Charge-Transfer Resonance and Surface Defect-Dominated WO₃ Hollow Microspheres as SERS Substrates for the miRNA 155...

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) WO₃ hollow microsphere is first developed as a SERS-active substrate. This 3D WO₃ has a smaller band gap and rich surface defects compared with flake WO₃. Interestingly, these properties in the WO₃ 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 WO₃ showed an excellent SERS performance with an enhancement factor (EF) of 1.6 × 10⁶. 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.