The reaction between TiCl4 and benzyl alcohol is a simple and nonaqueous procedure for the synthesis of highly crystalline titania nanoparticles at temperatures as low as 40 °C. XRD measurements ...prove the exclusive presence of the anatase phase. The particle growth depends strongly on temperature so that with the appropriate thermal conditions the particle size can be selectively adjusted in the range of 4−8 nm. Fine-tuning of the particle size is possible by a proper choice of the relative amounts of benzyl alcohol and titanium tetrachloride. Lowering the titanium tetrachloride concentration leads to a considerable decrease of particle size. BET measurements show particularly high surface areas, up to 345 m2/g for the smallest particles and 115 m2/g for the calcined material. TEM investigations reveal that the nanoparticles are nearly uniform in size and shape. The as-synthesized particles display only minor agglomeration, whereas the calcined material consists of completely nonagglomerated particles, with diameters ranging from 13 to 20 nm. The smallest particles are soluble in a THF/trioctylphosphine mixture that luminesces (425 nm) upon UV irradiation.
Various examples of composite titania-based nanostructured materials exhibiting cooperative functionalities between different active components are presented. The fabrication of these integrated ...composite materials is based on one-pot supramolecular templating techniques combined with acidic sol−gel chemistry. The defined 3-D nanoscale organization and integration of various functional components results in advanced optoelectronic and photonic applications such as visible light sensitization of mesoporous titania photocatalysts with cadmium sulfide nanocrystals acting as sensitizing integral part of the mesopore wall structure, narrow bandwidth emission from rare earth ion activated nanocrystalline mesoporous titania films, and mirrorless lasing in dye-doped hybrid organic/inorganic mesostructured titania waveguides.
The well‐ordered array of pores and walls made up of nanocrystallites in a mesoporous titania thin film can be doped with high concentrations of Eu3+ (up to 8 mol %) to create a bright red ...photoluminescent material (see picture). The photoluminescence arises from energy transfer through excitation of the titania nanocrystallites in their band gap to the crystal field states of the europium ions; photoluminescence concentration quenching is prevented because of the high surface area and nanocrystalline structure of the material.
Biominerals are widely exploited to harden or stiffen tissues in living organisms, with calcium-, silicon-, and iron-based minerals being most common. In notable contrast, the jaws of the marine ...bloodworm Glycera dibranchiata contain the copper-based biomineral atacamite$Cu_{2}(OH)_{3}Cl$. Polycrystalline fibers are oriented with the outer contour of the jaw. Using nanoindentation, we show that the mineral has a structural role and enhances hardness and stiffness. Despite the low degree of mineralization, bloodworm jaws exhibit an extraordinary resistance to abrasion, significantly exceeding that of vertebrate dentin and approaching that of tooth enamel.
Selected photoluminescence in the wavelength range of 600–1540
nm is generated by energy transfer from a light-gathering mesostructured host lattice to an appropriate rare earth ion. The mesoporous ...titania thin films, which have a well-ordered pore structure and two-phase walls made of amorphous titania and TiO
2 nanocrystallites, were doped with up to 8
mol% lanthanide ions, and the ordered structure of the material was preserved. Exciting the titania in its band gap results in energy transfer and it is possible to observe photoluminescence from the crystal field states of the rare earth ions. This process is successful for certain rare earth ions (Sm
3+, Eu
3+, Yb
3+, Nd
3+, Er
3+) and not for others (Tb
3+, Tm
3+). A mechanism has been proposed to explain this phenomenon, which involves energy transfer through surface states on titania nanocrystals to matching electronic states on the rare earth ions.
High-optical-quality titania-based mesostructured films with cubic or 2D-hexagonal symmetry were fabricated by combining trifluoroacetate (TFA)-modified titanium precursors with amphiphilic triblock ...poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) copolymers. The distribution, dynamics, and local environments of the TFA-modified titania, PEO, and PPO components of the hybrid were investigated. IR/Raman spectroscopy, in situ small-angle X-ray scattering, and transmission electron microscopy studies indicate that TFA coordinates the titanium center and forms a stable complex that is subsequently organized by the block copolymer species into ordered mesostructures. Solid-state NMR 19F→1H cross-polarization, 13C{1H} two-dimensional heteronuclear correlation, and 1H relaxation techniques were used to determine that PEO is predominantly incorporated within the TFA-modified titania, and that PPO environments encompass both microphase separated regions and interfacial regions composed of mixed PPO and TFA-modified titania. NMR 19F multiple-quantum spin counting measurements suggest that −CF3 groups of the trifluoroacetate ligands do not form clusters but instead randomly distribute within the inorganic component of the hybrid.
Nanoparticle vesicles were spontaneously assembled from homopolymer polyamine polyelectrolytes and water-soluble, citrate-stabilized quantum dots. The further addition of silica nanoparticles to a ...solution of quantum dot vesicles generated stable micrometer-sized hollow spheres whose walls were formed of a thick, inner layer of close-packed quantum dots followed by an outer layer of silica. The method employed here to assemble both the nanoparticle vesicles and the hollow spheres is in direct contrast to previous syntheses that use either tailored block copolymers or oil-in-water emulsion templating. We propose that the formation of charge-stabilized hydrogen bonds between the positively charged amines of the homopolymer polyelectrolytes and the negatively charged citrate molecules stabilizing the quantum dots is responsible for the macroscopic phase separation in this completely aqueous system. The ease and processibility of the present approach gives promise for the production of a diverse array of materials ranging in applications from drug delivery to catalysis to micrometer-scale optical devices.
Spontaneous formation of microspheres is observed when charged poly(amino acid)s are combined with certain oppositely charged, multivalent organic ions. The surfaces of the spheres are chemically ...active and act as templates for silica condensation, and the assemblies can be made hollow or polymer‐filled, depending on the silica precursor (see image; the fluorescent polymer forms a layer inside a colloidal‐silica‐coated sphere).
Highly ordered mesoporous films with a multicompositional nanocrystalline anatase titania/cadmium chalcogenide wall structure (see figure, scale bar is 20 nm) were synthesized by a fast and ...inexpensive one‐pot single‐precursor sol–gel‐chemistry route based on supramolecular templating. These films show enhanced sensitivity to visible light in photocurrent generation experiments.
A room-temperature synthesis route for the fabrication of a new type of hybrid organic/inorganic mesostructured material based on titania instead of silica as the inorganic component has been ...developed. This approach enables facile processing of the titania/block copolymer surfactant precursor solution into optically activated, transparent, and crack-free fibers and planar waveguides with adjustable thickness. Stabilization of the structures occurs upon solvent evaporation by formation of a solid, glasslike material without heat treatment. These dye-activated, high refractive index, titania-based composites show efficient waveguiding and mirrorless lasing at low thresholds without the need of an ultralow refractive index support layer.
