Regulating Triplet Excitons of Organic Luminophores for Promoted Bioimaging.

Afterglow materials with organic room temperature phosphorescence (RTP) or thermally activated delayed fluorescence (TADF) exhibit significant potential in biological imaging due to their long lifetime. By utilizing time-resolved technology, interference from biological tissue fluorescence can be mitigated, enabling high signal-- to-background ratio imaging. Despite the continued emergence of individual reports on RTP or TADF in recent years, comprehensive reviews addressing these two materials are rare. Therefore, this review aims to provide a comprehensive overview of several typical molecular designs for organic RTP and TADF materials. It also explores the primary methods through which triplet excitons resist quenching by water and oxygen. Furthermore, we analyze the principal challenges faced by afterglow materials and discuss key directions for future research with the hope of inspiring developments in afterglow imaging.

Hydrogen Bond-Mediated Strong Plasticization for High-Performance Alginate Plastics.

The increasingly severe plastic pollution has urged an inevitable trend to develop biodegradable plastic products that can take over synthetic plastics. As one of the most abundant natural polymers, polysaccharides are an ideal candidate to substitute synthetic plastics. The rigidity of polysaccharide chains principally allows for high strength and stiffness of their materials, however, challenges the facile orientation in material processing. Here, a general hydrogen bond-mediated plasticization strategy to regulate isotropic sodium alginate (SA) chains to a highly ordered state is developed, and alginate plastics with high performances are fabricated. It is revealed that hydroxyl groups in glycerol modulate the viscoelasticity of SA solids by forming strong hydrogen bonds with SA chains, achieving a large stretchability at a high solid content. Highly orientated alginate films exhibit a superior tensile strength of 575 MPa and toughness of 60.7 MJ m-3, outperforming most regenerated biomass films. The high solid content and large stretchability mediated by strong hydrogen bonding ensure plastic molding of solid-like SA with high fidelity. This hydrogen bond-mediated plasticity provides a facile but effective method to justify the high performances of polysaccharide-based plastics.

Multi-Responsive Afterglows from Aqueous Processable Amorphous Polysaccharide Films.

Polymer-based room-temperature phosphorescence (RTP) materials, especially polysaccharide-based RTP materials, earn sustained attention in the fields of anti-counterfeiting, data encryption, and optoelectronics owing to their green regeneration, flexibility, and transparency. However, those with both ultralong phosphorescence lifetime and excitation wavelength-dependent afterglow are rarely reported. Herein, a kind of amorphous RTP material with ultralong lifetime of up to 2.52 s is fabricated by covalently bonding sodium alginate (SA) with arylboronic acid in the aqueous phase. The resulting polymer film exhibits distinguished RTP performance with excitation-dependent emissions from cyan to green. Specifically, by co-doping with other fluorescent dyes, further regulation of the afterglow color from cyan to yellowish-green and near-white can be achieved through triplet-to-singlet Förster resonance energy transfer. In addition, the water-sensitive properties of hydrogen bonds endow the RTP property of SA-based materials with water/heat-responsive characteristics. On account of the color-tunable and stimuli-responsive afterglows, these smart materials are successfully applied in data encryption and anti-counterfeiting.

In-situ formation of thermo-responsive petal-like cellulose nanocrystals hybridized particles towards optimizing mechanical, rheological and dielectric properties of polylactic acid blends.

Enhancing the toughness of biodegradable polylactic acid (PLA) blends with minimal filler content meanwhile preserving their thermomechanical properties remains a highly desirable objective. Here, through a simple in situ mixing of PLA with cellulose nanocrystals (CNC) and cellulose nanocrystal nanofluids (CNCfs), the electrostatic interaction between CNCfs (+22.6 mv) and CNC (-9.07 mv) formed petal-like hybridized particles with CNCfs as the core and CNC particles as the outer layer. The rheological tests indicated a significant reduction in the zero-shear viscosity and storage modulus of PLA/CNCfs blends, while the viscosity of PLA/CNCfs@CNC slightly decreased but retained its storage modulus compared to pure PLA. The optimized PLA/CNCfs@CNC blends not only exhibited excellent melt processing performance, but also increased the elongation at break (increased by 184 % and 375 % at 8 °C and 45 °C, respectively) and enhanced toughness remarkably (increased by 3.5 and 3.3-fold at 8 °C and 45 °C, respectively) meantime retaining the modulus with 1 GPa. The addition of CNCfs@CNC hardly affects the glass transition temperature and thermo-mechanical properties of PLA. The dielectric properties of PLA/CNCfs1.0/CNC2.0 blends were maximized at 1000 Hz, reaching a value of 21, which can be attributed to the synergistic effect of multilayer interfacial polarization.

