Wang Yuci, Jiang Kai, Du Jiaren, Zheng Licheng, Li Yike, Li Zhongjun, Lin Hengwei
College of Chemistry, Zhengzhou University, Zhengzhou, 450001, People's Republic of China.
International Joint Research Center for Photo-Responsive Molecules and Materials, School of Chemical and Material Engineering, Jiangnan University, Wuxi, 214122, People's Republic of China.
Nanomicro Lett. 2021 Sep 16;13(1):198. doi: 10.1007/s40820-021-00718-z.
Near-infrared (NIR), particularly NIR-containing dual-/multi-mode afterglow, is very attractive in many fields of application, but it is still a great challenge to achieve such property of materials. Herein, we report a facile method to prepare green and NIR dual-mode afterglow of carbon dots (CDs) through in situ embedding o-CDs (being prepared from o-phenylenediamine) into cyanuric acid (CA) matrix (named o-CDs@CA). Further studies reveal that the green and NIR afterglows of o-CDs@CA originate from thermal activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) of o-CDs, respectively. In addition, the formation of covalent bonds between o-CDs and CA, and the presence of multiple fixation and rigid effects to the triplet states of o-CDs are confirmed to be critical for activating the observed dual-mode afterglow. Due to the shorter lifetime and insensitiveness to human vision of the NIR RTP of o-CDs@CA, it is completely covered by the green TADF during directly observing. The NIR RTP signal, however, can be readily captured if an optical filter (cut-off wavelength of 600 nm) being used. By utilizing these unique features, the applications of o-CDs@CA in anti-counterfeiting and information encryption have been demonstrated with great confidentiality. Finally, the as-developed method was confirmed to be applicable to many other kinds of CDs for achieving or enhancing their afterglow performances.
近红外（NIR），特别是含近红外的双/多模余辉，在许多应用领域都极具吸引力，但实现材料的这种性能仍然是一个巨大的挑战。在此，我们报道了一种简便的方法，通过将邻碳点（由邻苯二胺制备）原位嵌入氰尿酸（CA）基质（命名为o-CDs@CA）中来制备碳点（CDs）的绿色和近红外双模式余辉。进一步的研究表明，o-CDs@CA的绿色和近红外余辉分别源于o-CDs的热激活延迟荧光（TADF）和室温磷光（RTP）。此外，o-CDs与CA之间共价键的形成以及对o-CDs三重态的多重固定和刚性效应的存在被证实对激活所观察到的双模式余辉至关重要。由于o-CDs@CA的近红外RTP寿命较短且对人类视觉不敏感，在直接观察时它完全被绿色TADF所覆盖。然而，如果使用光学滤波器（截止波长为600 nm），则可以很容易地捕获近红外RTP信号。利用这些独特特性，o-CDs@CA在防伪和信息加密方面的应用已被证明具有高度保密性。最后，所开发的方法被证实适用于许多其他种类的碳点，以实现或增强它们的余辉性能。
