The current COVID-19 pandemic urges the extremely sensitive and prompt detection of SARS-CoV-2 virus. Here, we present a Human Angiotensin-converting-enzyme 2 (ACE2)-functionalized gold “virus traps” nanostructure as an extremely sensitive SERS biosensor, to selectively capture and rapidly detect S-protein expressed coronavirus, such as the current SARS-CoV-2 in the contaminated water, down to the single-virus level. Such a SERS sensor features extraordinary 10⁶-fold virus enrichment originating from high-affinity of ACE2 with S protein as well as “virus-traps” composed of oblique gold nanoneedles, and 10⁹-fold enhancement of Raman signals originating from multi-component SERS effects. Furthermore, the identification standard of virus signals is established by machine-learning and identification techniques, resulting in an especially low detection limit of 80 copies mL⁻¹ for the simulated contaminated water by SARS-CoV-2 virus with complex circumstance as short as 5 min, which is of great significance for achieving real-time monitoring and early warning of coronavirus. Moreover, here-developed method can be used to establish the identification standard for future unknown coronavirus, and immediately enable extremely sensitive and rapid detection of novel virus.

Understanding energy transfer mechanisms in graphene derivatives is strongly motivated by the unusually interesting electronic properties of graphene, which can provide a template for the creation of novel nanostructured derivatives. From a synthetic point of view, it is highly attractive to envision being able to synthesize pristine graphene from precursors such as graphene oxide (GO). While this goal may be challenging over large length-scales, it is possible to generate regions of graphene at the nanoscale, confirmed by Raman spectroscopy or other methods. We describe an in situ method of nucleating gold or palladium nanoparticles in the presence of ethylene glycol as a reducing agent, while simultaneously reducing GO to graphene. The Au nanoparticles aid in spectroscopic characterization by both quenching fluorescence, allowing the graphene D and G bands to be quantified, and yielding a surface enhancement of about two orders of magnitude. We observe the excitation profile (488–785 nm) of the surface enhanced Raman spectrum (SERS) of graphene with Au nanoparticles adsorbed on the surface. Both the D and G bands display a resonance at approximately 593 nm (2.09 eV). This resonance may be interpreted as a combination of the plasmon resonance at 548 nm and a likely contribution from charge transfer as well. In addition, we observe a stiffening of the G band compared with that of graphene. The mechanism of the SERS, whether plasmonic or charge transfer-based, enables insight into the electronic pathways available to the graphene–nanoparticle system. We discuss our results in the context of several existing studies of graphene-based nanostructure derivatives.