Defocused differential interference contrast microscopy imaging of single plasmonic anisotropic nanoparticles

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Differential Interference Contrast (DIC) microscopy is a widely used technique for visualizing unstained transparent specimens.
• Gold nanorods exhibit unique optical properties dependent on their size, shape, and surrounding environment.
• Understanding the imaging mechanisms of nanoparticles in microscopy is crucial for advanced characterization.

Purpose of the Study:

• To investigate the role of scattered light and defocus aberration in defocused DIC imaging of gold nanorods.
• To explore the potential of defocused DIC microscopy for determining the spatial orientation of gold nanorods.
• To establish a method for directly resolving nanoparticle orientation using optical microscopy.

Main Methods:

• Defocused differential interference contrast (DIC) microscopy was employed.
• Gold nanorods were used as the specimen.
• Analysis focused on the relationship between scattered light, defocus aberration, and observed DIC image patterns.

Main Results:

• Scattered light and defocus aberration were identified as critical factors in generating orientation-dependent DIC image patterns for gold nanorods.
• A direct correlation was observed between the alignment of the gold nanorod with polarization directions and the clarity of its spatial orientation in defocused DIC images.
• The study demonstrated the capability to resolve the spatial orientation of gold nanorods using this imaging approach.

Conclusions:

• Defocused DIC microscopy provides a valuable tool for characterizing the orientation of gold nanorods.
• The interplay of scattered light and defocus aberration is key to interpreting DIC images of nanorods.
• This technique offers a non-invasive method for direct spatial orientation determination of nanoparticles.