Selective Expression of Chromophores in a Single Molecule: Soft Organic Crystals Exhibiting Full‐Colour Tunability and Dynamic Triplet‐Exciton Behaviours

Molecular Motion and Nonradiative Decay: Towards Efficient Photothermal and Photoacoustic Systems

Nonradiative decay invariably competes with radiative decay during the deexcitation process of matter. In the community of luminescence research, nonradiative decay has been deemed less attractive than radiative decay. However, all things in their being are good for something and so is nonradiative decay. As the molecular motion-facilitated nonradiative decay (MMFND) effect is inevitable in photophysical processes, it provides a new avenue to convert the harvested light energy into exploitable forms by harnessing molecular motion. In many cases, active molecular motion enables thermal deactivation from excited states. In this Minireview, recent advances in photothermal and photoacoustic systems with MMFND character are summarized. We believe that this presentation of the rational engineering of molecular motion for efficient photothermal generation will deepen the understanding of the relationship between molecular motion and nonradiative decay and navigate people to rethink the positive aspects of nonradiative decay for the establishment of new light-controllable techniques.

Sensitive luminescence mechanochromism and unique luminescence thermochromism tuned by bending the P–O–P skeleton in the diphosphonium/iodocuprate(i) hybrid

The unique luminescence mechano/thermochromism of a diphosphonium/iodocuprate(i) hybrid is led by the mechanically induced adjustments in cuprophilic interactions and bent P–O–P backbone upon heating.

White Light Afterglow in Carbon Dots Achieved via Synergy between the Room-Temperature Phosphorescence and the Delayed Fluorescence

Carbon dot (CD) based long-lived afterglow emission materials have attracted attention in recent years, but demonstration of white-light room-temperature afterglow remains challenging, due to the difficulty of simultaneous generation of multiple long-lived excited states with distinct chromatic emission. In this work, a white-light room-temperature long-lived afterglow emission from a CD powder with a high efficiency of 5.8% and Commission International de l'Eclairage (CIE) coordinates of (0.396, 0.409) is realized. The afterglow of the CDs originates from a synergy between the phosphorescence of the carbon core and the delayed fluorescence associated with the surface CN moieties, which is accomplished by matching the singlet state of the surface groups of the CDs with the long-lived triplet state of the carbon core, resulting in an efficient energy transfer. It is demonstrated how the long-lived afterglow emission of CDs can be utilized for fabrication of white light emitting devices and in anticounterfeiting applications.

Regulation of Thermally Activated Delayed Fluorescence to Room-Temperature Phosphorescent Emission Channels by Controlling the Excited-States Dynamics via J- and H-Aggregation

Control of excited-state dynamics is key in tuning room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) emissions but is challenging for organic luminescent materials (OLMs). We show the regulation of TADF and RTP emissions of a boron difluoride β-acetylnaphthalene chelate (βCBF₂ ) by controlling the excited-state dynamics via its J- and H-aggregation states. Two crystalline polymorphs emitting green and red light have been controllably obtained. Although both monoclinic, the green and red crystals are dominated by J- and H-aggregation, respectively, owing to different molecular packing arrangements. J-aggregation significantly reduces the energy gap between the lowest singlet and triplet excited states for ultra-fast reverse intersystem crossing (RISC) and enhances the radiative singlet decay, together leading to TADF. The H-aggregation accelerates the ISC and suppresses the radiative singlet decay, helping to stabilize the triplet exciton for RTP.

Selective Expression of a Carbazole-Phenothiazine Derivative Leads to Dual-mode AIEE, TADF and Distinctive Mechanochromism

In this article, we report a newly designed D-A-D' derivative (CNCzPTZ), which displays selective expression of chromophores. This enables CNCzPTZ with solvatochromism, rare dual-mode AIEE properties, solid-state dual-emissions with phosphorescence and distinctive mechanochromism.CNCzPTZ exhibits dual-mode AIEE properties, since the emission band abruptly shifts from 550 nm to 500 nm as the water fraction increases. In the crystalline state, CNCzPTZ demonstrated dual emission bands of 478 nm and 538 nm.CNCzPTZ shows distinctive mechanochromic property in the solid state due to the planarization.

Ultralong Room-Temperature Phosphorescence from Boric Acid

For a long time, phosphors with long-lived emission are dominated by rare earth/transition metal ion-doped sulfides and oxides. Recently, organic materials capable of emitting long-lived room-temperature phosphorescence (RTP) are reported, carbon skeletons are almost the exclusive structural feature of the conjugated luminophores. Herein, we reported that boric acid, a non-metal and C-free material, could emit RTP with lifetime up to 0.3 s. Detailed investigations indicated the weak conjugation between the n electrons of the O atoms in the B-O confined space was the possible origin of RTP. Similar RTP was also found in electron-rich N/F systems, namely, BN and BF₃ (BF₄ ^- ). Importantly, the vacant p z 0 orbital of B was found to contribute to the relevant unoccupied molecular orbitals involved in excitation, which is different from previous reports on phosphorescence from arylboronic acids. The results confirm the unique role of B as a versatile structure motif for construction of new RTP materials.

Simple Vanilla Derivatives for Long-Lived Room-Temperature Polymer Phosphorescence as Invisible Security Inks

Developing novel long-lived room-temperature polymer phosphorescence (RTPP) materials could significantly expand their application scope. Herein, a series of RTPP materials based on eight simple vanilla derivatives for security ink application are reported. Attributed to strong mutual hydrogen bonding with polyvinyl alcohol (PVA) matrix, vanilla-doped PVA films exhibit ultralong phosphorescence emission under ambient conditions observed by naked eyes, where methyl vanillate shows the longest emission time up to 7 s. Impressively, when vanilla-doped PVA materials are utilized as invisible security inks, and the inks not only present excellent luminescent emission stability under ambient conditions but also maintain perfect reversibility between room temperature and 65°C for multiple cycles. Owing to the unique RTPP performance, an advanced anticounterfeiting data encoding/reading strategy based on handwriting technology and complex pattern steganography is developed.