Researchers at University of Michigan are investigating the use of circularly polarized light to help detect the presence of proteins and DNA strands that serve as biomarkers for cancer and other diseases. Their technique relies on tagging the target molecules with other molecules that are carrying a coating reflective of circularly polarized light. This kind of light being naturally rare is easily detected, but the equipment is large and expensive.
To overcome this problem The U of M team developed a special film that helps produce circularly polarized light, avoiding the use of traditional components and allowing for small devices that can be used at the patient bedside.
The team published results of their developments in Nature Materials. Here’s a snippet from the study abstract:
Nanostructures with chiral geometries exhibit strong polarization rotation. However, achieving reversible modulation of chirality and polarization rotation in device-friendly solid-state films is difficult for rigid materials. Here, we describe nanocomposites, made by conformally coating twisted elastic substrates with films assembled layer-by-layer from plasmonic nanocolloids, whose nanoscale geometry and rotatory optical activity can be reversibly reconfigured and cyclically modulated by macroscale stretching, with up to tenfold concomitant increases in ellipticity. We show that the chiroptical activity at 660 nm of gold nanoparticle composites is associated with circular extinction from linear effects. The polarization rotation at 550 nm originates from the chirality of nanoparticle chains with an S-like shape that exhibit a non-planar buckled geometry, with the handedness of the substrate’s macroscale twist determining the handedness of the S-like chains. Chiroptical effects at the nexus of mechanics, excitonics and plasmonics open new operational principles for optical and optoelectronic devices from nanoparticles, carbon nanotubes and other nanoscale components.
Study in Nature Materials: Reconfigurable chiroptical nanocomposites with chirality transfer from the macro- to the nanoscale…
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