Photochemical Reaction Enabling the Engineering of Photonic Spin-Orbit Coupling in Organic-Crystal Optical Microcavities.

The control and active manipulation of spin-orbit coupling (SOC) in photonic systems are fundamental in the development of modern spin optics and topological photonic devices. Here, we demonstrate the control of an artificial Rashba-Dresselhaus (RD) SOC mediated by photochemical reactions in a microcavity filled with an organic single crystal of photochromic phase-change character. Splitting of the circular polarization components of the optical modes induced by photonic RD SOC is observed experimentally in momentum space. By applying an ultraviolet light beam, we control the spatial molecular orientation through a photochemical reaction, and with that we control the energies of the photonic modes. This way, we realize a reversible conversion of spin splitting of the optical modes with different energies, leading to an optically controlled switching between circularly and linearly polarized optical modes in our device. Our strategy of in situ and reversible engineering of SOC induced by a light field provides a promising approach to actively design and manipulate synthetic gauge fields toward future on-chip integration in photonics and topological photonic devices.

SNHG15-mediated feedback loop interplays with HNRNPA1/SLC7A11/GPX4 pathway to promote gastric cancer progression.

Dysregulation of long noncoding RNA (lncRNA) expression plays a pivotal role in the initiation and progression of gastric cancer (GC). However, the regulation of lncRNA SNHG15 in GC has not been well studied. Mechanisms for ferroptosis by SNHG15 have not been revealed. Here, we aimed to explore SNHG15-mediated biological functions and underlying molecular mechanisms in GC. The novel SNHG15 was identified by analyzing RNA-sequencing (RNA-seq) data of GC tissues from our cohort and TCGA dataset, and further validated by qRT-PCR in GC cells and tissues. Gain- and loss-of-function assays were performed to examine the role of SNHG15 on GC both in vitro and in vivo. SNHG15 was highly expressed in GC. The enhanced SNHG15 was positively correlated with malignant stage and poor prognosis in GC patients. Gain- and loss-of-function studies showed that SNHG15 was required to affect GC cell growth, migration and invasion both in vitro and in vivo. Mechanistically, the oncogenic transcription factors E2F1 and MYC could bind to the SNHG15 promoter and enhance its expression. Meanwhile, SNHG15 increased E2F1 and MYC mRNA expression by sponging miR-24-3p. Notably, SNHG15 could also enhance the stability of SLC7A11 in the cytoplasm by competitively binding HNRNPA1. In addition, SNHG15 inhibited ferroptosis through an HNRNPA1-dependent regulation of SLC7A11/GPX4 axis. Our results support a novel model in which E2F1- and MYC-activated SNHG15 regulates ferroptosis via an HNRNPA1-dependent modulation of the SLC7A11/GPX4 axis, which serves as the critical effectors in GC progression, and provides a new therapeutic direction in the treatment of GC.

Dual-Stimuli-Responsive Modulation Organic Afterglow Based on N─H Proton Migration Mechanism.

Organic afterglow materials have significant applications in information security and flexible electronic devices with unique optical properties. It is vital but challenging to develop organic afterglow materials possessing controlled output with multi-stimuli-responsive capacity. Herein, dimethyl terephthalate (DTT) is introduced as a strong proton acceptor. The migration direction of N─H protons on two compounds Hs can be regulated by altering the excitation wavelength (Ex) or amine stimulation, thereby achieving dual-stimuli-responsive afterglow emission. When the Ex is below 300 nm, protons migrate to S1-2 DTT, where strong interactions induce phosphorescent emission of Hs, resulting in afterglow behavior. Conversely, when the Ex is above 300 nm, protons interact with the S0 DTT weakly and the afterglow disappears. In view of amine-based compounds with higher proton accepting capabilities, it can snatch proton from S1-2 DTT and redirect the proton flow toward amine, effectively suppressing the afterglow but obtaining a new redshifted fluorescence emission with Δλ over 200 nm due to the high polarity of amine. Moreover, it is successfully demonstrated that the applications of dual-stimuli-responsive organic afterglow materials in information encryption based on the systematic excitation-wavelength-dependent (Ex-De) behavior and amine selectivity detection.

Compact-Type Quasi-2D Perovskite Based on Two Conventional 3D Perovskites.

