Scientists in the US have used an optical-frequency comb – a laser that emits light at a range of equally spaced frequencies, like the teeth on a comb – to monitor how well a device designed to kill dangerous bacteria does its job. The comb was used to measure the concentrations of ozone, hydrogen peroxide and other reactive molecules in the stream of air and cold plasma produced by the decontamination device. The study reveals that decontamination is most efficient when both a plasma and hydrogen peroxide are present in the stream.
"Cold-air plasmas" – room-temperature gases of ionized air molecules – are widely used to kill dangerous bacteria, both in medical and food-processing environments. While the technique is good at dealing with antibiotic- and heat-resistant bacteria, the devices can be even more potent if the plasma is combined with an antibacterial chemical such as hydrogen peroxide. But understanding why this process occurs and how it could be improved is not easy because accurately measuring the relative abundances of different molecules in the stream – and how they interact – is tricky.