Rigid Environment Research Articles

Triarylmethanol Derivatives with Ultralong Organic Room-Temperature Phosphorescence.

Triphenylmethyl-based compounds such as rhodamines and fluoresceine representing an old and well-known class of triphenylmethane dyes, are widely used in fluorescent labeling of bioimaging. Inspired by ultralong room temperature phosphorescence of triphenylphosphine derivatives, herein we report a methoxy substituted triarylmethanol ((4-methoxyphenyl)diphenylmethanol, LJW-1) exhibits ultralong room temperature phosphorescence (RTP) under ambient condition with afterglows of about 7 seconds. Its multiple C-H···π intermolecular interactions, C-H···O intermolecular interactions, hydrogen bond and π-π interactions are beneficial for forming rigid environment in the aggregated state which is evidently an important factor in the appearance of excellent RTP. Different substituents on triarylmethanol result in compounds with different lifetimes varying from 7 µs to 818 ms. The substituent effects on the phosphorescence of triarylmethanol derivatives provide an efficient method for the design of organic RTP materials and may be enlightening the phosphorescence research of triarylmethanol derivatives.

Xylan-based full-color room temperature phosphorescence materials enabled by imine chemistry.

Developing sustainable matrix and efficient bonding mode for preparing room temperature phosphorescence (RTP) materials with full-color afterglows is attractive but still challenging. Here, xylan, a hemicellulose by-product from the paper mill, is used to construct full-color RTP materials based on imine bonds. Xylan is oxidation by periodate to introduce aldehyde groups to increase reaction sites; aromatic amines with different π conjugations can be readily anchored to dialdehyde xylan (DAX) by imine chemistry. The dual rigid environments were constructed by hydrogen bonding and imine covalent bonding, which can facilitate the triplet population and suppress non-radiative transitions, thus the xylan derivatives display satisfactory RTP performances. As the degree of conjugation of the chromophore increases, the afterglow colors can be changed from blue to green, yellow, and then to red. Thus, such a universal, facile, and eco-friendly strategy can be used to fabricate full-color RTP materials, which show a bright future in information encryption and advanced anti-counterfeiting. These results unambiguously state that the biodegradable paper mill waste-based RTP materials are convincingly expected to replace and surpass petroleum polymer-based counterparts.

Study on the Influence of Host-Guest Structure and Polymer Introduction on the Afterglow Properties of Doped Crystals.

Due to their low cost, good biocompatibility, and ease of structural modification, organic long-persistent luminescence (LPL) materials have garnered significant attention in organic light-emitting diodes, biological imaging, information encryption, and chemical sensing. Efficient charge separation and carrier migration by the host-guest structure or using polymers and crystal to build rigid environments are effective ways of preparing high-performance materials with long-lasting afterglow. In this study, four types of crystalline materials (MODPA: DDF-O, MODPA: DDF-CHO, MODPA: DDF-Br, and MODPA: DDF-TRC) were prepared by a convenient host-guest doping method at room temperature under ambient conditions, i.e., in the presence of oxygen. The first three types exhibited long-lived charge-separated (CS) states and achieved visible LPL emissions with durations over 7, 4, and 2 s, respectively. More surprisingly, for the DDF-O material prepared with PMMA as the polymer substrate, the afterglow time of DDF-O: PMMA was longer than 10 s. The persistent room-temperature phosphorescence effect caused by different CS state generation efficiencies and rigid environment were the main reason for the difference in LPL duration. The fourth crystalline material was without charge separation and exhibited no LPL because it was not a D-A system. The research results indicate that the CS state generation efficiency and a rigid environment are the key factors affecting the LPL properties. This work provides new understandings in designing organic LPL materials.

