Chemists create the brightest-ever fluorescent materials

Date:
August 6, 2020
Source:
Cell Press
Summary:
By formulating positively charged fluorescent dyes into a new
class of materials called small-molecule ionic isolation lattices
(SMILES), a compound's brilliant glow can be seamlessly transferred
to a solid, crystalline state, researchers report. The advance
overcomes a long- standing barrier to developing fluorescent solids,
resulting in the brightest known materials in existence.



FULL STORY ==========================================================================
By formulating positively charged fluorescent dyes into a new class
of materials called small-molecule ionic isolation lattices (SMILES),
a compound's brilliant glow can be seamlessly transferred to a solid, crystalline state, researchers report August 6 in the journal Chem. The
advance overcomes a long- standing barrier to developing fluorescent
solids, resulting in the brightest known materials in existence.


========================================================================== "These materials have potential applications in any technology that
needs bright fluorescence or calls for designing optical properties,
including solar energy harvesting, bioimaging, and lasers," says Amar
Flood, a chemist at Indiana University and co-senior author on the study
along with Bo Laursen of the University of Copenhagen.

"Beyond these, there are interesting applications that include
upconverting light to capture more of the solar spectrum in solar cells, light-switchable materials used for information storage and photochromic
glass, and circularly polarized luminescence that may be used in 3D
display technology," Flood says.

While there are currently more than 100,000 different fluorescent dyes available, almost none of these can be mixed and matched in predictable
ways to create solid optical materials. Dyes tend to undergo "quenching"
when they enter a solid state due to how they behave when packed close together, decreasing the intensity of their fluorescence to produce a
more subdued glow.

"The problem of quenching and inter-dye coupling emerges when the dyes
stand shoulder-to-shoulder inside solids," says Flood. "They cannot help
but 'touch' each other. Like young children sitting at story time, they interfere with each other and stop behaving as individuals." To overcome
this problem, Flood and colleagues mixed a colored dye with a colorless solution of cyanostar, a star-shaped macrocycle molecule that prevents
the fluorescent molecules from interacting as the mixture solidified,
keeping their optical properties intact. As the mixture became a solid,
SMILES formed, which the researchers then grew into crystals, precipitated
into dry powders, and finally spun into a thin film or incorporated
directly into polymers. Since the cyanostar macrocycles form building
blocks that generate a lattice-like checkerboard, the researchers could
simply plug a dye into the lattice and, without any further adjustments,
the structure would take on its color and appearance.

While previous research had already developed an approach to spacing the
dyes apart using macrocycle molecules, it relied on colored macrocycles
to do the job. Flood and colleagues found that colorless macrocycles
were key.

"Some people think that colorless macrocycles are unattractive, but they allowed the isolation lattice to fully express the bright fluorescence
of the dyes unencumbered by the colors of the macrocycles," says Flood.

Next, the researchers plan to explore the properties of fluorescent
materials formed using this novel technique, enabling them to work with
dye makers in the future to realize the materials' full potential in a
variety of different applications.

"These materials are totally new, so we do not know which of their innate properties are actually going to offer superior functionality," says
Flood. "We also do not know the materials' limits. So, we will develop
a fundamental understanding of how they work, providing a robust set of
design rules for making new properties. This is critical for putting
these materials into the hands of others -- we want to pursue crowd
sourcing and to work with others in this effort."

========================================================================== Story Source: Materials provided by Cell_Press. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Christopher R. Benson, Laura Kacenauskaite, Katherine
L. VanDenburgh, Wei
Zhao, Bo Qiao, Tumpa Sadhukhan, Maren Pink, Junsheng Chen, Sina
Borgi, Chun-Hsing Chen, Brad J. Davis, Yoan C. Simon, Krishnan
Raghavachari, Bo W. Laursen, Amar H. Flood. Plug-and-Play Optical
Materials from Fluorescent Dyes and Macrocycles. Chem, 2020; 6
(8): 1978 DOI: 10.1016/ j.chempr.2020.06.029 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200806111859.htm

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