Structural control and element doping are two popular strategies to produce semiconductors with surface enhanced Raman spectroscopy (SERS) properties. For TiO 2 based SERS substrates, maintaining a good crystallinity is critical to achieve excellent Raman scattering. At elevated temperatures (> 600 °C), the phase transition from anatase to rutile TiO 2 could result in a poor SERS performance. In this work, we report the successful synthesis of TiO 2 nanowhiskers with excellent SERS properties. The enhancement factor, an index of SERS performance, is 4.96 × 10 6 for methylene blue molecule detecting, with a detection sensitivity around 10 −7 mol·L −1. Characterizations, such as XRD, Raman, TEM, UV–vis and Zeta potential measurement, have been performed to decrypt structural and chemical characteristics of the newly synthesized TiO 2 nanowhiskers. The photo absorption onset of MB adsorbed TiO 2 nanowhiskers was similar to that of bare TiO 2 nanowhiskers. In addition, no new band was observed from the UV–vis of MB modified TiO 2 nanowhiskers. Both results suggest that the high enhancement factor cannot be explained by the charge-transfer mechanism. With the support of ab initio density functional theory calculations, we reveal that interfacial potassium is critical to maintain thermal stability of the anatase phase up to 900 °C. In addition, the deposition of potassium results in a negatively charged TiO 2 nanowhisker surface, which favors specific adsorption of methylene blue molecules and significantly improves SERS performance via the electrostatic adsorption effect.
Bibliographical note© 2019, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Funding: Natural Science Foundation of China (21878143, 21476106, and 21838004), Joint Re-search Fund for Overseas Chinese Scholars and Scholars in Hong Kong and Macao Young Scholars (21729601), the fund of State Key Laboratory of Materials-Oriented Chemical Engineering (ZK201702, KL16-01), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the U.S. National Science Foundation (NSF) Grant No. CHE-1710102.
- TiO nanowhisker
- potassium induced