A facile solvothermal route to photocatalytically active nanocrystalline anatase TiO_2 from peroxide precursors

摘要

This report describes the rapid synthesis of nanocrystalline powders of anatase TiO_2 using exothermic metathesis (exchange) reactions moderated by a high-boiling hexadecanc solvent. One reagent, TiBr_4, dissolved in hexadecane interacts with a dispersion of Na_2O_2 at elevated temperatures to produce TiO_2 and NaBr. Reactions occur within a few hours near the reflux point of hexadecane (bp 287 deg C). The isolated crystalline TiO_2 powders arc either anatase or anatasc/brookite mixtures, depending on how quickly the reagents were heated to reflux. Locally exothermic solution-surface events occur and are likely responsible for crystalline TiO_2 formation directly from the solvothermal reaction without need for any post-reaction annealing. Rapidly synthesized nanocrystalline TiO_2 exhibits elongated nanostructural features. Results from variations in reaction conditions and use of other halide and oxygen reagents are also discussed. The isolated TiO_2 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.