Crystal clear: Scientists develop new way to see inside crystals

The new technique allows scientists to see each particle that makes up colloidal crystals and to create dynamic three-dimensional models. Credit: Shihao Zang

Imagine being able to look inside a crystal as if you had X-ray vision. Scientists have now made this possible with a new technique called “Crystal Clear.”

This method combines transparent particles, microscopes, and lasers to create three-dimensional models of crystals, allowing researchers to see every detail inside them.

Stefano Sacanna, a chemistry professor at New York University, led the study published in Nature Materials.

He explains, “In the past, we could only see the surface of a crystal under a microscope. Now, we can see inside and know the position of every particle.”

Crystals are solid materials made up of atoms arranged in a repeating pattern. Sometimes, atoms are missing or out of place, creating defects that affect the crystal’s properties.

To study these structures more easily, scientists often use colloidal particles, which are tiny spheres much larger than atoms but still microscopic.

Sacanna’s team, led by PhD student Shihao Zang, wanted to see inside these colloidal crystals. They created transparent colloidal particles and labeled them with dye molecules, making them visible under a microscope using their fluorescence.

However, a regular microscope couldn’t provide a detailed view inside the crystals. So, they used a technique called confocal microscopy, which involves scanning a laser beam through the material to produce a fluorescent image from the dye molecules.

This method allowed the researchers to see each two-dimensional layer of the crystal, which they could then stack to build a three-dimensional digital model. They could rotate, slice, and examine these models to find any defects inside the crystals.

In one experiment, the researchers studied crystals that form when two of the same type grow together, a phenomenon known as “twinning.” They found a shared plane of the joined crystals, revealing the molecular origin of twinning. This discovery helps explain the unique shapes of these crystals.

The new technique also lets scientists observe how crystals change over time. For example, they melted a crystal with a structure similar to cesium chloride and found that the defects remained stable instead of moving around as expected. To confirm their findings, they used computer simulations, which matched the results seen in the crystals.

With this new method, scientists can better understand how crystals form and evolve. This knowledge could lead to improved ways of growing crystals and developing materials that interact with light. Sacanna believes that “being able to see inside crystals gives us greater insight into the crystallization process and can help us design better crystals.”

The research was funded by the US Army Research Office and the National Institute of Health, with additional support from NYU’s High Performance Computing resources.

Source: NYU.