Electromagnetic Field Gradient-Enhanced Raman Scattering in TERS Configurations

Abstract

Realizing in situ simultaneous measurement of full vibrational modes in tip-enhanced Raman spectroscopy (TERS) is of immense importance for improving the ability of quantitative analysis and measurement accuracy of the molecular spectrum. In this study, the electric field gradient effect in the TERS system was theoretically investigated by using the finite element method. The respective contributions of electric field and electric field gradient to dipole Raman and gradient Raman modes in the TERS spectrum were quantitatively distinguished. By comparing the relative intensity ratio between electric field gradient and electric field, the TERS configuration could be optimized to achieve a maximum of gradient Raman modes. Theoretical results indicate that molecular symmetries strongly influence the molecular hyperpolarizability, which significantly influences the plasmonic electric field gradient effects. Our theoretical results could reveal the contributions of electric field and electric field gradient to molecular vibration modes, useful for the design of the TERS platform with more spectrum information.

Progress of tip-enhanced Raman scattering for the last two decades and its challenges in very recent years

“…The plasmonic gradient effect on TERS has also been studied. 12,57,58 A "single molecule" can be investigated and mapped under ambient conditions. 55 Intramolecular and intermolecular interactions of single molecules can also be visualized.…”

Single-Walled Carbon Nanotubes as One-Dimensional Scattering Surfaces for Measuring Point Spread Functions and Performance of Tip-Enhanced Raman Spectroscopy Probes

“…Tip–sample interactions also effect enhancement and spatial resolution. Further spatial confinement and increased enhancement are achieved with plasmon-excition coupling , and the formation of tip–sample–tip gap modes, − while at small tip–sample separations quantum effects begin to reduce confinement . Furthermore, the substrate geometry influences the enhancement and spatial resolution.…”

“…Images formed using a given system are the convolution of the PSF and the true image . For TERS, the spot diameter of the PSF defines the spatial resolution, which depends on the volume of the near-field in the tip–sample junction . The image contrast is determined by I nf / I ff where the near-field signal is collected on a sample molecule and the far-field signal is collected on the substrate.…”

Exploration on Signal Processing Performance of Wireless Sensor in Electromagnetic Interference Environment

“…At the same time, the wireless sensors are always interfered with by the Electromagnetic (EM) Field (EMF) [1]. Therefore, how to reduce the impact of EMF on wireless sensors' Signal Processing (SP) performance has become one of the major problems [2,3]. Mehran et al optimized the concept of EM Compatibility (EMC) and proposed three necessary conditions for EM compatible systems: (1) The system would not affect or interfere with other systems.…”

“…Mehran et al optimized the concept of EM Compatibility (EMC) and proposed three necessary conditions for EM compatible systems: (1) The system would not affect or interfere with other systems. (2) The system would not be affected by other systems' radiation. (3) The system would not interfere with breeding.…”