石墨烯覆盖铝纳米光栅表面等离激元共振光谱及传感特性

Resonance Spectra and Sensing Characteristics of Plasmons in Graphene-Covered Aluminum Nano-Grating

表面等离激元共振技术具有无需标记、灵敏度高、实时检测等优点,已广泛应用于生物医疗、环境监测及食品安全等领域。相对于传统贵金属材料表面等离激元共振传感器而言,铝表面等离激元共振传感器具有价格低廉、共振光谱带宽小等优点,已逐渐成为了该领域的研究热点。针对铝材料存在与生物分子兼容性差、易氧化等缺点,利用石墨烯化学稳定性好、比表面积大、抗氧化能力强、生物兼容性好等独特优势,将其作为与被测分子直接接触的传感层,提出了一种石墨烯覆盖铝纳米光栅的表面等离激元共振传感器。首先,基于多物理场有限元仿真软件建立了该传感器的物理模型,分别分析了石墨烯层数和铝光栅结构参数(占空比、高度、周期)对传感器共振光谱的影响。结果表明,石墨烯与铝光栅的复合有效增强了入射光波与传感器的相互作用,采用单层石墨烯与铝光栅复合时,共振峰具有最窄的光谱带宽。当铝纳米光栅结构Λ=600nm,H=40nm,η=70%时,光谱反射率为零。进一步分析了结构优化后的传感器的传感特性。结果表明,单层石墨烯覆盖铝纳米光栅传感器具有最高的品质因数24.5RIU^(-1),其灵敏度高达626nm·RIU^(-1)。该传感器具有探测精度高、分子兼容性好等优点,能为生化分析、环境监测和食品安全等领域提供一个新的绿色传感平台。

Combining with the extraordinary advantages of fast-speed,label-free,high sensitivity,and real-time results,surface plasmon resonance（SPR）technology has been widely used in fields such as biochemical analysis,environmental monitoring and food safety as well as in many other aspects.In contrast to the SPR sensors utilizing the traditional noble metals（gold,silver）,SPR sensors based on aluminum plasmonic have recently drawn researchers＇ interests in these fields due to its superior features of low cost,narrow spectral bandwidth and amenability to manufacturing processes.However,aluminum exhibits the intrinsic shortcomings of bad biocompatibility and easy oxidation,which severely limit its applications.To address this problem,a surface plasmon resonance sensor based on graphene-covered aluminum nano-grating is proposed.A monolayer graphene is employed as the sensing layer that can contact directly with the molecular to be measured,because it emerged as a revolutionary two-dimensional material that shows the attractive properties of good chemical stability,large surface volume ratio,strong anti-oxidation ability,and excellent biocompatibility.Firstly,aphysical model of the sensor is built based on finite element method employing COMSOL multiphysics,and the influence of the graphene layers and structure parameters of aluminum nano-grating（occupation ratio,height,and period）on the resonance spectral characteristics is investigated.Simulation results show that the coating of the graphene on the aluminum nano-grating exhibits strongly enhanced interaction between incident light and the device.Moreover,the resonance spectrum possesses the narrowest bandwidth when the aluminum nano-grating is covered by a monolayer graphene,and the reflectance of resonance spectrum is zero when the structure parameters of nano-grating are Λ=600nm,H =40nm and η=70%,respectively.Secondly,we further investigate the sensing characteristic of the sensor with optimized structure parameters.The results demonstrate that the sensor with a monolayer graphene covered on aluminum nano-grating obtains the highest figure of merit of 24.5RIU（-1）,and the corresponding sensitivity is 626nm·RIU（-1）.Such a SPR sensor with high sensitivity and good biocompatibility provides a green platform for applications in fields such as biochemical analysis,environmental monitoring and food safety monitoring.