Tech Explained: Green Nanotech

How nanotechnology is being used to clean up the environment, save energy and reduce waste

The term green nanotechnology is actually used to describe two separate processes — making nanotech itself less toxic, and using it to make existing products and processes safer and more sustainable. Let’s look at some applications of green nanotechnology and how it’s being developed to drive sustainability.

Benefits of nanotechnology

Cleaning up: Researchers continue to find new ways of using nanoparticles to clean up toxic chemicals. For example, iron nanoparticles can be added to the toxic solvent tetrachloroethene (commonly used in dry cleaning). As the iron oxidizes, or rusts, it reacts with the tetrachloroethene to transform it into ethane, which is a safer hydrocarbon. Researchers are also working on ways to use nanoscale iron to reduce heavy metals and radionuclides.

Nanotechnology can be applied to water filtration systems to filter out bacteria and viruses. The wastewater is forced, under pressure, through nanoscale pores that are too small for bacteria or viruses to fit through.

Nanosensors are being developed that can detect contamination, pollution and pathogens in real time, allowing clean-up before a problem grows too large. Nanocoatings are being used to make substances such as paint, reducing the use of water and chemicals.

An Israeli company has also used nanotechnology to create an aerosol can that can spray without using ozone-harming chemicals.

Preserving the environment: Nanoparticles have been used as additives in glass, paints and film coatings to allow these materials to reflect or transmit specific wavelengths of solar energy, including heat energy. This allows windows and walls to either reflect or absorb heat, depending on the season, reducing energy bills.

Researchers are working on a way to make batteries out of electrodes packed with nanorods. These could be used to generate energy from the difference in salinity (levels of salt) between seawater and fresh water.

Green nanotech can also be used to solve problems caused by nanotech itself. Most sunscreens contain nanoparticles of titanium dioxide or iron oxide, which is toxic to marine life. Researchers at the University of Tennessee are working to create a greener alternative using nanoparticles extracted from English ivy. The particles are biodegradable, water-resistant and block UV rays.

In fact, there may be many green uses for naturally-occurring nanochemicals. Gold nanoparticles are used in applications such as fuel cells and chemical sensors, but producing them requires large amounts of toxic solvents. Researchers at the University of Oregon have developed a way to develop gold nanoparticles using non-toxic solvents and nano filtration. The process is greener, faster and cheaper than the previous method.

Cleaner energy: Researchers at the University of Antwerp and the University of Leuven in Belgium have created a device which uses a membrane created from nanomaterials to extract hydrogen from air pollution. This hydrogen can then be stored as a potential clean fuel source. The device runs on solar power. It could allow cities to convert their air pollution into an abundant source of clean energy.

At the University of Texas at Dallas and Hanyang University in South Korea, material engineers have developed a yarn made of spun carbon nanotubes which produces an electric current when stretched. The researchers created a shirt from the yarn that produced an electrical signal each time the wearer breathed. The signal was strong enough to power a sensor. They also demonstrated a way to use the yarn to harvest energy from waves.

Turning motion into energy is also the goal of researchers at Vanderbilt University, who have developed a system that uses nanotechnology to harvest energy from human motion. They have created nano-sheets of black phosphorous just a few atoms thick. Bending or pressing the nanosheets produces a small electrical current that can be harvested and stored in a battery. When incorporated into clothing, the sheets are capable of producing an electric current from basic activities such as sitting, standing and walking.

What’s next: Most of the green nanotech applications mentioned above have actually been created. The next steps will include making them work at scale, and for the right price. Yet, these innovations highlighted are only the tip of the green nanotech iceberg. Scientists around the world are continuing to work on new ways of using the tech to save energy and to clean up waste.