New structural phase transition may broaden the applicability of photo-responsive solids

March 26, 2019

A team of scientists from Waseda University in Tokyo and Rigaku Corporation discovered a new type of structural phase transition of an organic crystal, called the photo-triggered phase transition.

Hideko Koshima, a visiting professor at Waseda's Research Organization for Nano & Life Innovation and leading author of this study, says, "Phase transition mechanisms are widely used in memory, switch, and actuation materials, and we believe that this discovery of a new phase transition has potential for both basic science and application fields."

Their study was published in Communications Chemistry on February 20, 2019.

Induced by external stimuli such as temperature, pressure, electromagnetic fields, and light, a structural phase transition is a phenomenon that changes the physical properties and functions of solid-state materials. For instance, shape memory alloys, which have applications in robotics and in automotive, aerospace, and biomedical industries, recover its shape upon heating due to martensitic transitions. In recent years, organic crystals have been considered 'fascinating candidates' as materials for next-generation actuators because of their properties, such as its softness and light weight.

Prior to this study, the team has reported that they developed a mechanical crystal which bends with exposure to light, as well as a robotic crystal which 'walks and rolls' when heated and cooled. The actuation of these crystals can be respectively explained by a photochromic reaction, known as photoisomerization, and structural phase transition. To diversify the movements of such crystals, scientists have been looking for organic crystals which exhibit both phenomena.

Finding such crystal is no easy task and requires trial-and-error. However, when the team was studying an organic crystal called the photochromic chiral salicylideneamine crystal, not only did they find that this crystal exhibits both phenomena, but they also discovered the new structural phase transition.

"We accidentally stumbled upon the photo-triggered phase transition of the photochromic chiral salicylideneamine crystal, which exhibits a thermal phase transition that is reversible upon heating and cooling," explains Professor Koshima. "When irradiating this crystal with ultraviolet light at -50°C, a temperature lower than its thermal transition temperature (40°C), we found from an X-ray crystallographic analysis that the crystal undergoes transformation identical to that of a thermal phase transition."

The team also learned that the photo-triggered phase transition occurs because of the strain of molecules produced by photoisomerization, and Koshima adds that the photo-triggered phase transition differs from a photo-induced phase transition, which has appeared in other publications.

"The crystal phase due to the photo-induced phase transition appears only by light irradiation, which changes the electric and/or magnetic properties of the crystals within femto- or picoseconds. In the photo-triggered phase transition, the crystal phase triggered by light is identical to that via thermal phase transition, induced by heating, but unique with respect to its molecular conformation," she says.

Because the photo-triggered phase transition is induced by light irradiation and does not require heating and cooling for the structural phase transition to occur, the team's findings may 'lead to a new strategy to broaden applicability of photo-responsive solids' and contribute to research and development of next-generation sensing, switching, memory, and actuators that enable remote control and/or local operation by light.

The team is now planning to measure and quantitatively evaluate the magnitude of the crystal's strain caused by photoisomerization, systematically investigate whether the photo-triggered phase transition occurs in other crystals using materials informatics, and clarify its conditions.
-end-
About the published article

- Published in Communications Chemistry on February 20, 2019

- Title: Observation of dressed states of distant atoms with delocalized photons in coupled-cavities quantum electrodynamics

- Authors: Takuya Taniguchi, Hiroyasu Sato, Yuki Hagiwara, Toru Asahi, Hideko Koshima

- DOI: 10.1038/s42004-019-0121-8

University news on this research

About Waseda University

Located in the heart of Tokyo, Waseda University is a leading private research university which has long been dedicated to academic excellence, innovative research and civic engagement at both the local and global levels. Today, the student body at Waseda is approximately 50,000, over 7,000 of whom are from overseas, hailing from 120 countries. To learn more about Waseda University, visit https://www.waseda.jp/top/en-Hyperlink: Co

Waseda University

Related Memory Articles from Brightsurf:

Memory of the Venus flytrap
In a study to be published in Nature Plants, a graduate student Mr.

Memory protein
When UC Santa Barbara materials scientist Omar Saleh and graduate student Ian Morgan sought to understand the mechanical behaviors of disordered proteins in the lab, they expected that after being stretched, one particular model protein would snap back instantaneously, like a rubber band.

Previously claimed memory boosting font 'Sans Forgetica' does not actually boost memory
It was previously claimed that the font Sans Forgetica could enhance people's memory for information, however researchers from the University of Warwick and the University of Waikato, New Zealand, have found after carrying out numerous experiments that the font does not enhance memory.

Memory boost with just one look
HRL Laboratories, LLC, researchers have published results showing that targeted transcranial electrical stimulation during slow-wave sleep can improve metamemories of specific episodes by 20% after only one viewing of the episode, compared to controls.

VR is not suited to visual memory?!
Toyohashi university of technology researcher and a research team at Tokyo Denki University have found that virtual reality (VR) may interfere with visual memory.

The genetic signature of memory
Despite their importance in memory, the human cortex and subcortex display a distinct collection of 'gene signatures.' The work recently published in eNeuro increases our understanding of how the brain creates memories and identifies potential genes for further investigation.

How long does memory last? For shape memory alloys, the longer the better
Scientists captured live action details of the phase transitions of shape memory alloys, giving them a better idea how to improve their properties for applications.

A NEAT discovery about memory
UAB researchers say over expression of NEAT1, an noncoding RNA, appears to diminish the ability of older brains to form memories.

Molecular memory can be used to increase the memory capacity of hard disks
Researchers at the University of Jyväskylä have taken part in an international British-Finnish-Chinese collaboration where the first molecule capable of remembering the direction of a magnetic above liquid nitrogen temperatures has been prepared and characterized.

Memory transferred between snails
Memories can be transferred between organisms by extracting ribonucleic acid (RNA) from a trained animal and injecting it into an untrained animal, as demonstrated in a study of sea snails published in eNeuro.

Read More: Memory News and Memory Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.