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The European Physical Journal (EPJ) is a series of peer-reviewed journals covering the whole spectrum of physics and related interdisciplinary subjects. EPJ is committed to high scientific quality in publishing and is indexed in all main citation databases.

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EPJ D Highlight - Bringing measuring accuracy to radical treatment
Tuesday, 13 November 2012 17:13
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Comparison of the experiment and simulation laser induced fluorescence spectrum of hydroxyl. © Qing Xiong

Significant progress made in evaluating the density of active species used in medical applications of plasma physics could improve the accuracy of treatment

An international team of scientists working at the Plasma Technology research unit at Ghent University, Belgium, has determined for the first time the absolute density of active substances called radicals found in a state of matter known as plasma, in a study just published in EPJ D. These findings could have important implications for medicine—for example, for stimulating tissue regeneration, or to induce a targeted antiseptic effect in vivo without affecting neighbouring tissues.

Qing Xiong and colleagues utilised laser fluorescence spectroscopy (LIF), a detection method used to estimate the density of radicals in plasma. Plasma is made of charged species, active molecules such as radicals and atoms.

The authors chose to focus on OH radicals because they are one of the most important reactive species in plasma science due to their high level of oxidation. This means that chemical reactions with OH initiate the destruction of harmful components either in the human body or in nature such as carbon monoxide, volatile organic compounds and methane.

The problem is that, up to now, laser-induced fluorescent capability to measure the absolute density of radicals has been very limited because of issues with registering and analysing the fluorescence signal.

In this study, the authors present a simplified model which takes into account energy transfer stemming from the radicals’ vibrations. It can be used to analyse the LIF signal at regular atmospheric pressure. They then confirm the validity of their model experimentally, with a plasma jet made of Argon gas mixed with water molecules.

The calculation of one-dimensional line-averaged OH density made in this paper could also be extended to a two-dimensional spatial resolution of the OH radicals in future work.

Absolute OH density determination by laser induced fluorescence spectroscopy in an atmospheric pressure RF plasma jet. Q. Xiong, A. Nikiforov, L. Li, P. Vanraes, N. Britun, R. Snyders, X. P. Lu, C. Leys (2012), European Physical Journal D, DOI: 10.1140/epjd/e2012-30474-8

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