Nanoarchitecture of TiO 2 microspheres with expanded lattice interlayers and its heterojunction to the laser modified black TiO 2 using pulsed laser ablation in liquid with improved photocatalytic performance under visible light irradiation

Different morphologies and crystal phases of black titanium dioxide (TiO 2 ) were synthesized using Pulsed Laser Ablation in Liquid (PLAL). The synthesized laser modified black TiO 2 (LMB-TiO 2 ) structures included hydrogenated anatase TiO 2 nanoparticles, as the core shell structures, and TiO 2 microspheres. TiO 2 core-shell nanoparticles, which had crystalline-disordered structures, demonstrated the laser ablation pulse duration-dependence growth of amorphous shells and hence formation of disordered TiO 2 nanoparticles with different thickness of hydrogen-doped amorphous shells were shown. TiO 2 microspheres with the yolk–shell like structures (YSHL-TiO 2 microspheres), on the other hand, showed the formation of rutile phases in the shell which encapsulate Lattice Expanded Planes (LEPs) in the core. The microspheres demonstrated phase transitions from anatase to rutile and size-dependent lattice interlayers expansion from 0.35 nm to 0.94 nm. The maximum particle size growth occurred when the samples were subjected to the laser ablation for 120 min. The crystal phase transition, consequently, led to the formation of heterostructured photocatalysts through construction of hydrogenated anatase TiO 2 nanoparticles junctions with rutile TiO 2 microspheres. The photocatalytic degradation of methylene blue (MB) using LMB-TiO 2 heterostructure was tested under visible light irradiation Results showed approximately 99% of MB was degraded after 60 min. Enhanced visible light absorption and increased charge carrier lifetime due to formation of different types of heterojunctions may explain the higher photocatalytic performance of LM-TiO 2 samples. Moreover, the Photoluminescence analysis indicated that hydroxyl radicals were the main active species involved in the photocatalytic degradation tests and therefore the photocatalysis mechanism was accordingly suggested.