Superhydrophilic Silica-Coated Au Nanoislands for Efficient Capture and Enhanced SERS Detection of Airborne Biomarkers

Exhaled breath aerosols contain critical biomarkers for noninvasive and cost-effective early detection of respiratory and other infectious diseases. However, current methods still struggle with a low capture efficiency and limited detection sensitivity for trace biomarkers in complex aerosols. Here we report superhydrophilic ultrathin silica-coated gold nanoislands (scAuNIs) for the highly efficient capture and SERS detection of airborne biomarkers. The scAuNIs are wafer-level fabricated by repeated dewetting of gold thin films, followed by a 2 nm silica film deposition using atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) with a tetraethyl orthosilicate (TEOS) precursor. The ultrathin silica film increases the surface energy, leading to a 1.52× improvement in the capture efficiency of emulated breath aerosols. In addition, the high-index silica coating enhances the E-field intensity between scAuNIs by 1.66×. The combined effects result in a 1.95× increase in the SERS peak signal intensity, allowing nanomolar detection of acetic acid, adenosine, IL-6, EGFR, and the SARS-CoV-2 spike protein. The scAuNIs can serve as a breath biopsy platform for identifying diverse biomarkers in respiratory aerosols.