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MIL OSI Translation. Region: Russian Federation –

Source: Novosibirsk State University – Novosibirsk State University –

Researchers at the Laboratory of Low-Carbon Chemical Technologies Faculty of Natural Sciences, Novosibirsk State University (OREL Research Lab) are developing materials with an afterglow effect based on organic molecules.

— In my laboratory we study organic light-emitting materials. One of our areas of research is materials with an afterglow effect. Such materials, being exposed to light for some time, are then capable of emitting light themselves for a few seconds. Inorganic materials with such properties have been known for a very long time. However, most of them contain heavy metals, the presence of which causes the phosphorescence effect. In our work, we use a completely different approach – we abandon heavy metals in favor of organic molecules for the sake of less toxicity and greater availability. Using a variety of organic molecules, we tailor the system to make the material glow longer and more efficiently. This approach allows us to completely control the properties by varying the structure of the molecules used and, depending on the tasks set, to specifically obtain the necessary materials with the desired properties,” explains Evgeniy Mostovich, head of the laboratory.

В настоящее время ученые НГУ создали материал с очень высокой квантовой эффективностью послесвечения (>70%), in which the accumulation of light radiation is almost equal to its re-emission with a very effective contribution to the afterglow, the duration of which reaches up to three seconds. For organic materials this is quite long, but laboratory specialists intend to increase its duration. To do this, using various methods of time-resolved spectroscopy, they study the processes occurring in materials with afterglow over various periods of time from the moment of irradiation. And depending on the structure of the molecules, their concentration and the type of matrix used, they determine ways to optimize this system, increase its efficiency and increase the afterglow time. Researchers have studied various systems and found out which groups of atoms in organic molecules increase its duration, and which, on the contrary, reduce it. Now they are developing approaches to the targeted synthesis of organic molecules that will have either a longer or shorter afterglow time.

— As a rule, organic molecules do not have a long afterglow at room temperature. In order for an organic molecule to exhibit an afterglow, such as phosphorescence, it must be “frozen.” One of the molecules we developed for this purpose has a phosphorescence lifetime of up to 10 seconds, but only at a temperature of 77 Kelvin (i.e. -196 degrees Celsius). Researchers are interested in how to increase this operating temperature to room temperature. We have developed special molecules – emitters, in the structure of which there are so-called donor and acceptor parts. Such molecules have a property called thermally activated delayed fluorescence. We dissolve the emitter in a suitable matrix, a substance that “freezes” the vibrations of the emitter molecules, as a result, thermally activated delayed fluorescence is turned on, and we, in turn, obtain materials with very high afterglow efficiency. It is important that the amount of emitter in the matrix can be negligibly small – down to one molecule per billion molecules of the matrix. “We found that even at this concentration, the system continues to show a fairly effective afterglow, visible to the naked eye,” said the head of the laboratory.

Another task that the researchers set for themselves is to create an afterglow palette. Now created in the laboratory OREL Research Lab Afterglow materials glow yellow, green and blue, with plans to complement this color range with red and orange. This may be useful for bioimaging laboratory studies, for example, of living tissues. In this case, the dye can be delivered on the basis of specially prepared nanoparticles and can be used to stain tissue cells that need to be monitored during various processes.

— For bioimaging, various fluorescent dyes are usually used, however, in order to obtain a contrast and clear image, it is necessary to constantly irradiate the drug. This can lead to its destruction due to various photochemical processes, because light energy is sometimes quite enough to destroy chemical bonds, this is especially important if the study is carried out in vivo, that is, on living tissues. Organic materials with afterglow are not at risk of such destructive effects, since they do not require constant irradiation. Their use requires pulsed irradiation, since after each pulse the materials continue to glow for several seconds. Recently, materials with afterglow have found quite active use in bioimaging, but inorganic metal compounds and their complexes are still widely used. We offer an alternative to toxic bioimaging systems based on afterglow, and are now looking for partners who could test the afterglow materials we have developed in the study of biological objects,” explained Evgeniy Mostovich.

Another area of application of new materials is cryptography. The afterglow effect can be used to protect information, documents or a personal signature. In this case, materials with afterglow are used to apply protective images that appear not upon instant irradiation with light, for example, an ultraviolet flashlight, but only after a few seconds. Thus, during irradiation, false (confused) information first appears, and after a few seconds the true information appears. In this way, you can protect, for example, barcodes or QR codes, stamps and facsimiles of signatures, as well as any encoded information. The technical capabilities for this are already available even using a regular smartphone. If you use several materials with different persistence durations, you can create not two, but several levels of encryption with only one correct answer and several confusing ones. The researchers have no doubt that their development will find wide application in the future.

Note; This information is raw content directly from the source of the information. This is exactly what the source states and does not reflect the position of MIL-OSI or its clients.

Please note; This information is raw content directly from the information source. It is accurate to what the source is stating and does not reflect the position of MIL-OSI or its clients.

EDITOR’S NOTE: This article is a translation. Apologies should the grammar and or sentence structure not be perfect.

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