面向农药检测的复合SERS基底微纳加工技术研究

Surface–enhanced Raman scattering (Surface Enhanced Raman Scattering, SERS) induced by metal micro/nanostructures and two–dimensional materials has greatly promoted the application of the Raman spectroscopy in the field of the detection of chemical pesticide molecule. The fabrication of the composite substrate has become a research hotspot due to the high detection resolution of the composite substrate. However, there are still some shortcomings for nanofabrication methods, including the few suitable machining material and a low processing efficiency, such as electron beam and focused ion beam. The application of composite SERS substrates is limited by using nanofabrication methods. Therefore, the project first proposes a novel method based on the micro/nanoindentation, nanoparticle and graphene to fabricate composite SERS substrate. The intensity and the distribution of electric field with different micro/nanostructures, nanoparticles and graphene are revealed through theoretical simulation, and a relatively optimized composite SERS substrate is obtained. Then, the parameters of machining are optimized and the influence of micro/nanostructures is revealed for the Raman intensities. In addition, the enhancement mechanism of the composite SERS substrate structure is revealed by the detection of R6G molecules. The rhodamine 6G (R6G) is used as a marker to study the effects of the dimensional characteristics of the arrayed mirco/nanostructures on the composite SERS–active substrate on the intensity enhancement of the Raman signals. Finally, the optimized composite substrate is applied to detect chemical pesticide molecules. Generally, this project will contribute to a wider application of the Raman spectroscopy technique in the field to detect chemical pesticide molecules.

由金属微纳结构和二维材料复合而产生的表面增强拉曼散射(SERS)，极大地推动了拉曼光谱技术在化学农药分子检测领域的应用。由于复合基底具有检测分辨率高的优点，因而复合基底的制备成为了研究的热点。目前，采用纳米加工方法（电子束和聚焦离子束）存在可加工的基体材料少和效率低的特点，限制了其在复合SERS基底制备方面的应用。因此，本项目首先提出一种基于微纳压痕结构、纳米粒子和石墨烯相结合的制备复合基底的新方法。通过理论仿真，揭示不同微纳压痕结构、纳米粒子以及石墨烯共同耦合作用下的电场强度和电场分布规律，获得相对优化的复合基底结构，并优化加工工艺，揭示微纳结构形貌对拉曼信号强度的影响规律。此外，通过对R6G分子的检测，揭示复合基底表面上的微纳结构对其拉曼信号的增强机制，并将优化后的复合SERS基底应用于化学农药分子的检测。本项目的研究成果将促进拉曼光谱技术更加广泛地应用到化学农药分子的检测领域。

拉曼光谱作为表征分子振动的指纹光谱，已经被广泛地应用在食品安全领域。通常利用具有微纳结构的金属（金、银、铜）表面来增强拉曼信号的强度，而二维材料（石墨烯或二硫化钼）具有提高对目标分析物的化学吸附作用，有助于提高基底表面检测分析物的分辨率。当前，SERS基底表面微纳结构、二维材料及二者耦合作用对拉曼光谱增强的影响规律及复合SERS基底制备成为了国内外学者研究的热点和难点问题。本项目提出了一种基于纳米压痕、纳米粒子和石墨烯相结合的制备复合SERS基底的新方法，并将该基底用于农药分子的检测。其项目取得的成果如下：首先，采用多物理场仿真建立了微结构阵列、金纳米粒子数量、相邻粒子间距及石墨烯耦合关系对电场和热点分布的影响规律，获得了不同结构形状、结构间距、沟槽角度、结构深度和宽度等参数对拉曼信号的增强机制。第二，研究了复合SERS基底的加工工艺，提出了在铜基石墨烯表面上采用不同针尖形状实现压痕叠加制备复杂微纳结构的新方法，获得了力控制信号特征、压痕间距、材料特性、探针形状等对加工结果的影响规律。并结合镀膜技术实现了复合SERS基底要求的大范围规则微纳点阵结构的高效率加工。揭示了加工参数对石墨烯层数的影响规律。第三，以R6G为探针分子，对复合SERS基底进行拉曼测试，优化复合SERS基底结构，获得了复合SERS基底对R6G分子拉曼信号效果及增强因子的影响规律。同时，以孔雀石绿、百草枯和西维因等化学农药分子为研究对象，采用优化后的复合SERS进行测试。其中，选择圆锥压痕结构(Cone1)能够分别检测10-9mol/L孔雀石绿溶液和10-5mol/L的百草枯溶液，均达到了国家标准(GB 2763.1–2018)。本项目提出的制备复合SERS基底的新方法，为解决食品安全领域具有重要的科学意义。