Facile Fabrication of Superwetting PVDF Membrane for Highly Efficient Oil/Water Separation.

A novel superhydrophilic and underwater superoleophobic modified PVDF membrane for oil/water separation was fabricated through a modified blending approach. Pluronic F127 and amphiphilic copolymer P (MMA-AA) were directly blended with PVDF as a hydrophilic polymeric additive to prepare membranes via phase inversion induced by immersion precipitation. Then, the as-prepared microfiltration membranes were annealed at 160 °C for a short time and quenched to room temperature. The resultant membranes exhibited contact angles of hexane larger than 150° no matter whether in an acidic or basic environment. For 1, 2-dichloroethane droplets, the membrane surface showed a change from superoleophilic to superoleophobic under water with aqueous solutions with pH values from 2 to 13. This as-prepared membrane has good mechanical strength and can then be applied for oil and water mixture separation.

Accessing Excitation- and Time-Responsive Afterglows from Aqueous Processable Amorphous Polymer Films through Doping and Energy Transfer.

Smart afterglow materials in response to excitation and delay time, including crystals, polymeric films, and carbon dots, have attracted considerable attention on account of their fundamental value in photophysics and promising applications in optoelectronics. However, the fabrication of amorphous and flexible polymer films with fine control remains underexplored. Herein, new doped polymer films based on sodium alginate and aromatic carboxylates are developed, which demonstrate following advantages: (i) easy and fast fabrication through the aqueous solution process, (ii) flexible, transparent, and re-dissolvable characteristics, (iii) multi-tunable afterglow colors from blue to red and even white with fine control. Specifically, even better controllability can be achieved through co-doping and triplet-to-singlet Förster resonance energy transfer (TS-FRET). Multimode advanced anti-counterfeiting of these materials is demonstrated using their excitation- and time-dependent as well as TS-FRET-mediated afterglow colors.

Room-Temperature Sodium-Sulfur Batteries: Rules for Catalyst Selection and Electrode Design.

Seeking an optimal catalyst to accelerate conversion reaction kinetics of room-temperature sodium-sulfur (RT Na-S) batteries is crucial for improving their electrochemical performance and promoting the practical applications. Herein, theoretical calculations of interfacial interactions of catalysts and polysulfides in terms of the surface adsorption state, interfacial ions migration, and electronic concentration around the Fermi level are systematically proposed as guiding principles of catalyst selection for RT Na-S batteries. As a case, MoN catalyst is accurately selected from transition metal nitrides with different d orbital electrons, and for experiment, it is introduced into the carbon nanofibers as a dual-functioning host (MoN@CNFs). The MoN@CNFs can effectively anchor polysulfides and accelerate their conversion reaction. In addition, for the sodium anode, the MoN@CNFs can also induce uniform deposition of Na and inhibit dendrite growth, which are supported by in situ characterizations and finite element simulation technique. As a result, the as-prepared RT Na-S battery displays high reversible capacity of 990 mAh g-1 at 0.2 A g-1 after 100 cycles and long lifespan over 1500 cycles at 2 A g-1 . Even with high S loading of 5 mg cm-2 , the RT Na-S battery still exhibits a high areal capacity of 2.5 mAh cm-2 .

Liquefied Polysaccharides-Based Polymer with Tunable Condensed State Structure for Antimicrobial Shield by Multiple Processing Methods.

The phase behavior of biomolecules containing persistent molecular entities is generally limited due to their characteristic size that exceeds the intermolecular force field. Consequently, favorable properties normally associated with the liquid phase of a substance, such as fluidity or processability, are not relevant for the processing of biomolecules, thus hindering the optimal processing of biomolecules. The implied problem that arises is how to convert folded biomolecules to display a richer phase behavior. To alleviate this dilemma, a generic approach to liquefied polysaccharides-based polymers is proposed, resulting in a polysaccharide fluid with a tunable condensed state structure (solid-gel-liquid). Polysaccharide biobased fluids materials transcend the limits of the physical state of the biobased material itself and can even create completely new properties (different processing methods as well as functions) in a variety of polymeric structures. Considering the solvent incompatible high and low-temperature applications, this method will have a great influence on the design of nanostructures of biomolecular derivatives and is expected to transform biomass materials such as polysaccharide biopolymers from traditional use to resource use, ultimately leading to the efficient use of biomass materials and their sustainability.

