Chao-Hsien Wu

Special grain boundaries of anatase nanocondensates by oriented attachment

Anatase nanocondensates with a 1-D commensurate superstructure as prepared by the pulsed laser ablation of Ti in tetraethyl orthosilicate were identified by transmission electron microscopy to have special grain boundaries, i.e. symmetrical [100] tilt boundaries with (001) or (01) interfaces and an asymmetrical [10] tilt boundary with a (001)/(11) heterointerface. The [100] tilt boundaries are in fact due to basal twinning with a coherent (001) and a semi-coherent (01) interface, respectively, both following the Burgers vector = 1/2[00] + 1/4[00]. The (001)/(11) heterointerface is decorated with {101} ledges, both having a primitive coincidence site lattice for fair lattice coherency. These special grain boundaries can be rationalized by the (hkl)-specific rotation/coalescence of the crystalline nanocondensates.

C–H doped anatase nanospheres with disordered shell and planar defects synthesized by pulsed laser ablation of bulk Ti in tetraethyl orthosilicate

C–H doped anatase nanospheres with disorder-engineered surface layers were synthesized by pulsed laser ablation of Ti in tetraethyl orthosilicate and characterized using X-ray/electron diffraction and optical spectroscopy. The anatase (Ant) has (hkl)-specific twinning/faulting/ordering and follows a specific crystallographic relationship with the TiCxOy and β-Ti nuclei both having paracrystalline distribution of defect clusters due to solute trapping. The colloidal suspension containing composite nanocondensates with an amorphous C1−xSix:H shell showed visible absorbance indicating a minimum band gap of ca. 2 eV for potential photocatalytic applications.