具有双共振吸收峰的Au纳米粒子制备及其拉曼表征

表面增强拉曼散射(SERS)很大程度的弥补了拉曼散射强度弱的缺点，迅速成为科研工作者们的研究热点，在食品安全、环境污染、毒品以及爆炸物检测等领域应用广泛。纳米技术的发展使得目前对于SERS的研究主要集中于金属纳米颗粒基底的制备，金属纳米粒子的种类、尺寸及形貌对SERS增强和吸收峰峰位均有影响，要获得好的增强效果，需要对金属纳米结构进行工艺优化。特别是，需要结合金属纳米粒子的结构和激励光波长，以期获得更好的增强效果。为了研究SERS增强和吸收峰之间的关系，开展了具有双共振吸收峰的金属纳米粒子的研究。首先利用FDTD Solutions仿真建模，主要针对金纳米颗粒直径、金纳米棒长径比及分布状态对共振吸收峰进行仿真，得到金纳米球理论直径在50 nm左右，金纳米棒理论长径比在3.5~4.5左右时，吸收峰分别分布在532及785 nm附近，符合多波段激励光拉曼增强条件；对于激励光偏振方向，其沿金纳米棒长轴方向偏振时吸收峰位于785 nm附近，沿金纳米球短轴方向偏振时吸收峰位于532 nm附近。然后采用种子生长法，制备了可用于多种波长激励光的双吸收峰表面增强拉曼散射基底。通过改变硝酸银用量(5，10，20，30和40 μL)、盐酸用量(0.1和0.2 mL)以及其生长时间(15，17，21和23 h)等多种工艺参数来控制金纳米棒含量，得到了同时含有金纳米球及金纳米棒的双吸收共振峰金纳米粒子。最后用该样品作为基底，罗丹明6G(R6G)作为探针分子，分别测试其在532，633和785 nm激励光入射时的SERS表征，对分析物R6G最低检测浓度均达到了10-7 mol·L-1，增强因子达到了~105，满足了多波段SERS检测的需要。

Effects of Process Parameters on Double Absorption Resonance Peaks of Au Nanoparticles

Surface-enhanced Raman scattering(SERS)largely compensates for the shortcoming of the weak intensity of Raman scattering and quickly becomes a research hotspot for researchers.It is widely used in food safety,environmental pollution,drug and explosive detection and other fields.Due to nanotechnology’s development,the current research on SERS mainly focuses on the preparation of metal nanoparticle substrates.The type,size,and morphology of metal nanoparticles all affect the SERS enhancement and absorption peak positions.It is necessary to optimize the process of metal nanostructures.In particular,it is necessary to combine the structure of the metal nanoparticle and its corresponding excitation light wavelength to obtain a better enhancement effect.A study of metal nanoparticles with double resonance absorption peaks was conducted to get the relationship between SERS enhancement and absorption peaks.Firstly,through FDTD Solutions,the local surface plasmon resonance peaks of gold nanoparticles with different diameters,gold nanorods with different aspect ratios and distributions were simulated.We found that when Au nanoparticles’theoretical diameter is about 50 nm and the theoretical aspect ratio of Au nanorods is about3.5~4.5,the absorption peaks are distributed near 532 and 785 nm,respectively,which meets the multi-band excitation light Raman enhancement conditions.For the polarization direction of the excitation light,when the light polarization direction is along the long axis direction of Au nanorods,the absorption peak is near 785 nm,and when the light polarization direction is along the short axis of Au nanorods,the absorption peak is near 532 nm.A double-absorption SERS substrate that can be used for excitation light of various wavelengths was prepared by the seed growth method.In order to control the forming rate of Au nanorods,the process parameters were optimized,including the silver nitrate(5,10,20,30,40μL),the hydrochloric acid(0.1,0.2 mL)and the growth time(15,17,21,23 h).Double-absorption resonance peaks containing Au nanoparticles and Au nanorods were successfully obtained.Finally,using this sample as the substrate and Rhodamine 6 G(R6G)as the probe molecule,the SERS characterization of the excitation light at 532,633 and 785 nm was tested,achieving the multiple wavelength SERS detection with a concentration of 10^-7 mol·L^-1 of R6 G,and the enhancement factor is~105.