Color-Tunable, Excitation-Dependent, and Water Stimulus-Responsive Room-Temperature Phosphorescence Cellulose for Versatile Applications

Enabling High-Power-Density Zn-Air Batteries via Oxygen Trapping in Lotus-Effect-Inspired Hydrophobic Air Electrodes

The sluggish oxygen diffusion kinetics at the triple-phase boundary of the air cathode significantly limit the optimal power output of Zn-air batteries (ZABs). Inspired by the "lotus effect", this study developed a bifunctional electrocatalyst, Co─NCNTs, featuring a lotus leaf-like structure, and constructed a 3D hydrophobic architecture to expand the triple-phase boundaries. Consequently, the hydrophobic Co─NCNTs electrode (contact angle >140°) demonstrated enhanced oxygen adsorption on the air cathode surface compared to the hydrophilic Co─NC electrode (contact angle <70°). The assembled ZABs incorporating the lotus-effect-inspired bionic Co─NCNTs achieved a remarkable power density of 341 mW cm-2, nearly double that of the hydrophilic Co─NC-based battery (178 mW cm-2), and exhibited exceptional cycling stability, operating continuously for 700 h at a current density of 10 mA cm-2. This work highlights the efficacy of hydrophobic interface engineering in improving the reaction kinetics of air cathodes in ZABs through bionic design, offering a promising strategy for enhancing the power density of oxygen-involved energy storage systems.

High-Temperature Dynamic Organic Phosphorescence Based On Cyclodextrins Supramolecular Assemblies

Dynamic organic phosphorescent materials present great potential for practical applications. But the temperature-sensitive nature of organic phosphors makes the development of high-temperature dynamic organic phosphorescence (HTDOP) a significant challenge. Herein, we report a HTDOP system assembled from β-cyclodextrins (β-CDs) and 4-diphenylamino-benzoic acid (TPAC). The TPAC@β-CDs complex system exhibits only short-lived fluorescence at room temperature but transitions to phosphorescence emission with an ultralong emission lifetime of up to 567 ± 13 ms upon heating. A mechanistic study combining spectroscopic analysis, 1H NMR, and Fourier Transform Infrared Spectroscopy revealed that the intermolecular hydrogen bonding interactions effectively suppressed nonradiative relaxation of triplets even at temperature as high as 140 °C. Meanwhile, elevated temperatures also drive oxygen out of the system, significantly reducing quenching processes and ensuring the robust survival of HTDOP. Additionally, the introduction of fluorescent dyes permits color regulation of the afterglow from green to red through Förster resonance energy transfer from the triplet to the singlet state. Moreover, this system's fast and reliable response upon high temperature makes it an excellent candidate for overtemperature trace detection in electronic components and circuit diagnostics. This work discloses an effective strategy for constructing HTDOP systems that can be fully exploited in a range of fields.

Water-Resistant Organic Room-Temperature Phosphorescence from Block Copolymers

Room-temperature phosphorescence (RTP) polymers have demonstrated significant potential for various applications due to their unique luminescent properties. However, most conventional RTP polymers are vulnerable to moisture and water, which can disrupt the hydrogen bonding network within the polymer and accelerate the non-radiative decay of triplet excitons of phosphors, leading to the quenching of RTP. Herein, we present a universal strategy to achieve water-resistant RTP polymers by designing amphiphilic block copolymers with microphase-separated structures. Specifically, the rigid hydrophilic phase, which is rich in carboxyl groups, forms hydrogen bonds that suppress non-radiative decay of the chromophores, resulting in RTP. Meanwhile, the hydrophobic phase effectively prevents water molecules from penetrating and disrupting the rigid polymer network. By combining the functions of both the hydrophilic and hydrophobic phases, the resulting RTP copolymers exhibit good water-resistant properties. Even after being immersed in water for one month, the copolymers maintain a green afterglow with a lifetime of 629 ms. Moreover, the water-resistant nature of these RTP polymers has also been demonstrated in potential applications of afterglow displays and anti-counterfeiting. This research offers valuable insights into the design of RTP materials with stability in aqueous environments and broadens the scope of their potential applications in diverse settings.

Dynamic Chirality in Nature-Inspired Photonic Crystal Films: Ultralong Room Temperature Phosphorescence and Stimuli-Responsive Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) systems exhibiting room-temperature phosphorescence (RTP) are attracting considerable attention for applications in information encryption and smart sensing. However, achieving ultralong circularly polarized RTP (CPRTP) with tunable chirality and stimuli-responsive CPL remains challenging. Inspired by the color-changing properties of the Troides magellanus butterfly, we developed a cellulose nanocrystal (CNC)-based photonic crystal film with an ultralong RTP lifetime of 2.04 s. The helical pitch of photonic crystal film could be engineered by adding different amounts of glucose, leading to 3-fold and 4-fold enhancement of the phosphorescence and fluorescence quantum yields, respectively, compared to the samples without glucose. The system exhibited green afterglows lasting over 4 s and tunable photonic bandgap (PBG) that modulated chiroptical properties, achieving high glum values of -0.749 for fluorescence and -0.650 for phosphorescence. Additionally, the film demonstrated stimuli-responsive features such as humidity-responsive RTP and solvent-responsive CPL. Therefore, the biomimetic photonic crystal film offers promising opportunities for multilevel anticounterfeiting, information security, and smart sensing applications.

