A Single-step Process of Generating Hollow and Porous TiO2 Nanoparticles by Picosecond Laser Ablation in Deionised Water

摘要

Over the last two decades, hollow nanoparticles have received considerable attention from researchers due to their specificproperties that do not appear in other forms of nanoparticles. It has been recognised that TiO2 hollow nanoparticles havesuperior photocatalytic properties than solid TiO2 nanoparticles. Previous methods of producing hollow TiO2 nanoparticlestypically involve multiple-steps. In this paper, we report the production of hollow and porous TiO2 nanoparticles in a singlestep via high-repetition rate picosecond laser ablation in deionised water. The absorption spectra of the colloidalnanoparticles were obtained by UV-VIS spectroscopy. The size distribution and morphology were characterised bytransmission electron microscopy (TEM). The morphology and chemical composition of the nanoparticles werecharacterised using a High-Angle Annular Dark-Field – Scanning Transmission Electron Microscope (HAADF-STEM) andEnergy Dispersive X-ray Spectroscopy (EDS). In addition, the crystalline structures were investigated using X‐raydiffraction (XRD). The results show that a higher ratio of crystalline hollow and porous TiO2 nanoparticles (20 – 160 nm insize with majority of hollow nanoparticles at 20 nm and an average size of 37 nm) of mixed anatase, rutile and brookitephases, was produced at lower laser energy; the yield was increased from 8% to 25% by reducing the laser power from 9.12W to 3.35 W respectively. High laser powers result in reduced energy gap in the nanoparticles produced. The work showsthat laser power can be used to control the yield of hollow nanoparticles.