rGO nanocomposites as photocatalysts for degradation  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample ID**} & \multicolumn{3}{c}{**MB Dye**} & \multicolumn{3}{c}{**RhB Dye**} \\ \cline{2-7}  & \(R^{2}\) & \(k\times 10^{-3}\), Min\({}^{-1}\) & \(t_{\text{t}_{\  
of RhB and MB in an aqueous medium showed that the chemical integration of rGO with TiO\({}_{2}\) promoted synergistic effects which sped up the photodegradation of selected pollutants. The photodegradation efficiency of MB and RhB dye by the synthesized TiO\({}_{2}\)@rGO (5 wt.% of rGO) and TiO\({}_{2}\)@rGO (15 wt.% of rGO) nanocomposite photocatalysts after 120 min of exposure to the irradiation were significantly higher than for pure synthesized TiO\({}_{2}\) nanoparticles. TiO\({}_{2}\)@rGO (5%) presented a photodegradation of 99.6% for MB and 99.9% for RhB. The nanocomposite with a higher amount of rGO (TiO\({}_{2}\)@rGO (15%)) showed similar photodegradation results, 98.1% for MB and 99.8% for RhB. Meanwhile, the photoactivity evaluation of synthesized TiO\({}_{2}\) particles was significantly lower. Although these nanocomposite materials showed lower photocatalytic activity than P-25, their large layered structure allows a facile recovery from the aqueous medium after the photocatalytic reaction. These preliminary results show that the prepared TiO\({}_{2}\)@rGO nanocomposite photocatalyst may be explored as high-efficiency and green photocatalysts for simultaneous sorption and degradation of dyes that can be directly applicable in real effluent water treatment by solar exposition. The following are available online at [[https://www.mdpi.com/article/10.3390/app11093966/s1](https://www.mdpi.com/article/10.3390/app11093966/s1)]([https://www.mdpi.com/article/10.3390/app11093966/s1](https://www.mdpi.com/article/10.3390/app11093966/s1)). Conceptualization, M.K., M.P., and G.G. ; methodology, M.K., L.C., D.L., and G.G. ; software, M.K., G.O.-I, M.J.H., and G.G. ; validation, M.K. ; formal analysis, M.K., I.B. ([PERSON]), K.M., T.R., G.O.-I, M.J.H., M.P., and I.B. ([PERSON]); investigation, M.K. ; resources, L.C., I.B. ([PERSON]), M.P., and G.G. ; data curation, M.K., L.C., I.B. ([PERSON]), G.O.-I, M.J.H., and M.P. ; writing--original draft preparation, M.K., I.B. ([PERSON]), G.O.-I, M.J.H., and M.P. ; writing--review and editing, L.C., D.L., and G.G. ; visualization, M.K. and G.G. ; supervision, L.C. and G.G. ; project administration, M.K., L.C., and G.G. ; funding acquisition, L.C. All authors have read and agreed to the published version of the manuscript. This work was supported by the projects UIDB/00481/2020 and UIDP/00481/2020--FCT--Fundacao para a Ciencia e a Tecnologia; and CENTRO-01-0145-FEDER-022083--Centro Portugal Regional Operational Programme (Centro 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund. Thanks, are also due for the financial support to the H\({}_{2}\)O Value project (PTDC/NAN-MAT/30513/2017) also supported by FCT/MEC through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020 (CENTRO-01-0145-FEDER-030513).