Face masks have become an important tool in fighting the COVID-19 epidemic. However, improper use or disposal of masks can lead to “secondary transmission”. A research team at the City University of Hong Kong (CityU) has successfully produced graphene masks with an anti-bacterial efficiency of 80%, which can be increased to about 100% by exposure to sunlight for about 10 minutes. Initial tests also showed very promising results in the inactivation of two species of coronavir. Graphene masks are easily produced at low cost, and can help solve the problems of raw material sourcing and disposal of non-biodegradable masks.
Conducting the research Assistant Professor of Chemistry Department of CityU, Dr. It is done by Yu Ruquan in collaboration with other researchers. The findings were published in the scientific journal ACS Nano, Titled “Self-reporting and photothermally enhanced rapid bacterial killing on laser-induced graphene mask“.
Commonly used surgical masks are not anti-bacterial. This can pose a risk of secondary transmission of bacterial infection when people touch the contaminated surfaces of masks used or discard improperly. In addition, the melt-blown clothes used as a bacterial filter have an impact on the environment because they are difficult to rot. Therefore, scientists are looking for alternative materials to make masks.
Laser converting other materials to graphene
Dr. Y is studying the use of laser-induced graphene in developing sustainable energy. While he was studying for Ph.D. Several years ago at Rice University, the research team he attended and led by his supervisor found an easy way to produce graphene. They found that direct writing on carbon-containing polyimide films (a polymer plastic material with high thermal stability) using a commercial CO2 The infrared laser system can produce 3-D porous graphene. The laser changes the composition of the raw material and therefore produces graphene. That is why it is named laser-inspired graphene.
Graphene is known for its anti-bacterial properties, so at the beginning of last September, before the outbreak of COVID-19, production of outperforming masks with laser-induced graphene was already underway. It came to his mind. He then began the study with researchers from Hong Kong University of Science and Technology (HKUST), Nankai University and other organizations.
Excellent anti-bacterial efficiency
The research team e. Tested its laser-induced graphene with coli, and it achieved a high anti-bacterial efficiency of about 82%. In comparison, the anti-bacterial efficiency of activated carbon fiber and melt-blown clothing, both commonly used materials in masks, were 2% and 9%, respectively. The results of the experiment also showed that deposits on them e. More than 90% of the coli survived even after 8 hours, while most E. coli deposited on the surface of graphene were dead after 8 hours. Furthermore, laser-induced graphene had an improved anti-bacterial capacity for aerosolized bacteria.
Dr. Yeh said that more research is needed on the precise mechanism of graphene’s property killing bacteria. But they believed that it could be related to the loss of bacterial cell membrane by the sharp edge of graphene. And bacteria can be killed by dehydration induced by the hydrophobic (water-repellent) property of graphene.
Previous studies suggested that COVID-19 would lose its infectivity at high temperatures. The team therefore carried out experiments to test if the photothermal effect of graphene (generating heat after absorbing light) could be enhanced by its anti-bacterial effect. The results showed that the anti-bacterial efficiency of the graphene content could be improved to 99.998% within 10 minutes under sunlight, while activated carbon fiber and melt-blown fabrics showed efficiency of 67% and 85%, respectively. .
The team is currently working with laboratories in mainland China to test graphene content with two species of human coronaviruses. Initial tests showed that it became inactive in 90 minutes in five minutes and 10 minutes in about 100% sunlight. The team plans to test it later with the COVID-19 virus.
Their next step is to increase anti-virus efficiency and develop a reusable strategy for masks. They hope to design an optimal structure for the mask and release it to the market soon after obtaining the certificate.
Dr. Y described the production of laser-induced graphene as a “green technique”. All carbon-containing materials, such as cellulose or paper, can be converted to graphene using this technique. And the conversion can be done in ambient conditions without using chemicals other than raw materials, nor cause pollution. And energy consumption is less.
“Laser-induced graphene masks are reusable. If used for the production of biometric graphene, it can help solve the problem of sourcing raw materials for masks. And it is a non-biodegradable disposable mask. Could reduce the environmental impact due to this, ”he said. .
Dr. Yeh pointed out that laser-induced graphene production is easy. Within just one and a half minutes, an area of 100 cm can be converted to graphene as the outer or inner layer of the mask. Based on the raw material for the production of graphene, the laser-induced graphene mask is expected to be priced between the surgical mask and the N95 mask. He stated that by adjusting the laser power, the shape of the pores of the graphene material could be modified, so that the trachea was similar to a surgical mask.
A new way to check the status of a mask
To test whether the graphene masks are still in good condition after users have been used for a period of time, the team designed a hygroelectric generator. It is powered by moisture generated by human breath. By measuring the change in moisture-induced voltage when the user breathes through a graphene mask, it provides an indicator of the condition of the mask. Experiment results have shown that the more bacteria and atmospheric particles accumulate on the surface of the mask, the lower the voltage. “The standard of how often masks should be changed is better decided by professionals. Nevertheless, we can use this method as a reference,” Dr. Suggested this.
New self-sterilizing air filtration technology may include face masks and ventilation
Libya Huang et al, Self-Reporting and Enhanced Rapid Bacterial Killing on a Laser-Induced Graphics Device ACS Nano (2020). DOI: 10.1021 / acsnano.0c05330
Provided by City University of Hong Kong
Quotes: Researchers obtained an anti-bacterial graphene face mask (2020, 10 September) on 11 September 2020 from https://phys.org/news/2020-09-ant-bacterial-graphene-masks.html.
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