Quasi-2D perovskites are natural quantum well (QW) structures composed of insulating organic layers inserted between conducting [An-1PbnX3n+1]2- slabs. The presence of the bulky organic layer improves the stability but meanwhile sacrifices carrier transport performance. By utilizing two A-site cations of formamidinium (FA+) and cesium (Cs+), we synthesize unique compact-type quasi-2D perovskites CsPbBr3@FABr. Instead of the bulky organic cations, the FA+ cation was employed to work as interlayer "spacer", while the smaller Cs+ cation was chosen to occupy perovskite cages. Transient absorption reveals an energy transfer from small-n-value QWs to large-n-value QWs, enabling a photoluminescence quantum yield (PLQY) of 36.1%. After further promoting the formation of middle-n-value QWs, the homogeneous QW distribution provides a complete energy cascade to access more efficient energy transfer, leading to significant PLQY raise to 70.1%. We break the shackles to report the first case of compact-type quasi-2D perovskites, providing new guidelines for designing high-performance perovskite materials for optoelectronic devices.

Aggregation Enhanced Thermally Activated Delayed Fluorescence through Spin-Orbit Coupling Regulation.

Integrating aggregation-induced emission (AIE) into thermally activated delayed fluorescence (TADF) emitters holds great promise for the advancement of highly efficient organic light emitting diodes (OLEDs). Despite recent advancements, a thorough comprehension of the underlying mechanisms remains imperative for the practical application of such materials. In this work, we introduce a novel approach aimed at modulating the TADF process by manipulating dynamic processes in excited states through aggregation effect. Our findings reveal that aggregation not only enhances both prompt and delayed fluorescence simultaneously but also imposes constraints on molecular reorientation. This constraint reinforces spin-orbit coupling and reduces the energy gap between singlets and triplets. These insights deepen our understanding of the fundamental mechanisms governing the aggregation effect on TADF materials and provide valuable guidance for the design of high-efficiency photoluminescent materials.

Switching from Thermally Activated Delayed Fluorescence in Single Crystals for Low-Threshold Laser to Room-temperature Phosphorescence in Amorphous-Film for Highly Efficient OLEDs.

Metal-organic phosphorescent complexes containing Ir or Pt are work horse in organic light-emitting diode (OLED) technology, which can harvest both singlet and triplet excitons in electroluminescence (EL) owing to strong heavy-atom effect. Recently, organic room-temperature phosphorescence (ORTP) have achieved high photoluminescence quantum yield (PLQY) in rigid crystalline state, which, however, is unsuitable for OLED fabrication, therefore leading to an EL efficiency far low behind those of metal-organic phosphorescent complexes. Here, we reported a luminescence mechanism switch from thermally activated delayed fluorescence (TADF) in single crystal microwires to ORTP in amorphous thin-films, based on a tert-butylcarbazole difluoroboron ß-diketonate derivative of DtCzBF2. Tightly packed and well-faceted single-crystal microwires exhibit aggregation induced emission (AIE), enabling TADF microlasers at 473 nm with an optical gain coefficient as high as 852 cm-1 . In contrast, loosely packed dimers of DtCzBF2 formed in guest-host amorphous thin-films decrease the oscillator strength of fluorescence transition but stabilize triplets for ORTP with a PLQY up to 61 %, leading to solution-processed OLEDs with EQE approaching 20 %. This study opens possibilities of low-cost ORTP emitters for high performance OLEDs and future low-threshold electrically injected organic semiconductor lasers (OSLs).

Host Surface-Induced Excitation Wavelength-Dependent Organic Afterglow.

The design and construction of organic afterglow materials is an attractive but formidably challenging task due to the low intersystem crossing efficiency and nonradiative decay. Here, we developed a host surface-induced strategy to achieve excitation wavelength-dependent (Ex-De) afterglow emission through a facile dropping process. The prepared PCz@dimethyl terephthalate (DTT)@paper system exhibits a room-temperature phosphorescence afterglow, with the lifetime up to 1077.1 ± 15 ms and duration time exceeding 6 s under ambient conditions. Furthermore, we can switch the afterglow emission on and off by adjusting the excitation wavelength below or above 300 nm, showing a remarkable Ex-De behavior. Spectral analysis demonstrated that the afterglow originates from the phosphorescence of PCz@DTT assemblies. The stepwise preparation process and detailed experiments (XRD, 1H NMR, and FT-IR analysis) proved the presence of strong intermolecular interactions between the carbonyl groups on the surface of DTT and the entire frame of PCz, which can inhibit the nonradiative processes of PCz to achieve afterglow emission. Theoretical calculations further manifested that DTT geometry alteration under different excitation beams is the main reason for the Ex-De afterglow. This work discloses an effective strategy for constructing smart Ex-De afterglow systems that can be fully exploited in a range of fields.

Room-Temperature Electrical Field-Enhanced Ultrafast Switch in Organic Microcavity Polariton Condensates.

