Mathieu NICOLAS

Expertise

PhD subject

Mueller-matrix microscopy and functionalization of Pseudo-Chiral Resonators for the Optical Detection of Chiral Molecules

Summary

Biological, chemical and physical properties of numerous biomolecules (proteins, amino acids, peptides, etc) depend on their chirality. Consequently, it is relevant to study effective methods of analysis in order to discriminate enantiomers. However, due to the low chirality of biomolecules, conventional chiroptic method is not sufficiently sensitive to detect a low differential absorption of circularly polarized light. The use of plasmonic chiral resonators was shown to enhance the differential interaction of molecules and two resonators with opposite chirality up to 10⁶ times ^[1]. Pseudo-chiral resonators, U-shaped gold nanostructures used herein, were demonstrated that their circular dichroism depends on the light propagation direction and the sign changes by rotating 180° around the normal to the surface. Herein, the U-shaped gold resonators are realized using e-beam lithography. An antibacterial peptide-temporin has been chosen for the study. Temporin is linked by coupling its terminal thiol function to gold surfaces in forming covalent bonds sulfur-gold ^[2]. IR and UV spectroscopy are used to characterize the functionalized surface. Raman and X-ray photoelectron will be useful in the future. The measurement of the circular dichroism is realized thanks to a Mueller matrix microscope with two continuous rotating compensators ^[3].

A chiral molecule coupled with pseudo-chiral nanostructures modifies the state of polarization of the light

[1] Hendry et al, Nat. Nanotechnol. 2010, 5, pp 783–787.

[2] Lombana et al, J. Pept. Sci, 2014, 20, pp 563-569.

[3] Arteaga et al, Appl. Opt. 2014, 53, pp 2236–2245.