Recent progress in ion-regulated organic room-temperature phosphorescence.

Organic room-temperature phosphorescence (RTP) materials have attracted considerable attention for their extended afterglow at ambient conditions, eco-friendliness, and wide-ranging applications in bio-imaging, data storage, security inks, and emergency illumination. Significant advancements have been achieved in recent years in developing highly efficient RTP materials by manipulating the intermolecular interactions. In this perspective, we have summarized recent advances in ion-regulated organic RTP materials based on the roles and interactions of ions, including the ion-π interactions, electrostatic interactions, and coordinate interactions. Subsequently, the current challenges and prospects of utilizing ionic interactions for inducing and modulating the phosphorescent properties are presented. It is anticipated that this perspective will provide basic guidelines for fabricating novel ionic RTP materials and further extend their application potential.

Twofold rigidity activates ultralong organic high-temperature phosphorescence.

A strategy is pioneered for achieving high-temperature phosphorescence using planar rigid molecules as guests and rigid polymers as host matrix. The planar rigid configuration can resist the thermal vibration of the guest at high temperatures, and the rigidity of the matrix further enhances the high-temperature resistance of the guest. The doped materials exhibit an afterglow of 40 s at 293 K, 20 s at 373 K, 6 s at 413 K, and a 1 s afterglow at 433 K. The experimental results indicate that as the rotational ability of the groups connected to the guests gradually increases, the high-temperature phosphorescence performance of the doped materials gradually decreases. In addition, utilizing the property of doped materials that can emit phosphorescence at high temperatures and in high smoke, the attempt is made to use organic phosphorescence materials to identify rescue workers and trapped personnel in fires.

Organic room-temperature phosphorescence materials for bioimaging.

Organic room-temperature phosphorescence (RTP) materials are currently the focus of research in the field of bioimaging. In comparison with the conventional imaging modalities based on organic fluorescent dyes, RTP materials with long lifetime enable time-resolved imaging to improve the imaging resolution by avoiding autofluorescence. In this review, we will start with summarizing strategies for achieving high performance RTP materials for bioimaging, including the development of RTP-compounds, host-guest doping materials, and supramolecular assemblies. We then discuss the optimization of nanonization processes to obtain RTP nanoparticles with controllable size, high dispersibility, and improved stability. The differences between top-down and bottom-up approaches are further described. Finally, we briefly introduce the emerging methods for preparing RTP materials for bioimaging.

Microfluidic-based modulation of triplet exciton decay in organic phosphorescent nanoparticles for size-assisted photodynamic antibacterial therapy.

The modulation of triplet exciton decay in organic room-temperature phosphorescence (RTP) materials has been considered as a promising strategy for highly efficient photodynamic therapy. In this study, we report an effective approach based on microfluidic technology to manipulate the triplet exciton decay for generating highly reactive oxygen species (ROS). BQD shows strong phosphorescence upon doping into crystalline BP, indicating the high generation of triplet excitons based on the host-guest interaction. Through microfluidic technology, BP/BQD doping materials can be precisely assembled to form uniform nanoparticles with no phosphorescence but strong ROS generation. The energy decay of the long-lived triplet excitons of BP/BQD nanoparticles emitting phosphorescence has been successfully manipulated via microfluidic technology to generate 20-fold enhanced ROS than that of BP/BQD nanoparticles prepared by nanoprecipitation. The in vitro antibacterial studies indicate that BP/BQD nanoparticles have high specificity against S. aureus microorganisms with a low minimum inhibition concentration (10-7 M). BP/BQD nanoparticles below 300 nm show size-assisted antibacterial activity, demonstrated using a newly developed biophysical model. This novel microfluidic platform provides an efficient approach to convert host-guest RTP materials into photodynamic antibacterial agents and to promote the development of antibacterial agents without cytotoxicity and drug-resistance issues based on the host-guest RTP systems.

Stimulus-Responsive Organic Phosphorescence Materials Based on Small Molecular Host-Guest Doped Systems.