Color-Tunable, Excitation-Dependent, and Time-Dependent Afterglows from Pure Organic Amorphous Polymers.

Achieving persistent room-temperature phosphorescence (p-RTP), particularly those of tunable full-colors, from pure organic amorphous polymers is attractive but challenging. Particularly, those with tunable multicolor p-RTP in response to excitation wavelength and time are highly important but both fundamentally and technically underexplored. Here, a facile and general strategy toward color-tunable p-RTP from blue to orange-red based on amidation grafting of luminophores onto sodium alginate (SA) chains, resulting in amorphous polymers with distinct p-RTP and even impressively excitation-dependent and time-dependent afterglows is reported. p-RTP is associated with the unique semi-rigidified SA chains, effective hydrogen bonding network, and oxygen barrier properties of SA, whereas excitation-dependent and time-dependent afterglows should stem from the formation of diversified p-RTP emissive species with comparable but different lifetimes. These results outline a rational strategy toward amorphous smart luminophores with colorful, excitation-dependent, and time-dependent p-RTP, excellent solution processability, and film-forming ability for versatile applications.

Electrospinning of biocompatible alginate-based nanofiber membranes via tailoring chain flexibility.

Electrospinning of pure alginate or derivatives has always been a pursuing goal in biological fields in recent years owing to its fascinating biological characteristics and biomimetic structures. Yet it is still a severe challenge in view of its insufficient entanglements and strong electrostatic repulsions. Herein, alginate dialdehyde (ADA) with improved and adjustable chain flexibility was prepared via periodate-oxidation. Chain flexibility, concentration, ethanol and crosslinkers played key roles in electrospinning proved by persistence length (lp), the number of entanglement points (ne) and fiber morphology. Finally, insoluble ADA corsslinked nanofiber membranes were obtained, which exhibited excellent mechanical properties and adjustable degradability. Specially, biocompatibility assays confirmed that the preparing membranes were noncytotoxic, and could promote cell attachment and proliferation. Therefore, under the guidance of the relationship between chain flexibility and electrospinnability, pure alginate-based nanofiber membranes are expected to become promising scaffolds for biomedical applications, particularly for wound healing which demanding appropriate degradation.

3D-metal-embroidered electrodes: dreaming for next generation flexible and personalizable energy storage devices.

Flexible and Personalizable battery is a promising candidate for energy storage, but suffers from the weldablity and large-scale producibility of the electrode. To address the issues, we design a nickel foam catalyzed electroless deposition (NFED) derived 3D-metal-pattern embroidered electrodes. This is the first attempt to utilize this type of electrode in battery field. It is found that the current collector can be embroidered on any selected areas of any complex-shape electrodes, with high controllability and economical feasibility. As a result, the electronic conductivity of the flexible electrodes can be improved by nearly one order of magnitude, which can be easily and firmly weldded to the metal tab using the industry generic ultrasonic heating process. The embroidered electrodes could substantially promote the electrochemical performance under bending deformation, with both Li-S and Li-LiFePO4 batteries as the models. This innovation is also suitable to embroider all the VIII group elements on any electrodes with personalized shapes, which is widely attractive for the development of next generation flexible and personalizable energy storage devices.

Investigating the synergetic dispersing effect of hydrolyzed biomacromolecule Cellulase and SDS on CuPc pigment.

In this paper, the dispersion performance of biomacromolecule hydrolyzed cellulase from Trichoderma reesei on copper phthalocyanine (CuPc) pigment was first studied. The effect of hydrolysis time, cellulase concentration and environmental pH on the dispersion performance was investigated by particle size distribution and suspension transmittance measurement. The hydrolysis degree of cellulase was determined by FTIR, XRD, UV-vis and fluorescence spectra, potential and particle size analysis, respectively. Subsequently, the hydrolyzed cellulase was combined with sodium dodecyl sulfate (SDS) for acquiring better CuPc suspension based on their synergetic effects on dispersion. The optimal mass ratio of hydrolyzed cellulase to SDS was found to be 1:9. The resulting CuPc dispersion by this hydrolyzed cellulase/SDS composite was characterized by FTIR, TG, TEM, XRD analysis, respectively. This study demonstrated that there were strong interactions between hydrolyzed cellulase and SDS to result in synergistic dispersing effect on CuPc for better stability.

