Defocus-integration interferometric scattering microscopy for speckle suppression and enhancing nanoparticle...

Area of Science:

• Optical microscopy
• Nanotechnology
• Surface science

Background:

• Direct optical detection of single nanoparticles is crucial for many scientific fields.
• Current techniques like interferometric scattering microscopy (iSCAT) are limited by speckle noise from substrate surface undulations.
• This noise restricts the size of detectable nanoparticles.

Purpose of the Study:

• To develop a novel optical technique to suppress speckle noise in single nanoparticle detection.
• To enhance the imaging and detection capabilities for smaller nanoparticles on diverse substrates.
• To overcome the limitations of existing iSCAT methods.

Main Methods:

• Implementation of a defocus-integration interferometric scattering microscopy (iSCAT) technique.
• Analysis of scattering phase symmetry between nanoparticles and surface undulations to identify speckle origins.
• Experimental validation on ultra-flat glass and silicon wafer substrates.

Main Results:

• Significant suppression of speckle noise was achieved using the defocus-integration iSCAT.
• An enhancement of 6.9 dB in signal-to-noise ratio for nanoparticle detection was experimentally demonstrated.
• The technique proved effective for various nanoparticle materials and substrate types (low and high refractive index).

Conclusions:

• The developed defocus-integration iSCAT technique effectively overcomes speckle noise limitations in nanoparticle imaging.
• This advancement enables more sensitive and versatile detection of single nanoparticles across different materials and substrates.
• The findings pave the way for broader applications of optical microscopy in nanotechnology and materials science.