Morphology and photoluminescence study of titania nanoparticles

Room temperature ferromagnetism in D-D neutron irradiated rutile TiO2 single crystals

Room temperature ferromagnetism (RTFM) was observed in unirradiated rutile TiO2 single crystals prepared by the floating zone method due to oxygen vacancy (VO) defects. D-D neutrons mainly collide elastically with TiO2, producing VO, titanium vacancies (VTi) and other point defects; the density and kind of defect is related to the neutron irradiation fluence. D-D neutron irradiation is used to regulate the concentration and type of defect, avoiding impurity elements. As the irradiation fluence increases, the saturation magnetization (Ms) first increases, then decreases and then increases. To verify the origin of RTFM, the CASTEP module was used to calculate the magnetic and structural properties of point defects in TiO2. VO induces a 2.39 μ B magnetic moment, Ti3+ and F+ induce 1.28 μ B and 1.70 μ B magnetic moments, respectively, while VTi induces a magnetic moment of ∼4 μ B. Combining experimental and theoretical results, increases in VO concentration lead to Ms increases; more VO combine with electrons to form F+, inducing a smaller magnetic moment. VO and VTi play a key role and Ms changes accordingly with larger fluence. VO, F+ and VTi are the most likely origins of RTFM.

Utilising anatase nano-seeds coupled with a visible-light antennae system (Cu–Pd–N) for effective photo-organic transformations

Bandgap tuning TiO₂ nano-seeds with a three-component strategy (Cu, Pd, and N) has facilitated the selective photo-oxidation of cyclic alcohols.

Preparation and characterization of heat-resistant polyimide/titanium dioxide nanocomposite films containing triptycene side units by sol–gel processes

Thermally stable polyimide/titanium dioxide (PI/TiO2) hybrid nanocomposite films have been successfully synthesized through the in situ formation of TiO2 within a PI matrix via sol–gel process. Poly(amic acid) (PAA) solutions are prepared from bis(4-aminophenoxy)phenyl triptycene and 3,3′,4,4′-benzophenone tetracarboxylic dianhydride in N-methyl-2-pyrrolidinone solvent. The different amounts of tetraethyl orthotitanate and actylacetone (acac) are incorporated into PAA matrix, and then thermally imidized to form PI/TiO2. The chelating agent, acac, was applied to reduce the gelation rate of titanium alkoxide. Thermal decomposition temperatures with a 10% weight loss are in excess of 510°C, and char yields at 800°C under nitrogen atmosphere are higher than 69%. The chemical and morphological structures of the hybrid nanocomposites were characterized using Fourier transform infrared spectroscopy, x-ray diffraction, and transmission electron microscopy. The results show that the TiO2 particles are well dispersed in the PI matrix with particle size between 10 and 30 nm in diameter.

Combining mixed titania morphologies into a complex assembly thin film by iterative block-copolymer-based sol–gel templating

Sol–gel templating combined with iterative spin-coating steps are used to custom-tailor hierarchically structured titania thin films. Using poly(styrene-block-ethylene oxide) P(S-b-PEO) as the structure directing agent, a foam-like structure is combined with nanogranules. Both structural elements are merged into a complex assembly in thin film geometry. The resulting morphology is pictured by SEM and probed with GISAXS. The installed mesoporous titania sandwich structure exhibits holes with a size of 45 nm which makes it promising for applications in photovoltaics or photocatalysis. An optical characterization completes the structural investigation.