Small molecular host-guest doped materials exhibit superiority toward high-efficiency room-temperature phosphorescence (RTP) materials due to their structural design diversity and ease of preparation. Dynamic RTP materials display excellent characteristics, such as good reversibility, quick response, and tunable luminescence ability, making them applicable to various cutting-edge technologies. Herein, we summarize the advances in host-guest doped dynamic RTP materials that respond to external and internal stimuli and present some insights into the molecular design strategies and underlying mechanisms. Subsequently, specific viewpoints are described regarding this promising field for the development of dynamic RTP materials. This Perspective is highly beneficial for future intelligent applications of dynamic RTP systems.

Halogen Bonding: A New Platform for Achieving Multi-Stimuli-Responsive Persistent Phosphorescence.

Monotonous luminescence has always been a major factor limiting the application of organic room-temperature phosphorescence (RTP) materials. Enhancing and regulating the intermolecular interactions between the host and guest is an effective strategy to achieve excellent phosphorescence performance. In this study, intermolecular halogen bonding (CN⋅⋅⋅Br) was introduced into the host-guest RTP system. The interaction promoted intersystem crossing and stabilized the triplet excitons, thus helping to achieve strong phosphorescence emission. In addition, the weak intermolecular interaction of halogen bonding is sensitive to external stimuli such as heat, mechanical force, and X-rays. Therefore, the triplet excitons were easily quenched and colorimetric multi-stimuli responsive behaviors were realized, which greatly enriched the luminescence functionality of the RTP materials. This method provides a new platform for the future design of responsive RTP materials based on weak intermolecular interactions between the host and guest molecules.

Guest-host doped strategy for constructing ultralong-lifetime near-infrared organic phosphorescence materials for bioimaging.

Organic near-infrared room temperature phosphorescence materials have unparalleled advantages in bioimaging due to their excellent penetrability. However, limited by the energy gap law, the near-infrared phosphorescence materials (>650 nm) are very rare, moreover, the phosphorescence lifetimes of these materials are very short. In this work, we have obtained organic room temperature phosphorescence materials with long wavelengths (600/657-681/732 nm) and long lifetimes (102-324 ms) for the first time through the guest-host doped strategy. The guest molecule has sufficient conjugation to reduce the lowest triplet energy level and the host assists the guest in exciton transfer and inhibits the non-radiative transition of guest excitons. These materials exhibit good tissue penetration in bioimaging. Thanks to the characteristic of long lifetime and long wavelength emissive phosphorescence materials, the tumor imaging in living mice with a signal to background ratio value as high as 43 is successfully realized. This work provides a practical solution for the construction of organic phosphorescence materials with both long wavelengths and long lifetimes.

Clusterization-Triggered Color-Tunable Room-Temperature Phosphorescence from 1,4-Dihydropyridine-Based Polymers.

A series of poly(1,4-dihydropyridine)s (PDHPs) were successfully synthesized via one-pot metal-free multicomponent polymerization of diacetylenic esters, benzaldehyde, and aniline derivatives. These PDHPs without traditional luminescent units were endowed with tunable triplet energy levels by through-space conjugation from the formation of different cluster sizes. The large and compact clusters can effectively extend the phosphorescence wavelength. The triplet excitons can be stabilized by using benzophenone as a rigid matrix to achieve room-temperature phosphorescence. The nonconjugated polymeric clusters can show a phosphorescence emission up to 645 nm. A combination of static and dynamic laser light scattering was conducted for insight into the structural information on formed clusters in the host matrix melt. Moreover, both the fluorescence and phosphorescence emission can be easily tuned by the variation of the excitation wavelength, the concentration, and the molecular weight of the guest polymers. This work provides a unique insight for designing polymeric host-guest systems and a new strategy for the development of long wavelength phosphorescence materials.

Rational design of pyrrole derivatives with aggregation-induced phosphorescence characteristics for time-resolved and two-photon luminescence imaging.

