光谱学与光谱分析, 2020, 40 (7): 2116, 网络出版: 2020-12-04  

基于硅基微纳结构衬底的光操控-表面增强拉曼光谱方法研究

Surface-Enhanced Raman Scattering with Au Nanoparticles Optically Trapped by a Silicon-Based Micro-Nano Structure Substrate
作者单位
中国海洋大学青岛市光学光电子重点实验室, 山东 青岛 266100
摘要
表面增强拉曼散射(SERS)增强基底的制备是实现SERS技术高灵敏度探测的关键因素, 利用光操控技术制备金属纳米粒子聚集体是近来SERS领域研究的热点。 利用飞秒激光湿法刻蚀技术, 在硅片表面5 mm×5 mm范围内刻蚀横截面积(宽度×深度)为10 μm×7 μm, 30 μm×12 μm, 60 μm×15 μm, 70 μm×19 μm和90 μm×21 μm的狭槽线阵, 制备截面积不同的微纳硅基衬底(SiMS)。 应用光操控技术结合SERS方法, 在金纳米溶胶中加入硅基衬底。 并将激光对焦在衬底狭槽内, 在光辐射压力的作用下, 金纳米粒子沿光束的传播方向运动, 聚集于微纳结构表面的狭槽内, 形成金纳米粒子聚集体, 促进“热点”效应, 提高SERS探测的灵敏度, 实现了在硅基微纳结构衬底上探测物的SERS增强。 实验表明, 利用光辐射压力和光梯度力的合力, 金属纳米粒子能有效聚集在硅基微纳结构衬底表面的狭槽中, 形成更多的“热点”, 从而可大幅提高SERS增强效果。 以芘为探针分子, 随着狭槽截面积的增加, SERS信号逐渐增强, 狭槽截面积为70 μm×19 μm时达到最强, 超过该截面积后, 拉曼信号强度开始降低, SERS强度最高增强了约两个数量级, 最低检测浓度为5.0×10-9 mol·L-1, 在低浓度范围内(5.0×10-9~1.0×10-7 mol·L-1), 芘位于588和1 234 cm-1处特征峰强与浓度的关系曲线呈现较好的线性相关性, 其拟合方程及线性相关系数分别为0.992和0.971。 以截面积为70 μm×19 μm的微纳衬底进行了重复性实验, 每完成一次实验, 关掉激光器, 待激光的作用消失, 狭槽内聚集的金纳米粒子重新分散在溶液中, 进行下一次实验。 选取微纳衬底8个不同位置, 每个位置重复三次实验, 衬底不同位置芘的588和1 234 cm-1两个特征峰峰强的相对标准偏差(RSD)分别为9.9%和2.0%, 具有较好的重复性。 与仅使用金纳米颗粒相比, 该方法保留了金纳米颗粒重复性好的优势, 同时具有更高的增强效应和衬底清洗后可重复使用的优点。 研究表明, 基于硅基微纳结构衬底的光操控-SERS方法, 可极大地提高金纳米颗粒的SERS效应, 在化学和生物学等领域的物质检测分析方面具有广阔的应用前景。
Abstract
It is very important to prepare high sensitive surface enhanced Raman scattering (SERS) substrates in the SERS detection process. The preparation of metal nanoparticle aggregates by light manipulation technology is a hot topic in the field of SERS. In this paper, femtosecond laser wet etching technology was used to etch slot array with the cross-sectional area (width×depth) of 10 μm×7 μm, 30 μm×12 μm, 60 μm×15 μm, 70 μm×19 μm, 90 μm×21 μm in the range of 5 mm×5 mm on the surface of silicon wafer, a Silicon-based micro-nano structure substrate (SiMS) with the different cross-sectional area was prepared. SERS enhancement of analytes on the substrates was achieved using optical manipulation techniques combined with SERS technique. The laser was focused on the substrate slot, due to the action of the light radiation pressure, the gold nanoparticles move along the direction of the beam propagation and accumulate in the slots on the surface of the structure to form gold nanoparticle aggregates, which promote “hot spots” effect. The sensitivity of the SERS detection was improved, and the SERS enhancement of the probe on the substrates was achieved. Experiments show that the metal nanoparticles can effectively accumulate in the slot on the surface of the SiMS when the optical radiation pressure is greater than the optical gradient force, forming more “hot spots”, which can greatly improve the SERS enhancement effect. The SERS signal of pyrene is gradually enhanced with the increase of the cross-sectional area of the slot, the enhancement effect of the slot with width and depth of 70×19 μm2 was the best, SERS intensity of pyrene was increased by about two magnitudes, and the minimum detection concentration was 5.0×10-9 mol·L-1. Beyond this cross-sectional area, the SERS intensity begins to decrease. The lowest detection concentration of pyrene is 5.0×10-9 mol·L-1. In the low concentration range (5.0×10-9~1.0×10-7 mol·L-1). It demonstrated a good linear correlation between the SERS intensity of characteristic peaks at 588 and 1 234 cm-1 and concentration, and the fitting equation and linear correlation coefficient were 0.992 and 0.971, respectively. The SiMS with a cross-sectional area of 70×19 μm2 was used for repetitive experiments, and eight different positions on the substrate were selected. After each position was measured, the laser was switched off and the action of the laser was disappeared, the gold nanoparticles were re-dispersed in the solution. Three measures were repeated for each position. The relative standard deviation (RSD) of the two peaks at 588 and 1 234 cm-1 at different positions of the substrate were 9.9% and 2.0%, respectively, which showed good repeatability. The study showed that the SERS effect could be greatly improved by the optical manipulation-SERS method based on the SiMS and this method has potential for application in the detection and analysis of materials in fields such as chemistry and biology.

张旭, 辛坤, 史晓凤, 马君. 基于硅基微纳结构衬底的光操控-表面增强拉曼光谱方法研究[J]. 光谱学与光谱分析, 2020, 40(7): 2116. ZHANG Xu, XIN Kun, SHI Xiao-feng, MA Jun. Surface-Enhanced Raman Scattering with Au Nanoparticles Optically Trapped by a Silicon-Based Micro-Nano Structure Substrate[J]. Spectroscopy and Spectral Analysis, 2020, 40(7): 2116.

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