Raman enhancement on nonmetallic flat two-dimensional (2D) nanomaterial surfaces has attracted a great deal of attention since the discovery of graphene-enhanced Raman scattering. Molybdenum disulfide (MoS₂) is a flat 2D nanomaterial with unique electronic and physical properties that can be applied in surface-enhanced Raman spectroscopy (SERS). Herein, we report a lithium-exfoliated MoS₂ (Li-MoS₂) has a metallic phase content of about 70%, which is three times higher than the metallic phase content of 20% in thioglycolic acid-exfoliated MoS₂ (T-MoS₂). Li-MoS₂ therefore displays a 2–3 fold increase in the Raman signal for rhodamine 6G (R6G) used as an analyte. Furthermore, the conjugation of a thiol-terminated alkyne with Li-MoS₂ also provided a greater SERS signal at 2123 cm⁻¹ than that of T-MoS₂. A defect-rich metallic MoS₂ monolayer can therefore be used as the perfect substrate for surface-enhanced Raman scattering, although pristine MoS₂ hardly exhibits an SERS effect. This study proved that (1) defect-rich metallic MoS₂, (2) dipole–dipole interactions, and (3) the enhanced charge transfer effect of MoS₂ monolayers are the three primary and essential parameters for enhancing the Raman signals of analytes on MoS₂. Key observations include the fact that some alkyne groups were directly coordinated to the edges of Li-MoS₂ defect sites, which shifted the alkyne signal to 2153 cm⁻¹ in alkyne spectral mapping. More importantly, to quantify the SERS performance of Li-MoS₂, SERS imaging of live cells was demonstrated using the unique alkyne signal at 2123 cm⁻¹.

中文翻译：

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炔烃共轭MoS _2的表面增强拉曼散射：金属和半导体相之间的比较研究†

自从发现石墨烯增强的拉曼散射以来，非金属平面二维（2D）纳米材料表面上的拉曼增强已经引起了广泛的关注。二硫化钼（MoS ₂）是具有独特电子和物理特性的平面2D纳米材料，可应用于表面增强拉曼光谱（SERS）。在此，我们报道了锂剥落的MoS ₂（Li-MoS ₂）的金属相含量约为70％，是巯基乙酸剥落的MoS ₂（T-MoS）的20％的金属相含量的三倍。₂）。钼酸锂₂因此，用作分析物的若丹明6G（R6G）的拉曼信号显示增加了2-3倍。此外，硫醇封端的炔与Li-MoS ₂的共轭在2123 cm ^-1处也比T-MoS ₂提供了更大的SERS信号。尽管原始的MoS ₂几乎不表现出SERS效应，但是富含缺陷的金属MoS ₂单层可以用作表面增强拉曼散射的理想基材。这项研究证明（1）富含缺陷的金属MoS ₂；（2）偶极-偶极相互作用；（3）增强的MoS ₂电荷转移效应单层是增强MoS ₂上分析物拉曼信号的三个主要和必要参数。关键观察结果包括以下事实：一些炔烃基团直接与Li-MoS ₂缺陷位点的边缘协调，这在炔烃光谱映射中将炔烃信号转移到2153 cm ^-1。更重要的是，为了量化Li-MoS ₂的SERS性能，使用2123 cm ^-1处独特的炔烃信号对活细胞进行SERS成像。