Charge-Transfer Resonance and Surface Defect-Dominated WO Hollow Microspheres as SERS Substrates for the miRNA 155 Assay.

Chemical enhancement with charge transfer (CT) between the adsorbed Raman molecule and the semiconductor mainly contributed to semiconductor surface-enhanced Raman scattering (SERS). In this work, a three-dimensional (3D) WO hollow microsphere is first developed as a SERS-active substrate. This 3D WO has a smaller band gap and rich surface defects compared with flake WO. Interestingly, these properties in the WO hollow microspheres lead to an increase in charge transfer, which causes a strong CT interaction between the substrate-Raman molecule interfaces, resulting in a large SERS enhancement. The 3D WO showed an excellent SERS performance with an enhancement factor (EF) of 1.6 × 10. Finally, a SERS biosensor is constructed based on the above-mentioned semiconductor materials, which can be used for the sensitive detection of miRNA 155 with a limit of detection (LOD) of 0.18 fM by employing a catalytic hairpin assembly (CHA) strategy. This work provides important guidance for semiconductor topography design to improve the SERS performance, supplying a new strategy for biomolecular analysis and disease diagnosis.