(ORDO NEWS) — American scientists have discovered that hydrogen peroxide is formed in water droplets during condensation, but the mechanism of its appearance still remains a mystery.
Do not panic yet: the concentration of hydrogen peroxide is too low to harm the body. While a high level of the chemical can be extremely dangerous and you can read this article by Storemasta to see how it should be stored properly, this new discovery seems to be pretty harmless.
There is an opinion that the chemical processes occurring with water are limited to its dissociation into hydronium ions H3O + and hydroxyl OH- at room temperature. However, American scientists from Stanford University also found that when microdroplets of water are sprayed, hydrogen peroxide is formed, but they could not explain this phenomenon. Chemists put forward several hypotheses, among which were the triboelectric effect, asymmetric charge separation, contact electrification and oxidation of water due to the surface electric potential at the interface with air.
In continuation of the research, the scientists examined the condensation of drops on cooled substrates by assembling a chamber with controlled humidity and temperature of the substrate, which was cooled using a Peltier element, and the condensation process was observed through an optical microscope. A silicon wafer with low electrical conductivity and high thermal conductivity was chosen as the primary substrate. The plate was kept at a temperature of 3.5 degrees Celsius with a relative humidity of 55%. Within a minute, liquid microdroplets formed on its surface.
To test for the presence of peroxide, the scientists added them to a solution of 4-carboxyphenylboronic acid. Mass spectrometry indicated a reaction with the formation of boric and 4-hydroxybenzoic acids. The peroxide concentration in the solution was 68 micromoles per liter. The longer the scientists held the plate, the more water condensed on it. To test whether peroxide appears only on a silicon substrate, the scientists took Teflon, a glass plate, and a polished copper sheet. They found peroxide on every surface, but the most of it was released on the silicon substrate.
To test the effect of the substrate surface on the appearance of peroxide, the silicon surface was modified in three ways: a hydrophobic substance (1,7-dichloro-octamethyltetrasiloxane) was applied to the surface, treated with oxygen plasma, and etched with a laser. On a hydrophobic surface, water settles more slowly, so less peroxide was released during two minutes of water condensation than untreated silicon. The surface treated with oxygen plasma absorbed water, which made it impossible to capture low concentrations of hydrogen peroxide. The etched silicon surface enhanced its original properties: water condensation accelerated, the maximum peroxide production was observed after 30 seconds of exposure.
The scientists also tested the effects of air humidity, camera illumination, and substrate temperature. At 40% relative humidity, the peroxide concentration was four times less than at 55 and 70 percent. The emission of light did not affect the formation of peroxide, but most of all it was formed at a temperature of 3.5 degrees Celsius. Thus, the formation of peroxide in water droplets occurs not only under laboratory conditions, but also under quite common conditions.
Scientists could not explain the reason for this phenomenon. The droplets in which hydrogen peroxide is formed were no more than ten micrometers in size. Presumably, peroxide could appear due to OH radicals, which are formed due to the electric double layer between water and air. Chemists believe the research could help with the synthesis of hydrogen peroxide “in situ” for cleaning and disinfecting surfaces.
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