The integration of chirality with plasmonic materials allow a vast expansion and opportunities for nanophotonics including polarization control, enantiomeric sensing, and negative refractive index in the visible range. Recently, we developed a peptide-directed strategy for synthesizing chiral plasmonic nanoparticle with precise handedness control and excellent chiroptical responses. We demonstrated that interactions between peptides and gold surface enable “chirality transfer” to drive the spontaneous development of chirality. Also, control of seed morphology and chiral molecule structures allowed further tuning of chiral morphology within the same 432 point-group symmetry, which has been named as helicoid series. The highly twisted chiral components in the 432 helicoid gold nanoparticles gave a significantly strong chiroptical activity, which randomly dispersed nanoparticle solution showing dissymmetry factor of 0.2 at visible wavelengths. Despite already excellent chiroptic response, single nanoparticle dark-field chiral scatterometry analysis reveals that the full potential of helicoid nanoparticle is limited by the overall uniformity.<br/>Herein, we demonstrate multi-chirality-evolution step for chiral nanoparticle synthesis based on close understanding of chiral nanoparticle growth mechanism and interaction between kinetic modifiers and shape modifiers. Applied method induce significant enhancement in particle uniformity, hence resulting in increase of chiroptic response of the 432 helicoid III. Detailed time variant and reaction parameter study allowed synthetic design principles for 432 helicoid nanoparticles. The devised multi-chirality-evolution synthesis method generated a very specific chirality evolving environment for each growth step for a very controlled and systematic formation of chiral gap structures. Synthesized 432 helicoid III nanoparticle with high uniformity shows a significant increase in dissymmetry factor from 0.2 to 0.31 in solution and 24% decrease in its Full-Width-Half-Maximum (FWHM) value of chiroptic spectrum. While devised multi-chirality-evolution synthesis method has been demonstrated using 432 heliocid III, proposed synthesis method holds much significance as it could secure uniformity in nano-morphology and chiroptical response in general plasmonic metamaterial synthesis.

Uniform chiral gap synthesis for high dissymmetry factor in single plasmonic gold nanoparticle

ACS Fall 2020 Virtual Meeting

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