Novel LEDs Would Simultaneously Illuminate and Disinfect a Room

Hieu Nguyen’s pandemic-inspired lighting would not only illuminate classrooms, offices and airport lobbies, but also disinfect them with invisible ultraviolet light that destroys pathogens such as the novel coronavirus, SARS-CoV-2.

With three possible settings, his LED panels would emit visible light, ultraviolet light or both, irradiating air, water and surfaces in enclosed settings. Backed by a CAREER grant from the National Science Foundation, he is exploring novel nanotechnology to generate light that would cut the energy consumption of these devices by half.

“Combining both of these features in a single LED allows people to work in a room that is being kept sterile continuously — the powerful UV rays kill the virus within seconds,” he explains. “These disinfection systems currently operate when the space has been vacated.”

In the search for photonic weapons, Nguyen says, the trick is to identify wavelengths that are germicidal but not harmful to humans. To disable the coronavirus without penetrating the human body, the sweet spot is the higher regions of UV spectrum, called far-UV, where the wavelengths are shorter.

“For safety reasons, most UV light can’t be used around people, because it damages human cells. Wavelengths at 254 nm prove to be harmful, for example,” he said, noting, however, that recent research indicated that far-UV irradiation in the 200-222 nm range was effectively germicidal, but did not penetrate cells in the skin’s dermis layer. In 2018, some of the first tests on far-UV light showed that it was capable of deactivating the H1N1 influenza virus, while other studies suggest it also kills spores, such as Bacillus subtilis.

“I’m developing LED lighting that could potentially include several settings that each employ a different portion of the electromagnetic spectrum for a single purpose, meaning embedding different wavelengths on multiple LEDs on the same chip,” notes Nguyen. “These lights can destroy other viruses, such as Ebola and bacteria such as E. coli, salmonella and Methicillin-resistant Staphylococcus aureus (MRSA), as well as fungi.”

His work on virus disinfection expands upon his use of LEDs to kill bacteria in food processing and water systems. With funding from the New Jersey Health Foundation, he is developing LEDs operating in the 400-650 nm wavelength range, which includes the more energetic portion of the visible spectrum and near-UV light, for food storage and distribution, among other applications. 

These bandwidths could also be integrated into normal lighting systems, making them suitable for restaurants, supermarkets, hospitals and homes.

Bacterial cells contain light-sensitive compounds called porphyrins, which absorb light in the visible wavelength region of the electromagnetic spectrum. When that energy is transferred to oxygen compounds, it produces a poison that destroys the cell’s lipids, proteins and DNA. Ultraviolet light destroys a microorganism’s nucleic acids and disrupts its DNA, preventing it from replicating.

While the pandemic has accelerated research on UV disinfection, the field still faces a daunting hurdle: Most devices are incorporated into conventional lighting, such as lamps, that are inefficient and lose energy in heat. Nguyen is developing a new form of nanowire LED, based on a novel platform, to make these systems highly efficient.

In a cleanroom, he fabricates UV semiconductors by combining aluminum, indium and nitride (AlInN) gases on a silicon substrate, where it forms a nanowire, an ultrathin structure of around 100 nanometers in diameter, but variable lengths. These nanowires improve upon their precursor, aluminum gallium nitride (AlGaN), because they emit light more efficiently and can be grown on many different substrates, from silicon, to metal, to sapphire. 

“I have been searching for new materials that will improve a range of photonic and electronic applications,” he notes. “While AlInN nanowires are difficult to make — the temperature during fabrication must be very precisely controlled — they appear to be very useful. They are able to emit light from a very wide range of the spectrum, from deep ultraviolet at 210 nm to near infrared at 1900 nm.”

He says these next-generation nanowire light-emitters are promising candidates not only for medical and biochemical applications, but also for solid-state lighting, (as part of data storage), high-speed communications, information processing, optical recording and zero emission automobiles, among other areas. His research will lead to the first demonstration of nanowire LEDs operating in the ultraviolet range using AlInN nanostructures.

“My goal is to create a new material platform,” Nguyen says. “Down the road, I’d like to use them to make lasers and transistors.”