Modular Synthesis of a Tridecasaccharide Motif of Bacteroides vulgatus Lipopolysaccharides against Inflammatory Bowel Diseases through an Orthogonal One-Pot Glycosylation Strategy

Lipopolysaccharides from Bacteroides vulgatus represent interesting targets for the treatment of inflammatory bowel diseases. However, efficient access to long, branched and complex lipopolysaccharides remains challenging. Herein, we report the modular synthesis of a tridecasaccharide from Bacteroides vulgates through an orthogonal one-pot glycosylation strategy based on glycosyl ortho-(1-phenylvinyl)benzoates, which avoids the issues of thioglycoside-based one-pot synthesis. Our approach also features: 1) 5,7-O-di-tert-butylsilylene-directed glycosylation for stereoselective construction of the α-Kdo linkage; 2) hydrogen-bond-mediated aglycone delivery for the stereoselective formation of β-mannosidic bonds; 3) remote anchimeric assistance for stereoselective assembly of the α-fucosyl linkage; 4) several orthogonal one-pot synthetic steps and strategic use of orthogonal protecting groups to streamline oligosaccharide assembly; 5) convergent [1+6+6] one-pot synthesis of the target.     

Longitudinally Grafting of Graphene with Iron Phthalocyanine-based Porous Organic Polymer to Boost Oxygen Electroreduction

Iron phthalocyanine-based polymers (PFePc) are attractive noble-metal-free candidates for catalyzing oxygen reduction reaction (ORR). However, the low site-exposure degree and poor electrical conductivity of bulk PFePc restricted their practical applications. Herein, laminar PFePc nanosheets covalently and longitudinally linked to graphene (3D-G-PFePc) was prepared. Such structural engineering qualifies 3D-G-PFePc with high site utilization and rapid mass transfer. Thence, 3D-G-PFePc demonstrates efficient ORR performance with a high specific activity of 69.31 μA cm⁻², a high mass activity of 81.88 A g⁻¹, and a high turnover frequency of 0.93 e s⁻¹ site⁻¹ at 0.90 V vs. reversible hydrogen electrode in O₂-saturated 0.1 M KOH, outperforming the lamellar PFePc wrapped graphene counterpart. Systematic electrochemical analyses integrating variable-frequency square wave voltammetry and in situ scanning electrochemical microscopy further underline the rapid kinetics of 3D-G-PFePc towards ORR.     

Dearomative Ring-Fused Azafulleroids and Carbazole-Derived Metallofullerenes: Reactivity Dictated by Encapsulation in a Fullerene Cage

Herein, we report divergent additions of 2,2′-diazidobiphenyls to C₆₀ and Sc₃N@I_h-C₈₀. In stark contrast to that of the previously reported bis-azide additions, the unexpected cascade reaction leads to the dearomative formation of azafulleroids 2 fused with a 7-6-5-membered ring system in the case of C₆₀. In contrast, the corresponding reaction with Sc₃N@I_h-C₈₀ switches to the C−H insertion pathway, thereby resulting in multiple isomers, including a carbazole-derived [6,6]-azametallofulleroid 3 and a [5,6]-azametallofulleroid 4 and an unusual 1,2,3,6-tetrahydropyrrolo[3,2-c]carbazole-derived metallofullerene 5 , whose molecular structures have been unambiguously determined by single-crystal X-ray diffraction analyses. Among them, the addition type of 5 is observed for the first time in all reported additions of azides to fullerenes. Furthermore, unexpected isomerizations from 3 to 5 and from 4 to 5 have been discovered, providing the first examples of the isomerization of an azafulleroid to a carbazole-derived fullerene rather than an aziridinofullerene. In particular, the isomerism of the [5,6]-isomer 4 to the [5,6]-isomer 5 is unprecedented in fullerene chemistry, contradicting the present understanding that isomerization generally occurs between [5,6]- and [6,6]-isomers. Control experiments have been carried out to rationalize the reaction mechanism. Furthermore, representative azafulleroids have been applied in organic solar cells, thereby resulting in improved power conversion efficiencies.     

