Electron tomography is applied to photocatalytic gold/titanium oxide and gold/silver/titanium oxide samples. In order to obtain a tilt series for the electron tomography measurement, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) is used under cryogenic conditions. Dedicated programs have been developed for measuring volume, surface area, thickness distribution and nearest-neighbour distance of metallic nanoparticles on samples. Using these quantification programs, the 3D morphology of gold and silver nanoparticles is accurately characterized. We paid particular attention to the quantitative measurement of surface area. The measurement error of the method and appropriate magnification are defined using spherical nanoparticle models. We measured the 3D morphology of gold nanoparticles supported on titanium oxide (total volume=6.5×105[nm3], surface area=1.4×105[nm2], and average nearest-neighbour distance=40[nm]).
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