Overview: Surface-Enhanced Raman spectroscopy (SERS) is a highly sensitive and high-resolution molecular recognition technique with important applications in many fields. As an emerging low-cost, high-resolution, and highflexibility micro-nano processing method, femtosecond laser direct writing has been widely used in the field of preparing SERS substrates. Compared with traditional processing methods for preparing SERS substrates, femtosecond laser direct writing processing has certain advantages in terms of flexibility, three-dimensional molding, processing material range, processing accuracy, and other aspects. In this review, we classify the processing methods of femtosecond laser preparation of SERS substrates into four categories, including femtosecond laser two-photon metal reduction, femtosecond laser cutting metal, femtosecond laser cutting-sputtering, and femtosecond laser 3D printing. Femtosecond laser two-photon metal reduction uses the two-photon reduction effect to reduce metal cations in metal solutions to metals, such as silver ions in silver nitrate solutions to silver nanoparticles. This method is suitable for the one-step preparation of SERS substrates in closed microchannels. Femtosecond laser cutting metal directly prepares the SERS substrate structure on a metal substrate. This method takes advantage of the high peak power of the femtosecond laser to ablate the surface of the metal sample to obtain a patterned surface structure. At the same time, femtosecond laser ablation produces particle fragments, which are usually redeposited on the patterned surface, resulting in SERS "hot spots". Femtosecond laser direct cutting of metal can prepare SERS substrates in one step, which has the advantages of high processing efficiency and simple processing and is more conducive to the application of large-scale production of practical SERS detection. Femtosecond laser cutting-sputtering is to process any structure on non-metallic substrates such as polymers and then sputtering/evaporating metal nanoparticles on the surface of the structure. This method can prepare transparent and flexible SERS substrates, which are rich in application scenarios. Femtosecond laser 3D printing is to use the three-dimensional processing ability of femtosecond lasers to obtain rich "hot spots" by designing the structure of SERS substrates, and then using template-guided self-assembly technology with different driving forces to deposit/evaporate metal nanoparticles at designated locations. In this paper, we first introduce the current methods for preparing SERS and then conduct a comprehensive review of the processing methods of four femtosecond lasers to prepare SERS substrates. Finally, the advantages and disadvantages of the four femtosecond laser preparation methods for SERS substrate are briefly summarized, and the development prospects of this technology are prospected, aiming to provide it for future related research.

电力能源发展与国家经济发展关系密切, 因此电网稳定、 安全地运行是人民稳定生活的保障。 而与稳定可靠的电网的运行有关的是变压器的绝缘水平, 因此始终注意电气设备的状况和运行非常重要。 而仅由纸绝缘产生的糠醛是目前用于评估电力变压器老化状况最常用的指标之一, 所以准确测量变压器油中糠醛含量具有重大意义。 拉曼光谱法可以实现对待测物的快速、 无损检测, 但受限于拉曼散射信号弱, 对油中老化特征物这种微量物质检测难度大。 表面增强拉曼光谱可以解决痕量物质检测的灵敏性问题, 使溶解在变压器油中的老化特征物得到快速、 无损地检测。 故将SERS应用到变压器油中糠醛的检测对于变压器运行状况的评估具有重要的意义。 围绕着变压器油中糠醛作为痕量物质检测灵敏度低的问题, 基于置换反应在TEM铜网上制备了微纳米结构的SERS基底, 以检测变压器油中的糠醛, 为高效, 准确地检测变压器油的老化水平提供一种快速、 有效的新技术。 选择了特定的实验材料, 在控制特定的实验条件下基于置换反应制备出微纳结构SERS基底, 经过电镜扫描对其表面形貌进行表征; 在不同位置进行拉曼检测得到特征拉曼峰峰强的变异系数仅为3.55%, 表明该基底的“热点”分布均匀和检测可重复性高; 定性分析了一定浓度梯度的变压器油中糠醛和背景噪声的拉曼光谱。 选择了1 702 cm^-1的拉曼峰作为油中糠醛的特征拉曼峰。 定量分析中, 建立内标峰和1 702 cm^-1处峰强比与变压器油中糠醛浓度的线性函数, 得到良好的线性关系。 使用3δ准则计算变压器油中糠醛在微纳结构SERS基底上的检测下限约为0.51 mg·L^-1。 研究说明基于铜网置换反应的微纳结构SERS基底对于变压器油中糠醛具有更灵敏的检测。 这对于诊断电力变压器绝缘状况和维护电网稳定非常重要。