Researchers in Japan have developed a novel molecular system that dynamically shifts between one-, two-, and three-dimensional structures based on light intensity. This breakthrough, published in Chem on November 17, 2025, demonstrates a level of adaptive control over molecular assemblies previously unseen, offering potential for advanced materials that respond to environmental changes like living systems.
The Challenge of Adaptive Molecular Structures
Creating materials that exist outside of thermodynamic equilibrium – meaning they don’t naturally settle into their lowest energy state – is a major goal in materials science. Most systems require constant energy input (like heat or light) to maintain these states. What’s rare is a system that adjusts its structure based on how much energy it receives.
How the New System Works
The team, led by Professors Shiki Yagai (Chiba University), Christian Ganser (National Institutes of Natural Sciences), and Masaki Kawano (Institute of Science Tokyo), designed a molecule that combines a light-sensitive component (azobenzene) with a structure-shifting core (a barbituric acid-based merocyanine).
- Ambient Light: The molecule initially forms coiled one-dimensional nanofibers. Under normal room light, these spontaneously rearrange into stable two-dimensional nanosheets.
- Strong UV Light: Intense ultraviolet light forces the nanosheets to revert back into linear nanofibers. This happens because the light triggers a change in the azobenzene component, disrupting the hydrogen bonds that hold the nanosheets together. High-speed atomic force microscopy (HS-AFM) shows this transformation happens selectively on specific crystalline surfaces where the light-sensitive component is exposed.
- Weak UV Light: Low-intensity ultraviolet light causes smaller nanosheets to break down, while larger ones grow vertically into three-dimensional nanocrystals. This happens through a process called Ostwald ripening, where smaller structures dissolve and redeposit onto larger ones, causing them to grow. HS-AFM captured this process in real-time, including the formation of new crystals and their growth on existing structures.
Why This Matters
This research demonstrates that it is possible to design molecular systems that adapt their structure based on external energy levels. Unlike most materials that require constant energy to maintain non-equilibrium states, this system responds to changes in energy input. This could lead to materials that dynamically adjust their properties – for example, changing their conductivity, flexibility, or reactivity – in response to light, temperature, or other environmental factors.
This level of control over molecular assemblies opens up possibilities for creating “smart” materials that mimic the adaptability of biological systems
