Mn doping and core-shell engineering of silane-modified Mn-TiO2@SiO2 nanoparticles with drastically reduced photocatalytic activity for transparent UV-shielding hybrid materials

The photocatalytic ability and incompatibility with the organic matrix of TiO2 limit its application in UVshielding hybrid materials. Tuning the electronic structure and engineering the morphology of TiO2 are effective in reducing photocatalytic activity but remain challenging in drastic reduction. Herein, a Mn-TiO2@SiO2 structure with an average size of 24.4 nm is constructed via a combination strategy of Mn doping and core-shell engineering to accelerate the recombination of carriers and build surface barriers. Impressively, compared with pure TiO2, the 2 %Mn-TiO2@SiO2 shows 336, 447, and 237 times lower photocatalytic reaction rate constants (k) for the degradation of three dyes (reactive red 120, methyl orange, and methyl blue), respectively, demonstrating the drastically reduced photocatalytic activity of Mn-TiO2@SiO2 structure. The characterizations and density functional theory calculations reveal that Mn doping introduces an occupied deep level and an unoccupied shallow level, which facilitates the co-trapping of electrons and holes, accelerating the recombination of carriers, and the SiO2 shell serves as a barrier to mitigate the interfacial charge transfer. Additionally, surface modification using silanes enables monodisperse core-shell structure and improves its compatibility with substrates, providing the UV-shielding Mn-TiO2@SiO2-C12 silane/fluorocarbon hybrid coatings with high transparency and anti-UV aging ability.