Photo-induced fluorescence discoloration and photo-responsive room temperature phosphorescence carbon dot-based composites with excellent reversibility and water resistance

Photo-stimulation responsive room temperature phosphorescence (RTP) carbon dots (CDs) have potential applications in advanced dynamic information encryption and anti-counterfeiting. However, the development of photo-responsive long-wavelength RTP CD materials with excellent reversibility and water resistance, as well as CD materials with both photo-induced fluorescence discoloration and photo-responsive reversible RTP properties, remains a challenge. Here, pyrene, which has a large conjugated structure, and 4-(1,2,2-triphenylvinyl)benzaldehyde, which has a tetraphenylethylene structure, were selected as the main raw materials to synthesize two CDs. Then, by introducing a PMMA matrix, reversible photo-responsive long-wavelength red RTP emission with a lifetime of 257 ms from a CD-based composite is realized for the first time, and the combination of photo-induced fluorescence discoloration and photo-responsive reversible yellow RTP with a lifetime of 287 ms is realized. Importantly, photo-responsive reversible RTP has excellent water resistance. The fluorescence discoloration was caused by photocyclization under long-term UV irradiation due to the presence of the tetraphenylethylene structure. The rigid environment provided by the PMMA matrix and the hydrogen bonds formed between the PMMA and CDs promote the generation of RTP. The photo-responsiveness of RTP is caused by the conversion of molecular oxygen (3O2) to singlet oxygen (1O2) under continuous UV irradiation. It is filled with 3O2 again after being placed in air to inactivate the RTP, thus achieving reversible RTP behavior. Owing to their excellent photo-responsive properties and water resistance, these materials have the potential to achieve repeatable dynamic information encryption and multilevel pattern anti-counterfeiting while also broadening the range of applications in water environments.

Rigid coordination environment induced MOFs to achieve an efficient photothermal conversion efficiency

A rigid coordination environment contributes significantly to stabilizing the framework structure of Metal-Organic Frameworks (MOFs) and reducing the spatial distance between functional ligands, thereby inducing charge transfer effects. In this context, achieving partial and complete coordination of TTF(py)4 in MOFs involves regulating the number and position of carboxylic acid substitutions in the ligand. Notably, TTFBDAT-Zn-MOF demonstrates a more rigid coordination environment compared to TTFBCAT-Zn-MOF. This enhanced coordination environment facilitates energy transfer between donor and acceptor units in MOFs, enabling efficient photothermal conversion performance under 808 nm excitation. The maximum temperature of TTFBDAT-Zn-MOF can reach 190 °C, while the maximum temperature of TTFBCAT-Zn-MOF can only reach 118 °C. Therefore, TTFBDAT-Zn-MOF with rigid structure has superior photothermal conversion performance.

Design and Construction of Highly Luminescent Transparent Woody Materials Exhibiting Unique Fluorescence-Enhanced Staining Effects for Visualization of Intrinsic Microporous Networks.

Luminescent wood materials are an emerging class of biomass hybrid host materials owing to the hierarchical porous structure and functionalization versatility. The fluorescence properties are largely dependent on exogenous fluorophores, which are, however, often plagued by notorious aggregation effects. In this work, an efficient strategy for the preparation of luminescent transparent wood materials is developed by incorporating tetraphenylethylene-derived aggregation-induced emission (AIE)-active fluorophores during a delignification-backfill transparency process. These wood hybrids showed unexpected luminescence enhancement that significantly increased the fluorescence quantum yield of the fluorophores up to 99%, much higher than that of the fluorophores in other states such as crystalline solids or doped in a polymer substrate. Mechanistic investigations reveal that in situ polymerization of prepolymerized methyl methacrylate in delignified microporous wood frames produces high molecular weight ordered PMMA polymers, resulting in a rigid molecular environment that improves the luminescence efficiency of TPE-based fluorophores at the interfaces of PMMA polymer and cell walls. By confocal laser scanning microscopy (CLSM), this excellent fluorescence staining capability was furthermore utilized to visualize the intrinsic porous network of wood in three dimensions over a large volume with submicrometer resolution, thus providing an alternative approach to the study of structure-function relationships in such wood hybrids.

