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Determination of the volume-specific surface area by using transmission electron tomography for characterization and definition of nanomaterials.

Van Doren EA, De Temmerman PJ, Francisco MA, Mast J - J Nanobiotechnology (2011)

Bottom Line: Segmentation by isosurface rendering allowed visualizing the 3D information of an electron tomographic reconstruction in greater detail than digital slicing.The mean VSSA of all examined NM was significantly larger than the threshold of 60 m(2)/cm(3).The characterization and definition of the examined gold and silica NM can benefit from application of conventional bright field electron tomography: the NM can be visualized in 3D, while surface features and the VSSA can be measured.

View Article: PubMed Central - HTML - PubMed

Affiliation: EM-unit, CODA-CERVA, Groeselenberg 99, Brussels, Belgium.

ABSTRACT

Background: Transmission electron microscopy (TEM) remains an important technique to investigate the size, shape and surface characteristics of particles at the nanometer scale. Resulting micrographs are two dimensional projections of objects and their interpretation can be difficult. Recently, electron tomography (ET) is increasingly used to reveal the morphology of nanomaterials (NM) in 3D. In this study, we examined the feasibility to visualize and measure silica and gold NM in suspension using conventional bright field electron tomography.

Results: The general morphology of gold and silica NM was visualized in 3D by conventional TEM in bright field mode. In orthoslices of the examined NM the surface features of a NM could be seen and measured without interference of higher or lower lying structures inherent to conventional TEM. Segmentation by isosurface rendering allowed visualizing the 3D information of an electron tomographic reconstruction in greater detail than digital slicing. From the 3D reconstructions, the surface area and the volume of the examined NM could be estimated directly and the volume-specific surface area (VSSA) was calculated. The mean VSSA of all examined NM was significantly larger than the threshold of 60 m(2)/cm(3). The high correlation between the measured values of area and volume gold nanoparticles with a known spherical morphology and the areas and volumes calculated from the equivalent circle diameter (ECD) of projected nanoparticles (NP) indicates that the values measured from electron tomographic reconstructions are valid for these gold particles.

Conclusion: The characterization and definition of the examined gold and silica NM can benefit from application of conventional bright field electron tomography: the NM can be visualized in 3D, while surface features and the VSSA can be measured.

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Electron tomographic analysis of spherical gold nanoparticles. Figure 1A represents the micrograph gray value range that served for setting the threshold. The threshold was set at -15106.4, that is somewhere between the two peaks. Figure 1B shows a representative electron tomographic 3D-reconstruction of spherical gold NP. Bar: 50 nm. Figure 1C and Figure 1D show the correlation between the calculated and measured volumes and areas of ten electron tomograms.
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Figure 1: Electron tomographic analysis of spherical gold nanoparticles. Figure 1A represents the micrograph gray value range that served for setting the threshold. The threshold was set at -15106.4, that is somewhere between the two peaks. Figure 1B shows a representative electron tomographic 3D-reconstruction of spherical gold NP. Bar: 50 nm. Figure 1C and Figure 1D show the correlation between the calculated and measured volumes and areas of ten electron tomograms.

Mentions: Electron tomographic reconstruction allowed visualizing the spherical gold NP in three dimensions (Figure 1B). The particles measure approximately 20 nm in diameter while the general morphology of all examined gold NP was almost spherical. Some small extensions of the surface were observed at the polar regions of the reconstructed particles. Local flattening was observed in the equatorial regions. The latter coincided with small zones in the original micrographs showing diffraction contrast, indicative for a confined crystalline organization. In the original micrographs taken at a tilt angle of 0°, the outline of the particles was roughly circular, although angular regions corresponding with a local crystalline structure were observed in certain particles.


Determination of the volume-specific surface area by using transmission electron tomography for characterization and definition of nanomaterials.

Van Doren EA, De Temmerman PJ, Francisco MA, Mast J - J Nanobiotechnology (2011)

Electron tomographic analysis of spherical gold nanoparticles. Figure 1A represents the micrograph gray value range that served for setting the threshold. The threshold was set at -15106.4, that is somewhere between the two peaks. Figure 1B shows a representative electron tomographic 3D-reconstruction of spherical gold NP. Bar: 50 nm. Figure 1C and Figure 1D show the correlation between the calculated and measured volumes and areas of ten electron tomograms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3113930&req=5

Figure 1: Electron tomographic analysis of spherical gold nanoparticles. Figure 1A represents the micrograph gray value range that served for setting the threshold. The threshold was set at -15106.4, that is somewhere between the two peaks. Figure 1B shows a representative electron tomographic 3D-reconstruction of spherical gold NP. Bar: 50 nm. Figure 1C and Figure 1D show the correlation between the calculated and measured volumes and areas of ten electron tomograms.
Mentions: Electron tomographic reconstruction allowed visualizing the spherical gold NP in three dimensions (Figure 1B). The particles measure approximately 20 nm in diameter while the general morphology of all examined gold NP was almost spherical. Some small extensions of the surface were observed at the polar regions of the reconstructed particles. Local flattening was observed in the equatorial regions. The latter coincided with small zones in the original micrographs showing diffraction contrast, indicative for a confined crystalline organization. In the original micrographs taken at a tilt angle of 0°, the outline of the particles was roughly circular, although angular regions corresponding with a local crystalline structure were observed in certain particles.

Bottom Line: Segmentation by isosurface rendering allowed visualizing the 3D information of an electron tomographic reconstruction in greater detail than digital slicing.The mean VSSA of all examined NM was significantly larger than the threshold of 60 m(2)/cm(3).The characterization and definition of the examined gold and silica NM can benefit from application of conventional bright field electron tomography: the NM can be visualized in 3D, while surface features and the VSSA can be measured.

View Article: PubMed Central - HTML - PubMed

Affiliation: EM-unit, CODA-CERVA, Groeselenberg 99, Brussels, Belgium.

ABSTRACT

Background: Transmission electron microscopy (TEM) remains an important technique to investigate the size, shape and surface characteristics of particles at the nanometer scale. Resulting micrographs are two dimensional projections of objects and their interpretation can be difficult. Recently, electron tomography (ET) is increasingly used to reveal the morphology of nanomaterials (NM) in 3D. In this study, we examined the feasibility to visualize and measure silica and gold NM in suspension using conventional bright field electron tomography.

Results: The general morphology of gold and silica NM was visualized in 3D by conventional TEM in bright field mode. In orthoslices of the examined NM the surface features of a NM could be seen and measured without interference of higher or lower lying structures inherent to conventional TEM. Segmentation by isosurface rendering allowed visualizing the 3D information of an electron tomographic reconstruction in greater detail than digital slicing. From the 3D reconstructions, the surface area and the volume of the examined NM could be estimated directly and the volume-specific surface area (VSSA) was calculated. The mean VSSA of all examined NM was significantly larger than the threshold of 60 m(2)/cm(3). The high correlation between the measured values of area and volume gold nanoparticles with a known spherical morphology and the areas and volumes calculated from the equivalent circle diameter (ECD) of projected nanoparticles (NP) indicates that the values measured from electron tomographic reconstructions are valid for these gold particles.

Conclusion: The characterization and definition of the examined gold and silica NM can benefit from application of conventional bright field electron tomography: the NM can be visualized in 3D, while surface features and the VSSA can be measured.

Show MeSH