Salt Catalysts Containing Basic Anions and Acidic Cations for the Sol−Gel Process of Titanium Alkoxide:  Controlling the Kinetics and Dimensionality of the Resultant Titanium Oxide

Abstract

The sol−gel process from titanium alkoxide monomer to titanium oxide polymer was remarkably enhanced by salt catalysts containing basic anions and acidic cations. An ammonium carbonate catalyst promoted the precipitation of spherical titanium oxide particles at low concentrations of titanium alkoxide and water at room temperature. Dehydrative polycondensation in the sol−gel process involves both deprotonation and dehydroxylation, and the carbonate anion enhanced the deprotonation as a base catalyst while the ammonium cation enhanced the dehydroxylation as an acid catalyst. If the ammonium acetate catalyst was added, the monolithic titanium oxide gel which consists of sheetlike titanium oxide particles was formed. The acetate anion acted not only as the catalyst for the dehydrative polycondensation but also as a ligand coordinating to titanium for capping the polycondensation sites, resulting in planar titanium oxide particles.

Antibacterial effect of metallic glasses

“…Chitosan can prevent implantation of E. coli, cells by destroying the bacterial biofilm which protects them from being washed away [14]. The metallic glasses might be capable of the same action within their inhibition zones.…”

“…Since the post-separation of the powder catalyst in a slurry system is a major impediment in photocatalyst production [9,10], immobilized TiO 2 with high surface area (e.g., porous TiO 2 thin film) is favored for antimicrobial applications [2][3][4][11][12][13][14].…”

Pigments based on Cr and Sb doped TiO 2 prepared by microemulsion-mediated solvothermal synthesis for inkjet printing on ceramics

“…The literature reports approaches for the synthesis of nanoparticles of titania, including thermal hydrolysis [17,18], sol-gel [19,20], hydro/solvothermal method [21,22] and microemulsion processes [23,24]. Among them, solvothermal and microemulsion methods are extensively used for the preparation of nanomaterials.…”

Preparation of a transparent and flexible self-standing film of layered titania/isostearate nanocomposite

“…We have already found that the salt catalyst effectively accelerates the polycondensation of titanium alkoxide. 19,20,22,23 We also report the unique procedure for making a self-standing film of layered titania/isostearate nanocomposite by floating the sol on the water surface, which yields selfstanding films with good transparency and flexibility.…”

“…19 Without the deceleration of the hydrolysis, three-dimensional polymerization takes place due to very rapid hydrolysis of the titanium alkoxides. For the formation of layered materials, two-dimensional polymerization is required.…”