Visualizing On-Surface Decomposition Chemistry at the Nanoscale Using Tip-Enhanced Raman Spectroscopy

Abstract

Chemical imaging of molecular decomposition processes at solid–liquid interfaces is a long-standing problem in achieving mechanistic understanding. Conventional analytical tools fail to meet this challenge due to the lack of required chemical sensitivity and specificity at the nanometer scale. In this work, we demonstrate that high-resolution hyperspectral tip-enhanced Raman spectroscopy (TERS) imaging can be a powerful analytical tool for studying on-surface decomposition chemistry at the nanoscale. Specifically, we present a TERS-based hyperspectral approach to visualize the on-surface decomposition process of a pyridine-4-thiol self-assembled monolayer on atomically flat Au(111) surfaces under ambient conditions. Reactive intermediates involved in the degradation process are spectroscopically detected with 5 nm spatial resolution. With supporting density functional theory simulations, a key species could be assigned to the disulfide reaction intermediate. This work opens a new application area for studying on-surface decomposition chemistry and related dynamics quantitatively at solid–liquid interfaces with nanometer spatial resolution.

Multipolar Raman Scattering vs Interfacial Nanochemistry: Case of 4-Mercaptopyridine on Gold

“…Spatial averaging of the TER spectra across the entire field of view shown in Figure b results in the red spectrum in Figure a. The spatiotemporally averaged spectrum is generally consistent with prior TER spectra of self-assembled monolayers of MPY. , It exhibits 4 predominant resonances at 1607, 1197, 1085, and 997 cm –1 . A vector representation of the displacements that lead to these resonances is shown toward the top of Figure a.…”

Nanoscale Chemical Imaging of Human Cell Membranes Using Tip‐Enhanced Raman Spectroscopy

“…This is achieved by combining SPM and surface‐enhanced Raman spectroscopy (SERS) to exploit the best of both worlds, i.e., the nanoscale spatial resolution of SPM and molecular specificity and sensitivity of SERS. [7] Over the last two decades, TERS has been successfully applied to characterize a variety of different samples, including heterogeneous catalysts, [8] two‐dimensional (2D) materials,[ 9 , 10 , 11 ] polymer blends, [12] organic photovoltaic devices, [13] supported lipid membranes, [14] decomposition chemistry, [15] self‐assembled organic monolayers, [16] solid–liquid interfaces, [17] and 2D reactive systems. [ 18 , 19 ] Compared to these applications, studying cell membranes is more challenging because of their chemical complexity, roughness, and low Raman cross‐section of membrane components.…”

Nanoscale chemical analysis of 2D molecular materials using tip-enhanced Raman spectroscopy

“…16 In the last two decades, tip-enhanced Raman spectroscopy (TERS) has emerged as a powerful analytical technique that combines the high spatial resolution of AFM or STM and the chemical sensitivity and specificity of surface-enhanced Raman spectroscopy (SERS) to study surface chemistry at the nanoscale in a label-free and non-destructive manner. [16][17][18][19] TERS has been successfully applied for nanoscale analysis in several areas of scientific research such as 2D materials including graphene, MoS 2 and WSe 2 and graphitic sheets, [20][21][22][23][24] onsurface decomposition chemistry, 25 polymer blends, 26 photocatalytic reactions, [27][28][29] organic solar cells, 30 supported lipid membranes, 31 biomembranes, 32 and biological cells. 33 In TERS, Raman scattering from a nanoscopic volume of the sample is plasmonically enhanced by several orders of magnitude owing to a highly intense and localised electromagnetic (EM) field, which is generated at the apex of a metallic SPM probe via a combination of localised surface plasmon resonance and lightening rod effect.…”