Titanium dioxide (TiO2) forms the basis of devices for applications including sensing devices, solar cells, photo-electrochromics, and photocatalysis. Such devices exploit different phases of TiO2 within such devices and accordingly it would be beneficial to have an amorphous TiO2 precursor which allows crystalline phase spatial patterning, for the crystallization of the amorphous TiO2 precursor to be triggered at low energies, and with the crystalline phase controllable at room-temperature without necessitating complex handling whilst providing TiO2 phases that ate stable over a prolonged period of time. Accordingly, there ate provided processes for providing a TiO2 precursor and controlling the conversion of the TiO2 precursor from amorphous-to-anatase, amorphous-to-rutile, amorphous-to-mixture of anatase/rutile or from amorphous-to-anatase-to-rutile in a simple and efficient manner.

A method for the preparation of titanium dioxide, the method comprising the steps of subjecting a titanium containing leach residue to a concentrated sulfuric acid digest step; and in turn subjecting that residue to a leach in dilute sulfuric acid, whereby a black liquor is obtained and from which titanium dioxide is in turn obtained.

A method for the preparation of titanium dioxide, the method comprising the steps of subjecting a titanium containing leach residue to a concentrated sulfuric acid digest step; and in turn subjecting that residue to a leach in dilute sulfuric acid, whereby a black liquor is obtained and from which titanium dioxide is in turn obtained.

A silicon nanoparticle-containing hydrogen polysilsesquioxane sintered product-metal oxide complex comprising a silicon nanoparticle-containing hydrogen polysilsesquioxane sintered product and a metal oxide, wherein the silicon nanoparticle-containing hydrogen polysilsesquioxane sintered product contains 5 wt % to 95 wt % of silicon nanoparticles having a volume-based mean particle size of more than 10 nm but less than 500 nm, and a hydrogen polysilsesquioxane-derived silicon oxide structure that coats the silicon nanoparticles and is chemically bonded to the surfaces of the silicon nanoparticles. The silicon nanoparticle-containing hydrogen polysilsesquioxane sintered product is represented by the general formula SiO.sub.xH.sub.y (0.01<x<1.35, 0<y<0.35) and has Si—H bonds. The metal oxide consists of one or more metals selected from titanium, zinc, zirconium, aluminum, and iron.

A titanium oxide powder of the present invention contains a polyhedral-shaped titanium oxide particles, in which each particle of the polyhedral-shaped titanium oxide particles has eight or more faces and an average primary particle diameter is 300 nm or higher and 1000 nm or lower, and a crystallinity is 0.95 or higher.

In an amorphous complex metal oxide and a method for producing the same of the present disclosure, the amorphous complex metal oxide is a three-components metal oxide containing titanium (Ti), cerium (Ce), and zirconium (Zr), wherein the amorphous complex metal oxide is amorphous.

In one aspect of the invention, a dye sensitized solar cell has a counter-electrode including carbon-titania nanocomposite thin films made by forming a carbon-based ink; forming a titania (TiO.sub.2) solution; blade-coating a mechanical mixture of the carbon-based ink and the titania solution onto a substrate; and annealing the blade-coated substrate at a first temperature for a first period of time to obtain the carbon-based titania nanocomposite thin films. In certain embodiments, the carbon-based titania nanocomposite thin films may include solvent-exfoliated graphene titania (SEG-TiO.sub.2) nanocomposite thin films, or single walled carbon nanotube titania (SWCNT-TiO.sub.2) nanocomposite thin films.

In one aspect of the invention, a dye sensitized solar cell has a counter-electrode including carbon-titania nanocomposite thin films made by forming a carbon-based ink; forming a titania (TiO.sub.2) solution; blade-coating a mechanical mixture of the carbon-based ink and the titania solution onto a substrate; and annealing the blade-coated substrate at a first temperature for a first period of time to obtain the carbon-based titania nanocomposite thin films. In certain embodiments, the carbon-based titania nanocomposite thin films may include solvent-exfoliated graphene titania (SEG-TiO.sub.2) nanocomposite thin films, or single walled carbon nanotube titania (SWCNT-TiO.sub.2) nanocomposite thin films.

A co-assembly method for synthesizing inverse photonic structures is described. The method includes combining an onium compound with a sol-gel precursor to form metal oxide (MO) nanocrystals, where each MO nanocrystal has crystalline and amorphous content. The MO nanocrystals are combined with templating particles to form a suspension. A solvent is evaporated from the suspension to form an intermediate or compound product, which then undergoes calcination to produce an inverse structure.

A co-assembly method for synthesizing inverse photonic structures is described. The method includes combining an onium compound with a sol-gel precursor to form metal oxide (MO) nanocrystals, where each MO nanocrystal has crystalline and amorphous content. The MO nanocrystals are combined with templating particles to form a suspension. A solvent is evaporated from the suspension to form an intermediate or compound product, which then undergoes calcination to produce an inverse structure.