Developed a new type of stamp size capable of sterilizing by merely dropping it in water

ByLennart Tange

Although it is said to be safest in the world in Japan, it is safe to kill bacteria in water by chlorine disinfection. In developing countries where sewage treatment facilities are not in place, it is impossible to thoroughly disinfect water like Japan, but if it is a newly developed postage stamp size small device, it is very easy to sterilize water You may be able to do so.

SLAC, Stanford Gadget Grabs More Solar Energy to Disinfect Water Faster | SLAC National Accelerator Laboratory
https://www6.slac.stanford.edu/news/2016-08-15-slac-stanford-gadget-grabs-more-solar-energy-disinfect-water-faster.aspx


Even today in various scientific and technological developments, the technique of "boiling water" is adopted in many regions of the world in order to convert "water full of bacteria" into "clean drinkable water". There is also a method of putting water in a plastic bottle and keeping it exposed to sunlight, killing bacteria in the water with ultraviolet rays. However, since ultraviolet rays have only 4% of solar energy, if it is tried to secure drinking water by this method, it seems that it is necessary to keep exposing the PET bottle to sunlight for 6 to 48 hours.

Devices that can sterilize water much more efficiently than these methods are available from the US Department of EnergySLAC National Accelerator Research InstituteAnd developed by researchers at Stanford University. It is a postage stamp size nanostructure device which "can sterilize water in just a few minutes using the visible spectrum of sunlight". Ultra-violet rays can utilize only 4% of solar energy, whereas the newly developed nanostructured devices can utilize about 50% of solar energy.

This is a nanostructure device developed by researchers at SLAC and Stanford University. Although it is a small size of the fingertip, water can be sterilized in just a few minutes using sunlight.


A research report on this nanostructured device will be published in August 2016Nature NanotechnologyIt was published in. According to this report, sunlight falling on the surface of nanostructured devices produces hydrogen peroxide and other bactericidal substances, which sterilize bacteria in water in 99.99% in just 20 minutes. And after sterilization, the generated chemicals will disappear soon, so it seems that only pure water containing little impurities will remain.

"The device we developed looks like a small rectangular black glass, dropping it in water and putting it under sunlight, then the sun will sterilize the water." Research Mr. Jeong Riu, the first author of the report.

Looking at the surface of the nanostructure device with an electron microscope, you can see a pattern like a fingerprint. This line is a very thin thin film made of molybdenum disulfide, and researchers call it "nanoflake". This nanoflake is stacked in several layers, and it looks like a labyrinth.


Molybdenum disulfide, which is the raw material of this nanoflake, is usually used as industrial lubricant and so on. However, it is possible to derive different characteristics by making it a layer with a size of molybdenum disulfide atom level. Different properties mean that "photocatalyst" is to be obtained. By exposing molybdenum disulfide to light as a photocatalyst, many electrons move and a chemical reaction for killing bacteria occurs. In addition, by adjusting the thickness of the layer of molybdenum disulfide nanoflakes, we can absorb any visible spectrum.

In addition, by adding a layer of copper to the layer of molybdenum disulfide nanoflakes it is possible to react reactive to sunlight and generate reactive oxygen species such as hydrogen peroxide, which is a substance used for disinfectants It seems to be adjusting.


"Since molybdenum disulfide is an inexpensive and easy-to-produce material, it can be prepared extensively in developing countries and elsewhere," said Lee Ky who participated in the study.

However, this nanostructure device is not all-purpose. This is only a device for sterilizing bacteria in water, so you can not remove chemical contaminants in water. Also, in the research so far we have tested nanostructured devices against three kinds of bacteria and succeeded in sterilization, but it is still unknown whether or not it is effective against all other bacteria.

Also, since the test was only conducted on water mixed with specific bacteria made in the laboratory, it will be demonstrated in the future whether or not various actual pollutants will work effectively on mixed water There is a need to go.