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Herein, we report a unique surfactant‐free synthetic pathway for the synthesis of anatase TiO2 catalysts in the size range of 13 to 20 nm by solvothermal method using choline chloride‐urea deep eutectic solvent (DES) as green media and 2‐propanol as cosolvent. The composition of reline was tuned by adding 0 (pure reline), 5, 10, 20 and 50 wt% of 2‐propanol. The amount of cosolvent was found to have a significant influence on TiO2 particle size, N2 isotherms and the magnitude of Urbach energy formed within the band gap of mesoporous TiO2 nanostructures. The sample obtained with 10 wt% of propanol showed the best photocatalytic activity in the degradation of Rhodamine B (RhB), which is attributed to the combined effect of Urbach tail states, specific surface area, particle size and band gap energy of TiO2 NPs. Radical trapping experiments with scavengers revealed that OH⋅ radicals are primarily responsible for RhB decomposition.

First-principle calculations have been performed to explore the initial stages of the zinc blende-like germanium carbide epitaxial growth on the gallium nitride (001)-(2 × 2) surface. First, we studied the Ge/C monolayer adsorption and incorporation at high symmetry sites. Results show that the adsorptions at the top and hcp1 sites are the most stable structures of C and Ge, respectively. Different terminated surfaces were used on the GeC epitaxial growth. According to the surface formation energies, only the first two bilayers are stable; therefore, the GeC epitaxial growth is favorable only under N-rich conditions on a Ge-terminated surface and with Ge bilayers terminated. In addition, it is demonstrated that GeC bilayers on the C-terminated surfaces are unstable and preclude the epitaxial growth. Electronic properties have been investigated by calculating the density of states (DOS) and the projected density of states (PDOS) of the most favorable structures.