Sizing individual dielectric nanoparticles with quantitative differential interference contrast microscopy.

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Accurate sizing of dielectric nanoparticles is crucial across various scientific fields.
• Existing methods may lack the required precision, sensitivity, or throughput for comprehensive nanoparticle analysis.

Purpose of the Study:

• To introduce a novel, accurate, and precise method for measuring the size of individual dielectric nanoparticles.
• To demonstrate the method's applicability to nanoparticles relevant to environmental and material science.

Main Methods:

• Quantitative differential interference contrast (DIC) microscopy was employed.
• Optical phase changes induced by nanoparticles were converted to intensity changes.
• Wiener filtering was used to retrieve phase images, followed by a quantitative size extraction methodology.

Main Results:

• The method accurately determined the radius of 100 nm polystyrene beads within a few nanometers.
• Sensitivity limits down to 1.8 nm radius were inferred, with measurements on 15 nm beads demonstrated.
• Analysis of nanodiamonds revealed a mean size of 28 nm with a nearly exponential size distribution.

Conclusions:

• The developed quantitative DIC microscopy method provides accurate and sensitive nanoparticle size measurements.
• This technique is applicable to diverse dielectric nanoparticles, including nanoplastics and nanodiamonds.
• The method offers a powerful, high-throughput tool for nanoparticle analysis using widely available DIC microscopy.