Mechanism of photoluminescence properties of lyocell fibers changing with crystallinity

Although there have been sporadic reports that the crystallinity of cellulose has a significant impact on photoluminescence (PL) properties, the degree and pattern of this effect have not been thoroughly explored and elucidated. Here, we assume that crystallinity is positively correlated with PL emission. Then, lyocell fiber (CLY), a common man-made cellulose fiber, is selected to solve the above problems by exploring the PL emission properties of different crystallinity systems. Through the comparison of PL and persistent room temperature phosphorescence (p-RTP) emission properties under different crystallinity of CLYs, it is found that crystallinity is the key factor determining the above emission properties. The change trend of quantum yields is determined by the crystallinity. Through molecular interaction analysis and theoretical calculation, it is found that hexamers have more red shifted emission than tetramers, and to be more advantageous for phosphorescence emission. These interesting phenomena can be reasonably explained by clustering-triggered emission (CTE) and crystallization-Induced Phosphorescence (CIP) mechanism. Furthermore, these findings, in turn, offer more fundamental implications to the underlying mechanism of nonconventional chromophores. More meaningful is that these results can be used as a theoretical reference for real-time monitoring of CLY or other natural fiber in the actual mercerizing process.

Elucidating the mechanism behind the significant changes in photoluminescence behavior after powder compression into a tablet

Nonconventional luminogens have great potential for applications in fields like anti-counterfeiting encryption. But so far, the photoluminescence quantum yield (PLQY) of most of these powders is still relatively low and the persistent room temperature phosphorescence (p-RTP) emission is relatively weak. To improve their PLQY and p-RTP, pressing the powder into tablets has been preliminarily proven to be an effective method, but the specific mechanism has not been fully elucidated yet. Here, D-(+)-cellobiose has been chosen as the representative to study the problem. The results showed that the PLQY and p-RTP lifetimes of the tablet of D-(+)-cellobiose were improved compared to those of the powder. Using the mechanism of clustering-triggered emission (CTE) and theoretical calculations, it has been demonstrated that the enhanced molecular interactions after compression are the key reason, which result in the formation of cluster emission centers with stronger emission capabilities. And the combination of the powder and tablet has been proven to have application potential for advanced anti-counterfeiting encryption. The above results not only provide possible references for understanding the emission mechanism of small molecules and cellulose based emission materials, but also promote the process of more intuitive observation of emission centers for explaining emission mechanisms.

Cellulose-based fluorescent chemosensor with controllable sensitivity for Fe3+ detection

Polymer-based sensors, particularly those derived from renewable polymers, are gaining attention for their superior properties compared to organic small molecules. However, their complex preparation and poor, uncontrollable sensitivity have hindered further development. Herein, cellulose-based polymer photoluminescence (PL) chemosensors were fabricated using a straightforward and adjustable strategy. Specifically, water-soluble cellulose acetoacetate (CAA) was used as the substance for the in-situ synthesis of 1,4-dihydropyridine (DHPs) fluorescent rings on cellulose chains via a catalyst-free, room-temperature Hantzsch reaction. Benefiting from the synergetic through-space conjugation of DHPs rings and semi-rigid cellulose chains with heteroatoms, the sensors exhibit bright and stable PL properties. Based on this performance, the cellulose-based sensor excels in the specific recognition of Fe3+ in aqueous systems, showing exceptional selectivity, stability, and anti-interference performance due to the synergy between the inner filter effect (IFE) and intramolecular charge transfer (ICT). Theoretical calculations confirm the role of the extended π-conjugated structure at the DHPs-4 position in modulating the sensor sensitivity, achieving a low limit of detection (LOD) of 0.48 μM. Furthermore, the versatility of the Hantzsch reaction shows the potential of this strategy for developing a new generation of biomass-based polymer portable sensors for real-time and on-site detection.

