Lingyan Meng

Nanostructures facilitate ultrasensitive chiral measurements by enabling tunable plasmon-enhanced Raman optical activity (PEROA) spectra. Using finite element analysis, we systematically studied how structural parameters govern PEROA in chiral tip-nanorod configurations. Multipolar decomposition was performed to analyze the contribution of scattering multipole moments to PEROA. Interesting patterns of PEROA enhancement indicate different active areas for the out-of-plane and in-plane molecular vibration modes. Nanoscale spatial variations drastically alter both the magnitude and the sign of PEROA enhancement. Both hotspot positions and the out-of-plane PEROA enhancement exhibit a strong dependence on excitation wavelengths. The new PEROA mode originates from the enhanced differential scattering between RCP and LCP illuminations at the scattering minimum. Coherent superposition between PSPs-dominant scattering by the nanorod and LSPR-dominant scattering by the tip leads to high-directivity radiation patterns. Angularly resolved PEROA distributions reveal highly directional emission into the prism with a divergence angle ∘ . The directivity for the out-of-plane molecular modes is stronger than that for the in-plane modes. Our findings could advance high-sensitivity PEROA spectroscopy and guide the rational design of chiral spectra platforms.

Despite intensive research in tip‐enhanced Raman spectroscopy (TERS), the angular distribution of Raman scattering in the TERS gap remains experimentally unreported leaving its relevance to the TERS signal formation to be seldomly discussed. Here, we investigate the angular distribution of the tip‐enhanced Raman signal in the Fourier plane using a model system composed of flat‐lying cobalt (II) hexadecafluoro‐phthalocyanine (CoPcF ₁₆ ) molecules physically adsorbed on a smooth gold surface. Both in‐plane and out‐of‐plane vibrational modes are observed, where the out‐of‐plane Raman modes at about 678 and 740 cm ⁻¹ have different angular intensity distributions than those of in‐plane Raman modes at 1309 and 1373 cm ⁻¹ . We interpret the angular spectrum of the TERS signal considering the molecular vibrational modes computed with density functional theory (DFT) for the free and gold‐deposited molecule, and the directed Raman scattering by the gap‐mode predicted by finite‐difference time‐domain (FDTD) simulations. We contend that the TERS gap directs the Raman vibrational modes differently, leading to distinct angularly distributed Raman scattering intensities. These findings emphasize the nonnegligible role of the TERS detection scheme in understanding spectral features, such as the relative peak intensity ratio variations for studying molecular orientations, or for monitoring chemical reactions.

Optical nanocavity provides an opportunity to deeply study the light–matter interaction with notable findings such as Rabi splitting in strong coupling and Fano resonance in weak coupling. Here, we theocratically explore the plexcitons of a bilayer (BL) borophene synthesized on an Ag (1 1 1) film in a tip-enhanced Raman scattering (TERS) system, where the BL borophene is located in the nanocavity between the tip and substrate, stimulated by recent experimental synthesis [Liu et al., Nat. Mater. 21, 35 (2022)]. In the strong-coupling region, the negative real part of the dielectric function of the BL borophene manifests; the BL borophene is of plasmonic properties resulting in Rabi splitting of plexcitons with 310 meV. In the weak-coupling region, the spectra show typical asymmetry with a sharp change between a dip and a peak (Fano resonance). A balanced gain and loss facilitates single-mode lasing in the parity-time symmetry-broken regime, where single-mode lasing with a very narrow half-width is of ultrahigh enhancement factor up to 108. Fano-resonant propagating plexcitons are observed in the dip of Fano resonance, which is extremely sensitive to the excitation wavelength. Our results not only deepen the physical understanding of the plasmon–exciton coupling interaction in the TERS system but also provide a way to manipulate the light–matter interaction in the TERS system.

Metal nanohole arrays show excellent performance when applied for sensing, optical fibers, and surface-enhanced spectroscopy, but they are not ideal candidates for surface-enhanced coherent anti-Stokes Raman scattering (SECARS) because of their low enhancement factor (EF). Here, the finite element method was used to study the dependence of the period, width, and thickness of nanoslits on the EF of SECARS and optical transmission in Au nanohole-slit arrays. Nanoslits across the nanoholes significantly modulated the SECARS signal, and we observed a ~10⁶ improvement in the EF of SECARS compared with the nanohole-only structure. Uniform and stable 2D hotspots at the open surface of plasmonic nanohole-slit structures provided a huge SECARS EF as high as 18 orders of magnitude. Directional SECARS emission revealed strong forward and backscattering with high directionality, showing a smaller divergence angle of 14^o on the reflective side of the nanohole-slit array. These results provide a fundamental understanding of SECARS in coupled nanohole-slit arrays and are useful for designing a SECARS platform with high sensitivity.

In today’s business environment, due to the complexity of organizational phenomena, the quick repair methods used in traditional economic management control will have adverse effects and more serious problems. The focus of this article is to integrate traditional economic management thoughts related to economic and social management to improve contemporary economic management, and to demonstrate the potential contribution of socio-economic management methods to guiding overall sustainable performance.