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Abstract Sub-nanometer-resolved TERS provides a systematic way for investigating tip-molecule interaction and molecular motions, enabling a promising approach to examine on-surface reaction mechanisms and catalysis at the microscopic level. 

Abstract The chemical interrogation of individual atomic adsorbates on a surface significantly contributes to understanding the atomic-scale processes behind on-surface reactions. However, it remains highly challenging for current imaging or spectroscopic methods to achieve such a high chemical spatial resolution. Here we show that single oxygen adatoms on a boron monolayer (i.e., borophene) can be identified and mapped via ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) with ~4.8 Å spatial resolution and single bond (B–O) sensitivity. With this capability, we realize the atomically defined, chemically homogeneous, and thermally reversible oxidation of borophene via atomic oxygen in UHV. Furthermore, we reveal the propensity of borophene towards molecular oxygen activation at room temperature and phase-dependent chemical properties. In addition to offering atomic-level insights into the oxidation of borophene, this work demonstrates UHV-TERS as a powerful tool to probe the local chemistry of surface adsorbates in the atomic regime with widespread utilities in heterogeneous catalysis, on-surface molecular engineering, and low-dimensional materials. 

Inspired by the success of graphene, two-dimensional (2D) materials have been at the forefront of advanced (opto-)nanoelectronics and energy-related fields owing to their exotic properties like sizable bandgaps, Dirac fermions, quantum spin Hall states, topological edge states, and ballistic charge carrier transport, which hold promise for various electronic device applications. Emerging main group elemental 2D materials, beyond graphene, are of particular interest due to their unique structural characteristics, ease of synthetic exploration, and superior property tunability. In this review, we present recent advances in atomic-scale studies of elemental 2D materials with an emphasis on synthetic strategies and structural properties. We also discuss the challenges and perspectives regarding the integration of elemental 2D materials into various heterostructures. 

Gaining valuable insight into chemistry-related fields, such as molecular and catalytic systems, surface science, and biochemistry, requires probing physical and chemical processes at the sub-nanoscale level. Recent progress and advancements in nano-optics and nano-photonics, particularly in scanning near-field optical microscopy, have enabled the coupling of light with nano-objects using surface plasmons with sub-nanoscale precision, providing access to photophysical and photochemical processes. Herein, this review highlights the basic concepts of surface plasmons and recent experimental findings of tip-assisted plasmon-induced research works and offers a glimpse into future perspectives.