Stanford Revives 100-Year-Old Material for Cleaner Air Tech

Scientists at Stanford University just proved that sometimes the best solutions have been sitting right in front of us for over a century.

A team of materials engineers found a way to transform lead selenide and lead tin selenide—semiconductors first discovered more than 100 years ago—into powerful infrared sensors and light-emitting diodes. These updated devices could revolutionize how we monitor air quality, track greenhouse gases, and measure vital signs in hospitals.

"We taught an old dog new tricks," said Kunal Mukherjee, an assistant professor of materials science and engineering at Stanford. His team spent five years perfecting a technique to build these materials atom by atom, sometimes racing to the lab at 2 a.m. to keep their equipment running during power outages.

The breakthrough solves two major problems that have kept infrared technology expensive and bulky. First, these new devices work even when they're not built with absolute precision, something nearly impossible to achieve with such tiny crystals. That tolerance for imperfection could slash manufacturing costs significantly.

Second, because these semiconductors have been studied for decades, manufacturers can potentially produce them using existing chip-making equipment. No expensive factory overhauls needed.

The team's infrared diodes emit light in wavelengths perfect for detecting gases in the atmosphere or measuring carbon dioxide levels in medical settings. The researchers were surprised to find that the devices shined brightly despite containing billions of structural defects per square centimeter—flaws that would normally ruin modern semiconductors.

In a second discovery, graduate student Pooja Reddy found a way to control the infrared light by making precise temperature adjustments. These tiny temperature changes cause the crystal structure to shift between two perfectly ordered states, switching the light from transparent to opaque like a dimmer switch.

The Ripple Effect

This innovation arrives at a crucial moment for environmental monitoring. Current infrared technologies for detecting greenhouse gases tend to be expensive, bulky, and difficult to deploy widely. Mukherjee envisions a new generation of sleek, affordable devices that could make comprehensive air quality monitoring accessible to communities everywhere.

The applications extend far beyond environmental protection. Better medical sensors could improve patient monitoring in hospitals. Industrial facilities could detect gas leaks more reliably and affordably. The technology works across infrared wavelengths stretching nearly to 10,000 nanometers, opening possibilities scientists are just beginning to explore.

After five years of painstaking work building crystals layer by layer, the Stanford team has shown that innovation doesn't always mean starting from scratch—sometimes it means rediscovering forgotten potential.