可调谐的声学型石墨烯等离激元增强纳米红外光谱  

Tunable acoustic graphene plasmon enhanced nano-infrared spectroscopy

作　　者：段谕 戴小康 吴晨晨 杨晓霞[2,3] Duan Yu;Dai Xiao-Kang;Wu Chen-Chen;Yang Xiao-Xia(Henan Institute of Advanced Technology,Zhengzhou University,Zhengzhou 450001,China;CAS Key Laboratory of Nanophotonic Materials and Devices,CAS Key Laboratory of Standardization and Measurement for Nanotechnology,CAS Center for Excellence in Nanoscience,National Center for Nanoscience and Technology,Beijing 100190,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]郑州大学,河南先进技术研究院,郑州450001 [2]国家纳米科学中心,中国科学院纳米科学卓越创新中心,中国科学院纳米光子材料与器件重点实验室,中国科学院纳米标准与检测重点实验室,北京100190 [3]中国科学院大学,材料与光电研究中心,北京100049

出　　处：《物理学报》2024年第13期336-345,共10页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2023YFA1407003);国家自然科学基金(批准号:52022025,51972074);中国科学院青年团队计划(批准号:YSBR-086);中国科学院青年创新促进会资助的课题。

摘　　要：纳米红外光谱(nano-infrared spectroscopy,nano-IR)技术能够突破光的衍射极限,实现约10 nm空间分辨率的红外光谱检测,是研究纳米尺度物质化学成分和结构的重要技术手段.然而,由于纳米物质的尺寸与红外光的波长存在较大失配,导致其红外吸收信号微弱.本文理论提出了一种基于纳米腔室的声学型石墨烯等离激元(nanocavity-acoustic graphene plasmon,n-AGP)可调谐增强nano-IR检测平台.该平台可实现超高光场压缩(模式体积Vn-AGP≈10-7λ_(0)~3,λ_(0)=6.25μm)和约50倍电场增强的n-AGP激发.通过调控金纳米腔室结构和石墨烯费米能级,我们实现了n-AGP的宽频段动态调控(1290—2124 cm^(-1)).此外,由于n-AGP的电磁场高度局域在纳米腔室内,具有高的探测灵敏度,可实现单个蛋白质颗粒酰胺Ⅰ带和酰胺Ⅱ带振动指纹特征的探测(灵敏度提高约9倍).这一基于n-AGP的增强结构拓展了nano-IR技术在单分子尺度的表征能力,可广泛应用于生物、催化等领域.Nano-infrared spectroscopy(nano-IR)technology can exceed the diffraction limit of light,achieving infrared spectroscopic detection with a spatial resolution of about 10 nm,which is an important technical means for studying the chemical composition and structure of molecules on a nanoscale.However,the weak infrared absorption signals of nanoscale materials pose a significant challenge due to the large mismatch between their dimensions and the wavelength of infrared light.The infrared absorption signals of molecular vibrational modes are proportional to the squares of the electromagnetic field intensities at their positions,implying that higher electromagnetic field intensity can significantly improve the sensitivity of molecular detection.Acoustic graphene plasmons(AGPs),excited by the interaction between free charges in graphene and image charges in metal,exhibit strong optical field localization and electromagnetic field enhancement.These properties make AGPs an effective platform for enhancing nano-IR detection sensitivity.However,the fabrication of graphene nanostructures often introduces numerous edge defects due to the limitations of nano fabrication techniques,significantly reducing the electromagnetic field enhancement observed in experiments.Here,we use finite element simulation to theoretically propose a tunable enhanced nano-IR detection platform based on nanocavity-acoustic graphene plasmons(n-AGPs),which utilizes a graphene/air gap/gold nanocavity structure.This platform avoids needing the nanofabrication of graphene,thereby preventing defects and contamination from being introduced in processes such as electron beam exposure and plasma etching.By plotting the dispersion of n-AGP,it is found that n-AGP has a high wavelength compression capability comparable to AGP(λ_(0)/λ_(AGP)=48).Additionally,due to the introduction of the gold nanocavity structure,n-AGP possess an extremely small mode volume(V_(n-AGP)≈10~(-7)λ_(0)~3,λ_(0)=6.25μm).By calculating the electric field intensity distribution(|E_(n

关 键 词：石墨烯 纳米腔室 等离激元 表面增强红外光谱 

分 类 号：O657.33[理学—分析化学] TQ127.11[理学—化学]