Enhanced SERS Sensing via 3D Microstructures Hybridized with 2D MXenes

Surface-Enhanced Raman Spectroscopy (SERS) is an analytical technique that can be used to detect target particles on a plasmonically enhanced surface. This has applications in fields such as medicine and environmental pollution. The advantage of SERS detection is that it can be used to detect very small amounts of a sample and it is noninvasive. However, traditional SERS requires that the target particles be in contact with the plasmonic materials on the sensing surface. For the detection of very low concentration target particles in a liquid, traditional SERS techniques are limited by the diffusion limit. More specifically, it can take hours for nanoscale target particles in a liquid at very low concentrations to diffuse to the sensing surface for detection. In this study, we address the diffusion limitation by merging MXenes, a 2D material, with a 3D microstructure, establishing a micro-scaled surface optimized for detecting minute concentrations of target particles in a liquid. The 3D configuration composed of SU-8 is a self-assembled twin-tubular microstructure that creates a nanogap at the center curvature. When fluid is flown through this tubular structure, an enhanced Raman signal can instantly be obtained. As fluid is flown from one end of the twin tubular structure to the other end, some fluid will flow between the center curvature (a nanogap). At this center curvature, some of the analytes will be caught in between the nanogap of the center curvature. Furthermore, both sides of this nanogap have MXenes. Hence, the analytes will be in contact with the plasmonic surface and be ready for instant Raman measurement. Furthermore, this Raman signal demonstrates two levels of enhancement. The first level of enhancement is from the MXenes. MXenes can be used as a plasmonic material that can enhance the Raman signal. The second level of enhancement is from the proximity of the two MXenes surfaces at the center of the twin tubular 3D microstructure. This proximity is a function of the twin tubular structure. The twin tubular structure curves itself into a shape where there is a nanogap at the center between the two tubes. At this nanogap, there is also MXenes on both sides of the gap. This nanogap is the plasmonic surface where the enhanced Raman measurement will be taken. Capitalizing on the combined advantages of 3D structures and low-dimensional (0D, 1D, and 2D) materials, which counterbalances the limitations of 2D materials like MXenes, the approach of fusing 3D microstructures with these low-dimensional materials offers broad application possibilities.