Efficient multiplexed label-free detection by flexible MXene/graphene oxide fibers with enhanced charge transfer and hot spots effect

Sensors integrated with sampling and analysis processes are the key in analytical chemistry , environmental protection and national security. However, achieving reliable and sensitive large-scale rapid screening of target analytes is still challenging. Herein, we demonstrate a robust surface-enhanced Raman scattering (SERS) sensor by constructing dense and uniform plasmonic hotspots on the flexible Ti 3 C 2 Tx MXene/graphene oxide (MG) fibers through a self-assemble strategy at the oil-water interface. The produced SERS substrates exhibited an ultralow limit of detection (LOD, 1 ×10 −15 M for R6G), outstanding sensitivity (EF = 1.53 ×10 12 ) and high stability for R6G molecules (RSD = 9.47%, over 60 days storage). SERS experiments and theoretical simulations suggested that acidified Ti 3 C 2 Tx MXene further excited charge-transfer (CT) resonance of the system, while the assembled Ag nanostructures produced a large electromagnetic (EM) field enhancement. Thus, the fiber sensor not only realizes the multiplexed and powerful detection of pesticide residues (LOD of 10 −11 M) with an error < 7.3% via an established concentration-dependent standard color barcodes, but also allows the recognization of target molecules in a wide range of fields, such as methylene blue , crystal violet and nikethamide. This work provides new insights in the development of versatile label-free sensors for the rapid multiplexed analysis of target molecules in real samples.