化学
开尔文探针力显微镜
基质(水族馆)
密度泛函理论
无定形固体
分子
化学物理
振动耦合
非金属
拉曼光谱
拉曼散射
半导体
纳米材料
纳米技术
光化学
计算化学
光电子学
材料科学
结晶学
光学
金属
地质学
物理
海洋学
有机化学
原子力显微镜
作者
Xiaotian Wang,Wenxiong Shi,Shaoxiong Wang,Hewei Zhao,Jie Lin,Yang Zhao,Mo Chen,Lin Guo
摘要
Substrate–molecule vibronic coupling enhancement, especially the efficient photoinduced charge transfer (PICT), is pivotal to the performance of nonmetal surface-enhanced Raman scattering (SERS) technology. Here, through developing novel two-dimensional (2D) amorphous TiO2 nanosheets (a-TiO2 NSs), we successfully obtained an ultrahigh enhancement factor of 1.86 × 106. Utilizing the Kelvin probe force microscopy (KPFM) technology, we found that these 2D a-TiO2 NSs possessed more positive surface potential than their 2D crystalline counterpart (c-TiO2 NSs). First-principles density functional theory (DFT) was used to further reveal that the low coordination number of surface Ti atoms and the large amount of surface oxygen defects endowed the 2D a-TiO2 with high electrostatic potential, which allowed significant charge transfer from the adsorbed molecule to the 2D a-TiO2 and facilitated the formation of a stable surface charge-transfer (CT) complex. Significantly, comparing with the 2D c-TiO2, the smaller band gap and higher electronic density of states (DOS) of the 2D a-TiO2 effectively enhanced the vibronic coupling of resonances in the substrate–molecule system. The strong vibronic coupling within the CT complex obviously enhanced the PICT resonance and lead to the remarkable SERS activity of a-TiO2 NSs. To the best of our knowledge, this is the first report on the remarkable SERS activity of 2D amorphous semiconductor nanomaterials, which may bring the cutting edge of development of stable and highly sensitive nonmetal SERS technology.
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