Nav: Home

Smart fluorescent dyes

August 16, 2018

Controlling the excited electronic states in luminescent systems remains a challenge in the development of fluorescent and phosphorescent dyes. Now, scientists in Japan have developed a unique organic fluorophore that changes its emission color without loss of efficiency when externally stimulated. The study published in the journal Angewandte Chemie explains this behavior by a simple phase transformation of the solid substance, which could be relevant for optoelectronic applications such as in smart OLEDs.

Although luminescence is an extensively studied phenomenon and its theoretical basis is well understood, the development of new pigments and dyes with outstanding functionality is not straightforward. Phase transitions of a solid material may quench the fluorescence, and pigments in OLED applications are prone to aging. Now, the research group of Takuma Yasuda at Kyushu University, Fukuoka, Japan, has synthesized a green emitting pigment that responds to external stimuli by a remarkable color change into orange emission, and that without no observed loss in luminescence efficiency. This two-color behavior of one pigment might by highly useful for the development of smart optoelectronic and sensor systems.

To obtain efficient luminescent systems, scientists are increasingly focusing on the excited states and the electronic transitions: The more distinct and defined the electronic transitions are, the more efficient is the light emission when the substance is excited by light of other wavelengths or electric energy. On the other hand, disturbances of the molecular structure can trigger nonradiative relaxation, and then, most fluorescence is lost. Here, Yasuda and his group found that their synthesized fluorophore, which has an elongated and relatively simple symmetric structure incorporating well-known chromophores, can switch its emission colors between orange and green when changing solid-state morphologies.

The authors substantiated their findings with X-ray crystallographic analyses and theoretical calculations. They found that the amorphous phase holds a slightly relaxed excited state compared to the crystalline one. This was explained by a twist in the molecule, which occurred at a different angle when the crystal structure was broken. Accordingly, the light emitted from that amorphous-phase excited state was at a longer wavelength than that emitted from the excited crystalline state.

Such a two-color emission from different solid phases could be useful for sophisticated optoelectronic and sensor applications. The Japanese authors found that the substance emitted orange fluorescence when deposited as a thin film, but this color turned to green when the film was annealed, that is, kept at high temperature and cooled down again. Then they scratched the annealed film and found orange fluorescence exactly at the places of scratching; even writing words in orange fluorescence was possible.

A more demanding application is that in organic light-emitting devices, the OLEDs. Sandwiched in an OLED setup, the compound exhibited bright electroluminescence, either in green when in the crystalline phase or in orange color when in the amorphous phase. This two-color electroluminescence from one pigment might be highly interesting for the ongoing research on stimuli-responsive smart materials.
-end-
(3441 characters)

About the Author

Dr. Takuma Yasuda is Professor of Organic Materials Chemistry at the Inamori Frontier Research Center at Kyushu University, Fukuoka, Japan. His research group develops functional organic materials with semiconductor, luminescence, and photovoltaic properties.

http://www.inamori-frontier.kyushu-u.ac.jp/optoelectronics/

Wiley

Related Fluorescence Articles:

Novel 3D imaging technology makes fluorescence microscopy more efficient
A research team led by Dr Kevin Tsia from the University of Hong Kong (HKU), developed a new optical imaging technology -- Coded Light-sheet Array Microscopy (CLAM) -- which can perform 3D imaging at high speed, and is power efficient and gentle to preserve the living specimens during scanning at a level that is not achieved by existing technologies.
Staining cycles with black holes
In the treatment of tumors, microenvironment plays an important role.
Light-sheet fluorescence imaging goes more parallelized
In pursuit of 3D visualization of cells and organisms with minimal invasiveness and high spatiotemporal resolution, researchers demonstrated a new form of light-sheet imaging, coined CLAM, which allows scan-free, parallelized 3D fluorescence imaging that results in an even slower rate of photobleaching than scanning light-sheet imaging, yet without sacrificing the image speed and resolution.
Anti-carcinoembryonic antigen-related cell adhesion molecule antibody for fluorescence visualization
Oncotarget Volume 11, Issue 4: The research team's aim was to investigate mAb 6G5j binding characteristics and to validate fluorescence targeting of colorectal tumors and metastases in patient derived orthotopic xenograft models with fluorescently labeled 6G5j.
Dresden biologists make living sperm glow
By applying a novel method, biologists at TU Dresden have successfully analysed the metabolism of intact tissues of the fruit fly using a label-free microscopy technique.
Fluorescence spectroscopy helps to evaluate meat quality
Scientists of Sechenov University jointly with their colleagues from Australia proposed a new, quicker and cheaper way to assess meat quality.
New fluorescence method reveals signatures of individual microbes
University of Tsukuba researchers have developed a new method that reveals the unique fluorescence patterns produced by individual cells in mixtures of bacteria, yeast and fungi.
Quenching scientific curiosity with single-molecule imaging
New experimental insights allow researchers to probe protein-DNA interactions with greater precision.
Scientists engineer unique 'glowing' protein
Biophysicists from MIPT and their colleagues from France and Germany have created a new fluorescent protein.
Microglia turned on
Part of the immune system in the brain is made up of so-called microglia cells.
More Fluorescence News and Fluorescence Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.