Reusable dual-functional SERS sensor based on gold nanoflowers-modified red phosphorus nanoplates for ultrasensitive immunoassay and degradation of CA19-9

It is tremendously desirable for the timely and effective detection of cancer to facilitate the ultra-highly sensitive monitoring of tumor marker in clinical serum sample. In this study, an electromagnetic and chemical synergistically enabled recyclable immunoassay based on surface-enhanced Raman scattering (SERS) was proposed by realizing the anisotropic growth of sea-urchin-like gold nanoflowers (Au NFs) on two-dimensional red phosphorus (RP) nanoplates. Besides the achieved enhancement factor as high as 2.24 × 106, it was found that the photocatalytic and SERS activities were kept at a high level for the hybrid substrate of RP/Au NFs throughout 7 cycles of immunoassay. In combination with a non-metallic immunoprobe, the limit of detection was drove to 7.41 × 10-5 IU·mL-1 for cancer antigen 19-9. The comparative experiments of nonspecific monitoring verified the promising selectivity of this strategy. Considering the intriguing features of high sensitivity, recyclability, and specificity, the proposed multifunctional RP/Au NFs exhibited its superior role in the early detection of cancer and can be adapted for point-of-care diagnosis.