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High-resolution backscatter electron imaging of colloidal gold in LVSEM
S Erlandsen1, Y Chen, C Frethem
1Department of Genetics, Cell Biology and Development, University of Minnesota Medical School, Minneapolis, MN 55455, USA. erlan001@umn.edu
Journal of Microscopy
|September 3, 2003
Summary
High-resolution imaging of colloidal gold nanoparticles is possible using low-voltage field emission scanning electron microscopy (FESEM). This technique effectively distinguishes gold from platinum using backscattered electron detectors.
Area of Science:
- Materials Science
- Nanotechnology
- Electron Microscopy
Background:
- Accurate imaging of nanoscale materials is crucial for research and development.
- Field Emission Scanning Electron Microscopy (FESEM) offers high resolution but requires optimized detection methods for specific materials like colloidal gold.
Purpose of the Study:
- To evaluate the effectiveness of low-voltage backscattered electron (BSE) imaging for high-resolution visualization of colloidal gold nanoparticles.
- To determine the sensitivity thresholds of different BSE detectors for colloidal gold.
Main Methods:
- Utilized in-lens or below-the-lens FESEMs with Autrata-modified YAG:Ce scintillators or BSE/SE conversion plates.
- Performed high-resolution imaging of 6, 12, and 18 nm colloidal gold particles at magnifications up to 500,000x.
- Compared BSE imaging contrast between gold (atomic number 79) and platinum (atomic number 78) coated cell surfaces.
Main Results:
- Achieved high-resolution backscattered electron (BSE) imaging of colloidal gold at low voltages.
- Established BSE detection thresholds: 1.8 keV for YAG detectors and 1 keV for BSE/SE conversion plates.
- Clearly distinguished gold nanoparticles from platinum-coated cell surfaces using material contrast, demonstrating the technique's efficacy.
Conclusions:
- Low-voltage FESEM with specialized BSE detectors is a viable method for high-resolution imaging of colloidal gold.
- The technique provides excellent material contrast, enabling discrimination between gold and adjacent materials.
- BSE imaging demonstrates robustness against charging and carbon contamination, enhancing its utility for biological and materials science applications.