Proton transfer induced persistent triplet charge transfer phosphorescence in molecule-doped polymer systems

The intermolecular interactions between small molecules and the matrix in a highly polar environment could easily lead to non-radiative transitions, which significantly hampers the development of high-performance persistent room-temperature phosphorescence (pRTP) materials in such condition. Herein, we introduce a novel strategy that integrates consecutive proton transfer and photo-induced charge transfer to facilitate triplet charge transfer emission in highly polar polymer matrix. In particular, doping aza-arene guests including 1,10-phenanthroline (1,10-Phen), 2,9-dimethyl-1,10-phenanthroline (DM-Phen), and 7,8-benzoquinoline (7,8-BQ) into polyacrylic acid (PAA) resulted in superior pRTP properties compared to other polymer hosts. Spectroscopic investigations and theoretical calculations elucidate that this is attributed to the proton transfer and triplet charge transfer characteristics between the host and guest. Moreover, due to the rigid environment and space confinement provided by PAA, pRTP with the lifetime up to 841 ms is achieved. Capitalizing on the excellent water solubility of the doped PAA films, the inkjet printings have been executed, and showcasing the promising the potential applications of these pRTP materials in the field of information encryption.

Nucleosides as Organizing Architectural Moieties

Chemistry “beyond the molecule” is epitomized in nature by a plethora of relatively weak noncovalent interactions. The three-dimensional structures of most biopolymers are controlled with noncovalent interactions, either between different parts of the same strand (as in protein α-helices) or between two separate strands (as in the DNA duplex and protein β-sheet). While nature has refined the construction of biopolymers, our mastery of the subtle noncovalent interactions as synthetic tools is in an early stage of development. Only in the past two decades people begun to develop ways of mimicking the natural light-harvesting complexes by noncovalent assembly of porphyrin units aiming to obtain favored spacing and orientation between the chromophores. The construction of multi-chromophoric assemblies has led to resurgence of interest in coordination chemistry due to formation of ordered arrays directed through molecular recognition events. As a module in the construction of supramolecular assemblies, porphyrins and metallo-porphyrins can be exploited in two different ways: porphyrins can behave as donor building blocks insofar as they comprise meso-substituents, such as pyridyl groups, which can act as ligands that can suitably coordinate to metal cations, while metalloporphyrins can act as acceptor building blocks as soon as the metal atom inside the porphyrin core has at least one axial site available for coordination. For the last years, we have focussed on cofacial bis-porphyrin tweezers for host/guest interactions and investigated the possibilty to obtain self-coordinated molecular systems with predictable spectral and redox characteristics. We report here the synthesis of a di-nucleotide bearing pendant porphyrins dedicated to adopt a pre-organized coformation with face-to-face porphyrins, and capable to self-organize in a stable sandwich type complexe with bidentate base such as DABCO.1 Using a similar strategy as the one used in antisense research, an artificial nucleotidic backbone was built from modified deoxy-uridine units linked with a more rigid linker than the phosphodiester moieties found in natural oligonucleotides. Antisense research uses modified oligonucleotides, less flexible than natural strands, to pre-organize the system toward the obtaining of stable double helices between synthesized and natural oligonucleotides. A modified oligonucleotidic backbone was here used to target a parallel conformation of the porphyrins appended to each deoxy-uridine moiety. To provide a rigid environment for the porphyrins, the uridine units were coupled in 3’-5’ stepwise fashion using ether-ester type of spacer of suitable length, and porphyrins were anchored to the uridine by means of robust carbon-carbon bonds.Earlier studies demonstrated that a peptidic linker doesn’t provide sufficient pre-organization to enhance significantly the association constant with bidentate bases such as DABCO on the contrary of some flexible linkers such as uridine or 2’-deoxyuridine. We document herein that the gain in stability for the formation of sandwich type host-guest complex with DABCO can be even greater when a dinucleotide linker is used. Such pre-organization increases the association constants by one to two orders of magnitude when compared to the association constants of the same bidentate ligands with a reference Zn(II) porphyrin. Comparison of these results with those obtained for rigid tweezers shows a better efficiency of the flexible nucleosidic dimers.We thus document the fact that the choice of rigid spacers is not the only way to pre-organize bis-porphyrins, and that some well-chosen nucleosidic linkers offer an interesting option for the synthesis of such devices. Furthermore, the chirality and enantio-purity of the nucleosidic linkers paves the way toward the selective complexation of enantio-pure bidentate guests and the resolution of racemates. Acknowledgements This work was supported by the CNRS and the French Ministry of Research. References Solladié, R. Rein, S. Bouatra, S. Merkas, C. Sooambar, I. Piantanida, M. Žinić, J. Porphyrins Phthalocyanines 2020, 24, 636-645.

