Engineering of radiation of optically active molecules with chiral nano-meta-particles

Abstract

The radiation of optically active (chiral) molecule placed near chiral nanosphere is investigated. The optimal conditions for engineering of radiation of optically active (chiral) molecules with the help of chiral nanoparticles are derived. It is shown that for this purpose, the substance of the chiral particle must have both ε and µ negative (double negative material (DNG)) or negative µ and positive ε (µ negative material (MNG)). Our results pave the way to an effective engineering of radiation of "left" and "right" molecules and to creating pure optical devices for separation of drugs enantiomers.It is well known that nanoparticles influence substantially both fluorescence of molecules and Raman scattering of light by molecules. These effects are especially strong in the case of metallic nanoparticles where plasmon resonances can be excited. As a result, it is possible to detect radiation even from single molecule (surface enhanced Raman scattering SERS [1] and surface enhanced fluorescence SEF [2]) and to use this effect in various applications, in particular, for detection of certain proteins in disease diagnosis [3]. Recently it was shown that planar chiral metamaterials [4] and even nonchiral plasmonic nanoparticles [5] are able to dramatically (by several orders of magnitude) change the chiral dichroism of a chiral molecule and thus such metamaterials could form the basis for assaying technologies capable of detecting amyloid diseases and certain types of viruses.Interesting effects are also found in the study of influence of chiral nanoparticles [6] and nanoparticles with negative refraction index [7] on electric dipole radiations of atoms and molecules. Full quantum-electrodynamics theory of influence of nanospheres of various composition including media with negative refraction index on radiation of electric and magnetic dipoles was developed in [8]. However, the interference effects between these dipoles were not investigated there.Even more interesting problem is to investigate the possibility of controlling radiation of optically active molecules [9]. As far as we know this problem has not been investigated until now. The goal of present work is to investigate the influence of chiral nanoparticles on spontaneous emission of optically active molecules and to show that it is possible to discriminate drug enantiomers with pure optical methods. Geometry of the problem is shown in Fig. 1.As the model of an optically active molecule we assume FIG. 1:Geometry of the considered problem. An optically active (chiral) excited molecule is placed near chiral spherical nanoparticle having radius a. The total size of the region of molecule and nanobody is much less than the wavelength λ. Molecule is placed at the distance r0 from the center of co-ordinates, which coincides with the nanoparticle center, and characterized by its electric (d0) and magnetic (m0) dipole moments which induce corresponding dipole moments δd and δm of nanoparticle.that its radiation is of both electric dipole and magnetic dipole nature, ...

Universal spin-momentum locking of evanescent waves

“…Following the semiclassical theory of spontaneous emission [19][20][21], we approximate this chiral source to be…”

Giant circular dichroism of a molecule in a region of strong plasmon resonances between two neighboring gold nanocrystals

“…For example, it was a powerful method to differentiate a secondary structure of proteins which can appear in the forms of α-helix, random coil, or β-sheet. Recently the concepts of chirality and CD have been brought to the field of plasmonics [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] . One of the motivations for this development is plasmon-enhanced sensing of chiral molecules.…”

Controlling electric, magnetic, and chiral dipolar emission with PT-symmetric potentials

“…It has been shown that enantiomers exhibit enantio-specific coupling to the modes of a chiral scatterer, and that chiral structures can substantially modify the decay rate and radiation pattern of chiral molecules [27]. Here, we consider the radiation of a chiral molecule in the vicinity of our PT-symmetric structure, which, importantly, contains no chiral constituents.…”

“…The electric and magnetic dipoles are located 20 nm away from the interface, in the xy-plane with an angle θ between them. We assume that the ratio between the magnetic and electric dipoles is ξ = 0.1c, where c is the speed of light [27,34]. From Fig.…”