Search

The stimulus‐responsive room temperature phosphorescent (RTP) materials have endowed wide potential applications. In this work, by introducing naphthalene and spiropyran (SP) into polyacrylamide as the energy donor and acceptor respectively, a new kind of brilliant dynamic color‐tunable amorphous copolymers were prepared with good stability and processibility, and afterglow emissions from green to orange in response to the stimulus of photo or acid, thanks to multi‐responsibility of SP and the energy transfer between naphthalene and SP. In addition to the deeply exploring of the inherent mechanism, these copolymers have been successfully applied in dynamically controllable applications in information protection and delivery. [ABSTRACT FROM AUTHOR]

A luminescent cocrystal system is reported to undergo crystal‐to‐crystal phase transformation from yellow‐emitting polymorph I to green‐emitting polymorph II, triggered by THF fuming or heating, and the green emission can recover to the initial yellow emission by grinding. The established spectroscopic and crystallographic analyses demonstrate that the phase transition occurred and benefits from the combined effect of similar molecular arrange sequence and unique alteration of intermolecular interactions from halogen/hydrogen bonds in I to π–π stacking in II. Furthermore, I and II exhibit red‐shift emission under hydrostatic pressure. The emission of I and II shows a red‐shift and recovers towards the initial emission upon acid–base fuming. This is a rare example of reversible luminescent switching of cocrystal based upon crystal‐to‐crystal phase transition, and provides an alternative strategy to develop multi‐stimuli responsive materials. [ABSTRACT FROM AUTHOR]

There remains an urgent demand for high‐quality blue luminogens that can simultaneously achieve high photoluminescence quantum yield (PLQY) in film and high exciton utilization efficiency (EUE) in the electroluminescence (EL) process. In this study, a referable molecular design strategy is developed for blue luminogens via constructing low‐lying locally excited (LE) state with an aggregation‐induced emission (AIE) characteristic and high‐lying charge‐transfer (CT) state for the effective triplet‐to‐singlet conversion channel. 2TriPE‐BPI‐MCN with the insertion of p‐cyano and o‐methyl groups is designed to compare with its matrix framework (2TriPE‐BPI). They have analogous properties of the lowest singlet (S1) states with blue emission and free of concentration quenching in film; however, 2TriPE‐BPI‐MCN exhibits unusual response for hydrostatic pressure owing to its S2 state CT characteristics. Therefore, 2TriPE‐BPI‐MCN can harness more electrogenerated excitons than 2TriPE‐BPI, resulting in a better EL performance in nondoped blue organic light‐emitting diodes (OLEDs) (CIEx,y = 0.153, 0.147) with high external quantum efficiency of 4.6% and negligible efficiency roll‐off. These findings could open a feasible avenue to develop high‐quality blue luminogens for high‐performance nondoped blue OLEDs. [ABSTRACT FROM AUTHOR]

Abstract: 4‐(Anthracen‐9‐yl)‐N,N‐diphenylaniline (TPA‐AN) is a typical molecule belonging to a donor–acceptor system. Here, the ordered crystal and the powder of TPA‐AN are used for high‐pressure Raman and fluorescence experiments, and their spectroscopic features under the shearing force of grinding and the hydrostatic pressure applied by a diamond anvil cell (DAC) are compared. The mechanochromism of TPA‐AN is discussed in detail based on the analysis of its single‐crystal structure and pressure‐driven spectral changes. During the DAC compression process, the TPA‐AN crystal shows an obvious emission band shift (from 476 to 600 nm) along with a new intramolecular charge transfer state that is separated from the hybridized local and charge transfer excited state and extremely sensitive to external force. Once the pressure is relieved, the Raman and fluorescence spectra both entirely self‐recover without a secondary force. To the authors' knowledge, TPA‐AN crystal is one of the largest emission shift organic mechanochromic fluorescent materials among reported publications. The reversible mechanochromic property of TPA‐AN for a wide‐range emission shift implies a great application potential as smart stimuli‐responsive layer in the fields of sensing, organic light‐emitting diode displays, and data storage. [ABSTRACT FROM AUTHOR]

Organic cocrystals exhibiting active optical waveguide behaviors are strongly related to the total internal reflection, molecule stacking modes, and the spatial distribution of transition dipole moment (µ) in crystals. However, organic charge transfer (CT) cocrystals as new materials that exhibit optical waveguide property responses to anisotropic spatial distribution of µ are still unknown. Herein, prepared is a novel organic CT cocrystal 9AC‐TCNB (9AC = 9‐anthracene carboxylic acid, TCNB = 1,2,4,5‐tetracyanobenzene) with a mixed stacking structure of donor (D) and acceptor (A) along two different orientations on the same lattice plane. According to various spectroscopic analyses, two direction‐oriented asymmetric light propagate in the cocrystal derived from the anisotropic spatial distribution of µ have been confirmed. Photoluminescence (PL) microscopic images and spatial resolution PL spectra of 1D and 2D 9AC‐TCNB cocrystals further demonstrate that the CT cocrystals possess morphology and color‐dependent optical waveguide properties with anisotropy, which confirms the principle theory of light propagation. This result can open new potential applications of organic cocrystals in large‐scale optical waveguide devices and integrated optics. [ABSTRACT FROM AUTHOR]

An innovative elastic crystal based on barbituric acid derivatives (HBDT), which uniquely alters its fluorescence intensity under light exposure is developed. This crystal exhibits significant bending under 365 nm, 450 nm, white light, and sunlight while retaining its elasticity post‐bending. The photomechanical effect of this crystal is driven by intermolecular [2+2] cycloaddition reactions, resulting in light‐activated fluorescence enhancement. These properties open new avenues for applications in robotic arms, information identification, and optical waveguides, presenting a groundbreaking approach for sustainable and flexible crystal applications in material science and optical technology. [ABSTRACT FROM AUTHOR]