Simple Crystal Phase Control of TiO₂ Nanoparticles via Pulsed Laser Ablation in Nitric Acid

Experimental

The experimental setup for the generation of metal nanoparticles via PLAL is described in detail elsewhere.10 Briefly, the Ti (99.999%, Sigma-Aldrich) plate was fixed in a Pyrex vial filled with de-ionized (DI) water (10 mL) and the HNO3 solution under a nitrogen purge continuously stirred by a magnetic bar. A pulsed Nd:YAG laser (1064 nm, 10 Hz, 7 ns) was focused onto the surface of the Ti plate with a spot size of about 1 mm diameter using a lens with a focal length of 25 mm. Laser ablation was continued for 30 min with a laser pulse energy of 80 mJ/pulse. The HNO3 solutions used for PLAL were prepared at concentrations of 10−3, 1, 3, 6, and 10 M. The ablated solutions were washed several times with DI water using a centrifugation rate of 13000 rpm for 10 min to remove HNO3. The resulting sediments were collected and then individually sonicated after addition of DI water and centrifugation. This washing procedure was repeated several times. Each experiment was repeated at least 10 times and the sediments were collected and dried on a silicon substrate at room temperature. The morphology and structure of the nanoparticles produced by PLAL were investigated with a field emission scanning electron microscope [FE-SEM, XL30 S FEG, Philips (15 kV)] and transmission electron microscope [TEM, JEOL, JEM-2-10 (200 kV)]. X-ray diffraction (XRD) patterns of the nanoparticles were obtained with a Bruker AXS D8 DISCOVER with GADDS diffractometer using Cu Kα (0.1542 nm) radiation with a Bragg angle ranging from 10 to 90°.