Progress toward a VUV Raman spectrometer to detect pathogens

Rapid detection and identification of novel viruses, such as SARS-CoV-2, is critical to treat, isolate, or hospitalize those infected, ultimately, to curb the spread of the virus. Diagnostic assays, such as enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), are considered the gold standard for testing, but are labor-intensive and/or involve creating probe molecules specific to the virus. We propose Raman spectroscopy as an alternative method of detection because it can be label-free and can offer identifying information on many analytes within a sample. Specifically, we are developing a vacuum ultraviolet (VUV) Raman spectrometer using an incoherent excitation source that emits the hydrogen Lyman-α line radiation at 121.57 nm. The main benefit of using a VUV source is that the Raman scattering cross-section is inversely proportional to the fourth power of wavelength, which means that VUV photons would yield several orders of magnitude higher scattering cross-sections than excitation in the visible or near-infrared. In addition, the 121.57 nm wavelength transmits up to 2 cm in dry air, so the analyte can be oriented in standard testing formats. We have been successful in producing strong and consistent HLA emission using both a dielectric-barrier discharge (DBD) plasma source and a commercial source. In the near future, we expect to produce consistent Raman signatures in solid and liquid media. HLAS will transform diagnostic medicine and several other industries through its powerful capabilities of detecting real-time infections and important health markers.