Pure organic room-temperature phosphorescent (RTP) materials have been suggested to be promising bioimaging materials due to their good biocompatibility and long emission lifetime. Herein, we report a class of RTP materials. These materials are developed through the simple introduction of an aromatic carbonyl to a tetraphenylpyrrole molecule and also exhibit aggregation-induced emission (AIE) properties. These molecules show non-emission in solution and purely phosphorescent emission in the aggregated state, which are desirable properties for biological imaging. Highly crystalline nanoparticles can be easily fabricated with a long emission lifetime (20 µs), which eliminate background fluorescence interference from cells and tissues. The prepared nanoparticles demonstrate two-photon absorption characteristics and can be excited by near infrared (NIR) light, making them promising materials for deep-tissue optical imaging. This integrated aggregation-induced phosphorescence (AIP) strategy diversifies the existing pool of bioimaging agents to inspire the development of bioprobes in the future.

Influence of Guest/Host Morphology on Room Temperature Phosphorescence Properties of Pure Organic Doped Systems.

Guest/host phosphorescence materials have attracted much attention; traditionally, researchers have focused on the influence of the electronic properties and energy levels of the molecules on the phosphorescence activities. However, the effects of the morphology on the phosphorescence properties are ignored. Herein, three isoquinoline guests with different aliphatic rings and three hosts are selected to construct guest/host materials. Experimental results confirm that the guests are dispersed in the host in the form of clusters. More importantly, the morphologies of the guest/host directly affect the phosphorescence properties. In these systems, the guests have strong intermolecular interactions, which are beneficial to stabilize the triplet excitons; meanwhile, the hosts should have weak intermolecular interactions with easily changed morphology to accept the guest clusters, which synergistically ensure that the doped materials have excellent RTP properties. This is the first work focusing on the effect of molecular morphology on the phosphorescence characteristics of guest/host systems.

Efficient and organic host-guest room-temperature phosphorescence: tunable triplet-singlet crossing and theoretical calculations for molecular packing.

Organic host-guest doped materials exhibiting the room temperature phosphorescence (RTP) phenomenon have attracted considerable attention. However, it is still challenging to investigate their corresponding luminescence mechanism, because for host-guest systems, it is very difficult to obtain single crystals compared to single-component or co-crystal component materials. Herein, we developed a series of organic doped materials with triphenylamine (TPA) as the host and TPA derivatives with different electron-donating groups as guests. The doped materials showed strong fluorescence, thermally activated delayed fluorescence (τ: 39-47 ms), and efficient room temperature phosphorescence (Φ phos: 7.3-9.1%; τ: 170-262 ms). The intensity ratio between the delayed fluorescence and phosphorescence was tuned by the guest species and concentration. Molecular dynamics simulations were used to simulate the molecular conformation of guest molecules in the host matrix and the interaction between the host and guest molecules. Therefore, the photophysical properties were calculated using the QM/MM model. This work provides a new concept for the study of molecular packing of guest molecules in the host matrix.

Tunable Phosphorescence/Fluorescence Dual Emissions of Organic Isoquinoline-Benzophenone Doped Systems by Alkoxy Engineering.

Dual/multi-component organic doped systems with room-temperature phosphorescence (RTP) properties have been developed. However, the unknown luminescence mechanism still greatly limits the development of the doped materials. Herein, a new doped system exhibiting phosphorescence/fluorescence dual emission (Φphos =4-24 % and τphos =101-343 ms) is successfully constructed through prediction and design. A series of isoquinoline derivatives with different alkoxy chains were selected as the guests. Benzophenone was chosen as the host owing to the characteristics of low melting point and good crystallinity. The alkoxy chain lengths of the guests are first reported to be used to control the fluorescence and phosphorescence intensities of the doped materials, which results in different prompt emission colors. Additionally, the doped ratio of the guest and host can also control the luminous intensities of the materials. In particular, the doped materials still exhibit phosphorescent properties even if the ratio of the guest/host is as low as 1:100 000.

Wide-Range Color-Tunable Organic Phosphorescence Materials for Printable and Writable Security Inks.

