Ionic liquid-based microwave-assisted extraction of rutin from Chinese medicinal plants

An ionic liquid-based microwave-assisted extraction (ILMAE) method has been developed for the effective extraction of rutin from Chinese medicinal plants including Saururus chinensis (Lour.) Bail. (S. chinensis) and Flos Sophorae. A series of 1-butyl-3-methylimidazolium ionic liquids with different anions were investigated. The results indicated that the characteristics of anions have remarkable effects on the extraction efficiency of rutin and among the investigated ionic liquids, 1-butyl-3-methylimidazolium bromide ([bmim]Br) aqueous solution was the best. In addition, the ILMAE procedures for the two kinds of medicinal herbs were also optimized by means of a series of single factor experiments and an L₉ (3⁴) orthogonal design. Compared with the optimal ionic liquid-based heating extraction (ILHE), marinated extraction (ILME), ultrasonic-assisted extraction (ILUAE), the optimized approach of ILMAE gained higher extraction efficiency which is 4.879 mg/g in S. chinensis with RSD 1.33% and 171.82 mg/g in Flos Sophorae with RSD 1.47% within the shortest extraction time. Reversed phase high performance liquid chromatography (RP-HPLC) with ultraviolet detection was employed for the analysis of rutin in Chinese medicinal plants. Under the optimum conditions, the average recoveries of rutin from S. chinensis and Flos Sophorae were 101.23% and 99.62% with RSD lower than 3%, respectively. The developed approach is linear at concentrations from 42 to 252 mg L⁻¹ of rutin solution, with the regression coefficient (r) at 0.99917. Moreover, the extraction mechanism of ILMAE and the microstructures and chemical structures of the two researched samples before and after extraction were also investigated. With the help of LC-MS, it was future demonstrated that the two researched herbs do contain active ingredient of rutin and ionic liquids would not influence the structure of rutin.     

Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/nitrogen-doped reduced graphene oxide nanocomposite with enhanced lithium storage properties

The three-dimensional porous Li₃V₂(PO₄)₃/nitrogen-doped reduced graphene oxide (LVP/N-RGO) composite was prepared by a facile one-pot hydrothermal method and evaluated as cathode material for lithium-ion batteries. It is clearly seen that the novel porous structure of the as-prepared LVP/N-RGO significantly facilitates electron transfer and lithium-ion diffusion, as well as markedly restrains the agglomeration of Li₃V₂(PO₄)₃ (LVP) nanoparticles. The introduction of N atom also has positive influence on the conductivity of RGO, which improves the kinetics of electrochemical reaction during the charge and discharge cycles. It can be found that the resultant LVP/N-RGO composite exhibits superior rate properties (92 mA h g^?1 at 30 C) and outstanding cycle performance (122 mA h g^?1 after 300 cycles at 5 C), indicating that nitrogen-doped RGO could be used to improve the electrochemical properties of LVP cathodes for high-power lithium-ion battery application.

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Graphical abstract The three-dimensional porous Li₃V₂(PO₄)₃/nitrogen-doped reduced graphene oxide composite with significantly accelerating electron transfer and lithium-ion diffusion exhibits superior rate property and outstanding cycle performance.

     

Recent advances in the application of nanomaterials in enzymatic glucose sensors

Due to the critical role of glucose level in the diagnosis and treatment of diabetes, as well as the increasing number of diabetics, there is an overwhelming demand for developing glucose sensors. It is well acknowledged that these sensors, especially those based on glucose oxidase, have played an important role in blood glucose detection. Inspired by the attractive properties, nanomaterials, especially nanostructured carbon and metal/metal oxides, have been extensively explored to develop enzymatic glucose sensors with high sensitivity, fast response time, and satisfied stability. In this review, a brief history of glucose biosensors is firstly presented. Furthermore, we discuss the currently available fabrication possesses in the field of enzymatic glucose biosensors based on nanomaterials, focusing on the carbon-based, metal-based, and metal oxides-based nanocomposites. What is more, we discuss the challenges and attempt to give an outlook on the possible further developments.     

Immobilization of Modified Papain with Anhydride Groups on Activated Cotton Fabric

Papain (EC 3.4.22.2) has been chemically modified using two novel reagents including different anhydrides of 1,2,4-benzenetricarboxylic and pyromellitic acids. Then, the modified papain was immobilized on the activated cotton fabric by a two-step method. The number of free amino groups in the modified protein was investigated through the 2,4,6-trinitrobenzenesulfonic acid method. Energy dispersive spectrometer was used to characterize papain immobilization. Some parameters of both modified and native papain immobilized on cotton fabric, such as optimum temperature, optimum pH, and the stabilities for reservation in various detergents were studied and compared. The resultant papain had its optimum pH shifted from 6.0 to 9.0. Compared with immobilized native papain, the thermal stability and the resistance to alkali and washing detergent of immobilized modified enzyme were improved considerably. When the concentration of detergent was 20 mg/ml, the activity of the immobilized pyromellitic papain retained about 40% of its original activity, whereas the native papain was almost inhibited. This work demonstrated that the cotton fabric immobilized modified papain has potential applications in the functional textiles field.     

