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.

When the bright green-emitting SrAl2O4:Eu,Dy persistent phosphor was described in the literature in 1996, this presented a real breakthrough in performance, both in terms of initial brightness and afterglow duration. Since then, many new persistent phosphors, with emission spanning from the ultraviolet to the near infrared, have been developed. Very few materials, however, reach a similar afterglow time and intensity as SrAl2O4:Eu,Dy, which is still considered the benchmark phosphor. The present paper discusses the reasons for this—seemingly—fundamental limitation and gives directions for further improvements. An overview is given of the preparation methods of persistent phosphors and their properties. Much attention is paid to the correct evaluation of a persistent phosphor in absolute units rather than vague terms or definitions. State of the art persistent phosphors are currently used extensively in emergency signage, indicators, and toys. Many more applications could be possible by tuning the range of trap depths used for energy storage. Very shallow traps could be used for temperature monitoring in, for example, cryopreservation. Deeper traps are useful for x-ray imaging and dosimetry. Next to these applications, a critical evaluation is made of the possibilities of persistent phosphors for applications such as solar energy storage and photocatalysis.

Inspired by their excellent thermal stability and strong fatigue resistance, inorganic photochromic materials have been highlighted as promising candidates in various photonic applications ranging from photoswitches, anti-counterfeiting, and encryption to information storage. However, the lack of suitable inorganic materials with both fast photoresponse and strong coloration contrast heavily restricts their applications. Herein, a new strategy is proposed to achieve high photochromic performance via constructing deep-lying traps in ferroelectric ceramics. The obtained K 0.5 Na 0.5 NbO 3 -Eu (KNN-Eu) ceramic exhibits a reversible yellow-gray color change with high fatigue resistance upon alternating illumination (420 nm) and thermal stimulus (450°C). A fast response time of around 1 s and a large reflectivity difference of 39.2% between the colored and bleached states are simultaneously achieved in KNN-Eu ceramic, which is by far the best performance ever reported in inorganic photochromic materials. Benefiting from these excellent properties, KNN-Eu is the first ferroelectric photochromic ceramic to support an instant and hand-(re)writable information display. The enhanced photochromic performance is expected to facilitate the application of photochromic materials in numerous optical devices and provides a significant guidance to design other inorganic photochromic materials.

Inorganic materials combining photochromism and luminescence modulation characteristics have great potential in dual‐mode rewritable optical storage due to their unique optical features and excellent thermal stability. However, the failure of achieving a large luminescence modulation and a strong photochromic efficiency in photostimulated inorganic photochromic materials limits their applications. Herein, a new strategy for realizing an overlap between the photochromic absorption peak and the photoluminescent emission/excitation peak is proposed for designing high‐performance photochromic materials. The obtained BaMgSiO4: M (M = Ce3+, Mn2+, or Nd3+) ceramics exhibit a reversible white‐pink color change upon alternate 310 nm and 590 nm illumination (or thermal stimulus) accompanied by a high photochromic efficiency (>50%). Benefiting from a perfectly matched photochromic absorption peak and Mn2+ emission peak, a record luminescence modulation of 96.3% with excellent fatigue resistance is obtained in BaMgSiO4: Mn2+ ceramics. These properties are superior to all photochromic materials reported to date, demonstrating great potential in optical information storage applications. The trap‐related photochromic and regulated luminescence behavior is investigated together with a prototype of a dual‐mode information display. This work is expected to promote the practical application of photochromic materials in various optical devices and provides an effective strategy to develop other photochromic materials.