Advances in Halloysite Nanotubes-Polysaccharide Nanocomposite Preparation and Applications.

Halloysite nanotubes (HNTs), novel 1D natural materials with a unique tubular nanostructure, large aspect ratio, biocompatibility, and high mechanical strength, are promising nanofillers to improve the properties of polymers. In this review, we summarize the recent progress toward the development of polysaccharide-HNTs composites, paying attention to the main existence forms and wastewater treatment application particularly. The purification of HNTs and fabrication of the composites are discussed first. Polysaccharides, such as alginate, chitosan, starch, and cellulose, reinforced with HNTs show improved mechanical, thermal, and swelling properties. Finally, we summarize the unique characteristics of polysaccharide-HNTs composites and review the recent development of the practical applications.

Reevaluating Protein Photoluminescence: Remarkable Visible Luminescence upon Concentration and Insight into the Emission Mechanism.

It is a textbook knowledge that protein photoluminescence stems from the three aromatic amino acid residues of tryptophan(Trp), tyrosine (Tyr), and phenylalanine (Phe), with predominant contributions from Trp. Recently, inspired by the intrinsic emission of nonaromatic amino acids and poly(amino acids) in concentrated solutions and solids, we revisited protein light emission using bovine serum albumin (BSA) as a model. BSA is virtually nonemissive in dilute solutions (≤0.1 mg mL-1 ), but highly luminescent upon concentration or aggregation, showing unique concentration-enhanced emission and aggregation-induced emission (AIE) characteristics. Notably, apart from well-documented UV luminescence, bright blue emission is clearly observed. Furthermore, persistent room-temperature phosphorescence (p-RTP) is achieved even in the amorphous solids under ambient conditions. This visible emission can be rationalized by the clustering-triggered emission (CTE) mechanism. These findings not only provide an in-depth understanding of the emissive properties of proteins, but also hold strong implications for further elucidating the basis of tissue autofluorescence.

Design of injectable agar/NaCl/polyacrylamide ionic hydrogels for high performance strain sensors.

High performance strain sensors have recently attracted immense interest because of their potential applications in wearable devices. However, it remains a challenge in achieving critical feature combinations (e.g., high sensitivity, high mechanical properties, and easy fabrication) for soft wearable sensors. Herein, we fabricated new ionic strain sensors based on agar/NaCl/polyacrylamide double network hydrogels. By taking the advantage of the electric neutrality of agar, we can easily combine the sensitivity and mechanical properties into same ionic hydrogel by tuning the chemical compositions of the hydrogels. Moreover, thanks to the thermoreversible sol-gel properties of agar, the pregel can be injected into various complex shapes. The ionic hydrogels exhibit high strain sensitivity and many superior mechanical properties. The ionic sensor can monitor human motions such as joint motions, slight wrist pulse and subtle muscle movements of throat. Thus, this study demonstrates that the ionic hydrogels have potential applications as high performance strain sensors.

Multiple Weak H-Bonds Lead to Highly Sensitive, Stretchable, Self-Adhesive, and Self-Healing Ionic Sensors.

Herein, we demonstrate a ternary ionic hydrogel sensor consisting of tannic acid, sodium alginate, and covalent cross-linked polyacrylamide as skin-mountable and wearable sensors. Based on the multiple weak H-bonds and synergistic effects between the three components, the as-prepared hybrid hydrogel exhibits ultrastretchability with high elasticity, good self-healing, excellent conformability, and high self-adhesiveness to diverse substrates both in air and underwater. More importantly, the ternary hydrogel exhibits high strain sensitivity especially under subtle strains with a gauge factor of 2.0, which is close to the theoretical value of the ionic hydrogel sensors; an extremely large workable range of strain (0.05-2100%); and a low operating voltage 0.07 V. Consequently, the sensor demonstrates superior sensing performance for real-time monitoring of the large and subtle human motions, including limb motions, swallowing, smiling, and wrist pulse. Therefore, it is believed that the STP hydrogel has great potential applications in health monitoring, smart wearable devices, and soft robots.

