Metal organic framework wrapped gold nanourchin assembled on filter membrane for fast and sensitive SERS analysis

Plasmonic particle-metal organic framework hybrid received considerable attention in SERS analysis. However, most detection procedure suffers from long immersion time, low enhancement, and random substrate aggregation. To improve detection efficiency, sensitivity and reproducibility, gold nanourchins wrapped with metal organic framework MIL-100(Cu) (GNU@MOF) were prepared and assembled onto a filter membrane to develop a filtration detection mode. The substrate-analyte interaction time reduces from 60 min in immersion mode (GNU@MOF-I) to 10s in filtration mode (GNU@MOF-F). Interestingly, the SERS signal on GNU@MOF-F is comparable or 1-7 folds higher than that on GNU@MOF-I, depending on analyte concentration. Detection limit for toxic dye MG on GNU@MOF-F is 0.1 nM, which is 10- or 100-fold lower than that on GNU@MOF-I (60 min or 10 s). The signal reproducibility was also improved on GNU@MOF-F (RSD < 13%) compared with that on GNU@MOF-I (RSD > 30%). Comparison experiments reveal the improvement can be ascribed to the filtration induced enrichment of analyte together with even and dense assembly of GNU@MOF, which form more uniform and efficient hot spots. Similar results was found for practical detection of MB in lake water with good reusability. Such efficient SERS substrate with simple and fast operation holds great promise in chemical and environmental analysis.