Selective Excitation of Polarization‐Steered Chiral Photoluminescence in Single Plasmonic Nanohelicoids

Abstract

The development of chiral photoluminescence (PL) has drawn extensive attention owing to its potential applications in optical data storage, biosensing, and displays. Due to the lack of effective synthesis methods, colloidal metal nanostructures with intrinsic chiral PL have rarely been reported. Herein, the chiral excitation and emission properties of single gold nanohelicoids (GNHs) are reported for the first time. By measuring their circular dichroism (CD) response and excitation/emission polarizationresolved PL spectra, it is revealed that the intrinsic chirality arising from the geometric handedness of the GNHs induces the observed excitationpolarization-correlated chiral PL. Two models are developed to analyze the observed circular-polarization-steered effect: (1) a chiral PL phenomenological model quantitatively reproduces the PL dissymmetry features; (2) a chiral Purcell effect model reveals that the super-chiral near fields in the GNHs account for the far-field chiral responses such as the polarization-steered chiral PL. The findings not only provide an important understanding of the physical mechanism responsible for luminescent chiral plasmonic nanostructures, but also expand the research on chiral PL-active materials from achiral/chiral hybrid systems to metallic nanostructures with intrinsic structural chirality, thereby broadening the scope of applications in 3D chiral imaging and sensing as well as microstructure analysis.

Nanophotonic Approaches for Chirality Sensing

“…Chiral photoluminescence (PL) spectroscopy is also an important technique for chirality sensing. − Lei and co-workers reported that the emission from single Au helicoids is circularly polarized, and the intensity depends on the illumination handedness . Okamoto and co-workers also fabricated lightning-bolt shaped metamaterials that induced dissymmetry in the PL enhancement of nearby luminescent achiral dye molecules .…”

“…253−256 Lei and coworkers reported that the emission from single Au helicoids is circularly polarized, and the intensity depends on the illumination handedness. 257 Okamoto and co-workers also fabricated lightning-bolt shaped metamaterials that induced dissymmetry in the PL enhancement of nearby luminescent achiral dye molecules. 254 Large PL enhancement dissymmetry factors of g > 0.1 were obtained in the wavelength region near chiral multipolar plasmon resonances.…”

Optically Probing the Chirality of Single Plasmonic Nanostructures and of Single Molecules: Potential and Obstacles

“…In the above, we have discussed direct scattering, extinction, or absorption measurements of CD and ORD, which are matrix elements of the polarizability tensor. Another less direct way to characterize chirality is to look at the ellipticity of the fluorescence of chiral molecules − or of the photoluminescence of chiral nanoparticles. , Although these measurements are easier to perform on a single-molecule basis, we will not discuss them in this Perspective, because they have different experimental requirements than scattering and because their relation to the polarizability tensor is complex. Indeed, the chirality of a molecule when it absorbs may differ from its chirality in the emitting relaxed state.…”

Chiral biosensing at both interband transition and plasmonic extinction regions using twisted-stacked nanowire arrays

“…Chiral inorganic nanomaterials/nanostructures have emerged recently as one of the most dynamic and fastest growing areas of materials science and nanoscience. [1][2][3][4][5][6][7] Their high chiroptical activities show great potential in chiral recognition-based applications. [8][9][10] For example, Lin Yang et al used silver chiral nanoparticles with a sub-5 nm helical pitch for the enantioselective amplification of the optical activity of a molecule (in the deep UV region).…”