Size-dependent SERS property of red phosphorous in the transition from bulk to nanosheet and its application in immunosensing

Attributed to their structure-dependent chemical enhancement capability and perfect biocompatibility, semiconductors have attracted significant concern in surface enhanced Raman scattering (SERS)-based immunoassay. By continually adjusting the size of red phosphorus (RP) in the transition process from bulk to nanosheet, we investigated in detail about the improvement of high-efficient charge transfer (CT) resonance dependent on the perfect energy level matching within the substrate-molecule combination. The nano-sized RP has achieved an impressive three-fold enhancement in SERS intensity in comparison to the RP nanosheet. Furthermore, the RP-based immunosubstrate was combined with MoS 2 nanoflowers-based immunoprobe to construct a sandwich immunostructure for the accurate and efficient diagnostics of cancer marker prostate-specific antigen. A limit of detection as low as 3.99 × 10 −10  M was obtained in the SERS-based immunoassay with reliable specificity. This study presents an innovative approach to promote the SERS performance of semiconductors, which may find potential biological applications in the early screening of cancer.