Space-confined growth of molecularly imprinted membrane SERS substrate for rapid sample preparation and sensitive food safety analysis all-in-one

Rapid and accuracy sensing approach is urgent demand in food safety analysis. Development of multifunctional sensing material enabling the integration of molecularly imprinted sample preparation and surface-enhanced Raman scattering (SERS) detection all-in-one is a possible solution. However, the thickness of the molecularly imprinted polymers SERS (MIPs-SERS) substrates is critical to rapidity and sensitivity of analytical method by contributing both the selective enrichment and sufficient Raman signal amplification. A space-confined growth strategy was using for the thickness controllable fabrication of the MIPs-SERS in a microreactor device. As proofs of concept, two types of MIPs-SERS substrates were prepared to realize sample preparation and SERS detection all-in-one. The Au/MIPs membrane was prepared for leucomalachite green (LMG) selective separation, enrichment, chemical conversion and SERS detection with an imprinting factor ($\mathrm{IF}$) of 18.9 and a Raman enhancement factor ($\mathrm{EF}$) of 8.5 × 10⁶. Meanwhile, the Au/Ag@MIPs membrane was prepared for forchlorfenuron (CPPU) selective separation, enrichment and Au/Ag nanoparticles synergistic SERS detection with an $\mathrm{IF}$ of 10.5 and a $\mathrm{EF}$ of 2.8 × 10⁶. Based on the MIPs-SERS substrates, selective and sensitive analytical method were established with the limit of detections of 0.49 μg/L for LMG and 6.8 μg/L for CPPU, which meeting the requirement of food safety analysis. In the food safety analysis, LMG and CPPU were detected in a fish and jujube sample, respectively, and the results were verified by recovery tests and standard chromatographic methods. This work provides an alternative approach for rapid complex sample analysis as well as a thickness controllable polymer membrane fabrication strategy.