A facile solvothermal route to photocatalytically active nanocrystalline anatase TiO2 from peroxide precursors

This report describes the rapid synthesis of nanocrystalline powders of anatase TiO2 using exothermic metathesis (exchange) reactions moderated by a high-boiling hexadecane solvent. One reagent, TiBr4, dissolved in hexadecane interacts with a dispersion of Na2O2 at elevated temperatures to produce TiO2 and NaBr. Reactions occur within a few hours near the reflux point of hexadecane (bp 287 °C). The isolated crystalline TiO2 powders are either anatase or anatase/brookite mixtures, depending on how quickly the reagents were heated to reflux. Locally exothermic solution-surface events occur and are likely responsible for crystalline TiO2 formation directly from the solvothermal reaction without need for any post-reaction annealing. Rapidly synthesized nanocrystalline TiO2 exhibits elongated nanostructural features. Results from variations in reaction conditions and use of other halide and oxygen reagents are also discussed. The isolated TiO2 powders have organic surface coatings, but brief air calcination yields water-dispersible titania nanoparticulate powders that function as active UV photocatalysts for methylene blue solution oxidation.

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