Dopant-free, polymorphic design of TiO₂ nanocrystals by flame aerosol synthesis

A dopant-free aerosol synthesis of highly crystalline TiO₂ nanoparticles (20-35nm) with tunable polymorphic content is demonstrated by rapid flame spray pyrolysis. By controlling precisely the total ambient oxygen partial pressure of the combustion in a quartz tube enclosure, anatase content as high as 96wt% (4wt% rutile) was obtained at high oxic flame conditions, while rutile content as high as 94wt% (6wt% anatase) was obtained under anoxic flames. The polymorphic variability lies within a narrow range of combustion equivalence ratios, that is, 1.01.0) possibly due to physical hindrance by surface carbonaceous content (typically 2 nanocrystals, preserving hence its pristine state. © 2011 Elsevier Ltd.