Integrated electro-optical switches are essential as one of the fundamental elements in the development of modern optoelectronics. As an architecture for photonic systems exciton polaritons, hybrid bosonic quasiparticles that possess unique properties derived from both excitons and photons, have shown much promise. For this system, we demonstrate a significant improvement of emitted intensity and condensation threshold by applying an electric field to a microcavity filled with an organic microbelt. Our theoretical investigations indicate that the electric field makes the excitons dipolar and induces an enhancement of the exciton-polariton interaction and of the polariton lifetime. Based on these electric field-induced changes, a sub-nanosecond electrical field-enhanced polariton condensate switch is realized at room temperature, providing the basis for developing an on-chip integrated photonic device in the strong light-matter coupling regime.

High-Performance Organic Laser Semiconductor Enabling Efficient Light-Emitting Transistors and Low-Threshold Microcavity Lasers.

An organic light-emitting transistor (OLET) is a candidate device architecture for developing electrically pumped organic solid-state lasers, but it remains a critical challenge because of the lack of organic semiconductors that simultaneously possess a high solid-state emission efficiency (Φs), a high and balanced ambipolar mobility (µh,e), and a large stimulated emission cross-section. Here, we designed a molecule of 4,4'-bis(2-dibenzothiophenyl-vinyl)-biphenyl (DBTVB) and prepared its ultrathin single-crystal microplates with herringbone packing arrangements, which achieve balanced mobilities of µh = 3.55 ± 0.5 and µe = 2.37 ± 0.5 cm2 V-1 s-1, a high Φs of 85 ± 3%, and striking low-threshold laser characteristics. Theoretical and experimental investigations reveal that a strong electronic coupling and a small reorganization energy ensure efficient charge transport; meanwhile, the exciton-vibration effect and negligible π-π orbital overlap give rise to highly emissive H-aggregates and facilitate laser emission. Furthermore, OLET-based DBTVB crystals offer an internal quantum efficiency approaching 100% and a record-high electroluminescence external quantum efficiency of 4.03%.

Circularly Polarized Lasing from a Microcavity Filled with Achiral Single-Crystalline Microribbons.

Organic circularly polarized (CP) lasers have received increasing attention due to their future photoelectric applications. Here, we demonstrate a CP laser from a pure organic crystal-filled microcavity without any chiral molecules or chiral structures. Benefited from the giant anisotropy and excellent laser gain of organic crystals, optical Rashba-Dresselhaus spin-orbit coupling effect can be induced and is conductive to the CP laser in such microcavities. The maximum dissymmetry factor of the CP lasing with opposite helicities reachs 1.2. Our strategy may provide a new idea for the design of CP lasers towards future 3D laser displays, information storage and other fields.

Thermally Activated Long Persistent Luminescence of Organic Inorganic Metal Halides.

Long persistent luminescence (LPL) materials of SrAl2 O4 doped with Eu2+ or Dy3+ can maintain emission over hours after ceasing the excitation but suffer from insolubility, high cost, and harsh preparation. Recently, organic LPL of guest-host exciplex systems has been demonstrated via an intermediate charge-separated state with flexible design but poor air-stability. Here, we synthesized a nontoxic two-dimensional organic-inorganic metal hybrid halides (OIMHs), called PBA2 [ZnX4 ] with X=Br or Cl and PBA=4-phenylbenzylamine. These materials exhibit stable LPL emission over minutes at room-temperature, which is two orders of magnitude longer than those of previously reported OIMHs. The mechanism study shows that the LPL emission comes from thermally activated charge separation state rather than room-temperature phosphorescence. Moreover, the LPL of PBA2 [ZnX4 ] can be excited by low power sources, representing an effective strategy for developing low-cost and high-stability LPL systems.

Excitation-Wavelength-Dependent Organic Long-Persistent Luminescence Originating from Excited-State Long-Range Proton Transfer.

Stimuli-responsive functional luminescent materials with tunable color and long-persistent emission have emerged as a powerful tool in information encryption, anticounterfeiting, and bioelectronics. Herein, we prove a novel strategy for manipulating the proton transfer pathways in the salicylaldehyde derivative EQCN solutions/powder to produce excitation wavelength-dependent (Ex-De) performances with switchable emissions (blue-sky, green, and orange). The experiments and theoretical results demonstrated that the different luminous colors are originated from enol (E) form (blue-sky), Keto-1 (K1) form (orange) through the excited-state intramolecular proton transfer (ESIPT) process, and Keto-2 (K2) form (green) through the excited-state long-range proton transfer (ESLRPT) process. We leverage synergistic effects between the dopant and matrix (dimethyl terephthalate, DTT) to manipulate the excited-state proton transfer pathway in EQCN@DTT mixture powders to generate Ex-De long-persistent luminescence (Ex-De-LPL), which can be well applied in multilevel information encryption. This strategy not only paves an intriguing way for the construction and preparation of pure organic Ex-De materials but also offers a guideline for developing LPL materials based on ESLRPT processes.

