| Apr 17, 2024 |
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(Nanowerk News) A research team led by JIANG Changlong from Hefei Institutes of Physical Science devised a novel method to prepare carbonized polymer nanodots capable of emitting multi-color ultra-long room-temperature phosphorescent (RTP) from blue to green.
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“These materials exhibit potential applications in anti-counterfeiting and information encryption,” said ZHANG Qipeng, member of the team.
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The research findings have been published in Advanced Science (“Multiemitting Ultralong Phosphorescent Carbonized Polymer Dots via Synergistic Enhancement Structure Design”).
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| Schematic diagram of the preparation of multi-color long-lived room-temperature phosphorescent composite materials based on carbon dots and their potential applications in anti-counterfeiting. (Image: ZHANG Qipeng)
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RTP materials glow even after the light source is removed, making them valuable for various uses like security features, data protection, displays, and medical imaging. Carbon dots (CDs) are a kind of RTP material known for being easy to make, stable under light, and safe. But making bright and long-lasting RTP materials with CDs is tough due to non-radiative loss of energy. Also, it’s hard to get different phosphorescent colors from single carbon dots materials, limiting their use. Therefore, the development of multi-color, long-lived, and high quantum yield RTP carbon dots materials is imperative.
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The method developed in this research is to synthesize carbonized polymer nanodots using ortho-phenylenediamine (oPD) and polyacrylic acid (PAA) hydrothermal synthesis. Researchers mixed some chemicals called ortho-phenylenediamine (oPD) and polyacrylic acid (PAA) together in hot water to make these dots. Then, they baked these dots with boron oxide (B2O3) to make them glow for a long time, from blue to green.
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Adding oPD made these CDs glow in different phosphorescent colors because of the doping of nitrogen element. PAA, which is a long chain of molecules, made these CDs act like other carbonized polymer nanodots made from polymers. The long-chain cross-linking structures of these polymers fix the luminescent groups inside carbonized polymer dots through covalent bonds and hydrogen bonds, reducing non-radiative losses and thereby enhancing the phosphorescence of CDs.
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The boron oxide, which is like a hard shell around the CDs, also helped keep the phosphorescent engry from non-radiative losses. The synergistic effect of cross-linked polymer structures inside carbon dots and their rigid shells enables these carbon dots to exhibit excellent phosphorescence, with a visible duration of up to 49 seconds and a maximum phosphorescence quantum yield of 19.5%. They also demonstrate remarkable resistance to photobleaching. As a result, these carbon dot materials hold great promise for applications in anti-counterfeiting and information encryption.
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This research not only improves our understanding of RTP materials but also paves the way for creating versatile and high-performance materials for security and data protection, according to the team.
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