Electrochemical Synthesis of 3D Plasmonic-Molecule Nanocomposite Materials for In Situ Label-Free Molecular Detections

For several decades, the precise positioning of chemicals and biomolecules at nanosized electromagnetic hotspots has posed a challenge to achieving ultrasensitive and reliable label-free molecular detection. Here, the authors report the rapid ultrasensitive direct detection of chemicals and biomacromolecules (i.e., enveloped virus) through the in situ electrochemical synthesis of a 3D plasmonic-probe molecule composite skin layer on a 3D Au nanopillar array. The bottom-up growth of plasmonic nanomaterials in the presence of target probe molecules provides intimate contact between the Au and the target molecules, thereby enhancing light-matter interactions in 3D spaces. These enhanced interactions result in highly sensitive and rapid direct detection of both small molecules and large influenza A virus (H1N1) with hierarchical complex structures. The virus serves as a structural motif for the formation of Au-virus nanocomposite structures through Au electrodeposition, which results in the in situ formation of hotspots for the surface-enhanced Raman spectroscopy (SERS) detection of spike proteins. The proposed SERS detection system with fast composite plasmon-molecule skin layer formation provides a general platform for highly sensitive and rapid label-free direct detection for chemical and biomedical applications.