Biomass-derived carbon dots with pharmacological activity for biomedicine: Recent advances and future perspectives

Carbon dots (CDs), a type of nanoparticle with excellent optical properties, good biocompatibility, and small size, are finding increasing application across the fields of biology and biomedicine. In recent years, biomass-derived CDs with pharmacological activity (BP-CDs) derived from herbal medicines (HMs), HMs extracts and other natural products with demonstrated pharmaceutical activity have attracted particular attention. Herein, we review recent advances in the development of BP-CDs, covering the selection of biomass precursors, different methods used for the synthesis of BP-CDs from natural sources, and the purification of BP-CDs. Additionally, we summarize the many remarkable properties of BP-CDs including optical properties, biocompatibility and pharmaceutical efficacy. Moreover, the antibacterial, antiviral, anticancer, biosensing, bioimaging, and other applications of BP-CDs are reviewed. Thereafter, we discuss the advantages and disadvantages of BP-CDs and Western drug-derived CDs, highlighting the excellent performance of BP-CDs. Finally, based on the current state of research on BP-CDs, we suggest several aspects of BP-CDs that urgently need to be addressed and identify directions that should be pursued in the future. This comprehensive review on BP-CDs is expected to guide the precise design, preparation, and future development of BP-CDs, thereby advancing the application of BP-CDs in biomedicine.

Highly transparent cellulose-based phosphorescent materials with tunable afterglow colors and white emission

Room temperature phosphorescence (RTP) materials with wood as framework are highly desirable due to their extended afterglow, high haze and good mechanical properties, which is highly desired in lighting materials. However, it remains challenging to obtain wood-based RTP materials that possess on-demand afterglow colors while maintaining high transparency across the entire visible spectrum. In this study, long-persistent phosphorescent transparent composite with tunable afterglow color is fabricated by infiltrating delignified wood with phosphors (including carbazole, naphthalene, and pyrene) doped polymethyl methacrylate (PMMA). Such RTP woods indicate remarkable transparency, over 70 %, and an extended afterglow duration of up to 8 s. Here, PMMA serves as rigid surrounding to suppress the non-radiative transition of phosphors to ensure phosphorescence, and to fulfill in the wood lumen to match the refractive index of cellulose for transparency. By formulating phosphors with different types and concentration ratios, transparent woods with diverse phosphorescence colors, and white emission, are successfully achieved. Furthermore, the RTP woods demonstrate dynamically tunable afterglow colors over time based on the varied phosphorescent lifetimes. Characterized by their high transparency and tunable colors, these natural wood-based RTP materials have great potentials for application in the fields of LED materials, optics, and building materials.

Wide-Range Excitation-Dependent Phosphorescence of Coordination Polymers Exhibiting Dynamic Anticounterfeiting, White-Light Emission, and Antibacterial Performance

Multicolor-tunable room-temperature phosphorescence (RTP) is attracting wide attention in optoelectronic applications. Here, we propose a coordination-oriented assembly approach to achieve wide-range RTP with a benzimidazole derivative (2,7-diazabenzimidazole, DZBIM) as a luminogen. These two compounds exhibit unexpected excitation-responsive RTP emission, and the phosphorescence emission nearly covers the entire visible region with the change of the excitation wavelength from 360 to 620 nm. To the best of our knowledge, this is the first report of coordination polymers with such a full-color-tunable RTP. Compound 1 also shows white-light emission upon excitation at 280 nm. Experimental and theoretical results demonstrate that multiple intermolecular interactions and emission centers from different aggregates are responsible for the generation of multicolor emission. The white-light emission and multiple anticounterfeiting are explored. Besides, compound 1 exhibits high antibacterial activity benefiting from efficient 1O2 generation. This work provides an efficient way to prepare a color-tunable RTP.

Room Temperature Phosphorescent Nanofiber Membranes by Bio-Fermentation

Stimuli-responsive materials exhibiting exceptional room temperature phosphorescence (RTP) hold promise for emerging technologies. However, constructing such systems in a sustainable, scalable, and processable manner remains challenging. This work reports a bio-inspired strategy to develop RTP nanofiber materials using bacterial cellulose (BC) via bio-fermentation. The green fabrication process, high biocompatibility, non-toxicity, and abundant hydroxyl groups make BC an ideal biopolymer for constructing durable and stimuli-responsive RTP materials. Remarkable RTP performance is observed with long lifetimes of up to 1636.79 ms at room temperature. Moreover, moisture can repeatedly quench and activate phosphorescence in a dynamic and tunable fashion by disrupting cellulose rigidity and permeability. With capabilities for repeatable moisture-sensitive phosphorescence, these materials are highly suitable for applications such as anti-counterfeiting and information encryption. This pioneering bio-derived approach provides a reliable and sustainable blueprint for constructing dynamic, scalable, and processable RTP materials beyond synthetic polymers.

