Laser-Induced Chirality of Plasmonic Nanoparticles Embedded in Porous Matrix

Abstract

Chiral plasmonic nanostructures have emerged as promising objects for numerous applications in nanophotonics, optoelectronics, biosensing, chemistry, and pharmacy. Here, we propose a novel method to induce strong chirality in achiral ensembles of gold nanoparticles via irradiation with circularly-polarized light of a picosecond Nd:YAG laser. Embedding of gold nanoparticles into a nanoporous silicate matrix leads to the formation of a racemic mixture of metal nanoparticles of different chirality that is enhanced by highly asymmetric dielectric environment of the nanoporous matrix. Then, illumination with intense circularly-polarized light selectively modifies the particles with the chirality defined by the handedness of the laser light, while their “enantiomers” survive the laser action almost unaffected. This novel modification of the spectral hole burning technique leads to the formation of an ensemble of plasmonic metal nanoparticles that demonstrates circular dichroism up to 100 mdeg. An unforeseen peculiarity of the chiral nanostructures obtained in this way is that 2D and 3D nanostructures contribute almost equally to the observed circular dichroism signals. Thus, the circular dichroism is neither even nor odd under reversal of direction of light propagation. These findings will help guide the development of a passive optical modulator and nanoplatform for enhanced chiral sensing and catalysis.

Laser-Based Reshaping of Self-Organized Metasurfaces of Supported Ag Nanoparticles for Encoding Tunable Linear Dichroism Patterns

“…12−15 More complex structures, such as chiral nanostructures, are more challenging to produce. 16,17 These can be either individual anisotropic nanoparticles obtained by chemical synthesis 18,19 or complexes of isotropic NPs helically arranged, for example, on DNA. 20,21 The latter method shows promising possibilities for obtaining complex chiral structures using DNA origami to obtain various plasmonic "enantiomers" from nanorods or nanospheres.…”

“…These applications are possible due to the excitation of localized surface plasmon resonance in metallic nanoparticles (NPs) (collective oscillations of conduction electrons) when interacting with incident light. The spectral position of the plasmon resonance depends on the composition and size of the nanoparticle, the dielectric environment, and to a greater extent on the shape of the NP. − In relatively dense arrays of such NPs, the interparticle plasmonic coupling will cause changes in the plasmon resonance characteristics and the extinction spectrum. − Moreover, for individual anisotropic NPs or as in array, the absorption and scattering will strongly depend on the polarization of the incident electromagnetic wave. − More complex structures, such as chiral nanostructures, are more challenging to produce. , These can be either individual anisotropic nanoparticles obtained by chemical synthesis , or complexes of isotropic NPs helically arranged, for example, on DNA. , The latter method shows promising possibilities for obtaining complex chiral structures using DNA origami to obtain various plasmonic “enantiomers” from nanorods or nanospheres. − …”

“…Moreover, little attention has been paid to the impact of polarized radiation on closely spaced ensembles of NPs. On the other hand, significant circular dichroism can be induced in the originally isotropic and achiral ensembles of NPs depending on their mutual arrangement and laser light polarization. , Therefore, the effect of linearly polarized laser radiation on metallic nanostructures close to their percolation threshold should be studied in detail.…”