By formulating positively charged fluorescent dyes into a new class of materials called small-molecule Ionic isolation cages (SMILES), the bright glow of a compound can be seamlessly transferred into a solid, crystalline state, researchers reported on August 6 in the journal Chem. Progress has overcome a long-standing hurdle in the development of fluorescent solids, which exist and make up the brightest materials known.
“These materials have potential applications in any technology that requires bright fluorescence or calls to design optical properties such as solar energy harvesting, bio-imaging and lasers,” says Amar Flood, a chemist at Indiana University and lead author of the study. The second executive author of the study is Bo Laursen of the University of Copenhagen.
Flood says:”beyond these, materials that convert light to capture more of the solar spectrum in solar cells, light-interchangeable materials used for information storage and photochromic glass, and circular polarized luminescence that can be used in 3-D display technology can be obtained”.
While there are now more than 100,000 different fluorescent dyes available, almost none of them can be mixed and matched in predictable ways to create solid optical materials. Because of the behavior it exhibits when dyes are stacked close together, they tend to “quench” when they become solid, their brightness becomes less because the intensity of their fluorescence decreases.
“The problem caused by damping and intercooling occurs when the dyes stand shoulder to shoulder inside the solids,” Flood says. “They can’t touch each other. Like young children sitting in story time, they interfere with each other and do not behave like adult individuals.”
To overcome this problem, Flood and his colleagues mixed a colored dye with a colorless cyano-star solution, a star-shaped macrohalpy molecule that kept its optical properties intact, preventing fluorescent molecules from interacting as the mixture solidified. As the mixture solidified, the structure of SMILES occurred, where it turned into crystals, collapsed as dry powders, and finally turned into a thin film or joined directly into polymers. Because the cyano-star macrohalves form a cage-like checkerboard, researchers can add paint to the cage and make it take on the structure’s color and appearance without further adjustment.
Although previous research had developed an approach to separate dyes using macrohalka molecules, colored macrohalka was needed to do the job. Flood and his colleagues found that colorless macro cycles play an important role. “Some people think colorless macrohalcas are unattractive, but they have allowed smiles to fully express the bright fluorescence of dyes, unobstructed by the colors of macrohalcas,” Flood says.
Next, the researchers planned to investigate the properties of fluorescent materials created using this new technique, enabling them to work with paint manufacturers in the future to realize the full potential of the materials in various paint applications.
” These materials are completely new, so we don’t know what their innate properties will actually offer superior functionality, ” says Flood. “Nor do we know the limits of materials. Therefore, we will provide a solid set of design rules for making new substances and develop a basic understanding of how they work. In this way, we have made a critical decision to deliver these materials into the hands of others – we want to continue the search for crowd resources and work with others in this effort. “