Hong Kong, Sep 12 (IANS): To fight against the Covid-19 pandemic, the scientists have successfully produced graphene masks with an anti-bacterial efficiency of 80 per cent, which can be enhanced to almost 100 per cent with exposure to sunlight for around 10 minutes.

According to the study, published in the journal ACS Nano, 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," said the study authors from the City University of Hong Kong (CityU).

The researchers revealed that 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.

Study's main researcher Dr Ye Ruquan 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 Ruquan's mind (study's main researcher).

For the findings, the research team tested their laser-induced graphene with E. coli, and it achieved high anti-bacterial efficiency of about 82 per cent. In comparison, the anti-bacterial efficiency of activated carbon fibre and melt-blown fabrics, both commonly-used materials in masks, were only 2 per cent and 9 per cent respectively.

Experiment results also showed that over 90 per cent 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 eight 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 per cent within 10 minutes under sunlight, while activated carbon fibre and melt-blown fabrics only showed an efficiency of 67 per cent and 85 per cent respectively.

The team is currently working with laboratories in mainland China to test the graphene material with two species of human coronaviruses. 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.