Recently, College of Materials and Energy, South China Agricultural University, Bio-based Materials and Energy, Key Laboratory of the Ministry of Education, , Guangdong Optical Agricultural Engineering Technology Research Center, Professor Liu Yingliang Team has made important progress in the research of carbon dot-based room temperature phosphorescence material. The relevant research results are "Carbon Dots in Hydroxy Fluorides: Achieving Multicolor Long-Wavelength Room-Temperature Phosphorescence and Excellent Stability via Crystal The title Confinement" was published in the internationally authoritative journal "Nano Letters". Liang Ping, a master's student in the School of Materials and Energy, and Zheng Yihao, a research assistant, (a undergraduate graduate of the 2019 Materials Science and Engineering degree) are the co-first authors of the paper, and Professor Zhuang Jianle, Professor Liu Yingliang and Professor Huang Weiyang from Hong Kong Polytechnic University are the co-corresponding authors.
Carbon dots (CDs) As an emerging carbon-based luminescent material, it has aroused extensive research interest in the field of luminescence. In recent years, the room temperature phosphorescence (RTP) performance of CDs has attracted much attention. Some existing strategies have been used to prepare CDs-based RTP materials with excellent performance, including the introduction of heavy or heteroatoms and embedding CDs into substrates, where matrix-assisted methods have been widely used. When CDs are introduced into a rigid matrix, the triplet state exciton of CDs can be protected and activated by some restriction effects (such as hydrogen bonds, covalent bonds, covalent bonds, spatial restriction, etc.) to produce efficient RTP emission. However, it remains a challenge to obtain multicolor CDs-based RTP materials with excellent stability. According to previous reports, when different CDs are dispersed in some common substrates such as boric acid and urea , multicolor RTP can be achieved more easily. However, these substrates are susceptible to external factors such as water, acids or alkalis, which in turn leads to phosphorescence quenching of the carbon dots. When CDs are embedded in inorganic rigid substrates (such as zeolite and silica ), the resulting composite material has high RTP and good stability. However, its phosphorescence color is mainly green, and multi-color long-wavelength RTP is difficult to achieve. Although red RTP has been reported to be implemented in CDs@zeolite and CDs@silica systems, they mainly utilize energy transfer from CDs to metal ions or fluorescent dyes to achieve red emission. In addition, light-stimulating multicolor RTP of single-component CDs has been implemented, but this is due to the excitation-dependent nature generated by multiple emission centers in CDs, which requires light sources of different excitation wavelengths to achieve emission at different wavelengths. Therefore, it is of great significance to develop a universal matrix that can achieve multicolor long-wavelength RTP with CDs under the same excitation and ensure material stability.
Based on this, the author developed a novel and general "CDs-in-YOHF" strategy to synthesize carbon dot-based room temperature phosphorescent materials with bright green, yellow and orange afterglows by introducing CDs into Y(OH)xF3-x (YOHF) matrix. This type of inorganic material has been first discovered as a matrix for activating room temperature phosphorescence of CDs. Research shows that the spatial constraints of the YOHF matrix on CDs and the hydrogen bonds and C-F bonds between CDs and YOHFs together produce multiple restriction effects, greatly inhibiting the intramolecular vibration and rotation of CDs, thereby effectively stabilizing the triplet excitons of CDs and promoting phosphorescence emission. This effect has been proven to be effective for most CDs stable triplet states and thus produce RTP emission, i.e., YOHF matrix has good universality.
In addition, has strong protection effect on YOHF rigid matrix, and the resulting CDs@YOHF exhibits excellent photostability, thermal stability, chemical stability and time stability, which is conducive to the long-term use of CDs@YOHF in different environments. In view of its excellent performance, the team initially explored the application of CDs@YOHF in information encryption, anti-counterfeiting and fingerprint recognition. In short, these efforts provide an effective design strategy for the construction of multicolor and stable carbon dot-based RTP materials, and also promote their application in information security and protection, especially in complex environments.
This research work has been funded by National Natural Science Foundation of China, Guangdong Province Basic and Applied Basic Research Fund , Guangzhou Science and Technology Plan Project, etc.
Source: South China Agricultural University
Paper link:
https://pubs.acs.org/doi/10.1021/acs.nanolett.2c00603
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