Dual-functional Au-porous anodic alumina (PAA) sensors for enrichment and label-free detection of airborne virus with surface-enhanced Raman scattering

The development of a rapid and sensitive method for the enrichment and direct detection of airborne viruses has become urgently needed to prevent their spread. We have developed a dual-functional, label-free platform for the enrichment and optical identification of airborne viruses. This platform allows for the on-site enrichment and identification of airborne viruses through a virus enrichment component combined with surface-enhanced Raman scattering (SERS). In this work, we created an Au-porous anodic alumina (PAA) composite film with a porous structure by ion sputtering Au nanoparticles (Au NPs). The Au-PAA serves as a dual-functional sensor, utilizing ultrafiltration for virus enrichment due to the vertical nanopores in PAA, and a plasma substrate based on the combination of surface plasmon near-field enhancements within the nanochannel structure. This platform demonstrates an extraordinary enrichment efficiency (about 98%) of obtained bioaerosols and enables simultaneous, sensitive detection at the single-virus level. Finite-difference time-domain (FDTD) simulations have revealed the electric field intensity and charge distribution of the Au-PAA. This Au-PAA composite film offers a powerful system for on-site, label-free visual particle enrichment and SERS detection. Contaminated air containing viruses can be collected in a few minutes and analyzed immediately by this platform, which is particularly beneficial for timely monitoring of viruses in public atmospheres. Additionally, this system can also be applied to evaluate the built environment and indoor air quality.