Synthesis of Bitten Gold Nanoparticles with Single‐Particle Chiroptical Responses

Abstract

The introduction of structural complexity to nanoparticles brings them interesting properties. Regularity breaking has been challenging in the chemical synthesis of nanoparticles. Most reported chemical methods for synthesizing irregular nanoparticles are complicated and laborious, largely hindering the exploration of structural irregularity in nanoscience. In this study, the authors have combined seed‐mediated growth and Pt(IV)‐induced etching to synthesize two types of unprecedented Au nanoparticles, bitten nanospheres and nanodecahedrons, with size control. Each nanoparticle has an irregular cavity on it. They exhibit distinct single‐particle chiroptical responses. Perfect Au nanospheres and nanorods without any cavity do not show optical chirality, which demonstrates that the geometrical structure of the bitten opening plays a decisive role in the generation of chiroptical responses.

Tuning the Geometry and Optical Chirality of Pentatwinned Au Nanoparticles with 5-Fold Rotational Symmetry

“…According to previous reports, the peaks in CD spectra of chiral NPs typically show a synergistic contribution from the electric quadrupole and electric dipole of plasmon resonance. 25,40,56,57 In most cases, the main peak (first peak) of plasmonic CD is dominated by the electric quadrupole. In our case, we think the origin of CD peaks follows a mechanism similar to that of other chiral Au NPs.…”

“…In principle, the CDS is built on a conventional dark-field scattering microscope, allowing for the detailed correlation of scattering-based chiroptical signals with the structural features of individual NPs. Recent works have further demonstrated the capability of the CDS technique in detecting heterogeneities in the chiroptical properties of plasmonic materials. ,, However, a diverse set of CD signals was often observed, which can be attributed to broad distribution in size, chiral feature, and defects of chiral NPs as well as the potential anisotropic effect when chiral NPs were deposited on substrates for single-particle optical measurements. , Therefore, we also carried out finite difference time-domain (FDTD) simulations to more quantitatively understand the far-field and near-field optical properties of pentatwinned chiral Au NPs.…”

Rapid and Facile Synthesis of Gold Trisoctahedrons for Surface-Enhanced Raman Spectroscopy and Refractive Index Sensing

“…In recent decades, significant attention and research efforts have been devoted to the preparation of Au nanostructures with controllable shapes, as there is a strong correlation between their morphologies and properties. − Nanostructures with high-index facets, possessing at least one of the three Miller indices larger than 1, are of particular interest due to their greater density of atomic kinks, steps, and edges, which often result in higher chemical-reaction activities compared to the low-index-faceted nanostructures. , Furthermore, high-index-faceted nanostructures exhibit a greater number of well-defined sharp tips and edges that present much stronger local electromagnetic fields, leading to more efficient surface-enhanced Raman scattering performances and higher sensitivities for sensing. , Despite their promising properties, synthesizing Au nanostructures with high-index facets remains a remarkable challenge because of their high surface energy, which causes fast atom deposition rates and makes these facets disappear during the growth process. As a result, nanoparticles tend to display low-index facets, such as {100}, {111}, and {110}, to minimize their surface energy .…”