A Japanese research team from Chiba University introduced an innovative device that combines light emission and color control using clay compounds, offering a versatile solution for multifunctional displays. The study was published in the Journal of Materials Chemistry C.
Researchers develop a dual-mode electrochemical device using the clay-based hybrid system. This clay-based device integrates light emission and color control, enabling an efficient and sustainable solution for modern displays. Image Credit: Reproduced from Journal of Materials Chemistry C (Cover Image, Issue 4, 2025) with permission from the Royal Society of Chemistry.
Stimuli-responsive materials based on electrochemical reactions are shaping the future of cutting-edge display devices. The device simultaneously controls color and light emission at low voltage by embedding color-changing viologen derivatives and luminescent europium(III) complexes in a layered clay matrix.
An environmentally friendly method of improving the performance of electronic devices is also highlighted by the use of clay-based materials. This invention has the potential to completely transform sensor development and display technology by making them more sensitive to variations in illumination.
With the growing popularity of electrochemical stimuli-responsive materials, the field of display technology is poised for a revolutionary development. These materials can instantaneously electrochemical reactions in response to external stimuli like low voltage. These electrochemical reactions, which can produce a variety of colors, could revolutionize the era of display solutions. Electrolytes and electrodes make up an electrochemical system. Combining the coloration and luminescent molecules on the electrodes rather than the electrolyte can provide increased stability and efficiency for display devices.
The research team utilized clay membranes to seamlessly integrate coloration and luminescence molecules. Led by Professors Norihisa Kobayashi and Kazuki Nakamura, with co-authors Ms. Rong Cao and Mr. Naoto Kobayashi from Chiba University’s Graduate School of Science and Engineering, the study introduces an innovative dual-mode electrochemical device that combines light emission and color change.
This research showcases a highly adaptable and energy-efficient approach to modern display technology, highlighting the potential of advanced materials science in practical applications.
Our approach introduces a game-changing concept in dual-mode display design by uniting luminescence and coloration within a single device. This advancement not only enhances performance but also expands the versatility of displays across diverse environments.
Norihisa Kobayashi, Professor and Distinguished Faculty Member, Graduate School of Sciences and Engineering, Chiba University
The device uses smectite, a layered clay compound known for its potent adsorption capabilities and ion exchange capacity. This clay matrix stabilizes and improves two essential components—europium(III) (or Eu(III)) complexes, which produce vivid luminescence, and heptyl viologen (HV2+) derivatives, which permit striking color changes. Combined, these substances produce a hybrid solution enabling coordinated electrochemical color and light modulation.
The team produced a complex by combining triphenylphosphine oxide (TPPO), hexafluoroacetylacetone (hfa-H2), and Eu(III). After that, the team built the apparatus by covering indium tin oxide (ITO) electrodes with hybrid films of smectite, HV2+, and Eu(hfa)3(TPPO)2. Upon applying a voltage, these films displayed dynamic optical properties. In particular, the HV2+ molecules displayed exact control over both functions by producing a striking cyan coloration upon electrochemical reactions and quenching the luminescence from the Eu (III) complex.
This creative material integration has positive environmental effects in addition to scientific significance. The gadget allays growing worries about the sustainability of electronic devices by using low-voltage operations and consuming less energy.
Additionally, using clay compounds that are naturally abundant provides an environmentally friendly substitute for synthetic materials that are frequently used in comparable applications.
The dual-mode functionality operates flawlessly in a variety of environmental settings. The study also sheds light on the interactions between the embedded molecules and the clay matrix, demonstrating how the clay's structural characteristics support improved performance. According to the researchers, the clay's interlayer spacing improved electron mobility and allowed for quicker and more effective reactions.
This technology bridges the gap between energy-efficient reflective displays and high visibility emissive screens. Its adaptability to different lighting conditions makes it an ideal solution for various applications, from digital signage to portable devices.
Kazuki Nakamura, Professor and Esteemed Faculty, Graduate School of Sciences and Engineering, Chiba University
Clear optical changes were produced by the effective energy transfer between the luminescent and color-active states that occurred when a bias voltage of −2.0 V was applied. The inner filter effect and fluorescence resonance energy transfer are two mechanisms that guarantee efficient component interaction and provide this dual-mode performance.
There are many possible uses for this gadget. It might open the door for cutting-edge, energy-efficient displays still visible in bright and dim lighting. For instance, this technology could greatly help digital signage and reflective tablets, solving issues like low visibility in direct sunlight or high power consumption in emissive screens. By adding more materials, the team hopes to increase the device’s functionality, possibly increasing its adaptability and creating new commercial opportunities.
Our ultimate goal is to design display technologies that are not only more sustainable but also more versatile.
Norihisa Kobayashi, Professor and Distinguished Faculty Member, Graduate School of Sciences and Engineering, Chiba University
The New Energy and Industrial Technology Development Organization, the Izumi Science and Technology Foundation, the Iketani Science and Technology Foundation, and JSPS KAKENHI funded the study, and JST SPRING provided additional assistance.
Journal Reference:
Cao, R., et al. (2025) Electrochemically controllable emission and coloration using a modified electrode with a layered clay compound containing viologen derivative and europium(III) complex. Journal of Materials Chemistry C. doi.org/10.1039/d4tc04026k