Activatable Type I Photosensitizer with Quenched Photosensitization Pre and Post Photodynamic Therapy

The phototoxicity of photosensitizers (PSs) pre and post photodynamic therapy (PDT), and the hypoxic tumor microenvironment are two major problems limiting the application of PDT. While activatable PSs can successfully address the PS phototoxicity pre PDT, and type I PS can generate reactive oxygen species (ROS) effectively in hypoxic environment, very limited approaches are available for addressing the phototoxicity post PDT. There is virtually no solution available to address all these issues using a single design. Herein, we propose a proof-of-concept on-demand switchable photosensitizer with quenched photosensitization pre and post PDT, which could be activated only in tumor hypoxic environment. Particularly, a hypoxia-normoxia cycling responsive type I PS TPFN-AzoCF₃ was designed to demonstrate the concept, which was further formulated into TPFN-AzoCF₃ nanoparticles (NPs) using DSPE-PEG-2000 as the encapsulation matrix. The NPs could be activated only in hypoxic tumors to generate type I ROS during PDT treatment, but remain non-toxic in normal tissues, pre or after PDT, thus minimizing side effects and improving the therapeutic effect. With promising results in in vitro and in vivo tumor treatment, this presented strategy will pave the way for the design of more on-demand switchable photosensitizers with minimized side effects in the future.     

Dibenzothiophene Sulfone-Based Ambipolar-Transporting Blue-Emissive Organic Semiconductors Towards Simple-Structured Organic Light-Emitting Transistors

The development of blue-emissive ambipolar organic semiconductor is an arduous target due to the large energy gap, but is an indispensable part for electroluminescent device, especially for the transformative display technology of simple-structured organic light-emitting transistor (SS-OLET). Herein, we designed and synthesized two new dibenzothiophene sulfone-based high mobility blue-emissive organic semiconductors (DNaDBSOs), which demonstrate superior optical property with solid-state photoluminescent quantum yield of 46–67 % and typical ambipolar-transporting properties in SS-OLETs with symmetric gold electrodes. Comprehensive experimental and theoretical characterizations reveal the natural of ambipolar property for such blue-emissive DNaDBSOs-based materials is ascribed to a synergistic effect on lowering LUMO level and reduced electron injection barrier induced by the interfacial dipoles effect on gold electrodes due to the incorporation of appropriate DBSO unit. Finally, efficient electroluminescence properties with high-quality blue emission (CIE (0.179, 0.119)) and a narrow full-width at half-maximum of 48 nm are achieved for DNaDBSO-based SS-OLET, showing good spatial control of the recombination zone in conducting channel. This work provides a new avenue for designing ambipolar emissive organic semiconductors by incorporating the synergistic effect of energy level regulation and molecular-metal interaction, which would advance the development of superior optoelectronic materials and their high-density integrated optoelectronic devices and circuits.     

Improving Low-temperature Performance and Stability of Na2Ti6O13 Anodes by the Ti−O Spring Effect through Nb-doping

Na₂Ti₆O₁₃ (NTO) with high safety has been regarded as a promising anode candidate for sodium-ion batteries. In the present study, integrated modification of migration channels broadening, charge density re-distribution, and oxygen vacancies regulation are realized in case of Nb-doping and have obtained significantly enhanced cycling performance with 92 % reversible capacity retained after 3000 cycles at 3000 mA g⁻¹. Moreover, unexpected low-temperature performance with a high discharge capacity of 143 mAh g⁻¹ at 100 mA g⁻¹ under −15 °C is also achieved in the full cell. Theoretical investigation suggests that Nb preferentially replaces Ti3 sites, which effectively improves structural stability and lowers the diffusion energy barrier. What's more important, both the in situ X-ray diffraction (XRD) and in situ Raman furtherly confirm the robust spring effect of the Ti−O bond, making special charge compensation mechanism and respective regulation strategy to conquer the sluggish transport kinetics and low conductivity, which plays a key role in promoting electrochemical performance.     