Encapsulation of Bovine Primordial Follicles in Rigid Alginate Does Not Affect Growth Dynamics.

The only fertility preservation and subsequent restoration option for many patients facing gonadotoxic treatments is ovarian tissue cryopreservation and transplantation. While this process is successful for some, there is significant room for improvement to extend the life of the transplant and to make it safe for patients that may have metastatic disease within their ovarian tissue. We need a deeper understanding of how the physical properties of the ovarian microenvironment may affect folliculogenesis to engineer an environment that supports isolated follicles and maintains primordial follicle quiescence. Bovine ovaries were used here as a monovulatory model of folliculogenesis to examine the effects of primordial follicle activation and growth under different physical conditions. We found that there were no differences in activation, growth or survival when primordial follicles were cultured in isolation or in situ (remaining in the tissue) under two significantly differently rigid alginate gels. To determine if the extra rigid environment did not affect activation in isolated follicles due to an immediate activation event, we used 5-ethynyl-2'-deoxyuridine (EdU) to track follicle activation during the isolation process. We identified EdU incorporation in granulosa cells after primordial follicles were isolated from the surrounding extracellular matrix (ECM). These findings support that isolation of primordial follicles from the ECM is an activating event and that the differentially rigid environments assessed here had no effect on follicle growth. Further work is needed to suppress activation in primordial follicles to maintain the ovarian reserve and extend the life of an ovarian tissue transplant.

Crystal-Rigidifying Strategy in Hybrid Manganese Halide to Achieve Narrow Green Emission and High Structural Stability.

Although organic-inorganic hybrid Mn2+ halides have advanced significantly, achieving high stability and narrow-band emission remains enormously challenging owing to the weak ionic nature and soft crystal lattice of the halide structure. To address these issues, we proposed a cationic engineering strategy of long-range cation π···π stacking and C-H···π interactions to simultaneously improve the crystal structural stability and rigidity. Herein, two organic zero-dimensional (0D) manganese halide hybrids of (BACQ)2MnX4 [BACQ = 4-(butylamino)-7-chloroquinolin-1-ium; X = Cl and Br] were synthesized. (BACQ)2MnX4 display strong green-light emissions with the narrowest full width at half-maximum (fwhm) of 39 nm, which is significantly smaller than those of commercial green phosphor β-SiAlON:Eu2+ and most of reported manganese halides. Detailed Hirshfeld surface analyses demonstrate the rigid environment around the [MnX4]2- units originating from the interactions between [BACQ]+. The rigid crystal structure weakens the electron-phonon coupling and renders narrow fwhm of these manganese halides, which is further confirmed by temperature-dependent emission spectra. Remarkably, (BACQ)2MnX4 realizes outstanding structural and luminescence stabilities in various extreme environments. Benefiting from the excellent performance, these Mn2+ halides are used to assemble light-emitting diodes with a wide color gamut of 105% of the National Television System Committee 1931 standard, showcasing the advanced applications in liquid-crystal-display backlighting.

Surgical Tattoos in Infrared: A Dataset for Quantifying Tissue Tracking and Mapping.