Self-assembled nanoparticle probes for recognition and detection of biomolecules

Colloidal gold nanocrystals have been used to develop a new class of nanobiosensors that is able to recognize and detect specific DNA sequences and single-base mutations in a homogeneous format. At the core of this biosensor is a 2.5-nm gold nanoparticle that functions as both a nano-scaffold and a nano-quencher (efficient energy acceptor). Attached to this core are oligonucleotide molecules labeled with a thiol group at one end and a fluorophore at the other. This hybrid bio/inorganic construct is found to spontaneously assemble into a constrained arch-like conformation on the particle surface. Binding of target molecules results in a conformational change, which restores the fluorescence of the quenched fluorophore. Unlike conventional molecular beacons with a stem-and-loop structure, the nanoparticle probes do not require a stem, and their background fluorescence increases little with temperature. In comparison with the organic quencher Dabcyl (4,4'-dimethylaminophenyl azo benzoic acid), metal nanoparticles have unique structural and optical properties for new applications in biosensing and molecular engineering.     

Electrospray ionization tandem mass spectrometric study of the aconitines in the roots of aconite

Fragmentation pathways of aconitine-type alkaloids were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry. Low-energy collision-induced dissociation of protonated aconitines follows a dominant first step, the elimination of the C(8)-substituent as acetic acid or fatty acid in MS(2) spectra. Successive losses of 1-4 CH(3)OH molecules, 1-3 H(2)O, CO, benzoic acid, and CH(3) or C(2)H(5) (N-substituents) are all fragmentation pathways observed in MS(3) and MS(4) spectra. By applying knowledge of these fragmentation pathways to the aconitines in the ethanolic extract of aconite roots, all the known aconitines were detected and also 23 unknown aconitine-type alkaloids, in which the lipo-alkaloids containing residues of 15C, 17C and 19C saturated or unsaturated fatty acids were characterized. These odd-carbon-number fatty acid substituents have not been reported previously.     

快淬法制备La_(0.8)Ce_(0.2)Fe_(11.4)Si_(1.6)合金的磁熵变研究

为了探求La系磁熵变材料的短时退火工艺,利用两种方法制备了磁制冷材料La0.8Ce0.2Fe11.4Si1.6合金,其一为将电弧熔炼合金退火5天(样品A),其二为将合金利用铜模铸造方法得到快淬样品,再退火2 h(样品B)。X射线衍射表明,样品A和B主相为NaZn13相结构。通过对比发现,尽管样品A的最大磁熵变值大于样品B的,但样品B在制冷温区和制冷能力方面优于样品A。因此,快淬加短时间热处理可以大大节省时间和能量,是一种制备La0.8Ce0.2Fe11.4Si1.6磁制冷材料的高效且性能优越的方法。     

Optical and crystallization behavior in Dy doped 40GeSe2–25Ga2Se3–35CsI glass

Dy³⁺ doped 40GeSe₂–25Ga₂Se₃–35CsI (GGC) glass was synthesized, and optical spectrum, such as infrared transmission and Vis-Nir absorption was measured. Base on the Judd–Ofelt theory, the three Judd–Ofelt parameters Ω_t (t = 2, 4, 6) were calculated and the results were compared with other chalcogenide glasses. The small Ω₂ in GGC glass is ascribed to the weak covalency of Se–Dy bond. The theory of crystallization kinetics under non-isothermal condition was developed, and was applied to analyze this Dy³⁺ doped GGC glass. From the heating-rate dependence of crystallization temperature, the activation energy for crystallization E = 148 kJ/mol is obtained, and this value is much smaller than that of the undoped glass host, indicating the introduction of Dy³⁺ ions into the GGC glass will get the host crystallized easily.     

Direct electrosynthesis and characterization of a new soluble polyfluorene derivative containing carboxyl group in boron trifluoride diethyl etherate

High-quality poly(fluorene-9-acetic acid) (PFAA), a new soluble polyfluorene derivative, was synthesized electrochemically by direct anodic oxidation of fluorene-9-acetic acid (FAA) in boron trifluoride diethyl etherate (BFEE) containing a certain amount of trifluoroacetic acid (TFA). This electrolyte enables facile anodic oxidation of FAA monomer at lower potential (1.05 V vs. SCE). PFAA films with conductivity of 0.53 S cm⁻¹ obtained from this medium showed better redox activity and thermal stability in relation to unsoluble poly(fluorene-9-carboxylic acid). Fluorescent spectral studies indicate that PFAA film with high fluorescence quantum yields and photochemical stability is a good blue-light emitter. The structure and morphology of the polymer were studied by UV–vis, FT-IR, ¹H NMR spectra and scanning electron microscopy, respectively.