Seo Jihyung, Lee Junghyun, Kim Yongchul, Koo Donghwan, Lee Geunsik, Park Hyesung
Department of Energy Engineering, School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Perovtronics Research Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
Nano Lett. 2020 Mar 11;20(3):1620-1630. doi: 10.1021/acs.nanolett.9b04645. Epub 2020 Feb 7.
Two-dimensional (2D) materials have been promoted as an ideal platform for surface-enhanced Raman spectroscopy (SERS), as they mitigate the drawbacks of noble metal-based SERS substrates. However, the inferior limit of detection has limited the practical applicability of 2D material-based SERS substrates. Here, we synthesize uniform large-area ReOS thin films via solution-phase deposition without post-treatments and demonstrate a graphene/ReOS vertical heterostructure as an ultrasensitive SERS platform. The electronic structure of ReOS can be modulated by changing the oxygen concentration in the lattice structure, obtaining efficient complementary resonance effects between ReOS and the probe molecule. In addition, the oxygen atoms in the ReOS lattice generate a dipole moment on the thin-film surface, which increases the electron transition probability. These synergistic effects outstandingly enhance the Raman effect in the ReOS thin film. When ReOS forms a vertical heterostructure on a graphene as the SERS substrate, the enhanced charge-transfer and exciton resonances improve the limit of detection to the femtomolar level, while achieving remarkable flexibility, reproducibility, and operational stability. Our results provide important insights into 2D material-based ultrasensitive SERS based on chemical mechanisms.
二维（2D）材料已被推崇为表面增强拉曼光谱（SERS）的理想平台，因为它们可减轻基于贵金属的SERS基底的缺点。然而，检测下限限制了基于二维材料的SERS基底的实际应用。在此，我们通过溶液相沉积合成了均匀的大面积ReOS薄膜，无需后处理，并展示了一种石墨烯/ReOS垂直异质结构作为超灵敏SERS平台。ReOS的电子结构可通过改变晶格结构中的氧浓度来调制，从而在ReOS与探针分子之间获得有效的互补共振效应。此外，ReOS晶格中的氧原子在薄膜表面产生偶极矩，这增加了电子跃迁概率。这些协同效应显著增强了ReOS薄膜中的拉曼效应。当ReOS在作为SERS基底的石墨烯上形成垂直异质结构时，增强的电荷转移和激子共振将检测下限提高到飞摩尔水平，同时实现了出色的柔韧性、可重复性和操作稳定性。我们的结果基于化学机制为基于二维材料的超灵敏SERS提供了重要见解。
