Green Science Alliance Generates Quantum Dot Based Anti-Bacterial Material From Biomass Waste

KAWANISHI-CITY, Japan -- The vision of Green Science Alliance is to offer actual cutting-edge technology for sustainable, carbon neutral society. They are also trying to replace all of the petroleum, fossil fuel-based chemicals with plant, biomass based chemical products. This time, they developed quantum dot based anti-bacterial materials from biomass waste, organic waste such as wood waste, paper waste, food waste, orange peel waste etc.

Anti-bacterial materials are drugs or medicines used for bacterial infection. Antibiotics, probiotics, bacteriophages, anti-peptide, nano-materials are the anti-bacterial materials which influence the behavior of bacteria. Compared to conventional anti-bacterial materials which are made by chemical synthesis, or obtained from microorganisms, nano-materials have tendency to adhere to bacteria surface stronger than those commercial anti-bacterial materials. Nano-materials may interact or permeate into bacterial cell membrane or cell wall stronger, because the size of nano-materials could be so small as a few nanometers. In addition, due to the existence of surface chemical groups on quantum dots, they attach to the bacteria surface stronger. For these reasons, metal nanoparticles such as copper and silver nano-particles are known to possess anti-bacterial properties although this type of products have problems in terms of economical cost. 

Quantum dots are super tiny nano-materials (0.5 - 9 nm) with optical properties that follow the rules of quantum chemistry and quantum mechanics. These quantum dots are also called "artificial atoms or artificial molecules" because each quantum dot comprises several dozens to thousand number of atoms or molecules. At this size range, the energy levels of electrons are no longer continuous and are separated due to the physical phenomenon known as the quantum confinement effect. Under this condition, the wavelength of emission light depends on the size of the quantum dot. The Nobel Prize was awarded to the people who discovered and developed these quantum dots in 2023. 

Green Science Alliance has been developing various types of quantum dots and quantum dot composites and this time, Dr. Ryohei Mori has invented quantum dot based anti-bacterial materials from biomass waste, organic waste such as wood waste, paper waste, food waste and orange peel waste etc. Obviously, this kind of quantum dot based anti-bacterial materials can be cheaper than copper or silver nanoparticles. This type of biomass and organic based quantum dots are regarded as carbon quantum dots or organic quantum dots and they also attach to bacterial cell membrane or cell wall strongly and permeates into bacterial cell. Then after, they will influence bacteria gene or cause active oxygen species so that bacterial will be destroyed.

Some study also explained that carbon quantum dots may inhibit enzyme activity in bacteria to suppress peptidoglycan production which eventually destroy bacteria. 

Plant based anti-bacteria materials are flavonoids, polyphenol, alkaloid, catechin, terpenoid, saponin etc. Since carbon quantum dots are made from plant biomass, they may inherit anti-bacteria characteristics which originated from these chemicals.

In addition, when they are applied in agricultural industry such as at the field, excited electron, exciton, active oxygen species are generated which have anti-bacteria, anti-virus properties just as photocatalytic effect, under the sun light illumination.

Recently, the emergence of dangerous multidrug resistance bacteria caused by continuous usage of antibiotics over decades by human, has become a severe scary problem. There are some reports that this type of carbon quantum dots could be one of the solutions to mitigate that severe issue since the bacteria attack mechanism is different, compared to conventional anti-bacteria drugs.

It should be noted here that this plant, biomass-based carbon quantum dot is suggested to possess anti-virus as well as anti-fungus effect although Dr. Ryohei Mori is planning to confirm those possibilities. It may have the possibility to replace conventional anti-bacteria, anti-virus drugs such as alcohol, sodium hypochlorite etc. which were frequently used for COVID-19.

Green Science Alliance is promoting to apply this plant, biomass-based quantum dots materials as anti-bacteria, anti-virus, anti-fungus as well as pesticides, insecticide for agriculture etc.