A Review of Paper-Based Substrates as Surface-Enhanced Raman Spectroscopy (SERS) Biosensors and Microfluidic Paper-Based SERS Platforms

Raman spectroscopy is an important method for identifying molecules and has many uses in determining the chemical and structural properties of different materials. Despite the structure of the intelligently enhanced substrates used in laboratory research, the development of a simple, flexible, and cost-effective substrate is also important for enhancing the application of surface-enhanced Raman spectroscopy (SERS) in practical analysis. Recently, paper has been considered for the fabrication of flexible SERS substrates. Compared to other SERS substrates, paper substrates have the unique advantage of strong mechanical properties, various components, and adjustable pore size. These features give many advantages to paper-based substrates for SERS analysis in practice, such as low-cost and straightforward substrate preparation, high efficiency, separation, and detection methods. Therefore, paper-based substrates in SERS analysis have been promising in applications such as environmental monitoring, food safety with high sensitivity and efficiency, etc. This review presents a summary of the research related to paper involving SERS analysis. First, a brief introduction to understanding its background is provided, followed by a brief history of the paper-based substrates. Then, the preparation of the paper-based substrate and the role of the paper are summarized, and the applications of paper-based SERS substrate in the analysis are presented. Then, in a separate section, several studies reported in the field of microfluidic paper-based SERS platforms are reviewed. Finally, the challenges and perspectives of this issue are discussed.