Theoretical insight into phosphoric acid-catalyzed asymmetric conjugate addition of indolizines to α,β-unsaturated ketones

A theoretical investigation of the mechanism and origin of enantioselectivity for phosphoric acid-catalyzed asymmetric conjugate addition of indolizines to α,β-unsaturated ketones.     

TiO2/EDTA-rich carbon composites: Synthesis,characterization and visible-light-driven photocatalytic reduction of Cr(VI)

TiO₂/EDTA-rich carbon composites exhibits excellent photoreduction of Cr(VI) activity via ligand-to-metal charge transfer process.     

Carbon Nanozymes: Enzymatic Properties,Catalytic Mechanism,and Applications

Nanozymes have advantages over natural enzymes, such as facile production on large scale, long storage time, low costs, and high stability in harsh environments. Carbon nanomaterials (CNMs), including fullerenes, carbon nanotubes, graphene, carbon quantum dots, and graphene quantum dots, have become a star family in materials science. As a new class of nanozymes, the catalytic activity of CNMs and their hybrids has been extensively reported. In this Minireview, recent progress of CNMs based artificial enzymes, focusing on those with peroxidase‐like activity, has been summarized. The enzymatic properties, catalytic mechanisms, and novel applications of CNM nanozymes in sensing, therapy, and environmental engineering are discussed in detail. Additionally, we also highlight the remaining challenges and unsolved problems. With the fast development of bionanotechnology, the unique enzymatic properties and advantages of CNM nanozymes have received much attention and will continue to be an active and challenging field for the years to come.     

Enhanced redox stability and optical contrast of electrochromic copolymers from selenophene and 3-methylthiophene

Journal of Solid State Electrochemistry - A series of poly(selenophene-co-3-methylthiophene) films were synthesized by electrochemical copolymerization of selenophene and 3-methylthiophene under...     

Highly Sensitive Silver Nanorod Arrays for Rapid Surface Enhanced Raman Scattering Detection of Acetamiprid Pesticides

The determination of pesticide residue on agricultural products is increasingly important.Exposure to pesticides can cause severe acute reactions in humans, including aplastic anemia and leukemia.In this work, we developed a rapid and sensitive method to detect acetamiprid pesticide residue based on surface-enhanced Raman scattering.Silver nanorod (AgNR) arrays were fabricated by oblique angle deposition technology and were used as SERS substrates.Prior to detection, the AgNR arrays were cleaned with nitric acid solution or a mixture of methanol and acetone.Compared to the unwashed AgNR arrays, the AgNR arrays washed with methanol and acetone shows a signal enhancement 1000 times greater than the unwashed AgNR array due to the effective removal of the impurities on its surface.The limit of detection of acetamiprid was determined to be 0.05 mg/L.In addition, the molecular structure of acetamiprid was simulated and the corresponding vibration modes of the characteristic bands of acetamiprid were calculated by density function theory.To demonstrate its practical application, the AgNRs array substrates were applied successfully to the rapid identification of acetamiprid residue on a cucumber's surface.These results confirmed possibility of utilizing the AgNRs SERS substrates as a new method for highly sensitive pesticide residue detection.     

A highly stable black phosphorene nanocomposite for voltammetric detection of clenbuterol

A nanocomposite was prepared from graphene-like two-dimensional black phosphorene (BP, an allotrope of phosphorus) and nafion (Nf) treated with isopropanol (IP). A glassy carbon electrode (GCE) modified with this nanocomposite was found to be a viable sensor for voltammetric determination of clenbuterol (CLB). Unlike previously reported pure BP, the BP nanocomposite was stable towards water and oxygen. Its morphology, structure, electrochemically active surface area and electrochemical stability were investigated. The BP-Nf (IP) modified GCE displayed good electrochemical stability and electrocatalytic capacity with a low working potential of 0.94 V (vs. SCE), excellent peak current response for CLB in a linear concentration range of 0.06–24 μM with a detection limit of 3.7 nM (3σ/m) and a sensitivity of 0.14 μA·μM^?1·cm^?2 under optimal conditions. A sensing mechanism for the electro-oxidation of CLB was suggested and verified by density functional theory calculations under imitation of aqueous solution conditions. The sensor was successfully applied to the determination of CLB in bovine meat and bovine serum samples.

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Graphical abstract Highly-stable black phosphorene (BP) nanocomposite based on Nafion (Nf) was used to modify a glassy carbon electrode (GCE). It is shonw to be a viable electrochemical platform for sensitive voltammetric determination of trace clenbuterol (CLB) in bovine beef and bovine serum.

     

Grayanane diterpenoids with diverse bioactivities from the roots of Pieris formosa

During our continuing study on the roots of Pieris formosa, twelve new grayanane diterpenoids (1–12), together with eight known compounds (13–20), were obtained. Their structures with absolute configurations were characterized by a series of spectroscopic methods and X-ray diffraction. Compounds 1, 2, 4–5, 7–8, 14, and 19 exhibited significant analgesic activity in an acetic acid-induced writhing test. In particular, 7 and 14 were found to be 5 times more potent than morphine in the acetic acid-induced writhing test model. Compounds 1, 4, 9, 13, and 18 showed antifeedant activity against Plutella xylostella at 0.5 mg/mL. Compound 4 exhibited a 38.3% inhibitory effect against the KCNQ2 potassium channel at a concentration of 10 μM.     

Diterpenoids from the fruits of Rhododendron molle, potent analgesics for acute pain

Rhododendron molle G. Don is one of the most potent traditional Chinese medicines for pain relief. Prior investigations have shown that Rhododendrons are rich sources of terpenoids. In our continuing efforts to identify structurally unique and biologically interesting diterpenoids, the fruits of R. molle were collected from Guangxi Province. A chemical study was carried out on the EtOH extract, which led to the isolation of 18 diterpenoids including 12 new compounds. The isolation and structural elucidation of new compounds 1–12, as well as the evaluation of the antinociceptive activities of these compounds were reported.     

Simultaneous Quantification of Puerarin and Daidzein in Rat Plasma by High-Performance Liquid Chromatography with Post-Column Modification and Fluorescence Detection

A sensitive HPLC method based on post-column modification and fluorescence detection has been developed for determination of puerarin and daidzein in rat plasma. Chromatographic separation was performed on a C₈ column with a linear gradient prepared from 0.5% aqueous acetic acid and 0.5% acetic acid in acetonitrile, delivered at a flow rate of 0.8 mL min⁻¹. Naringin was used as the internal standard. It was necessary to use acetic acid in the mobile phase to achieve good separation, but this led to fluorescence signal suppression, because puerarin and daidzein have native fluorescence at pH 8.0–9.0. To enhance the sensitivity, post-column modification with alkaline buffer was adopted. After this modification, detection sensitivity for puerarin and daizein increased more than 500-fold and 600-fold, respectively, compared with direct fluorescence detection. Signal-to-noise ratios for detection for puerarin were more than 150 times better than for UV detection after use of the same method of sample preparation. This sensitive analytical method was successfully used to determine pharmacokinetic data for puerarin and daidzein in rat plasma after oral administration of a single dose of Puerariae radix extract containing puerarin (approx. 8.4 mg) and daizein (approx. 5.9 mg) to male SD rats.