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Crystal melts and changes color in light.


Rare Chemical Property Discovered in Crystal

A team of chemists from Osaka University in Japan have identified a rare property in a crystal. When exposed to the cool glow of ultraviolet (UV) light, the solid organic material transforms into a liquid.

Interesting Luminescence Changes

What’s more, this crystal undergoes an interesting series of changes in its luminescence as it melts that point to changes in the structure of the crystal at the molecular level. Though unusual, it’s not the first substance found to undergo what’s known as photo-induced crystal-to-liquid transition (PCLT). But being able to study the transition using light could help scientists understand it better, potentially opening up a whole range of potential uses in photonics, electronics, and drug delivery.

Organic Compound ‘SO’

The material is a type of organic compound known as a heteroaromatic diketone, one the team dubbed ‘SO’ after the sulfur and oxygen in its two rings. When first exposed to UV light, the SO crystal compound glows in a faint green light. As the exposure continues, however, it glows yellow and slowly melts. Based on close observations of the sharpness of the boundary between the states, it’s clear heating isn’t responsible for the transition.

Research and Analysis

Using theoretical calculations and a variety of study techniques (including X-ray analysis and thermodynamic property analysis), plus data from previous research, the team determined that diketone SO was actually switching from one molecular form (“skew”) to another (“planar”). Further insights were obtained from other similar crystal compounds, that either didn’t melt or did melt but didn’t change color. That tells the researchers something about the molecular changes that occur as these crystals shift from solids to liquids.

The Possibility of Controlling Materials with Light

And being able to control materials with light could be very useful: it’s relatively affordable and simple to do, environmentally friendly, and non-invasive. One example application suggested by the researchers is a reversible adhesive that can be modified through light exposure. What’s key to the progress outlined in this study is the way that diketone SO changed color, giving the researchers a vital insight into what was going on at the smallest scales inside the crystal compound.


In conclusion, the discovery of a rare property in SO crystals by chemists in Japan is a significant achievement in understanding photo-induced crystal-to-liquid transition. The research conducted sheds more light on the properties of SO crystals, opening up many potential applications for photonics, electronics, and drug delivery. The findings could also lead to developing materials controlled with light that could be useful for many things, including reversible adhesives.

1) What is photo-induced crystal-to-liquid transition?
Photo-induced crystal-to-liquid transition (PCLT) refers to the property of some substances that change from a solid crystalline state to a liquid state when exposed to certain types of light.

2) What is diketone SO?
Diketone SO is a type of organic compound known as a heteroaromatic diketone, named after the sulfur and oxygen in its two rings.

3) What are the potential uses of photo-induced crystal-to-liquid transition?
Potential uses of photo-induced crystal-to-liquid transition include photonics, electronics, and drug delivery. The ability to control materials using light could be very useful, from developing materials with reversible adhesives to environmentally friendly and non-invasive ways of working with materials.

4) What did the researchers from Osaka University use in their study?
The researchers from Osaka University used theoretical calculations, X-ray analysis, thermodynamic property analysis, and data from previous research to determine how diketone SO changed from a solid to a liquid when exposed to ultraviolet (UV) light.


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