The first carbon dot (CD)-based organic long persistent luminescence (OLPL) system exhibiting more than 1 h of duration was developed. In contrast to the established OLPL systems, herein, the reported CDs-based system (named m-CDs@CA) can be facilely and effectively fabricated using a household microwave oven, and more impressively, its LPL can be observed under ambient conditions and even in aqueous media. XRD and TEM characterizations, afterglow decay, time-resolved spectroscopy, and ESR analysis were performed, showing the successful composition of CDs and CA, the formation of exciplexes and long-lived charged-separated states. Further studies suggest that the production of covalent bonds between CA and CDs plays pivotal roles in activating LPL and preventing its quenching from oxygen and water. To the best of our knowledge, this is a very rare example of an OLPL system that exhibits hour-level afterglow under ambient conditions. Finally, applications of m-CDs@CA in glow-in-the-dark paints for emergency signs and multicolored luminous pearls were preliminarily demonstrated. This work may provide new insights for the development of rare-earth-free and robust OLPL materials.

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.

A high‐selectivity dual‐polarization filtering antenna with metamaterial is presented in this letter. The multilayer coupled radiation structure of the antenna determines a filtering function. With the metamaterial layer designed above the antenna, a sharp roll‐off rate at high pass band edge and a better out‐of‐band rejection occurs, thus a better high selective filtering characteristic can be achieved. Simulating and measuring the antenna, the impedance bandwidth (VSWR <2) of the antenna is from 3.25 GHz to 3.85 GHz; meanwhile, the maximum gain can reach 9dBi. The gain of antenna can quickly decrease 43dBi at the high pass band edge from 3.85 GHz to 4.05 GHz and the antenna has an out‐of‐band rejection level of 27dBi from 4.05 GHz to 5 GHz. The tested results verify our designs and the antenna could be a good candidate for the 5G anti‐interference wireless terminal communication system.

In this letter, a new integrated filtering monopole antenna with wideband harmonic suppression is presented. In the design of the proposed antenna, a compact multiple harmonic suppression low pass filter is introduced and its stopband characteristic from 5 to 20 GHz is well integrated with the common monopole antenna. The final integrated filtering antenna can work from 2.88 to 4.02 GHz, and its wideband harmonic suppression successfully achieves 5.8 times of the central working frequency. The good performances of the present filtering antenna are shown by the simulated results and measured results, which could be a good candidate for the 5G anti‐interference wireless terminal communication system.

In this letter, a new wide stopband and high gain Quasi‐Yagi filtering antenna is proposed. At the beginning of feeder line in the improved Balun filtering antenna, it is integrated with the stripline low‐pass filter that contributes to wide out‐of‐band suppression. The proposed filtering antenna works from 2.25 GHz to 2.55 GHz, with a maximum gain of 8dBi at 2.5 GHz. Moreover, it possesses a faster roll‐off rate from 2.55 GHz(8 dB) to 2.8 GHz (−20 dB) and a better rejection up to 12 GHz(5 times of central frequency) outside the working band.