Experimental Insights into the Growth of Single Truncated Anatase Bipyramids.

Fluorine has been recognized to selectively stabilize anatase titanium dioxide (TiO2 ) crystal facets; however, resolving its physical location at the nanometer scale remains empirically elusive. Here, we provide direct experimental evidence to reveal the spatial distribution of fluorine on single truncated anatase bipyramids (TABs) using nanoscale secondary ion mass spectrometry (NanoSIMS). Fluorine was found to preferentially adsorb on the (001) facet compared to the (101) facet of TABs. Moreover, NanoSIMS depth profiling exhibited a significantly different fluorine distribution between these two facets in the near-surface region, illustrating the essential role of lattice-doped fluorine in the anisotropic crystal growth of TABs.