Large-Scale Flexible Surface-Enhanced Raman Scattering (SERS) Sensors with High Stability and Signal Homogeneity

Abstract

Flexible surface-enhanced Raman scattering (SERS) sensors have attracted great attention as a portable and low-cost technique for chemical and bio-detecting. However, flexible SERS sensors tend to suffer low signal spatial homogeneity due to their uneven active plasmonic nanostructures (hot-spots) distribution, and quick degradation of SERS sensors' sensitivity due to low adhesion of hot-spots and flexible substrates during fast sampling. Herein, a large area (20×20 cm2) polyimide (PI) based SERS sensor is exploited for trace detection with high signal homogeneity and stability. The SERS sensor is constructed from PI through in situ growth of silver and gold core-shell nanoparticles (Ag@Au NPs) based on chemical reduction and galvanic replacement process. Benefiting from the abundant carboxyl groups on the surface cleavaged PI, densely and uniformly distributed Ag@Au NPs are successfully prepared on the film under ambient conditions. The high Raman enhancement factor (up to 1.07 × 107) and down detection capability of nanomolar (10-9 M) detection limits are obtained for this flexible SERS sensor. The uniform Raman signals in the random region show well signal homogeneity with a low variation of 8.7%. Moreover, the flexible SERS sensor exhibited superior efficiency durability after storage 30 days even after mechanical stimuli (bending or torsion) 500 cycles. The pesticide thiram (TMTD) residue has been rapidly traced by direct sampling from the apple surface, and a sensitivity of 10 ng/cm2 for TMTD was achieved. These findings show that the PI-based SERS sensor is a very strong candidate for broad and simple utilization of flexible SERS for both laboratory and commercial applications in chemical and biomolecule detections.