Biomedical Engineering Reference
In-Depth Information
30
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Wavelength (nm)
Figure 1.21
Top: Schematic of the two possible extreme cases of chiral
molecule coated Ag NPs: Left: Monolayer-coated particles for Ag:molecule
ratio 4:1; Right: molecular stack-coated particles for Ag:molecule 32:1. (a)
Calculation of the CD spectrum for a dipolar particle-stack interaction at
different particle-molecule average separation distances. (b) The experi-
mental CD spectrum for an Ag:molecule 4:1 sample, showing the broad
negative plasmonic CD around 400 nm. (c) A calculation of the plasmonic
CD for a particle with a chiral surface distortion taking the first 20 and 25
spherical harmonicsintoaccount.(d)Theexperimental-inducedplasmonic
CD spectrum for the Ag:molecule 32:1 sample. Adapted with permission
from Ref. [48].Copyright 2012, American Chemical Society.
chiral supramolecular structures made of chiral molecular building
blocks.Bychangingthemetal-atom:moleculeratio,itwaspossibleto
obtain either a molecular monolayer coating of the NPs (see the top
right scheme of Fig. 1.21) or chiral stacks of molecules coating the
NPs(seethetopleftschemeofFig.1.21).Inthelattercase,thechiral
stack-plasmon coupling induced a CD signal at the surface plasmon
resonance absorption band of the silver NPs (see Fig. 1.21b). The
sensitivity of this induction effect to temperature, which affected
the stacking of the molecules (i.e., the level of chirality), indicated