The Universal Super Cation-Conductivity in Multiple-cation Mixed Chloride Solid-State Electrolytes

As exciting candidates for next-generation energy storage, all-solid-state lithium batteries (ASSLBs) are highly dependent on advanced solid-state electrolytes (SSEs). Here, using cost-effective LaCl₃ and CeCl₃ lattice (UCl₃-type structure) as the host and further combined with a multiple-cation mixed strategy, we report a series of UCl₃-type SSEs with high room-temperature ionic conductivities over 10⁻³ S cm⁻¹ and good compatibility with high-voltage oxide cathodes. The intrinsic large-size hexagonal one-dimensional channels and highly disordered amorphous phase induced by multi-metal cation species are believed to trigger fast multiple ionic conductions of Li⁺, Na⁺, K⁺, Cu⁺, and Ag⁺. The UCl₃-type SSEs enable a stable prototype ASSLB capable of over 3000 cycles and high reversibility at −30 °C. Further exploration of the brand-new multiple-cation mixed chlorides is likely to lead to the development of advanced halide SSEs suitable for ASSLBs with high energy density.     

Highly Recyclable and Tough Elastic Vitrimers from a Defined Polydimethylsiloxane Network

Despite intensive research on sustainable elastomers, achieving elastic vitrimers with significantly improved mechanical properties and recyclability remains a scientific challenge. Herein, inspired by the classical elasticity theory, we present a design principle for ultra-tough and highly recyclable elastic vitrimers with a defined network constructed by chemically crosslinking the pre-synthesized disulfide-containing polydimethylsiloxane (PDMS) chains with tetra-arm polyethylene glycol (PEG). The defined network is achieved by the reduced dangling short chains and the relatively uniform molecular weight of network strands. Such elastic vitrimers with the defined network, i.e., PDMS-disulfide-D, exhibit significantly improved mechanical performance than random analogous, previously reported PDMS vitrimers, and even commercial silicone-based thermosets. Moreover, unlike the vitrimers with random network that show obvious loss in mechanical properties after recycling, those with the defined network enable excellent thermal recyclability. The PDMS-disulfide-D also deliver comparable electrochemical signals if utilized as substrates for electromyography sensors after the recycling. The multiple relaxation processes are revealed via a unique physical approach. Multiple techniques are also applied to unravel the microscopic mechanism of the excellent mechanical performance and recyclability of such defined network.     

Dual-Plasmon Resonance Coupling Promoting Directional Photosynthesis of Nitrate from Air

Photocatalysis, particularly plasmon-mediated photocatalysis, offers a green and sustainable approach for direct nitrogen oxidation into nitrate under ambient conditions. However, the unsatisfactory photocatalytic efficiency caused by the limited localized electromagnetic field enhancement and short hot carrier lifetime of traditional plasmonic catalysts is a stumbling block to the large-scale application of plasmon photocatalytic technology. Herein, we design and demonstrate the dual-plasmonic heterojunction (Bi/Cs_xWO₃) achieves efficient and selective photocatalytic N₂ oxidation. The yield of NO₃⁻ over Bi/Cs_xWO₃ (694.32 μg g⁻¹ h⁻¹) are 2.4 times that over Cs_xWO₃ (292.12 μg g⁻¹ h⁻¹) under full-spectrum irradiation. The surface dual-plasmon resonance coupling effect generates a surge of localized electromagnetic field intensity to boost the formation efficiency and delay the self-thermalization of energetic hot carriers. Ultimately, electrons participate in the formation of ⋅O₂⁻, while holes involve in the generation of ⋅OH and the activation of N₂. The synergistic effect of multiple reactive oxygen species drives the direct photosynthesis of NO₃⁻, which achieves the overall-utilization of photoexcited electrons and holes in photocatalytic reaction. The concept that the dual-plasmon resonance coupling effect facilitates the directional overall-utilization of photoexcited carriers will pave a new way for the rational design of efficient photocatalytic systems.     

Engineering Graphdiyne for Solar Photocatalysis

Graphdiyne (GDY) with a direct band gap, excellent carrier mobility and uniform pores, is regarded as a promising photocatalytic material for solar energy conversion, while the research on GDY in photocatalysis is a less developed field. Herein, the distinctive structure, adjustable band gap, and electronic properties of GDY for photocatalysis is firstly summarized. The construction and progress of GDY-based photocatalysts for solar energy conversion, including H₂ evolution reaction (HER), CO₂ reduction reaction (CO₂RR) and N₂ reduction reaction (NRR) are then elaborated. At last, the challenges and perspectives in developing GDY-based photocatalysts for solar fuel production are discussed. It is anticipated that a timely Minireview will be helpful for rapid progress of GDY in solar energy conversion.