Xie Songyang, Chen Dong, Gu Chenjie, Jiang Tao, Zeng Shuwen, Wang Ying Ying, Ni Zhenhua, Shen Xiang, Zhou Jun
The Photonic Research Institute, Ningbo University, No. 818 Fenghua Road, Ningbo 315211, China.
XLIM Research Institute, CNRS/University of Limoges, Avenue Albert Thomas, 87060 Limoges, France.
ACS Appl Mater Interfaces. 2021 Jul 21;13(28):33345-33353. doi: 10.1021/acsami.1c03848. Epub 2021 Jul 7.
By virtue of their high uniformity and stability, metal oxide-based surface-enhanced Raman spectroscopy (SERS) substrates have attracted enormous attention for molecular trace detection. However, strategies for further enhancing the SERS sensitivity are still desired. Herein, MoO/WO nano-heterojunctions are constructed by mixing MoO and WO together (MoO/WO hybrid) with diverse weight ratios. Using a 532 nm laser as the excitation source and R6G as the Raman reporter, it is shown that the Raman signal intensity (for the peak @ 1360 cm) obtained on the optimal MoO/WO hybrid (MoO/WO = 1:1/3) is twice that observed on a pure MoO or WO substrate. Moreover, a limit of detection of 10 M and an enhancement factor of 10 are achieved. In the SERS enhancement mechanism investigation, it is revealed that MoO and WO form a staggered band structure. During the SERS measurement, electron-hole pairs are generated in the nano-heterojunction using the incident laser. They are then separated by the built-in potential with the electrons moving toward WO. The accumulated electrons on WO are further transferred to the R6G molecules through the coupling of orbitals. Consequently, the molecular polarizability is amplified, and SERS performance is enhanced. The abovementioned explanation is supported by the evidence that the contribution of the chemical enhancement mechanism in the optimal MoO/WO hybrid substrate is about 2.5 times or 5.9 times that in the pure WO or MoO substrate.
基于金属氧化物的表面增强拉曼光谱（SERS）基底因其高度的均匀性和稳定性，在分子痕量检测方面引起了广泛关注。然而，仍需要进一步提高SERS灵敏度的策略。在此，通过将MoO和WO以不同重量比混合在一起（MoO/WO混合物）构建了MoO/WO纳米异质结。使用532 nm激光作为激发源，R6G作为拉曼报告分子，结果表明，在最佳MoO/WO混合物（MoO/WO = 1:1/3）上获得的拉曼信号强度（对于1360 cm处的峰）是在纯MoO或WO基底上观察到的两倍。此外，实现了10 M的检测限和10的增强因子。在SERS增强机制研究中，发现MoO和WO形成了交错能带结构。在SERS测量过程中，利用入射激光在纳米异质结中产生电子-空穴对。然后它们被内建电势分离，电子向WO移动。WO上积累的电子通过轨道耦合进一步转移到R6G分子上。因此，分子极化率被放大，SERS性能得到增强。上述解释得到了以下证据的支持：在最佳MoO/WO混合基底中化学增强机制的贡献约为纯WO或MoO基底中的2.5倍或5.9倍。
