Size, Composition and Structural Changes of TiO₂ Rutile Nanoparticles by Pulsed Laser Ablation in Water

Abstract

The rutile-type TiO2 powders originally whitish and micrometer in size were successfully reduced in size with accompanied structure, composition and optical property change to become dark bluish by pulsed laser ablation in liquid under 532 nm excitation and 400 mJ per pulse at a specified water depth (5 or 15 mm) for up to 30 min. Transmission electron microscopic observations indicated the newly formed anatase nanoparticles are ca. 5 nm in size with spindle-like shape having well-developed {101} faces and -(001) facets for mutual coalescence into unity. The -(001)-specific coalescence twin of anatase was also observed. There are also amorphous nanoparticles in association with anatase, minor brookite and relic rutile with 2 x (110) superstructure. The resultant colloidal TiO2 nanoparticles are (Ti3+, Ti2+, H+) co-signified according to optical spectroscopic results and have a bimodal minimum band gaps 3.12 and 2.66 eV due to nanocrystals and amorphous phase, respectively, for potential optocatalytic applications in UV-visible range.

Special grain boundaries of anatase nanocondensates by oriented attachment

“…2 degree off the perfect (001) twin boundary. 4 The combined evidences of the symmetrical [100] tilt boundaries with the (001) and (011 ¯) interface and asymmetrical [11 ¯0] tilt boundary with the (001)/(112 ¯) heterointerface, as reported here, strongly suggest that these special planar boundaries were formed by the (hkl)-specific coalescence of the anatase nanocondensates. In contrast, the [001]-oriented anatase domains parallel epitaxially nucleated from the TiO (001) film by the NaCl (001) substrate 21 failed to form such special boundaries.…”

“…5 Such spherical anatase condensates have many solute-modified facets for competitive attachment growth as a bicrystal with special grain boundaries. By comparison, the PLA of TiO 2 rutile powder in water caused the formation of spindle-like anatase condensates with welldeveloped {101} faces and ~(001) facets for mutual coalescence into unity or almost a twinned bicrystal with imperfectly adjoined (001) planes, 4 and the PLA of Ti in water caused the formation of multiple condensates of TiO, Ti 2 O 3 , and TiO 2 rutile with a considerable extent of nonstoichiometry. 6 As for the minor anatase nanocondensates formed by the PLA of Ti in an oxygen background, they showed a (001)-specific coalescence as unity, a (112)-specific coalescence as a twin/fault and three twin variants by a martensitic transformation from the parent fluorite-type TiO 2 .…”

“…Fig. 6 of Chang et al 4 ). Nevertheless the exact (011) or (001) plane of the anatase crystallites for oriented attachment as an asymmetrical/heterogeneous interface with specific atomic configurations and coherency were not reported.…”

“…Whereas the anatase nanocondensates produced by PLA of rutile powder in water tended to coalesce over the {101} or (001) surface for unification. 4 From a crystallographic viewpoint, anatase having a screw c-axis over a glide plane, i.e. 4 1 /a operation in the space group I4 1 /amd (no.…”

Nano to Micro Particle Size Distribution Measurement in the Fluid by Interactive Force Apparatus for Fine Particle Processing

“…Also the magnetic particle size measurement in the silicon oil base magnetic fluid is possible applying electric field. 14 Also the size distributions of many kinds of prepared nanoparticle [15][16][17] described in the J. of Nanoscience and Nanotechnology would be able to be measured by using this technique. .…”