Lasers and gold nanoparticles enable on-demand crystal growth for new materials

Researchers at Michigan State University have discovered how to “draw” on demand the crystals used in many crucial technologies, from solar panels and LED lighting to medical imaging.

Appearing in the journal ACS Nano, the breakthrough was achieved by striking gold nanoparticles with a single laser pulse.

“We’re just beginning to scratch the surface of what’s possible. This is opening a new chapter in how we design and study materials,” said Elad Harel, associate professor in the Department of Chemistry and senior author of the study.

Take the time to look around, and you’ll find a world that runs on crystals. From smoke alarms and television screens to ultrasounds and sonar, the unique optical and electrical properties of these chemical structures place them at the cutting-edge of most innovations.

Growing crystals, however, isn’t easy.

“When using traditional growing methods, crystals can form at random times and locations, so the results might not always be the same,” Harel said.

As technologies and materials rapidly improve, they rely on crystals of exceptional quality being placed in just the right spot, so this lack of control is a major hurdle for researchers.

To tackle this challenge, Harel turned to his lab’s specialty—lasers, and in particular, fast lasers.

At MSU, Harel uses short laser pulses to shine a light on the mysteries of the natural world. This includes a recent breakthrough that leveraged ultra-fast lasers to actually “hear biology.”

In the new publication, the researchers tried their hand at growing types of crystals called lead halide perovskites. These crystals are crucial for LEDs, solar cells and medical imaging.

Rather than move through the typical complicated steps of crystal growth or even use a small “seed” crystal to jumpstart the process, Harel’s team aimed their lasers at a tiny glittering target: gold nanoparticles less than one thousandth the width of a human hair.

The scientists revealed that these particles generated heat where the laser light struck, and that this interaction led to crystallization. Using special, high-speed microscopes, they were even able to watch the process unfold in real time.

Like a laser used to engrave artwork into metal or wood, this sort of crystal creation offers researchers the ability to “draw” crystals with levels of control that could transform fields ranging from clean energy to quantum technologies. The findings also help expand our understanding of how crystals form—a notoriously tricky area of chemistry.

“With this method, we can essentially grow crystals at precise locations and times,” said Dr. Md Shahjahan, a research associate at MSU and first author of the paper. “It’s like having a front-row seat to watch the very first moments of a crystal’s life under a microscope. Only here can we also steer how it develops.”

With their gold nanoparticles now in the spotlight, Elad’s team is heading back to the lab for future experiments with big potential.

These include using multiple lasers of different colors to “draw” even more intricate crystal patterns and attempting to create entirely new materials that can’t be made through conventional methods.

“Now that we can ‘draw’ crystals with lasers, the next step is to make larger and more complex patterns, and to test how these crystals perform in real devices,” Harel said.