Browsing by Author "Hällsten, Susanna"

Chiral assemblies of metal nanoparticles absorb and/or scatter left and right handed circularly polarized light with different intensities usually from the visible light spectral region. This difference in the absorption called circular dichroism (CD) and closely related anisotropy factor (g-factor), which is the CD spectrum normalized with the overall absorption, describe the optical activity of the chiral assemblies. The aim of this thesis was to study and optimize the different structural parameters affecting the g-factor of a chiral gold nanorod (AuNR) dimer to reach the highest possible value. The structure consisted of two AuNRs bound together with a DNA origami in a crossed fingers conformation. The properties studied were silver as a coating material of the AuNRs, the dimensions of the AuNRs, angle between the long axes of the AuNRs and the interparticle distance. The dimensions comparison was studied with different sized AuNRs, the angle was controlled by changing the DNA strands working as a bridge between the two bundles in the DNA origami and the distance between the AuNRs was controlled by the length of the thiol treated DNA strands used for the AuNR binding to the origami. The experiments showed that the best g-factor was achieved with 33×74 nm sized AuNRs with an angle of approximately 55° and an interparticle distance of 24nm. Optimized assembly made a notable increase in the g-factor from 0.05 to 0.12. This is a highest g-factor recorded in a AuNR dimer structure up to date and thus the assembly could be of great use in the chiral sensing field in the future.