Laser-assisted synthesis of ultra-small anatase TiO2 nanoparticles

• Published in: Applied surface science Vol. 348; pp. 30 - 37
• Main Authors: Amin, M., Tomko, J., Naddeo, J.J., Jimenez, R., Bubb, D.M., Steiner, M., Fitz-Gerald, J., O’Malley, S.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2015
• Subjects: Ablation; Anatase; Fragmentation; Laser synthesis; Lasers; Mathematical models; Photocatalysis; Quantum confinement; Shock waves; Shockwave propagation; Titanium dioxide; Titanium dioxide nanoparticles; Shockwave propagation; Titanium dioxide nanoparticles; Laser synthesis; Photocatalysis; Fragmentation
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.12.191

•Transformation of polymorphic TiO2 NPs to ultra-small particles via laser processing.•Bandgap shift explained by quantum confinement and the Brus model.•High-frequency shockwave ripples related to laser induced stress-wave reflections.•Visible light sensitization observed for LAL prepared polymorphic particles. Titanium dioxide is one of the most important materials today in terms of green technology. In this work, we synthesis ultra-small titanium dioxide nanoparticles (NPs) via a two step process involving infrared laser ablation of a bulk titanium target in DDI water and subsequent irradiation of the colloidal solution with visible light. The as-prepared NPs contain defect states related to oxygen vacancies which lead to visible light sensitization as observed by photodegradation of methylene blue. Irradiation of the colloidal TiO2 solution, with a 532nm picosecond laser, lead to fragmentation and ultimate formation of ultra-small (<3nm) anatase particles. Shadowgraph was utilized to capture shockwave and cavitation bubble propagation during both the ablation and fragmentation processes. High-frequency ripples within the primary shockwave are identified as coming from laser induced stress-wave reflections within the metal target. A blueshift of the bandgap, for the ultra-small NPs, is explained by quantum confinement effects and rationalized using the Brus model.