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Nanoscopic control and quantification of enantioselective optical forces
Yang Zhao1, Amr A E Saleh1,2, Marie Anne van de Haar3
1Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
Nature Nanotechnology
|September 26, 2017
Summary
Researchers developed a new method to measure tiny forces from circularly polarized light (CPL). This technique uses a special atomic force microscope probe and optical tweezers to precisely map chiral forces, enabling better chiral resolution and nanostructure assembly.
Area of Science:
- Optics
- Nanotechnology
- Chemical Physics
Background:
- Circularly polarized light (CPL) interacts differently with chiral molecules.
- Measuring small enantioselective optical forces is difficult due to their low magnitude and spatial variation.
- Existing methods lack the resolution and sensitivity for precise force quantification.
Purpose of the Study:
- To develop a technique for strengthening and visualizing enantioselective optical forces.
- To enable precise control and quantification of chiral forces at the nanoscale.
- To demonstrate the application of this technique for chiral resolution and nanostructure assembly.
Main Methods:
- Coupling a chiral atomic force microscope (AFM) probe with a plasmonic optical tweezer.
- Illuminating the plasmonic tweezer with CPL to generate chiral forces on the AFM tip.
- Mapping chiral forces with high lateral resolution (2 nm) using the AFM tip.
Main Results:
- Demonstrated that CPL exerts handedness-dependent forces on a chiral AFM tip.
- Observed attractive forces with left-CPL and repulsive forces with right-CPL for a left-handed tip.
- Achieved force differences exceeding 10 pN between opposite-handed specimens and mapped forces with 2 nm resolution.
Conclusions:
- The developed technique effectively strengthens and visualizes enantioselective optical forces.
- This method allows for high-resolution mapping of chiral forces, revealing distinct spatial distributions.
- The findings open new avenues for chiral resolution and controlled assembly of chiral nanostructures.
