Bicomponent supramolecular self‐assemblies studied with tip‐enhanced Raman spectroscopy

Abstract

The formation of well‐ordered supramolecular self‐assembly based on cytosine and 4,4′‐bipyridine on Ag(111) has been investigated with subnanometer‐resolved tip‐enhanced Raman spectroscopy (TERS) using a low‐temperature ultrahigh‐vacuum scanning tunneling microscope (STM). The co‐deposition of two molecules on the Ag(111) surface held at room temperature results in well‐ordered hydrogen‐bonded monolayer islands, which transform into well‐aligned double‐stranded chains after thermal annealing. Site‐dependent TERS spectra help to identify the packing structures of molecular assemblies. The changes of molecule‐specific vibrational fingerprints across the assemblies can be clearly monitored by combining high‐resolution TERS spectra with advanced multivariate analysis. Furthermore, the peak positions and relative intensities for characteristic vibrational modes of the two molecules are found to vary due to the changes of the local hydrogen bonding and interaction environment in different molecular samples. Our findings demonstrate that TERS is sensitive to the local molecular interactions, provides new potentials to monitor the functionality of molecular architectures on demand, and opens new opportunities to probe surface chemistry at the nanoscale.

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

“…They show that the TERS signal is sensitive to local molecular interactions and can provide new opportunities to monitor molecular processes and probe nanoscale surface chemistry and photocatalysis. [ 10 ]…”

“…They show that the TERS signal is sensitive to local molecular interactions and can provide new opportunities to monitor molecular processes and probe nanoscale surface chemistry and photocatalysis. [10] Oh, Nam, et al in their minireview, introduce key issues for quantitative SERS and present the fundamental SERS features obtained by single-particle analysis. They categorize the nanogap particle-based SERS platforms into two different classes: plasmonic nanogap structures with an intergap and plasmonic nanogap structures with an intragap.…”

Chemically imaging nanostructures formed by the covalent assembly of molecular building blocks on a surface with ultrahigh vacuum tip-enhanced Raman spectroscopy

“…By bringing Raman spectroscopy into the near-field, tip-enhanced Raman spectroscopy (TERS) enables the full characterization of molecules and low-dimensional materials at the subnanoscale [13][14][15]. It is especially sensitive to intermolecular interactions [16][17][18], binding conformations [19][20][21][22], molecule-substrate interactions [23,24], and even chemistry at the single-bond level [25][26][27], resulting in an ideal tool to consider the interactions and reactions that drive the formation of two-dimensional (2D) covalent networks on surfaces [28].…”

Introduction to the Journal of Raman Spectroscopy Emerging Investigators Special Issue

“…This has been especially true for imaging where rapid, real‐time, label‐free chemically specific targeting can be highly beneficial for biomedical applications. Zhang (Purdue, University, USA) 11 has reviewed recent achievements in Raman imaging using coherent anti‐Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) to study the quantity, distribution, composition, and dynamics of lipid droplets which are ubiquitous organelles found in most mammalian cells and play a pivotal role in various cellular functions. Hyper‐spectral CARS and SRS imaging in both cells and living organisms are discussed.…”