Controlled synthesis of sodium alginate electrospun nanofiber membranes for multi-occasion adsorption and separation of methylene blue.

Herein, the three kinds of water-insoluble alginate-based nanofiber membranes were prepared by electrospinning and followed with crosslinking by calcium chloride (CaCl2), glutaraldehyde vapor (GA), and trifluoroacetic acid (TFA) crosslinking, respectively. All the sodium alginate(SA) nanofiber membranes present excellent integrated adsorption performance toward methylene blue (MB). Among these, CaCl2 crosslinked SA membranes exhibit the maximum actual adsorption capacity of 2230 mg/g and shortest adsorption equilibrium time of 50 min to date. On the basis of the selective adsorption of SA, the nanofiber membranes can separate MB/ methyl orange (MO) mixture solution and maintain high separation efficiency even after five cycles. In addition, respective applicable condition for differentially crosslinked SA nanofiber membranes was evaluated. The TFA crosslinked membranes have the least reduction in the adsorption capacity in acidic environment and GA crosslinked membranes adsorb better in alkaline environment. For seawater environment, GA crosslinked membranes show obvious adsorption performance than other crosslinked membranes.

Clustering-Triggered Emission and Persistent Room Temperature Phosphorescence of Sodium Alginate.

Nonconventional biomacromolecular luminogens have attracted extensive interest due to their fundamental importance and potential applications in diverse areas. To explore novel luminogens and, moreover, to gain deeper insights into their emission mechanism, we study the emission behaviors of sodium alginate (SA), a natural anionic polysaccharide composed of mannuronic (M) and guluronic acids (G). We find that the luminescence from aqueous SA solutions exhibits distinct concentration enhanced emission and aggregation-induced emission (AIE) characteristics. Meanwhile, the ratio of M/G also matters. Rheological measurements reveal the distinct regimes of the solutions, which are consistent with the observed emission, indicative of strong association between the chain entanglement and emission. Moreover, we observe persistent room temperature phosphorescence (RTP) in the amorphous SA solids, which is a rare case even in pure organic aromatic luminogens. Such unique emission can be remarkably enhanced via coordination with Ca2+ ions. These emission behaviors can be well rationalized by the clustering-triggered emission (CTE) mechanism. Namely, the emission is caused by the electron cloud overlap due to the clustering of oxygen atoms and carboxylate units, together with conformation rigidification. Owing to its biocompatibility, intrinsic emission, and, moreover, persistent RTP, SA shows great potential for anticounterfeiting, encryption, intracellular imaging, and so on.

Functionalized alginate with liquid-like behaviors and its application in wet-spinning.

Alginate is a kind of marine-derived plant polysaccharide with useful properties including inherent flame-retardancy and biocompatibility, yet poor flowability and low processing efficiency induced by high viscosity impede its further industrial applications. In this study, PEG-substituted tertiary amines were adapted to functionalize alginate with different molecular weight via acid-base reaction to improve the flowability. Based on alginate with low molecular weight, alginate fluids exhibited excellent flowability at room temperature in the absence of solvent. For alginate with high molecular weight, gelatinous precipitated phase exhibited significant shear-thinning properties and higher solid content despite lack of solvent-free flowability, which was applied to wet-spinning. The alginate fibers exhibited increased tensile strength by 104% and elongation at break by 132% compared with conventional alginate fibers, and the spinning efficiency was significantly improved. The proposed strategy is expected to extend to highly efficient processing of other polysaccharides to obtain high-performance biomedical materials.

Improve the flame retardancy of cellulose fibers by grafting zinc ion.

Zinc ion as the only flame retardant of cellulose fibers was successfully grafted onto cellulose fibers. Grafting maleic anhydride onto cellulose fibers via homogeneous acylation reaction between N,N-dimethyl formamide (DMF) as the first step. Then, graft zinc ion onto the formed cellulose fibers was conducted with zinc carbonate. The resulting copolymers were characterized by FTIR. Flame retardancy and thermal degradation of zinc-ion-modified cellulose fibers (cellulose-Zn fibers) was investigated by limiting oxygen index (LOI), cone calorimeter (CONE), XRD, TG and SEM. Zinc ion could effectively improve flame retardancy and thermal degradation when its content increases up to 4.96 wt%.