New dammarane-type saponins from the leaves of Panax notoginseng

Two new triterpenoid saponins, notoginsenoside-Ng3 (1) and notoginsenoside-Ng4 (2), along with three known saponins (3-5), were isolated from a water extract of the leaves of Panax notoginseng. The absolute configuration of notoginsenoside Fa (3) with five sugars was confirmed by the single-crystal X-ray diffraction for the first time.     

Portable detection of serum HER-2 in breast cancer by a pressure-based platform

Analytical and Bioanalytical Chemistry - A high serum HER-2 extracellular domain (sHER-2 ECD) level has a reverse association with tumor behaviors. In this study, a portable platform for the...     

Ionic Liquid-Based Ultrasound-Assisted Extraction of Chlorogenic Acid from Lonicera japonica Thunb

Hydrophilic ionic liquid of [BMIM][BF₄] was successfully applied for the ultrasound-assisted extraction (UAE) of hydrophilic chlorogenic acid from Lonicera japonica Thunb. To explore this extraction procedure, the corresponding extraction parameters including the sample size, [BMIM][BF₄] concentration, pH, extraction temperature, ultrasonic power and extraction time were investigated. The results revealed that the [BMIM][BF₄]-based UAE efficiency of chlorogenic acid was higher than that of the ethanol-based UAE and the traditional refluent ethanol extraction. And the study on the method reliability further confirmed that the [BMIM][BF₄]-based UAE is suitable for the effective extraction of chlorogenic acid from honeysuckle.     

Elucidating the Electrocatalytic CO2 Reduction Reaction over a Model Single‐Atom Nickel Catalyst

Designing effective electrocatalysts for the carbon dioxide reduction reaction (CO₂RR) is an appealing approach to tackling the challenges posed by rising CO₂ levels and realizing a closed carbon cycle. However, fundamental understanding of the complicated CO₂RR mechanism in CO₂ electrocatalysis is still lacking because model systems are limited. We have designed a model nickel single‐atom catalyst (Ni SAC) with a uniform structure and well‐defined Ni‐N₄ moiety on a conductive carbon support with which to explore the electrochemical CO₂RR. Operando X‐ray absorption near‐edge structure spectroscopy, Raman spectroscopy, and near‐ambient X‐ray photoelectron spectroscopy, revealed that Ni⁺ in the Ni SAC was highly active for CO₂ activation, and functioned as an authentic catalytically active site for the CO₂RR. Furthermore, through combination with a kinetics study, the rate‐determining step of the CO₂RR was determined to be *CO₂^?+H⁺→*COOH. This study tackles the four challenges faced by the CO₂RR; namely, activity, selectivity, stability, and dynamics.     

Fluorographites (CFx)n Exhibit Improved Heterogeneous Electron‐Transfer Rates with Increasing Level of Fluorination: Towards the Sensing of Biomolecules

Halogenated sp² materials are of high interest owing to their important electronic and electrochemical properties. Although methods for graphite and graphene fluorination have been extensively researched, the fundamental electrochemical properties of fluorinated graphite are not well established. In this paper, the electrochemistry of three fluorographite materials of different carbon‐to‐fluorine ratio were studied: (CF_0.33)_n, (CF_0.47)_n, and (CF_0.75)_n. Our findings reveal that the carbon‐to‐fluorine ratio of fluorographite will impact the electrochemical performance. Faster heterogeneous electron‐transfer (HET) rates and lowered oxidation potentials for ascorbic acid and uric acid are progressively obtained with increasing fluorine content. The fluorographite (CF_0.75)_n was in fact found to exhibit the most improved electrochemical performances with the fastest HET rates and significantly lowered overpotentials in the oxidation of ascorbic acid. Analytical parameters such as sensitivity and linearity were subsequently investigated by applying the fluorographite (CF_0.75)_n in the analysis of ascorbic acid and uric acid, which can be simultaneously detected. We determined good linear responses towards the detection of both ascorbic and uric acid. Fluorographites outperform graphites in sensing applications, which will have a profound impact on applications of fluorographites and fluorographene in sensing and biosensing.     

Precise Tuning of the Charge Transfer Kinetics and Catalytic Properties of MoS2 Materials via Electrochemical Methods

MoS₂ has become particularly popular for its catalytic properties towards the hydrogen evolution reaction (HER). It has been shown that the metallic 1T phase of MoS₂, obtained by chemical exfoliation after lithium intercalation, possesses enhanced catalytic activity over the semiconducting 2H phase due to the improved conductivity properties which facilitate charge‐transfer kinetics. Here we demonstrate a simple electrochemical method to precisely tune the electron‐transfer kinetics as well as the catalytic properties of both exfoliated and bulk MoS₂‐based films. A controlled reductive or oxidative electrochemical treatment can alter the surface properties of the film with consequently improved or hampered electrochemical and catalytic properties compared to the untreated film. Density functional theory calculations were used to explain the electrochemical activation of MoS₂. The electrochemical tuning of electrocatalytic properties of MoS₂ opens the doors to scalable and facile tailoring of MoS₂‐based electrochemical devices.     

微波消解–电感耦合等离子体光谱法测定预包装食品中的钠含量

采用微波消解样品,建立电感耦合等离子体光谱(ICP–AES)测定预包装食品中钠含量的方法。结果表明,钠的质量浓度在0~100 mg/L范围内与光谱强度呈良好线性关系,相关系数为0.999 9,钠的检出限为0.006 mg/L,加标回收率为95.5%~106.2%,测定结果的相对标准偏差为2.43%(n=6)。测定大米、菠菜、茶叶、脱脂奶粉和猪肉5个标准物质对方法进行验证,测定值与标准值吻合。该方法操作简便,适用于预包装食品中钠含量的检测。     

N-acetylcysteine induced quenching of red fluorescent oligonucleotide-stabilized silver nanoclusters and the application in pharmaceutical detection

In this work, we reported a new, simple and sensitive method for determination of N-acetylcysteine (NAC) based on quenching of the red fluorescence of oligonuleotide-protected silver nanoculsters (Ag NCs) with the quantum yield of 68.3 ± 0.3%. This method was successfully used for the assay of NAC granules presenting a linear range from 100 nM to 1200 nM (LOD of 50 nM) with minimal interferences from potential coexisting substances. It is for the first time that quenching performance of the thiol-containing compound was found to follow a non-linear Stern–Volmer profile, indicative of a complicated quenching mechanism with static quenching dominating, in which DNA-template of Ag NCs was partly replaced by NAC, as elucidated by spectral investigations. This study extended the analytical application of silver nanoclusters as well as provided a more insightful understanding of the quenching mechanism of thiol-compounds on the fluorescence of Ag NCs.     

An Amorphous Molybdenum Polysulfide Cathode for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) attract research interest owing to the low cost and high reliability, but the design of cathode materials is the major difficulty of their development. The bivalent magnesium cation suffers from a strong interaction with the anion and is difficult to intercalate into traditional magnesium intercalation cathodes. Herein, an amorphous molybdenum polysulfide (a-MoS_x) is synthesized via a simple one-step solvothermal reaction and used as the cathode material for RMBs. The a-MoS_x cathode provides a high capacity (185 mAh g⁻¹) and a good rate performance (50 mAh g⁻¹ at 1000 mA g⁻¹), which are much superior compared with crystalline MoS₂ and demonstrate the privilege of amorphous RMB cathodes. A mechanism study demonstrates both of molybdenum and sulfur undergo redox reactions and contribute to the capacity. Further optimizations indicate low-temperature synthesis would favor the magnesium storage performance of a-MoS_x.