Latest ArticlesColorimetric and fluorescent probes have emerged as a potent tool for pH sensing due to easy operation and high sensitivity. However, most of the existing bimodal probes require complicated synthesis, which greatly limits their wide applications. Herein, a simple fluorescent dye (called BFCUR) featuring a D-π-A-π-D conjugated system was developed from the natural polyphenol curcumin (CUR). BFCUR exhibited significant red-shift in UV absorption and fluorescence emission as pH increased because of the deprotonation of the phenolic hydroxyl groups, which resulted in the enhanced intramolecular charge transfer (ICT). The ratiometric pH detection of BFCUR was achieved with remarkable accuracy by monitoring both the absorbance ratio A500/A650 and the fluorescence intensity ratio I622/I743 under various pH values. In addition, the clear color changes of BFCUR under different pH conditions were visible, which enabled BFCUR to be used in test strips for rapid, visual pH detection. Moreover, BFCUR exhibited low cytotoxicity, and was successfully applied for intracellular pH detection, where the fluorescence intensity was linearly related to pH value. This study highlighted the great potential of CUR-derived BFCUR as colorimetric and fluorescent probes for ratiometric-pH sensing and cell imaging.
Vitamin B12 (macrocyclic cobalamin) has been recently reported to be capable of electrochemically catalyzing water oxidation in a neutral phosphate buffer solution. In this work, density functional calculations were employed to elucidate the water oxidation mechanism catalyzed by vitamin B12. The calculations showed that the catalytic cycle starts from the L•-CoII-OH2 complex 1. A proton-coupled electron transfer process then leads to the formation of a L•-CoIII-OH complex 2, followed by another proton-coupled electron transfer event to afford a corrin ligand radical cation intermediate 3 (L•-CoIII-O•). The redox non-innocent nature of the corrin ligand plays an essential role in the oxidation process. 3 is capable of triggering the O-O bond formation via a water nucleophilic attack mechanism, in which a hydrophosphate dianion functions as a base to accept a proton from the water nucleophile. A dioxygen molecule is released after the oxidation of the CoIII-OOH intermediate. The rate-determining step was calculated to be the O-O bond formation with a total barrier of 16.5 kcal/mol. While the use of water molecules as the proton acceptor was found to be less feasible for the O-O bond formation, with a barrier of 31.2 kcal/mol, further highlighting the crucial of phosphate in water oxidation.
Li‒S batteries have shown great potential as secondary energy batteries. However, the side reaction between Li anodes and polysulfides seriously limited their practical application. Herein, the artificial protective film, which is consisted of Li-Nafion and TiO2, was designed and successfully prepared to achieve a corrosion-resistant Li anode in Li-S battery. In the composite protective film, the Li-Nafion could efficiently prevent the contact between Li anodes and polysulfides, and the incorporation of TiO2 nanoparticles into the Nafion could significantly increase the ionic conductivity and mechanical strength of the protective film. Li-Li symmetric cells with an optimal artificial protective film exhibited an extended cycle-life of 750 h at a current density of 1 mA/cm2 in Li2S8 electrolyte. Moreover, the Li‒S full battery with an optimal protective Li anode exhibited higher capacity retention of 777.4 mAh/g after 100 cycles at 0.1 C as well as better rate performance than the cell with a pure Li anode. This work provides alternative insights to suppress the side reaction for Li‒S batteries with high capacity retention.
Mufolinin A (1), a ring A-seco rearranged limonoid with an unprecedented ethyl at C-10 and novel 6/6/6/5 fused-ring skeleton, together with three new potential precursors (ring A-seco limonoids, 2–4) were isolated from Munronia unifoliolata. Their structures and absolute configurations were confirmed by nuclear magnetic resonance (NMR), high resolution electrospray ionization mass spectroscopy (HRESIMS), X-ray crystallography, electronic circular dichroism (ECD) calculations and NMR calculations with DP4+ analyses. The unprecedented ethyl group of 1 was hypothesized to be derived from methyl migration and ring reduction rearrangement of ring A-seco limonoid 4. Compounds 2 and 4 showed significant multidrug resistance (MDR) reversal activities in MCF-7/DOX cells with reversal fold (RF) values of 13.1 and 8.0, respectively.
Lanthipeptides are one of the largest groups of ribosomally synthesized and post-translationally modified peptides (RiPPs) and are characterized by the presence of lanthionine (Lan) or methyllanthionine residues (MeLan). Only very few lanthipeptides contain a C-terminal 2-aminovinyl-cysteine (AviCys) motif, but all of them show potent antibacterial activities. Recent advances of genome sequencing led to the rapid accumulation of new biosynthetic gene clusters (BGCs) for lanthipeptides. In this study, through our genome mining strategy, we found the AviCys containing lanthipeptides are widespread in the bacterial kingdom. A lanthipeptide-type biosynthetic gene cluster was identified from public bacterial genome database. Two new lanthipeptides, daspyromycins A and B (1 and 2) containing AviCys motif, along with two degraded products, daspyromycins C and D (3 and 4), were obtained after heterologous expression of the gene cluster in Streptomyces albus J1074. Daspyromycins A and B showed potent antimicrobial activity against a spectrum of Gram-positive and -negative bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE).
