Anti-bacterial graphene face masks

Date:
September 10, 2020
Source:
City University of Hong Kong
Summary:
Researchers have successfully produced laser-induced graphene
masks with an anti-bacterial efficiency of 80 percent, which
can be enhanced to almost 100 percent within 10 minutes under
sunlight. Initial tests also showed very promising results in the
deactivation of two species of coronaviruses. The graphene masks are
easily produced at low cost, and can help to resolve the problems
of sourcing raw materials and disposing of non-biodegradable masks.



FULL STORY ==========================================================================
Face masks have become an important tool in fighting against the
COVID-19 pandemic. However, improper use or disposal of masks may lead
to "secondary transmission." A research team from City University of
Hong Kong (CityU) has successfully produced graphene masks with an anti-bacterial efficiency of 80%, which can be enhanced to almost 100%
with exposure to sunlight for around 10 minutes. Initial tests also
showed very promising results in the deactivation of two species of coronaviruses. The graphene masks are easily produced at low cost, and
can help to resolve the problems of sourcing raw materials and disposing
of non-biodegradable masks.


==========================================================================
The research is conducted by Dr Ye Ruquan, Assistant Professor
from CityU's Department of Chemistry, 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 a Laser-Induced Graphene Mask." Commonly used surgical
masks are not anti-bacterial. This may lead to the risk of secondary transmission of bacterial infection when people touch the contaminated
surfaces of the used masks or discard them improperly. Moreover, the
melt-blown fabrics used as a bacterial filter poses an impact on the environment as they are difficult to decompose. Therefore, scientists
have been looking for alternative materials to make masks.

Converting other materials into graphene by laser Dr Ye has been studying
the use of laser-induced graphene in developing sustainable energy. When
he was studying PhD degree at Rice University several years ago, the
research team he participated in and led by his supervisor discovered
an easy way to produce graphene. They found that direct writing on carbon-containing polyimide films (a polymeric plastic material with
high thermal stability) using a commercial CO2 infrared laser system
can generate 3D porous graphene. The laser changes the structure of
the raw material and hence generates graphene. That's why it is named laser-induced graphene.

Graphene is known for its anti-bacterial properties, so as early as last September, before the outbreak of COVID-19, producing outperforming masks
with laser-induced graphene already came across Dr Ye's mind. He then kick-started the study in collaboration with researchers from the Hong
Kong University of Science and Technology (HKUST), Nankai University,
and other organisations.



========================================================================== Excellent anti-bacterial efficiency The research team tested their laser-induced graphene with E. coli, and it achieved high anti-bacterial efficiency of about 82%. In comparison, the anti- bacterial efficiency
of activated carbon fibre and melt-blown fabrics, both commonly-used
materials in masks, were only 2% and 9% respectively. Experiment results
also showed that over 90% of the E. coli deposited on them remained alive
even after 8 hours, while most of the E. coli deposited on the graphene
surface were dead after 8 hours. Moreover, the laser-induced graphene
showed a superior anti-bacterial capacity for aerosolised bacteria.

Dr Ye said that more research on the exact mechanism of graphene's
bacteria- killing property is needed. But he believed it might be related
to the damage of bacterial cell membranes by graphene's sharp edge. And
the bacteria may be killed by dehydration induced by the hydrophobic (water-repelling) property of graphene.

Previous studies suggested that COVID-19 would lose its infectivity at
high temperatures. So the team carried out experiments to test if the graphene's photothermal effect (producing heat after absorbing light)
can 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 fibre and melt-blown fabrics only showed an efficiency of 67% and 85% respectively.

The team is currently working with laboratories in mainland China to test
the graphene material with two species of human coronaviruses. Initial
tests showed that it inactivated over 90% of the virus in five minutes
and almost 100% in 10 minutes under sunlight. The team plans to conduct testings with the COVID-19 virus later.



========================================================================== Their next step is to further enhance the anti-virus efficiency and
develop a reusable strategy for the mask. They hope to release it to
the market shortly after designing an optimal structure for the mask
and obtaining the certifications.

Dr Ye described the production of laser-induced graphene as a "green technique." All carbon-containing materials, such as cellulose or paper,
can be converted into graphene using this technique. And the conversion
can be carried out under ambient conditions without using chemicals
other than the raw materials, nor causing pollution. And the energy
consumption is low.

"Laser-induced graphene masks are reusable. If biomaterials are used for producing graphene, it can help to resolve the problem of sourcing raw
material for masks. And it can lessen the environmental impact caused
by the non- biodegradable disposable masks," he added.

Dr Ye pointed out that producing laser-induced graphene is easy. Within
just one and a half minutes, an area of 100 cm^2 can be converted into
graphene as the outer or inner layer of the mask. Depending on the raw materials for producing the graphene, the price of the laser-induced
graphene mask is expected to be between that of surgical mask and N95
mask. He added that by adjusting laser power, the size of the pores of
the graphene material can be modified so that the breathability would
be similar to surgical masks.

A new way to check the condition of the mask To facilitate users
to check whether graphene masks are still in good condition after
being used for a period of time, the team fabricated a hygroelectric
generator. It is powered by electricity generated from the moisture in
human breath. By measuring the change in the moisture-induced voltage
when the user breathes through a graphene mask, it provides an indicator
of the condition of the mask. Experiment results showed that the more
the bacteria and atmospheric particles accumulated on the surface of the
mask, the lower the voltage resulted. "The standard of how frequently a
mask should be changed is better to be decided by the professionals. Yet,
this method we used may serve as a reference," suggested Dr Ye.

Dr Ye is one of the corresponding authors of the paper. The other two corresponding authors are Professor Tang Benzhong from HKUST, and Dr
Zhu Chunlei from Nankai University. The first author of the paper is
Huang Libei, Dr Ye's PhD student. Other CityU team members are Xu Siyu,
Su Jianjun, and Song Yun, all from the Department of Chemistry. Other collaborators included researchers from HKUST, Nankai University, as
well as Dr Chen Sijie of the Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet.

The study was supported by CityU and Nankai University.


========================================================================== Story Source: Materials provided by City_University_of_Hong_Kong. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Libei Huang, Siyu Xu, Zhaoyu Wang, Ke Xue, Jianjun Su, Yun Song,
Sijie
Chen, Chunlei Zhu, Ben Zhong Tang, Ruquan Ye. Self-Reporting and
Photothermally Enhanced Rapid Bacterial Killing on a Laser-Induced
Graphene Mask. ACS Nano, 2020; DOI: 10.1021/acsnano.0c05330 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200910110839.htm

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