Particle size distributions by transmission electron microscopy: an interlaboratory comparison case study

Area of Science:

• Materials Science
• Nanotechnology
• Metrology

Background:

• Accurate nanoparticle size distribution measurement is crucial for material properties.
• Transmission electron microscopy (TEM) is a key technique, but standardized protocols are needed.
• Automated analysis enhances efficiency and reproducibility in nanoparticle characterization.

Purpose of the Study:

• To evaluate an interlaboratory protocol for measuring nanoparticle size distribution using TEM.
• To compare different statistical models for analyzing particle size data.
• To establish a framework for assessing measurement uncertainty in nanoparticle sizing.

Main Methods:

• An interlaboratory comparison involving eight laboratories measuring NIST RM8012 gold nanoparticles.
• Automated image capture and particle analysis using TEM.
• Statistical analysis including data quality assessment, reference model fitting (normal, lognormal, Weibull, Rosin-Rammler-Bennett), and uncertainty evaluation.

Main Results:

• The interlaboratory mean area-equivalent diameter (27.6 nm ± 2.4 nm) closely matched the reference value.
• The lognormal reference model demonstrated superior performance with lower relative standard errors for its parameters compared to other models.
• Parameter estimate errors were primarily associated with the breadth of the distributions, not the mean.

Conclusions:

• The developed TEM protocol and statistical analysis framework are effective for nanoparticle size distribution assessment.
• The lognormal model is recommended for characterizing the size distribution of these types of nanoparticles.
• Automated TEM image analysis combined with robust statistical methods provides a reliable approach for nanoparticle metrology.