Dr. Yeni’s team uses a CO2 infrared laser system to produce graphene. The experiment results show that the graphene they make shows better anti-bacterial efficacy than fabrics with activated carbon fiber and molten fabrics. Credit: City University of Hong Kong
Anti-bacterial efficacy is close to 100% under 10-minute sunlight and promising results of inactivating the coronavirus.
Face masks have become an important tool in the fight against COVID-19 Nationwide epidemic. However, improper use or disposal of the mask can lead to “secondary transmission”. A research team from City University (CTU) in Hong Kong has successfully constructed Graphene Mask with 0% anti-bacterial efficacy, which can be increased to about 100% with exposure to sunlight for about 10 minutes. Preliminary tests also showed very promising results of inactivating two species of coronavirus. Graphene masks are easily produced at low cost, and can help solve the problems of raw material sourcing and disposal of non-biodegradable masks.
In collaboration with other researchers, Dr. Assistant Professor of Chemistry, CTU. This research has been done by Yeh Rukn. These findings were published in the scientific journal ACS. Were published in Nano, entitled “Self-Reporting and Photothermally Enhanced Rapid Bacterial Killing on a Laser-Induced Graphene Mask.”
The most commonly used surgical mask is not anti-bacterial. When people touch the contaminated surfaces of the masks used or use them improperly, there is a risk of secondary transmission of bacterial infections. Moreover, the molten blowing cloth used as a bacterial filter affects the environment because it is difficult to decompose. Therefore, scientists are looking for alternative materials to make masks.
Converting other materials to graphene by laser
D Ye. They are studying the use of laser-induced graphene in the development of sustainable development. While he was studying for a PhD degree at Rice University many years ago, the research team he participated in and led by his supervisor found an easy way to produce graphene. They found that direct writing on carbon-containing polyimide films (polymeric plastic materials with high thermal stability) using commercial CO2 infrared laser systems could produce 3D porous graphene. The laser alters the composition of the raw material and therefore produces graphene. That is why it is named laser-induced graphene.
Most carbon-containing materials can be converted to graphene using a commercial CO2 infrared laser system. Credit: City University of Hong Kong
Graphene is known for its anti-bacterial properties, so in early September, before the outbreak of COVID-19, Dr. before making an outperforming mask with laser-induced graphene. Yena came to mind. He then began studying in collaboration with researchers from Hong Kong University of Science and Technology (G (HKUST)), Nankai University and other institutions.
Excellent anti-bacterial efficacy
The research team tested their laser-induced graphene with E. coli, and it achieved a high anti-bacterial efficacy of about 3%. In comparison, the anti-bacterial efficacy of activated carbon fiber and molten blowing fabrics, both materials commonly used in masks, was only 2% and 9%, respectively. The results of the experiment also showed that more than 90% of the E. coli deposited on them survived after hours, while most of the E. coli deposited on the surface of the graphene died after 8 hours. Moreover, laser-induced graphene exhibits excellent anti-bacterial ability for aerated cells.
Research shows that more than 90% of E. coli accumulates on activated carbon fibers (Fig. C and D) and molten fabrics (Fig. E and F) survive even after 8 hours. In contrast, most of the E. coli (Fig. A and B) deposited on the graphene surface died. Credit: DOI: 0.1021 / acsnano.0c05330
Dr. Ye said more research is needed on the specific mechanism of graphene’s bactericidal-killing property. But he believes it may be related to damage to the bacterial cell membrane by the sharp edge of graphene. And bacteria can die from dehydration induced by the hydrophobic (water rippling) properties of graphene.
Previous studies suggest that Covid-19 will lose its infection at high temperatures. Therefore, the team conducted experiments to see if the photothermal effect of graphene (generating heat after absorbing light) could enhance the anti-bacterial effect. The results showed that the anti-bacterial efficiency of the graphene material could be improved to 99.998% within 10 minutes under sunlight, while activated carbon fiber and molten fabrics showed only 67% and 85% efficiency, respectively.
The team is currently working with laboratories in mainland China to test graphene content with two species of human coronavirus. Preliminary tests show that it is more than 90% of the virus in five minutes and almost 100% inactive in 10 minutes under sunlight. The team plans to take tests with the COVID-19 virus later.
Their next step is to further enhance anti-virus efficiency and develop a reusable strategy for masks. They hope to introduce it to the market soon after receiving the composition and certificates of the best composition for the mask.
Dr. He described the production of laser-induced graphene as a “green technology”. All carbon-containing materials, such as cellulose or paper, can be converted to graphene using this technique. And conversion can occur in the surrounding conditions, without the use of chemicals other than raw materials, as well as without causing pollution. And .rja consumption is low.
To measure the change in moisture-induced voltage when the user breathes through a graphene mask, the team builds a hydroelectric generator. Credit: DOI 10.1021 / acsnano.0c05330
“Laser-inspired graphene masks can be reused. If biomaterials are used to produce graphene, it can help solve the problem of sourcing raw materials for masks. And it can reduce the environmental impact caused by non-biodegradable disposable masks, ”he added.
Dr. Ye pointed out that laser-induced graphene is easy to produce. Within just two and a half minutes, an area of 100 cm can be turned into graphene as the outer or inner layer of the mask. Depending on the raw material used to produce graphene, the cost of a laser-induced graphene mask is expected to be between a surgical mask and an N95 mask. He added that by adjusting the laser power, the size of the pores of the graphene material can be changed so that the breathing power will be the same as the surgical mask.
A new way to check the condition of the mask
To test users to see if they were in good condition even after using the graphene mask for a while, the team created a hydroelectric generator. It is powered by electricity generated from the moisture of human breath. By measuring the change in moisture-induced voltage when the user breathes through the graphene mask, it provides an indicator of the condition of the mask. The results of the experiment showed that the more bacteria and atmospheric particles that accumulate on the surface of the mask, the lower the voltage. “It is better for professionals to decide how often to change the mask. However, we can use this method as a reference, ”he suggests.
References: “Self-Reporting and Photothermally Rapid Bacterial Killing on Laser-Inspired Graphene” by Libai Huang, Xiu Xu, Zhao Wang, Ke Xu, Jianju Su, Yun Song, Siji Chen, Chunle Xu, Ben Zong Tang and Rukan. August 11, 2020 ACS Nano.
DOI: 10.1021 / acsnano.0c05330
De Ye is one of the corresponding authors of the paper. The other two corresponding authors are Professor Tang Benzong of HQST and Dz Xu Chunlei of Nankai University. The first author of the paper is Huang Libi, a PhD student. The other members of the CTU team are Zee Siu, Su Jinjun and Song Yun, all from the chemistry department. Other collaborators include researchers from HKUST, Nankai University, as well as Dr. Chen Chen CG of the Ming Yi Lau Center for Reparative Medicine at the Karolinska Institute.
The study was supported by CTU and Nankai University.
