Ultrasensitive and Reliable SERS Chip Based on Facile Assembly of AgNPs on Porous LIG to Enhance the Local Electromagnetic Field

Low-concentration molecular detection is of great value in chemical analysis, environmental monitoring, biological analysis, and other trace detection fields. Surface-enhanced Raman scattering (SERS) is widely used in the analysis of low-concentration molecules with great potential for biological detection due to nondestructive measurement. However, detection uniformity and repeatability are challenges in the application of SERS, especially as regards ultrasensitive detection. Here, a AgNPs@LIG SERS chip with excellent sensitivity and uniformity was fabricated by electroplating Ag nanoparticles (AgNPs) on a laser-induced graphene (LIG) surface prepared on a polyimide (PI) film, which realized large-scale production with controllable shape and area. Such an SERS chip features a limit of detection (LOD) of 10^–14 M, an enhancement factor (EF) of 3 × 10¹⁰, and fine uniformity (∼9.6% relative standard deviation) for rhodamine 6G, benefiting from excellent local electromagnetic field enhancement generated by the gap of AgNPs and excellent performance of porous LIG. Finally, the chip was applied to the detection of melamine with the LOD of 10^–9 M, which confirmed the potential application value of the SERS chip for pollutant analysis. In addition, the preparation of the composite SERS chip is simple for mass production, which provides great potential for the development of ultrasensitive SERS biosensors for various biological and chemical analyses.