Developing non-noble-metal-based materials with an excellent surface-enhanced Raman scattering (SERS) effect is indispensable for cost-effective, fast and nondestructive detection of trace amounts of molecules. Two-dimensional metallic transition metal dichalcogenides (TMDCs) are emerging in SERS fields by virtue of their ultra-flat atomic surface, high surface activity and abundant density of states (DOS) near the Fermi level. However, how to further decrease the limits of detection of TMDCs substrates is crucial but very challenging. In this contribution, large-area NbSe₂ flakes from monolayer to few-layer are controllably synthesized via an ambient pressure chemical vapor deposition route. The ultrasensitive SERS effect of NbSe₂ is demonstrated by optimizing the layer-dependent structure–effect correlation both experimentally and theoretically. As a proof of concept, Rhodamine 6G (R6G) molecules with an ultralow concentration of 5 × 10⁻¹⁶ M can be detected on 6L-NbSe₂, which is five orders of magnitude lower than that on 1L-NbSe₂. The ultrasensitive SERS effect of few-layer NbSe₂ is attributed to the strong adsorption energy and efficient charge transfer between R6G and NbSe₂ with specific layers induced by the highest DOS at the Fermi level. Our study provides new insight into the molecular sensing research of 2D TMDCs and paves the way for designing ultrasensitive SERS substrates.

中文翻译：

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几层二硒化铌的超灵敏分子传感

开发具有出色的表面增强拉曼散射（SERS）效果的非贵金属基材料对于经济高效，快速且无损地检测痕量分子是必不可少的。二维金属过渡金属二卤化物（TMDC）由于其超平原子表面，高表面活性和费米能级附近的高态密度（DOS）而出现在SERS领域。但是，如何进一步降低TMDCs底物的检测限是至关重要的，但非常具有挑战性。通过这种贡献，通过环境压力化学气相沉积途径可控地合成了从单层到几层的大面积NbSe ₂薄片。NbSe ₂的超敏SERS效应通过在实验和理论上优化与层相关的结构效应相关性来证明这一点。作为概念证明，可以在6L-NbSe ₂上检测到超低浓度5×10 ^-16 M的若丹明6G（R6G）分子，该分子比1L-NbSe ₂低5个数量级。少层NbSe的超灵敏SERS效应₂归因于R6G和NbSe之间的强吸附能量和有效的电荷转移₂与费米能级诱导最高DOS特定层。我们的研究为2D TMDC的分子传感研究提供了新的见识，并为设计超灵敏SERS底物铺平了道路。