Quantifying performance of methods for tracking and mapping tissue in endoscopic environments is essential for enabling image guidance and automation of medical interventions and surgery. Datasets developed so far either use rigid environments, visible markers, or require annotators to label salient points in videos after collection. These are respectively: not general, visible to algorithms, or costly and error-prone. We introduce a novel labeling methodology along with a dataset that uses said methodology, Surgical Tattoos in Infrared (STIR). STIR has labels that are persistent but invisible to visible spectrum algorithms. This is done by labelling tissue points with IR-fluorescent dye, indocyanine green (ICG), and then collecting visible light video clips. STIR comprises hundreds of stereo video clips in both in vivo and ex vivo scenes with start and end points labelled in the IR spectrum. With over 3,000 labelled points, STIR will help to quantify and enable better analysis of tracking and mapping methods. After introducing STIR, we analyze multiple different frame-based tracking methods on STIR using both 3D and 2D endpoint error and accuracy metrics. STIR is available at https://dx.doi.org/10.21227/w8g4-g548.

Versatile room temperature phosphorescence polymer with luminophore content as low as 0.05 wt%

To impart processability and practical serviceability to organic room temperature phosphorescence (RTP) molecules, and address phase separation and rigid confinement environment of conventional RTP polymers, a small amount of Schiff base bonds crosslinked tetraphenylene luminescence networks are pinned to the borate ester bonds crosslinked epoxy networks producing reversible interlocked polymer networks-based halogen-free RTP material. By taking advantage of the conjugation interaction of Schiff base linkages, and phase separation inhibition/molecular confinement effects of the interlocking networks, excellent fluorescence quantum yield (up to 78.9 %), RTP lifetime (660 ms) and quantum yield (16.7 %) are achieved with ultra-low concentration of luminophores (0.05 wt%). Moreover, the resultant acquires decent tensile strength (3.8 MPa) and a high elongation-at-break (365 %) owing to its unique molecular design. The phosphorescence lifetimes (457 ∼ 602 ms) are only slightly affected even after cyclic stretching (at 50 % strain for 100 cycles), or soaking in water (for 30 days), or heating (90 °C). The built-in reversible covalent bonds and the topological network reorganization further enable injection molding and self-healing of the material. Having been repeatedly crushed/hot-pressed, the recycled material still shows RTP lifetime and quantum yield of 398 ms and 14.6 %, respectively. The present work provides a feasible approach to fabricate multifunctional robust organic phosphorescent materials with application prospects.

Nylons with Highly-Bright and Ultralong Organic Room-Temperature Phosphorescence

Endowing the widely-used synthetic polymer nylon with high-performance organic room-temperature phosphorescence would produce advanced materials with a great potential for applications in daily life and industry. One key to achieving this goal is to find a suitable organic luminophore that can access the triplet excited state with the aid of the nylon matrix by controlling the matrix-luminophore interaction. Herein we report highly-efficient room-temperature phosphorescence nylons by doping cyano-substituted benzimidazole derivatives into the nylon 6 matrix. These homogeneously doped materials show ultralong phosphorescence lifetimes of up to 1.5 s and high phosphorescence quantum efficiency of up to 48.3% at the same time. The synergistic effect of the homogeneous dopant distribution via hydrogen bonding interaction, the rigid environment of the matrix polymer, and the potential energy transfer between doped luminophores and nylon is important for achieving the high-performance room-temperature phosphorescence, as supported by combined experimental and theoretical results with control compounds and various polymeric matrices. One-dimensional optical fibers are prepared from these doped room-temperature phosphorescence nylons that can transport both blue fluorescent and green afterglow photonic signals across the millimeter distance without significant optical attenuation. The potential applications of these phosphorescent materials in dual information encryption and rewritable recording are illustrated.

Excellent Persistent Near-Infrared Room Temperature Phosphorescence from Highly Efficient Host-Guest Systems.

Organic near-infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal-to-background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy-gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten-folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host-guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs.