Tunable Triplet-Mediated Multicolor Lasing from Nondoped Organic TADF Microcrystals.

Thermally activated delayed fluorescent (TADF) emitters have received great attention in organic light-emitting diodes and laser diodes because of high exciton utilization efficiency and low optical loss caused by triplets. However, the direct observation of lasing emission from nondoped TADF microcrystals has yet to be reported. Here, we demonstrated a three-color (green, yellow, and red) microlaser from three nondoped TADF microcrystals with well-controlled geometries. The temperature-dependent dynamic analyses testify that the regenerated singlets which originated from the reverse intersystem crossing process at room temperature are beneficial for population inversion and reduce triplet-absorption/annihilation optical loses, together resulting in thermally activated lasing actions. Thanks to single-crystalline structures of TADF emitters, the relationship between triplet-harvesting capability and the molecular structure was systematically investigated. The results not only offer rational design of pure TADF gain materials but also provide guidance for the high-performance electrically driven organic solid-state lasers and multicolor laser integration.

Organic Nanoparticles-Assisted Low-Power STED Nanoscopy.

Stimulated emission depletion (STED) nanoscopy plays a key role in achieving sub-50 nm high spatial resolution for subcellular live-cell imaging. To avoid re-excitation, the STED wavelength has to be tuned at the red tail of the emission spectrum of fluorescent probes, leading to high depletion laser power that might damage the cell viability and functionality. Herein, with the highly emissive silica-coated core-shell organic nanoparticles (CSONPs) enabling a giant Stokes shift of 150 nm, ultralow power STED is achieved by shifting the STED wavelength to the emission maximum at 660 nm. The stimulated emission cross section is increased by ∼20-fold compared to that at the emission red tail. The measured saturation intensity and lateral resolution of our CSONP are 0.0085 MW cm-2 and 25 nm, respectively. More importantly, long-term (>3 min) dynamic super-resolution imaging of the lysosomal fusion-fission processes in living cells is performed with a resolution of 37 nm.

An Organic Laser Based on Thermally Activated Delayed Fluorescence with Aggregation-Induced Emission and Local Excited State Characteristics.

The spatial separation between the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) in thermally activated delayed fluorescent (TADF) molecules leads to charge transfer (CT) states, which degrade the oscillator strength of emission transition and sacrifices high solid-state photoluminescence quantum yield (PLQY), together limiting its application in organic solid-state lasers (OSSLs). Here, we demonstrated organic microwire lasers from TADF emitters that combine aggregation induced emission (AIE) and local excited (LE) state characteristics. The unique AIE and LE feature lead to a PLQY approaching 50 % and a high optical gain of 870 cm-1 for TADF microwires. The regenerated singlet excitons by reverse intersystem crossing (RISC) process are conducive to population inversion. As a result, we demonstrated microwire lasers around 465 nm with a low threshold of 3.74 µJ cm-2 . Therefore, our work provides insight to design TADF materials for OSSLs.

Water-Soluble Doubly-Strapped Isolated Perylene Diimide Chromophore.

Perylene diimides (PDIs), a well-studied class of organic dyes, have a strong tendency to self-aggregate in water, thus greatly restricting their phototheranostic applications. Herein, we report a water-soluble PDI cyclophane "Gemini Box" (GBox-14+ ), consisting of a central PDI chromophore enclosed by double-sided cationic molecular straps. Owing to the effective spatial isolation, the chromophore self-aggregation can be completely eliminated, even in a concentrated aqueous solution up to 2 mM. To our knowledge, GBox-14+ represents an interesting example of a fluorescent PDI cyclophane in water, capable of being employed for lysosome-targetable live-cell imaging. More importantly, the highly concentrated aqueous solution of PDI radical anion can be significantly stabilized by GBox-14+ to exhibit an excellent near-infrared photothermal effect, which was further exploited for efficient and selective antibacterial applications. This work provides a new access to water-soluble non-aggregated organic dyes and promotes their potential biomedical applications.

UBE3C promotes proliferation and inhibits apoptosis by activating the ß-catenin signaling via degradation of AXIN1 in gastric cancer.

