Latest ArticlesThe first phloroglucinol-triterpenoid hybrids, myrtphlotritins A–E (1–5), were rapidly recognized and isolated from two species of Myrtaceae by employing the building blocks-based molecular network (BBMN) strategy. Compounds 1–5 featured new carbon skeletons in which phloroglucinol derivatives were coupled with lupane- and dammarane-type triterpenoids through different linkage patterns. Their structures and absolute configurations were elucidated by comprehensive analysis of spectroscopic data and quantum chemical calculations. Biosynthetic pathways for compounds 1–5 were proposed on the basis of the coexisting precursors. Guided by the biogenetic pathways, the biomimetic synthesis of compound 1 was also achieved. Additionally, compounds 2, 3, and 5 exhibited potent antiviral activities against herpes simplex virus type-1 (HSV-1) infection, and compounds 2 and 5 displayed significant anti-inflammatory activities on RAW264.7 cells.
Side reactions and dendrite growth triggered by the unstable interface and inhomogeneous deposition have become the biggest obstacle to the commercialization for lithium metal batteries. In this study, a highly-chlorinated organic-inorganic hybrid interfacial protective layer is developed by rationally tuning the interfacial passivation and robustness to achieve the convenient and efficient Li metal anode. The polyvinyl chloride (PVC) can effectively resist water and oxygen, which is confirmed by density functional theory. The organic-dominant solid electrolyte interphases (SEI) with lithium chloride are investigated by the X-ray photoelectron spectroscopy (XPS) with little mineralization of oxide, such as Li2O and Li2CO3. With such artificial SEI, a uniform and dense lithium deposition morphology are formed and an ultra-long stable cycle of over 500 h are achieved even at an ultra-high current density of 10 mA/cm2. Moreover, the simple and convenient protected anode also exhibits excellent battery stability when paired with the LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiFePO4 (LFP) cathode, showing great potential for the commercial application of lithium metal batteries.
All-solid-state lithium batteries (ASSLBs) based on sulfide electrolytes promise next-generation energy storage with high energy density and safety. However, the sulfide electrolytes suffer from phase instability and sluggish interfacial charge transport when pairing with layered oxide cathodes at high voltages. Herein, a simple and efficient strategy is proposed using two-dimensional Ti3C2T MXene as starting material to in-situ construct a 15 nm Li2TiO3 layer on a typical oxide cathode, LiCoO2. The in-situ transformation of Ti3C2T into Li2TiO3 layer occurs at a low temperature of 500 ℃, avoiding the phase deterioration of LiCoO2. The thin Li2TiO3 layer is Li+ conducting and electrochemically stable, thereby preventing the interfacial decomposition of sulfide electrolytes induced by LiCoO2 at high voltages and facilitating Li+ transport at the interface. Moreover, Li2TiO3 can stabilize the layer structure of LiCoO2 at high voltages. Consequently, the sulfide-based ASSLB using LiCoO2@Li2TiO3 cathode can operate stably at a high voltage of up to 4.5 V (vs. Li+/Li), delivering an outstanding initial specific discharge capacity of 138.8 mAh/g with a high capacity retention of 86.2% after 100 cycles at 0.2 C. The in-situ transformation strategy may also apply to other MXenes, offering a general approach for constructing other advanced lithiated coatings for oxide cathodes.
FeS2 shows significant potential as cathode material for all-solid-state lithium batteries (ASSLBs) due to its high theoretical specific capacity, low cost, and environmental friendliness. However, the poor ion/electron conductivity and large volume variation effect of FeS2 inhibit its practical applications. Here, the influence of particle size of FeS2 on the corresponding sulfide-based solid-state batteries is carefully investigated by tuning FeS2 size. Moreover, low operating temperature is chosen to mitigate the large volume changes during cycling in the battery. S-FeS2 with smaller particle sizes delivers superior electrochemical performances than that of the larger L-FeS2 in Li5.5PS4.5Cl1.5-based ASSLBs under different operating temperatures. S-FeS2 shows stable discharge capacities during 50 cycles with a current density of 0.1 mA/cm2 under -20 ℃. When the current density rises to 1.0 mA/cm2, it delivers an initial discharge capacity of 146.9 mAh/g and maintains 63% of the capacity after 100 cycles. This work contributes to constructing ASSLBs enables excellent electrochemical performances under extreme operating temperatures.
Lithium (Li) metal anodes (LMAs) have garnered significant attention as a potential solution for developing high-energy density batteries, given their theoretical specific capacity and redox potential. However, safety concerns and internal cycling stability issues originated from uncontrollable Li dendrite growth have impeded the practical application of LMAs. Probing the interface between Li metal and electrolyte is a crucial process that offers valuable insights into the characteristics and regularity of primary circular reactions. To illustrate the intrinsic characteristic of Li metal batteries (LMBs) in spatial and temporal, it is imperative to employ electron microscopes to characterize the structural components distribution of Li with atomic resolution. This paper summarizes the progress in the characterization and analysis of the interfaces in LMBs with electron microscopes based on the principles of electron-matter interactions. Finally, future trends and the potential of electron microscopes are also discussed to advance our understanding of LMBs.