Organic materials with long-lived, color-tunable phosphorescence are potentially useful for optical recording, anti-counterfeiting, and bioimaging. Herein, we develop a series of novel host-guest organic phosphors allowing dynamic color tuning from the cyan (502 nm) to orange red (608 nm). Guest materials are employed to tune the phosphorescent color, while the host materials interact with the guest to activate the phosphorescence emission. These organic phosphors have an ultra-long lifetime of 0.7 s and a maximum phosphorescence efficiency of 18.2 %. Although color-tunable inks have already been developed using visible dyes, solution-processed security inks that are temperature dependent and display time-resolved printed images are unprecedented. This strategy can provide a crucial step towards the next-generation of security technologies for information handling.

Revealing Insight into Long-Lived Room-Temperature Phosphorescence of Host-Guest Systems.

The control of the emission properties of doping materials through molecular design makes organic materials potentially promising candidates for many optoelectronic applications and devices. However, organic doping systems with high quantum yields and persistent luminescence processes have rarely been reported, and their luminescence mechanisms are still not well established. Here we developed a series of purely organic heavy-atom-free doping systems. The guest molecules can dope either donor or acceptor matrixes, both leading to an enhanced fluorescence (Φ = 63-76%) and room-temperature phosphorescence (Φ = 7.6-14.5%, τ = 119-317 ms) under ambient conditions. XRD measurements and density functional calculations results indicated ultralong phosphorescence was determined by both the cocrystalline state and the energy levels between the host and guest materials. The doping materials are fairly stable to light, heat, and humidity. This work may provide unique insight for designing doping systems and expanding the scope of organic phosphorescence applications.

Triphenylquinoline (TPQ)-Based Dual-State Emissive Probe for Cell Imaging in Multicellular Tumor Spheroids.

Insufficient intratumoral penetration and limited stroma distribution of the imaging probes or theranostics can lead to a poor-quality diagnosis or therapeutic resistance. Multicellular tumor spheroids can recapitulate the physiological environment of tumor tissues with the extracellular matrix and is thus a better in vitro tumor model to evaluate the imaging performance and barrier penetration capability of advanced cancer imaging probes. In this Article, we designed and synthesized a series of quinoline-based fluorophores with strong emissions in both solution and solid states. The quinoline core can be constructed via a one-pot iron-catalysis reaction. Optical properties and single crystal structures of these quinoline derivatives were tuned by varying the substitutes at the 6-position of the quinoline core. The twisted intramolecular charge transfer effect can enhance the fluorescent efficiency, resulting in the high quantum yield of TPQ-TPA in both solution (70%) and solid (48%) states (TPQ, triphenylquinoline; TPA, triphenylamine). In addition, TPQ-TPA exhibited a good biocompatibility and can deeply penetrate into 3D tumor spheroids within 12 h. The results indicated that quinoline can be a new fluorescent scaffold, and the employment of quinoline-based probes will provide a new platform for biological applications.

[Expression and significance of TRAF4 protein in breast carcinoma].

BACKGROUND & OBJECTIVE: The researches about the expression of tumor necrosis factor receptor-associated factor 4 (TRAF4) in breast cancer are disputable. This study was to investigate the expression of TRAF4 in normal breast, breast carcinoma tissue, and cell lines with different invasive abilities. METHODS: The expression of TRAF4 in 70 specimens of breast carcinoma and 14 specimens of normal breast tissues was detected by SP immunohistochemistry. The expression of TRAF4 in breast cancer cell lines, MDA-MB-231 with high invasive ability and MCF-7 with low invasive ability, was detected by Western blot. RESULTS: TRAF4 was expressed both in cell cytoplasm and nuclei in normal breast tissues. The cytoplasmic positive rates of TRAF4 were 78.57% in normal breast tissues, 88.57% in non-invasive ductal carcinoma, and 91.43% in invasive ductal carcinoma (P>0.05). The nuclear positive rate of TRAF4 was significantly higher in normal breast tissues than in non-invasive ductal carcinoma (64.28% vs. 28.57%, P<0.01), and higher in non-invasive ductal carcinoma than in invasive ductal carcinoma (28.57% vs. 5.70%, P<0.05). The protein level of TRAF4 was slightly higher in MDA-MB-231 cells than in MCF-7 cells (P>0.05). CONCLUSION: The nuclear expression of TRAF4 in breast carcinoma is suppressed, and correlated to the invasive ability of breast cancer.