In this Review article, we systematically summarize the design and applications of various kinds of long-lived emissive probes for bioimaging and biosensing via time-resolved photoluminescence techniques. The probes reviewed, including lanthanides, transition-metal complexes, organic dyes, carbon and silicon nanoparticles, metal clusters, and persistent phosphores, exhibit longer luminescence lifetimes than that of autofluorescence from biological tissue and organs. When these probes are internalized into living cells or animals, time-gated photoluminescence imaging selectively collects long-lived signals for intensity analysis, while photoluminescence lifetime imaging reports the decay details of each pixel. Since the long-lived signals are differentiated from autofluorescence in the time domain, the imaging contrast and sensing sensitivity are remarkably improved. The future prospects and challenges in this rapidly growing field are addressed.

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Smart luminescent materials that are responsive to external stimuli have received considerable interest. Here we report ionic iridium (III) complexes simultaneously exhibiting mechanochromic, vapochromic and electrochromic phosphorescence. These complexes share the same phosphorescent iridium (III) cation with a N-H moiety in the N^N ligand and contain different anions, including hexafluorophosphate, tetrafluoroborate, iodide, bromide and chloride. The anionic counterions cause a variation in the emission colours of the complexes from yellow to green by forming hydrogen bonds with the N-H proton. The electronic effect of the N-H moiety is sensitive towards mechanical grinding, solvent vapour and electric field, resulting in mechanochromic, vapochromic and electrochromic phosphorescence. On the basis of these findings, we construct a data-recording device and demonstrate data encryption and decryption via fluorescence lifetime imaging and time-gated luminescence imaging techniques. Our results suggest that rationally designed phosphorescent complexes may be promising candidates for advanced data recording and security protection. D ata recording, storage and security technologies have been widely utilized in economic and military fields as well as in our daily life. Smart luminescent materials that are responsive to external stimuli have received considerable attention in the construction of optical data recording and storage devices [1][2][3][4][5] . These materials have been classified on the basis of the types of external stimuli that they are responsive to. Mechanochromic materials show changes in emission colour in the presence of mechanical stimuli (for example, shearing, grinding and rubbing) because of the interruption of intermolecular interactions (for example, p-p stacking and hydrogen bonds) [6][7][8][9][10] . Vapochromic luminescence has been observed in materials that are responsive to volatile organic compounds 11,12 . Electric field is an important external stimulus. Electrochromism occurs in p-conjugated polymers because of the reversible transition between two redox states [13][14][15][16] . However, materials showing electrochromic luminescence, which is distinct luminescence colour responses to an electric field, are scarce. We envision the potential commercial applications of electrochromic luminescent materials because they can be conveniently integrated into semiconductor-based electronic devices. In addition, it is conceivable that compounds simultaneously showing mechanochromic, vapochromic and electrochromic luminescence are of great use to the development of multifunctional materials.Phosphorescent transition-metal complexes, such as those of Ir(III) and Pt(II), have been extensively studied for various photonic and electronic applications because of their rich excited-state properties, including high luminescence quantum yields, long emission lifetimes, large Stokes shifts, high photostability and various luminescence colours [17][18][19][20] . These complexes have also been utilized a...

Due to the characteristics of optical rotation, selective emission of polarized light, and circular dichroism, circularly polarized luminescent materials have aroused extensive attentions, and they have exhibited wide optoelectronic applications, such as optical data storage, liquid crystal display, and backlights in 3D displays. Here, the research progress of circularly polarized luminescent materials for organic optoelectronic devices is summarized. First, the definition and measurement of the circularly polarized light, such as optical rotatory dispersion, circular dichroism, and circularly polarized luminescence, are systematically introduced. Subsequently, the design strategies for various kinds of circularly polarized luminescent materials, including luminescent lanthanide and transition‐metal complexes, small organic luminophores, conjugated polymers, supramolecules, and liquid crystals are summarized. These materials exhibit circularly polarized luminescence with different magnitudes of luminescence dissymmetry values (glum). They are further applied in optoelectronic devices with excellent performance, and the influence factors on the glum values of these materials are presented in detail. Finally, the current opportunities and challenges in this rapidly growing research field are discussed systematically. The circularly polarized luminescent materials with large glum and high luminescence efficiency are very promising for applications in organic optoelectronic fields.