Gastric cancer (GC) remains one of the most frequent cancers worldwide. Previous studies have shown that E3 ubiquitin ligase E3C (UBE3C) promotes the progression of multiple types of cancer. However, little is known about the expression and molecular mechanism of UBE3C in GC. In this study, UBE3C is upregulated in clinical GC samples and RNA-seq data from The Cancer Genome Atlas, and the UBE3C upregulation is correlated with poor clinical outcomes in patients with GC. In vitro, knockdown of UBE3C suppresses proliferation and enhances apoptosis in GC cells by inhibiting ß-catenin signaling pathway. In contrast, in vitro overexpression of UBE3C promotes GC cell proliferation and inhibits apoptosis through the upregulation of ß-catenin signaling by promoting ubiquitination of AXIN1. In vivo, knockdown of UBE3C inhibits tumor growth in a nude mouse model. Concurrently, the UBE3C knockdown resulted in an increase of AXIN1 and a reduction of ß-catenin in the nucleus and cytoplasm in the xenograft tumor tissues. Our results demonstrate that UBE3C promotes GC progression through activating the ß-catenin signaling via degradation of AXIN1. Our data suggest that UBE3C exerts oncogenic effects in GC and thus provides a promising prognostic biomarker and a potential therapeutic target for GC therapy.

High-Lying 31Ag Dark-State-Mediated Singlet Fission.

Singlet fission (SF), the conversion of one high-energy singlet to two low-energy triplets, provides the potential to increase the efficiency of photovoltaic devices. In the SF chromophores with C2h symmetry, exemplified by polyenes, singlet-to-triplet conversion generally involves a low-lying 21Ag dark state, which serves as either a multiexciton (ME) intermediate to promote the SF process or a parasitic trap state to shunt excited-state populations via internal conversion. This controversial behavior calls for a deep understanding of dark-state-related photophysics involving the higher-lying singlet state. However, the optical "dark" and "transient" nature of these dark states and strong correlation feature of double exciton species make their characterization and interpretation challenging from both experimental and computational perspectives. In the present work combining transient spectroscopy and multireference electronic structure calculations (XDW-CASPT2), we addressed a new photophysical model, i.e., a high-lying 31Ag dark-state-mediated ultrafast SF process in the benzodipyrrolidone (BDPP) skeleton. Such a 31Ag dark state with distinctive double excitation character, described as the ME state, could be populated from the initial 11Bu bright state on an ultrafast time scale given the quasi-degeneracy and intersection of the two electronic states. Furthermore, the suitable optical band gap and triplet energy, high triplet yield, and excellent photostability render BDPP a promising SF candidate for photovoltaic devices. These results not only enrich the arsenal of SF materials but also shed new insights into the understanding of dark-state-related photophysics, which could promote the development of new SF-active materials.

Experimental Measurement of the Divergent Quantum Metric of an Exceptional Point.

The geometry of Hamiltonian's eigenstates is encoded in the quantum geometric tensor (QGT), containing both the Berry curvature, central to the description of topological matter, and the quantum metric. So far, the full QGT has been measured only in Hermitian systems, where the role of the quantum metric is mostly limited to corrections. On the contrary, in non-Hermitian systems, and, in particular, near exceptional points, the quantum metric is expected to diverge and to often play a dominant role, for example, in the enhanced sensing and in wave packet dynamics. In this Letter, we report the first experimental measurement of the quantum metric in a non-Hermitian system. The specific platform under study is an organic microcavity with exciton-polariton eigenstates, which demonstrate exceptional points. We measure the quantum metric's divergence, and we determine the scaling exponent n=-1.01±0.08, which is in agreement with the theoretical description of second-order exceptional points.

Exciton Transport in Molecular Semiconductor Crystals for Spin-Optoelectronics Paradigm.

Organic semiconductors with long-range exciton diffusion length are highly desirable for optoelectronics but currently remain rare. Here, the estimated diffusion length of singlet excitons (LD ) in 2,6-diphenyl anthracene (DPA) crystals grown by solvent evaporation was shown to be up to approximately 124 nm. These crystals showed a previously unseen parallelogram morphology with layer-by-layer edge-on molecular stacking, isotropic optical waveguiding, radiation rate and non-radiation rate constants of 0.15 and 0.26 ns-1 respectively, as well as good field-effect transistor hole mobility and theoretically computed strong electronic couplings as high as 109 meV. Photoresponse experiments revealed that the photoconductivity of DPA crystals is surprisingly not related to the radiative pathway but associated with rapid exciton diffusion to the crystal surface for charge separation and carrier bimolecular recombination. Taken together, DPA was shown to be a promising semiconducting material for a new organic optoelectronics paradigm.