Understanding the lineshape of surface-enhanced infrared absorption spectra

• 作 者: Shunping Zhang Hongxing Xu
• 机 构: School of Physics and Technology, Center for Nanoscience and Nanotechnology, and Key Laboratory of A
• 出 处: 国家科学评论（英文版）
• 发表日期: 2021年4期

Infrared absorption spectroscopy offers fingerprint identification of molecular analytes through their vibrational or rotational degrees of freedom.However, the absorption cross-section of a single molecule is very small because the size of the molecule is far smaller than the wavelength of light, typically ranging from 2.5 to 25 μm.Therefore, infrared absorption experiments always require a large number of target molecules within the detection volume.Surface-enhanced infrared absorption (SEIRA) spectroscopy is a technique that typically uses metallic nanostructures to amplify absorption of the molecule, enabling detection of the analytes down to a trace amount [1].In most cases, this works via giant field enhancement in the vicinity of the metal surfaces, provided by the localized surface plasmons [2].However, the lineshape of SEIRA usually becomes complicated as the coupling of molecular vibrations and the plasmon gets stronger, which hampers accurate readout of the vibrational frequencies and spectral intensities for chemical identification or quantitative analysis.