Nanoarchitecture of TiO2 microspheres with expanded lattice interlayers and its heterojunction to the laser modified black TiO2 using pulsed laser ablation in liquid with improved photocatalytic performance under visible light irradiation

Different morphologies and crystal phases of black titanium dioxide (TiO2) were synthesized using Pulsed Laser Ablation in Liquid (PLAL). The synthesized laser modified black TiO2 (LMB-TiO2) structures included hydrogenated anatase TiO2 nanoparticles, as the core shell structures, and TiO2 microspheres. TiO2 core-shell nanoparticles, which had crystalline-disordered structures, demonstrated the laser ablation pulse duration-dependence growth of amorphous shells and hence formation of disordered TiO2 nanoparticles with different thickness of hydrogen-doped amorphous shells were shown. TiO2 microspheres with the yolk–shell like structures (YSHL-TiO2 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 TiO2 nanoparticles junctions with rutile TiO2 microspheres. The photocatalytic degradation of methylene blue (MB) using LMB-TiO2 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-TiO2 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.