NYU develops eco-friendly way to see in the dark

30 Sep 2025

Environmentally compliant quantum dots avoid toxic heavy metals in infrared imaging.

Advances in infrared sensor performance have allowed dramatic strides in night vision systems, with quantum dots emerging as promising materials for IR detection.

These materials often involve the use of environmentally unfriendly materials, however, with the presence of mercury or lead meaning they cannot easily conform to increasingly strict environmental regulations.

This regulatory pressure has slowed the broader adoption of infrared detectors across civilian applications, just as demand in fields like autonomous vehicles, medical imaging and national security is accelerating, according to a project at New York University (NYU) that has developed a possible answer.

The breakthrough, discussed in ACS Applied Materials & Interfaces, involves the design and manufacture of more environmentally friendly colloidal quantum dots to detect infrared light without relying on restricted materials.

"The industry is facing a perfect storm where environmental regulations are tightening just as demand for infrared imaging is exploding," said Ayaskanta Sahu from NYU Tandon School of Engineering. "This creates real bottlenecks for companies trying to scale up production of thermal imaging systems."

Photodetectors based on silver selenide (Ag₂Se) are known to offer a potential route to sensors with more compliant chemical compositions, but they have not been studied in depth because of challenges involved in their manufacture. Electrochemical instability, cracks and voids have been recurring problems, noted the NYU team.

IR detection where few materials exist for the task

The NYU answer was to use a solution-phase ligand exchange (SPLE) technique to create the silver selenide sensors, the first time this approach had been taken. This solution-based process yields smooth and uniform coatings in a single step, ideal for scalable manufacturing.

"This approach allows for the formation of IR-active inks that can quickly form crack-free films reproducibly and may be deposited using a variety of techniques," noted the project in its paper.

The team also built on earlier research into transparent electrodes made from silver nanowires, which remain highly transparent to infrared light while efficiently collecting electrical signals. So the quantum dots provide environmentally compliant sensing capability, while the transparent electrodes handle signal collection and processing.

In trials, devices based around the new architecture "set new performance benchmarks for Ag₂Se-based systems, with photoconductors achieving reproducible responsivities up to 150 mA/W," said the project. Although this performance falls short of the best heavy-metal-based detectors in some measurements, NYU expects continued advances in quantum dot synthesis and device engineering could reduce the gap.

"What excites me is that we can take a material long considered too difficult for real devices and engineer it to be more competitive," said lead author Shlok Paul. "With more time this material has the potential to shine deeper in the infrared spectrum where few materials exist for such tasks."