Fully Exploiting Clusterization‐Triggered Room Temperature Phosphorescence of Cellulose by Stepwise Rigidification for Long‐Lived and Excitation Wavelength‐Dependent Afterglows

AbstractAchieving long‐lived room temperature phosphorescence (RTP) in nonconventional luminophores devoid of any conjugated units is fascinating but remains formidably challenging due to their low intersystem crossing efficiency and strong nonradiative decay. Herein, a stepwise rigidification strategy is developed to suppress the nonradiative decay and fully exploit the clusterization‐triggered RTP performance of cellulose. Specifically, the crystallinity is enhanced, and hydrogen bonding is reconstructed by a directed oxidation‐reduction reaction to afford a more rigid environment of cellulose; then, the reconstructed cellulose is further cross‐linked by boric acid to activate double confinement architecture. In return, the phosphorescence lifetime of the target cellulose increases almost one order of magnitude, and the phosphorescence quantum yield increases more than 27 folds. Moreover, the afterglow of the RTP cellulose can be regulated from blue to green by changing excitation wavelength, which is useful for advanced information encryption and anti‐counterfeiting. The stepwise rigidification strategy is also applicable for preparing other nature polysaccharides‐based long‐lived RTP materials, such as chitosan and sodium alginate. Nature polysaccharides are completely biodegradable; thus, this work paves the way for the development of eco‐friendly and practical color‐variable RTP materials.

Ultrafast Primary Dynamics and Isomerization Mechanism of a Far-Red Sensing Cyanobacteriochrome.

Far-red cyanobacteriochromes (CBCRs) are bilin-based photosensory proteins that promise to be novel optical agents in optogenetics and deep tissue imaging. Recent structural studies of a far-red CBCR 2551g3 have revealed a unique all-Z,syn chromophore conformation in the far-red-absorbing Pfr state. Understanding the photoswitching mechanism through bilin photoisomerization is important for developing novel biomedical applications. Here, we employ femtosecond spectroscopy and site-directed mutagenesis to systematically characterize the dynamics of wild-type 2551g3 and four critical mutants in the 15Z Pfr state. We captured local relaxations in several picoseconds and isomerization dynamics in hundreds of picoseconds. Most mutants exhibited faster local relaxation, while their twisting dynamics and photoproducts depend on specific protein-chromophore interactions around the D-ring and C-ring. These results collectively reveal a unique dynamic pattern of excited-state evolution arising from a relatively rigid protein environment, thereby elucidating the molecular mechanism of Pfr-state photoisomerization in far-red CBCRs.

Visible-light-excited robust room-temperature phosphorescence of dimeric single-component luminophores in the amorphous state

Organic room temperature phosphorescence (RTP) has significant potential in various applications of information storage, anti-counterfeiting, and bio-imaging. However, achieving robust organic RTP emission of the single-component system is challenging to overcome the restriction of the crystalline state or other rigid environments with cautious treatment. Herein, we report a single-component system with robust persistent RTP emission in various aggregated forms, such as crystal, fine powder, and even amorphous states. Our experimental data reveal that the vigorous RTP emissions rely on their tight dimers based on strong and large-overlap π-π interactions between polycyclic aromatic hydrocarbon (PAH) groups. The dimer structure can offer not only excitons in low energy levels for visible-light excited red long-lived RTP but also suppression of the nonradiative decays even in an amorphous state for good resistance of RTP to heat (up to 70 °C) or water. Furthermore, we demonstrate the water-dispersible nanoparticle with persistent RTP over 600 nm and a lifetime of 0.22 s for visible-light excited cellular and in-vivo imaging, prepared through the common microemulsion approach without overcaution for nanocrystal formation.

