Imaging Contrast of Diamond Nanoparticle Structures on Different Supporting Films.

Electron microscopy is essential for nanoparticle research because it provides the critical structural data of particle size, morphology, crystallography, and elemental composition that are essential for tailoring and for predicting nanoparticles' optical, electronic, catalytic, and mechanical properties. The weak scattering from nanoparticles results in low contrast in electron microscope images. Therefore, observing and interpreting such images requires special care to avoid erroneous conclusions. This study investigates the imaging contrast of diamond structures on different supporting films. When the nanodiamond is overlapped with a carbon film, particle edge details cannot be explained, and the overlapping interference lattices produce a pattern of interference fringes that is much coarser than the original pattern. Single graphene oxide (GO) sheets, as the ideal support film, are highly electron-transparent for the study of nanoparticles. As a low-background and high-transparency support to identify the dominant structural information of the nanodiamond, GO is superior to carbon support film. Quantitative contrast analysis reveals that GO film improves the contrast-to-noise ratio (CNR) by a factor of 3.0 for 8 nm particles compared with conventional amorphous carbon films. The {111} lattice-fringe detection rate increases from 35% on carbon film to 85% on GO for the same particle size. These results establish GO as a quantitatively superior support film for high-resolution electron microscopy (HRTEM) imaging of sub-10 nm nanoparticles.