Researchers developed a new type of carbon dot that changes its fluorescence color based on the liquid it’s in and incorporated the dots into foldable plastic films. Credit: Adapted from ACS Central Science 2026, DOI: 10.1021/acscentsci.6c01482
Fluorescent materials usually emit a single consistent color. They are typically made from dyes or metallic components. In contrast, researchers reporting in ACS Central Science have created carbon dots that can fluoresce in a range of colors under UV light, depending on the concentration and the liquid they’re in.
Researchers at Zhengzhou University wanted to make more versatile fluorescent materials that shift between different colors in response to their surroundings. They were especially interested in these materials for environmental sensing and dynamic information encryption. They turned to carbon dots—tiny particles that can fluoresce brightly and whose surfaces are adjustable. By tuning those surfaces, they found that the same dot could fluoresce in different colors in varying conditions.
First, the researchers heated two carbon-based compounds in an organic solvent under pressure, forming particles with carbon-rich cores and chemically responsive surfaces. They made two versions, CD1 and CD2, using different ratios of the starting materials.
In tests, CD1 fluoresced red in acidic water and green in alkaline water. Shifting the pH caused the color change to reverse repeatedly without changing the dots’ brightness. Similarly, when suspending CD1 and CD2 in different liquids—for example, water, toluene, methanol, and ethanol—or varying the dots’ concentration, the researchers observed that the dots changed their fluorescence, emitting colors from blue to red.
Next, the researchers mixed carbon dot solutions with polymers to make blue, green, yellow, and red materials. They incorporated carbon dot-polymer powders into crafts, including molded Chinese characters and decorative bottles, and folded flexible films into different shapes.
They also used the dots’ color changes to create a multidimensional encryption system, encoding information through unique light, liquid, and acidity conditions. Together, these findings demonstrate potential uses of the new carbon dots in data security and anti-counterfeiting technologies.
The researchers are actively exploring opportunities to commercialize the CDs, particularly for information encryption. Next, the team will evaluate long-term stability, large-scale manufacturing and production cost.
Data from American Chemical Society