Plasma Discharge Ionization Emission Spectra of Analytes and SARS-CoV-2 for Label-Free Sensing Applications

Ionization spectra of substances are extensively used in their label free detection. Here we demonstrate the possibility of using plasma ionization to detect airborne and saliva SARS-COV-2 viruses through their emission spectra. It consists of an ionization chamber monitored by a fiber-optic UV-VIS spectrometer. The technique is completely label-free and can be programmed in real-time to detect different viral particles through their ionization emission spectra. Its average sensitivity for detecting deoxyribonucleic acid (DNA) bases in water is 20%/g in 1 mL of water. Its selectivity for DNA bases is through their relative emission peaks for adenine at 439.5 nm, cytosine at 440, thymine at 440.5, and guanine at 421.5 nm. The emission spectra of different electrode materials were also obtained to account for their contributions to the emission spectra of analytes. Gold electrodes were used owing to their resistance to corrosion and very low reaction with ionized species. The technique has the potential to be used in the point-of-care diagnostic and testing applications.