Surface-Enhanced Raman Scattering Monitoring of Oxidation States in Defect-Engineered Two-Dimensional Transition Metal Dichalcogenides

Abstract

Recent studies have found that some transition metal dichalcogenides (TMDs) with their own defects are difficult to store in the air for a long time. Worse stability of TMDs under extreme conditions has also been reported. Therefore, monitoring the oxidation and degradation processes of TMDs can directly guide the stability prediction of TMD-based devices and monitor TMDs quality. Herein, with the case of molybdenum disulfide, UV–ozone defect engineering is used to simulate the oxidation and degradation of TMDs under severe conditions. Surface-enhanced Raman scattering based on a chemical mechanism was first introduced to the dynamic monitoring of defect evolution in the oxidation and degradation of TMDs, and succeeds in tracking the TMDs oxidation state by the quantitative method. It is expected that this technology can be extended to the quantification and tracking of oxidation and degradation of other 2D materials.

Synthesis of Single- and Few-Layer Nitrogen-doped Graphene and Layer-Dependent Surface-Enhanced Raman Scattering Properties

“…A-terms are the molecule HOMO to the VB edge and the VB edge to molecule LUMO charge transfer. B- and C-terms consider the coupling of photoinduced charge transfer and μ ex or μ mol by Herzberg–Teller coupling . μ ex and μ mol are charge transfers from VB to CB of NG and HOMO to LUMO of R6G, respectively.…”

“…Since the discovery of graphene in 2004, two-dimensional (2D) layered materials have received great attention due to their unique mechanical, thermal, optical, and electrical properties. − Nowadays, 2D materials (e.g., graphene − and transition metal dichalcogenides) have been considered as promising candidates for next-generation SERS platforms due to their atomic uniformity, biological compatibility, seamless structure, atomic thickness, and chemical inertness. Studies have shown that CM plays a major role in the SERS of 2D materials and the fluorescence background of molecules can be effectively quenched by 2D materials. ,, However, the enhancement factor and limit of detection of 2D substrates are still not high enough, e.g., detection limit of MoS 2 is above 10 –7 M. To increase the enhancement factor of SERS for 2D materials, various defect engineering schemes are developed. For example, the MoS 2 -molecular interaction is magnified by oxygen incorporation-assisted strategies .…”

The origin of ultrasensitive SERS sensing beyond plasmonics

“…Glass et al reported that semiconductor-based SERS enhancements could be used as a direct method of surface oxygen vacancies concentration quantification [198]. Besides, our group reported that the oxidation process of ultraviolet-ozone-treated MoS 2 could be successfully monitored by using plasmon-free SERS technology [134]. During the oxidation process, the changes in energy bands caused by defects in MoS 2 would remarkably affect SERS.…”

Evolution of spectroscopy features in layered MoSxSe(2-x) solid solutions

“…CVD techniques for the growth of monolayer MX 2 -type structures have seen a huge progress in the last few years and show remarkable results [21][22][23]. For example, a simple method to synthetize Mo-W alloyed triangular monolayers [24] with a wide range of stoichiometry morphologies has been achieved by varying CVD conditions, like the introduction of Se together with S during the growth to produce changes in the bandgap of the monolayers [25][26][27][28] and photoluminescence (PL) emission. Another technique utilizes a pre-seeding strategy, where tungsten oxide nanoparticles are used to coat the substrate surface in order to get a uniform single layer growth [8].…”

“…For both bulk and monolayer crystals, the simultaneous incorporation of chalcogen atoms like Se and S, or transition metal atoms like W and Mo, have a definitive impact on the morphology and electronic properties. It is precisely the stoichiometric ratios that determine the vibrational behavior of the layers and whose normal modes of vibration are perceptible using spectroscopic techniques [27,[33][34][35][36]. In this work, we study spectroscopic features of MoS x Se 2-x bulk crystals.…”