Organic single crystals (OSCs) have received increasing interest in the last decades for their potential applications in flexible electronics. Although there are various subtractive manufacturing methods of organic electronics, the subtractive manufacturing of OSCs is still a challenge, since OSCs are assembled via weak van-der-Waals interactions which are vulnerable and cannot afford damages and suffer the degradation of performances after the process. Here, we develop an epitaxial etching strategy which clips the OSCs and keeps high-quality crystalline nature of the resulting materials. As a result, high-quality organic micro-ribbon arrays are fabricated which maintains 89% charge mobility in average compared with original OSCs, showing great potential of this subtractive manufacturing method in future organic electronics.
Carbonaceous nanomaterials with porous structure have become the highly promising anode materials for potassium-ion batteries (PIBs) due to their abundant resources, low-cost, and excellent conductivity. Nevertheless, the sluggish reaction kinetics and inferior cycling life caused by the large radius of K ions severely restrict their commercial development. Herein, B,N co-doped hierarchically porous carbon nanosheets (BNPC) are achieved via a facile template-assisted route, followed by a simple one-step carbonization process. The resultant BNPC possesses a unique porous structure, large surface area, and high-level B,N co-doping. The structural features endows it with remarkable potassium storage performances, which delivers a high reversible capacity (242.2 mAh/g at 100 mA/g after 100 cycles), and long cycling stability (123.1 mAh/g at 2000 mA/g and 62.9 mAh/g at 5000 mA/g after 2000 cycles, respectively). Theoretical simulations further validate that the rich B doping into N-modified carbon configuration can greatly boost the potassium storage capability of the BNPC anode.
With the aim of discovering new bioactive pesticides for crop protection, a series of novel sulfide-containing amide derivatives A were efficiently synthesized via a strategy of modifying the "amide" structure of anthranilic diamide insecticides. The single-crystal structures of A2-3 and A4-5 were firstly reported. The bioassay results showed that most of the synthesized compounds display moderate to high insecticidal activities. Particularly, some sulfone-containing compounds, e.g., A2-3, A3-3 and A6-3, not only possessed favorable lethality rate (50%–100%) against P. xylostella at a concentration of 0.1 mg/L, but also held good activities towards a variety of agricultural pests such as M. separata, C. pipiens pallen, H. armigera and O. nubilalis; the larvicidal activities of A4-1 and A6-1 towards P. xylostella were close to that of chlorantraniliprole at 0.01 mg/L. The calcium imaging experiments revealed that the representative compounds A2-3 and A6-3 are potential ryanodine receptor (RyR) modulators. The structure–activity relationships were discussed in detail. These results provide useful information for further design and development of novel insecticides.
Transitional metal selenides have high conductivity, even metal quality, which makes them great for using as electrode materials for fabricating supercapacitors. Here, hierarchical Ni3Se2 nanosheet-on-nanorods on Ni foam (NSR-Ni3Se2/Ni) was fabricated by a facile three-dimensional (3D) substrate-assisted confinement assembly method, and used as a freestanding electrode material for hybrid supercapacitors (HSCs). In this design, metallic Ni3Se2 with hybrid 1D/2D architecture could effectively enhance the active specific surface area of electrode and improve space utilization, as well as significantly facilitate electrons transport, while Ni foam served as the Ni source of Ni3Se2 and provided 3D multi-electron transport channels, thus boosting the specific capacity. The constructed hierarchical NSR-Ni3Se2 electrode delivered a superior areal specific capacity of 1.068 mAh/cm2 (7.69 F/cm2) at 2 mA/cm2 and retained 68.2% of the initial capacity when the current density increases by 15 times. Furthermore, the as-assembled NSR-Ni3Se2 device exhibited an ultrahigh energy density of 56.4 Wh/kg and high power density of 4640.3 W/kg, and a capacity retention of 92.6% even after 6000 cycles.
To reduce the greenhouse effect caused by the surgery of nitrogen-oxides concentration in the atmosphere and develop a future energy carrier of renewables, it is very critical to develop more efficient, controllable, and highly sensitive catalytic materials. In our work, we proposed that nitric oxide (NO), as a supplement to N2 for the synthesis of ammonia, which is equipped with a lower barrier. And the study highlighted the potential of CeO2 (111) nanosheets with La doping and oxygen vacancy (OV) as a high-performance, controllable material for NO capture at the site of Vo site, and separation the process of hydrogenation. We also reported that the Eads of -1.12 eV with horizontal adsorption and the Bader charge of N increasing of 0.53|e| and O increasing of 0.17|e| at the most active site of reduction-OV predicted. It is worth noting that ΔG of NORR (NO reduction reaction) shows good performance (thermodynamically spontaneous reaction) to synthesize ammonia and water at room temperature in the theoretical calculation.
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