Room‐Temperature Phosphorescence Hydrogel with Multiple Color Based on Salt‐Induced Aggregation

AbstractOrganic photoluminescent materials with room‐temperature phosphorescence (RTP) are of great interest, yet achieving RTP in hydrogels faces challenges due to water‐quenching effects. In this study, a straightforward method is presented to achieve RTP hydrogel using a self‐healing and salt‐hardening hydrogel. The hydrogel is synthesized by polymerizing acrylic acid (AA) with diethylenetriamine (DETA) as the dynamic crosslinker. The poly(acrylic acid)/DETA hydrogel could achieve an afterglow lasting 1.6 s after soaking with NaBr solution. The salt‐enhanced hydrophobic aggregation of the hydrogel network promotes the clustering of carboxyl groups and oxygen atoms, resulting in a rigid environment that suppresses nonradioactive transitions and leads to the manifestation of RTP. Additionally, the dynamic association of AA‐DETA allows the freeze‐dried hydrogel powder to be blended with various hydrophobic dyes, leading to a remodelable hydrogel with delayed emission of multiple colors. In general, by combining salt‐hardening property with self‐healing property together, a RTP hydrogel platform that can be facilely loaded with various organic dyes is proposed.

Host-guest doped room/high-temperature phosphorescence of diarylfuro[3,2-b]pyridine derivatives

Due to the high temperature that can easily lead to non-radiative transitions of triplet excitons, obtaining high-temperature phosphorescence (HTP) materials is challenging. Herein, using diarylfuro[3,2-b]pyridines as the guest molecules and polyacrylic acid (PAA) as the host molecule, the two-component doped materials exhibit green room-temperature phosphorescence (RTP) with afterglow times of 2–8 s, delayed lifetimes of 256–939 ms, and phosphorescence quantum efficiencies of 140.3–21.2 %, and green HTP emissions with 2 s afterglow and 208 ms delayed lifetime at 373 K. The HTP activity of the doped system originates from the rigid environment provided by PAA, planar and rigid molecular structures of diarylfuro[3,2-b]pyridines, and strong interactions between PAA and diarylfuro[3,2-b]pyridines. Furthermore, using organic small molecules as the reference host molecules, compared to benzophenone, 5-methylphthalic anhydride, and butane-1,2,3,4-tetracarboxylic acid with chemical structures similar to PAA result in better RTP/HTP properties, revealing that strong interactions between host and guest molecules play a very important role in ultralong phosphorescence emissions of these host–guest doped materials. Moreover, these doped materials based on diarylfuro[3,2-b]pyridines can be developed as advanced anti-counterfeiting and encryption materials. This result provides valuable reference for developing excellent RTP/HTP materials based on N,O-containing fused-ring compounds.

Precise Structural and Dynamical Details in Zeolites Revealed by Coupling-Edited 1H-17O Double Resonance NMR Spectroscopy.

Despite the extensive industrial and research interests in zeolites, their intrinsic catalytic nature is not fully understood due to the complexity of the hydroxyl-aluminum moieties. 17O NMR would provide irreplaceable opportunities for much-needed fine structural determination given the ubiquitous presence of oxygen atoms in nearly all species; however, the low sensitivity and quadrupolar nature of oxygen-17 make its NMR spectroscopic elucidation challenging. Here, we show that state-of-the-art double resonance solid-state NMR techniques have been combined with spectral editing methods based on scalar (through-bond) and dipolar (through-space) couplings, which allowed us to address the subtle protonic structures in zeolites. Notably, the often-neglected and undesired second-order quadrupolar-dipolar cross-term interaction ("2nd-QD interaction") can actually be exploited and can help gain invaluable information. Eventually, a comprehensive set of 1H-17O/1H-27Al double resonance NMR with J-/D-coupling spectral editing techniques have been designed in this work and enabled us to reveal atomic-scale precise structural and dynamical details in zeolites including: 1) The jump rate of the bridging acid site (BAS) proton is relatively low, i.e., far less than 100 s-1 at room temperature. 2) The Al-OH groups with 1H chemical shift at 2.6-2.8 ppm, at least for nonseverely dealuminated H-ZSM-5 catalysts, exhibit a rigid bridging environment similar to that of BAS. 3) The Si-OH groups at 2.0 ppm are not hydrogen bonded and undergo fast cone-rotational motion. The results in this study predict the 2nd-QD interaction to be universal for any rigid -17O-H environment, such as those in metal oxide surfaces or biomaterials.