Tailored Fabrication of Full-Color Ultrastable Room-Temperature Phosphorescence Carbon Dots Composites with Unexpected Thermally Activated Delayed Fluorescence

The development of single-system materials that exhibit both multicolor room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) with tunable after glow colors and channels is challenging. In this study, four metal-free carbon dots (CDs) are developed through structural tailoring, and panchromatic high-brightness RTP is achieved via strong chemical encapsulation in urea. The maximum lifetime and quantum yield reaches 2141 ms and 56.55%, respectively. Moreover, CDs-IV@urea, prepared via coreshell interaction engineering, exhibits a dual afterglow of red RTP and green TADF. The degree of conjugation and functional groups of precursors affects the binding interactions of the nitrogen cladding on CDs, which in turn stabilizes triplet energy levels and affects the energy gap between S1 and T1 (ΔEST) to induce multicolor RTP. The enhanced wrapping interaction lowers the ΔEST, promoting reverse intersystem crossing, which leads to phosphorescence and TADF. This strong coreshell interaction fully stabilizes the triplet state, thus stabilizing the material in water, even in extreme environments such as strong acids and oxidants. These afterglow materials are tested in multicolor, time, and temperature multiencryption as well as in multicolor in vivo bioimaging. Hence, these materials have promising practical applications in information security as well as biomedical diagnosis and treatment.

Assembly-Induced Dynamic Structural Color in a Host-Guest System for Time-Dependent Anticounterfeiting and Double-Lock Encryption

Manipulation of periodic micro/nanostructures in polymer film is of great importance for academics and industrial applications in anticounterfeiting. However, with the increasing demand on information security, materials with time-dependent features are urgently required, especially the material where the same information can appear more than once on the time scale. Here, one concise strategy to realize time-dependent anticounterfeiting and "double-lock" information encryption based on a host-guest system is proposed, with one photoresponsive azopolymer as the host and one liquid-crystalline molecule as the guest. The system exhibits a tunable mass transport in pre-designed periodic micro/nanostructures by tailoring the process of cis-to-trans recovery of azo groups and assembly of mesogenic trans-isomers, resulting in a dynamic structural color in film. Taking advantage of this extraordinary feature, time-dependent dynamic anticounterfeiting has been achieved. More importantly, the time of each state's appearance in the whole process can be modulated by changing the host-guest ratio. Combining the manipulatable process of mass transport with the unique decoding method, the stored information in film can be decrypted correctly. This work provides an unprecedented dynamic approach for advanced anticounterfeiting technology with a higher level of security and high-end applications in information encryption.

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.

Host-guest interaction induced room-temperature phosphorescence enhancement of organic dyes: a computational study

To achieve the effective regulation of organic room temperature phosphorescence (RTP) in supramolecular systems, the elucidation of host-guest interactions in RTP is of vital importance. Herein, we employed two organic dyes (PYCl and PYBr) and their four host-guest complexes with CB[6] and CB[7] and explored the mechanism of host-guest interaction induced RTP enhancement using quantum mechanics/molecular mechanics (QM/MM) approach. For the two organic dyes, we found that the better RTP performance of PYBr than PYCl is attributed to intersystem crossing (ISC) augmentation induced by the heavy atom effect. Binding to CB[6] through host-guest interactions can simultaneously accelerate the radiative decay process by increasing the transition dipole moment of T1 → S0 (μT1→S0), block the nonradiative decay process, and promote the ISC process, eventually leading to a remarkably boosted RTP. Upon complexation, the conversion of S1 from 1(n, π*) to 1(π, π*) is key to μT1→S0 enhancement; reduced reorganization energies reflect the suppression of the nonradiative decay process by restricting the rotation of rings A and B in organic dyes. In addition, the promoted ISC process is due to the activation of more ISC channels between S1 and high-lying triplet states with large spin-orbital coupling constants and small energy gap. The case of CB[7]-type complexes is much different, because of the extremely large cavity size of CB[7] for encapsulation. This work proposes the mechanism of host-guest interaction-induced RTP enhancement of organic dyes, thus laying a solid foundation for the rational design of advanced RTP materials based on supramolecular assemblies.

Recent Developments in Functional Polymers via the Kabachnik-Fields Reaction: The State of the Art

Recently, multicomponent reactions (MCRs) have attracted much attention in polymer synthesis. As one of the most well-known MCRs, the Kabachnik-Fields (KF) reaction has been widely used in the development of new functional polymers. The KF reaction can efficiently introduce functional groups into polymer structures; thus, polymers prepared via the KF reaction have unique α-aminophosphonates and show important bioactivity, metal chelating abilities, and flame-retardant properties. In this mini-review, we mainly summarize the latest advances in the KF reaction to synthesize functional polymers for the preparation of heavy metal adsorbents, multifunctional hydrogels, flame retardants, and bioimaging probes. We also discuss some emerging applications of functional polymers prepared by means of the KF reaction. Finally, we put forward our perspectives on the further development of the KF reaction in polymer chemistry.