Exhaled ammonia (NH3) can be used as a crucial biomarker of kidney and liver diseases. However, the high humidity in the detection conditions remains a challenge for accurate detection by gas sensors. Herein, a copper-based metal-organic framework (CH3-Cu-BTC) with methyl (CH3-) functionalization of trimesic acid was synthesized for NH3 colorimetric sensing. The CH3-Cu-BTC exhibited a strong response for 5 ppm NH3 with high selectivity under high relative humidity (75% RH). Density functional theory (DFT) simulations indicated that the NH3 molecules interacted more strongly with CH3-Cu-BTC than H2O molecules did, and the corresponding color switching was attributed to the lone-pair electron in NH3 changing the coordination environment of Cu2+ ions, leading to an obviously visible color switching response from ruby green to blue. Based on the tailor-made pore chemistry, the precise detection of trace amounts of NH3 in exhaled air was realized through functionalized MOF materials. The strategy used in this study not only offers a new pathway for the rapid detection of low concentration NH3 under humid conditions, but also shows a method for early respiration diagnosis of kidney and liver diseases.
A new aggregation-induced emission (AIE)-based fluorescence sensor, TPEPy-SS-C14, for simultaneous recognition of adenosine triphosphate (ATP) and hydrogen sulfide (H2S) has been reported via the aggregation-disaggregation mechanism. The probe self-assembles nano-structure aggregations in aqueous solution. It shows fluorescence turn-on response toward ATP for the complexation-enhanced aggregation, but leads to fluorescence quenching of H2S for cleavage the aggregations.
Covalent organic frameworks (COFs) exhibiting reversible redox behaviors have been identified as promising candidates for constructing electrode materials in lithium-ion batteries (LIBs). However, their extensive application has been limited due to finite redox sites and poor structural stability. In this study, we design and synthesize a novel polyimide covalent organic framework (PI-COF) using the traditional solvothermal method and successfully apply it as an anode material for LIBs. The large conjugated structure of PI-COF accelerates charge transfer, while its large surface area provides more active sites, making PI-COF an attractive anode material for LIBs. Furthermore, the PI-COF anode material demonstrates high reversible specific capacity and excellent long-term cycling stability due to its COF characteristics. Specifically, the PI-COF electrodes deliver a specific capacity of 800 mAh/g at a current density of 200 mA/g after 200 cycles, while a specific capacity of 450 mAh/g at a current density of 1000 mA/g is sustained after 800 cycles. The outstanding lithium storage capacity, particularly the satisfactory long-term cycling stability, establishes PI-COF as a promising material for LIBs.
Surface modification of microporous bone scaffolds using nanoparticles has been broadly studied in bone tissue engineering. Aiming at improving vascularized bone regeneration (VBR), zeolitic imidazolate framework-8 (ZIF-8) was encapsulated with dimethyloxallyl glycine (DMOG) and the drug-carrying nanoparticles (D@Z) could be uniformly coated onto the surface of the bone scaffold. The osteogenic and angiogenic actions of D@Z are closely correlated with the amount of slowly released DMOG, and in general, exhibited a favorable association. Then, the D7.5@Z group, which showed the greatest capacity to induce in vitro osteogenesis–angiogenesis coupling, was utilized for surface modification of the bone scaffold. Biological processes including phosphate-containing compound metabolic process, cell differentiation, cell proliferation and cell motility might contribute to enhanced ability to induce VBR by the coated scaffold and signaling pathways such as Rap1, Ras, phosphatidylinositol 3-kinase/protein kinase B (PI3K-AKT) and vascular endothelial growth factor (VEGF) signaling pathways participated in these processes. Finally, as depicted by in vitro real time-polymerase chain reaction (RT-PCR), Western blot (WB) and in vivo cranial bone defect model, the microporous scaffold coated with nano-D7.5@Z greatly promoted VBR. To conclude, nano-D@Z has significant promise for practical application in modification of microporous bone scaffolds to enhance VBR, and DMOG loading quantity has a beneficial influence on D@Z to improve osteogenesis–angiogenesis coupling.
The seven-membered ring motifs are found in bioactive pharmaceuticals and a wide range of natural products, including alkaloids and terpenoids, which hold significant importance in synthetic chemistry and has garnered considerable attention from both academia and industry. Despite the challenges faced in the past decade, the total synthesis of natural products incorporating the non-aromatic cycloheptane skeletons remains a compelling pursuit. Recently, numerous elegant strategies for constructing the seven-membered ring system have been successfully developed. This review focuses on the recent advancements in this field from 2017 to April 2023, highlighting key transformations utilized to construct the non-aromatic cycloheptane core structures and serves as a valuable guide for synthetic chemists engaged in the total synthesis of natural products containing seven-membered ring motifs.
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