This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Scientists from Tokyo Metropolitan University have found a way to make plasma more effective for its wide-ranging uses, from antimicrobial applications to surface conditioning in the semiconductor industry. They mapped the production of atomic oxygen, a key ingredient of oxygen plasma, while a high voltage was applied across oxygen gas.
They discovered that the amount of atomic oxygen available for reactions increased at pressures moderately lower than atmospheric pressure. Their findings promise more energy-efficient, higher-performance plasma technologies. Plasma is often called the fourth state of matter, alongside gas, liquid and solid.
Made of charged atoms and electrons, plasma makes up an estimated 99.9% of all matter in the universe. Although it is rarely encountered on Earth except during lightning storms, artificial plasmas can be generated by applying high electrical voltages across gases, creating so-called nonthermal plasmas. In these plasmas, only the electrons are driven to a high temperature, leaving the atoms in a highly reactive "radical" state.
Nonthermal plasmas are widely used to kill microorganisms, chemically modify materials and break down contaminants. Ways to make them more effective would have a major impact on industry and society. Oxygen plasma is particularly popular because of the powerful oxidizing ability of atomic oxygen, the key radical species generated when oxygen gas is broken down.
Although widely used, oxygen plasma faces a key challenge: Its short lifetime at atmospheric pressure. Frequent collisions with gas molecules mean fewer oxygen radicals react with the intended target. A team led by Associate Professor Yusuke Nakagawa from Tokyo Metropolitan University has shown how reducing pressure can make oxygen plasma treatments more effective.
The work is published in the Journal of Physics D: Applied Physics. They studied pulsed electrical discharges across oxygen gas at pressures slightly lower than atmospheric pressure. Using lasers to cause atomic oxygen to fluoresce at a specific wavelength of light, they mapped how much atomic oxygen was produced at different locations around the positive and negative electrodes on either side of the gap.
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