氮掺杂长竹节状碳纳米管的制备及其生长机理

本文采用电弧放电法,通过阳极棒与不锈钢片的共蒸发,制备了氮掺杂长竹节状碳纳米管。借助扫描电子显微镜（SEM）、场发射高分辨透射电子显微镜（HRTEM）及其附带能量色散X射线（EDX）光谱仪和电子能量损失谱（EELS）、透射电子显微镜（TEM）等表征方法,对产物的形貌、结构和组成进行表征。表征结果表明,氮掺杂长竹节状碳纳米管的长度在640~835nm之间,其内径在23~35nm之间,外径在28~47nm之间;且在每一节“竹节”与另一节“竹节”的连接处形成的内腔中均有一个黑色纳米颗粒,其直径尺寸以及产物中的氮掺杂长竹节状碳纳米管的含量均与熔化、蒸发的不锈钢片的面积有关。本文还对氮掺杂长竹节状碳纳米管的生长机理进行了简单的探讨。     

Synthesis of A-B-A Type Block Copolymer of Methyl Methacrylate and Styrene by Living Free-Radical Polymerization†

Abstract

A newly synthesized iniferter, N,N′-dimethyl-N,N′-bis(phenethyl)-thiuram disulfide, has been used in the free-radical living polymerization of styrene by a photochemical method. The low molecular weight (M _w = 6000) difunctionalized polystyrene was used as a macroiniferter to photopolymerize methyl methacrylate, and was fractionated to obtain an A-B-A type block copolymer containing two poly(methyl methacrylate) units and one polystyrene unit in each block. The glass transition temperature, thermal stability, and ¹³C NMR of the block copolymer are discussed.     

Determination of terbinafine in human plasma using UPLC–MS/MS: Application to a bioequivalence study in healthy subjects

A high‐throughput and sensitive ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method has been developed for the determination of terbinafine in human plasma. The method employed liquid–liquid extraction of terbinafine and terbinafine‐d7 (used as internal standard) from 100 μL human plasma with ethyl acetate–n‐hexane (80:20, v/v) solvent mixture. Chromatography was performed on a BEH C₁₈ (50 × 2.1 mm, 1.7 μm) column using acetonitrile–8.0 mm ammonium formate, pH 3.5 (85:15, v/v) under isocratic elution. For quantitative analysis, MS/MS ion transitions were monitored at m/z 292.2/141.1 and m/z 299.1/148.2 for terbinafine and terbinafine‐d7, respectively, using electrospray ionization in the positive mode. The method was validated according to regulatory guidance for selectivity, sensitivity, linearity, recovery, matrix effect, stability, dilution reliability and ruggedness with acceptable accuracy and precision. The method shows good linearity over the tested concentration range from 1.00 to 2000 ng/mL (r² ≥ 0.9984). The intra‐batch and inter‐batch precision (CV) was 1.8–3.2 and 2.1–4.5%, respectively. The method was successfully applied to a bioequivalence study with 250 mg terbinafine in 32 healthy subjects. The major advantage of this method includes higher sensitivity, small plasma volume for processing and a short analysis time.     

Synthesis and Characterization of Organosilicon Substituted Fluorenyl Derivatives

Friedel‐Crafts cycloalkylation of biphenyl with 2,3‐dichlorobutyltrichlorosilane(Cl₃Si‐CH₂CHClCHClCH₃) at a temperature of 100°C in the presence of anhydrous aluminum chloride catalyst gave cyclized product, 9‐methyl‐9‐(2‐trichlorosilylethyl)fluorene 1a , in 33% yield. Methylation of 1a with nucleophilic reagent such as methyl magnesium chloride, gave 9‐methyl‐9‐(2‐trimethylsilylethyl)fluorene 2 while bromination of 2 with excess amount of bromine in DMF resulted in 2,7‐dibromo‐9‐methyl‐9‐(2‐trichlorosilyl)fluorene 3 in good yield. All the compounds were structurally identified by GC/MS, ¹H and ¹³C‐NMR spectroscopy.     

Supramolecular assemblies of a naturally derived sophorolipid

Acidic sophorolipid (SL) molecules derived from yeasts represent a novel type of asymmetrical bolaamphiphiles due to their unique structural features that include an asymmetrical polar head size (disaccharide vs COOH), a kinked hydrophobic core (cis-9-octadecenoic chain), and a non-amide polar-nonpolar linkage. Light microscopy, small- and wide-angle X-ray scattering, FT-IR spectroscopy, and dynamic laser light scattering were used to investigate the supramolecular structures of the self-assembled aggregates of SL molecules at different pH values. In acidic conditions (pH < 5.5), giant twisted and helical ribbons of 5-11 microm width and several hundreds of micrometers length were observed for the first time. Increase in solution pH values slowed ribbon formation, decreased ribbon yield, and increased the helicity and entanglements of the giant ribbons. An interdigitated lamellar packing model of acidic SL-COOH molecules with a long period of 2.78 nm, stabilized by both the strong hydrophobic association between the cis-9-octadecenoic chains and strong disaccharide-disaccharide hydrogen bonding, is proposed. The neutralization of SL-COOH in water to SL-COONa produced clear solutions with the formation of short-range ordered aggregates. At concentrations below 1.0 mg/mL, the size of self-assembled aggregates increased as the concentration increased. At concentrations above 1.0 mg/mL, narrowly distributed micellar aggregates with a constant hydrodynamic radius (R(h)) of about 100 nm are formed. The large micelles show strong angular dependence with the fast mode appearing at scattering angle theta >/= 60 degrees.     

KO(t)Bu mediated synthesis of phenanthridinones and dibenzoazepinones

Synthesis of substituted phenanthridinones and dibenzoazepinones has been realized from 2-halo-benzamides in the presence of potassium tert-butoxide and a catalytic amount of 1,10-phenanthroline or AIBN. This new carbon-carbon bond forming reaction gives direct access to various biaryl lactams containing six- and seven-membered rings chemoselectively. Carbon-carbon coupling seems to proceed by the generation of a radical in the amide ring which leads to C-H arylation of aniline.     

Synthesis,characterisation and supramolecular interaction of Rh-biphenylic-imidazole-phenanthroline with antibiotics

A novel rhodium biphenylic imidazole phenanthroline metal-organic complex (BIP-MC) has been synthesised and characterised as a stable supramolecule. The structure of compound was established on the basis ESI, ¹H NMR and UV–vis spectroscopic data. The selectivity of BIP-MC as a new fluorescent chemosensor for various antibiotics has been explored. The supramolecular interaction of amoxicillin with BIP-MC enhanced the fluorescence activity of BIP-MC. A linear response of the sensor was observed in the measuring ranges of excitation 240–298 nm and emission 290–360 nm with detection limits of up to 10 μg/ml at an optimum pH 8.0. Based on the observations made here, a new quantitative method for the determination of this drug in synthetic samples without the use of separation of matrix is developed. It is also inferred that the possible fluorescence enhancement is due to the formation of exciplex between the BIP-MC and amoxicillin. These finding will thus help in pharmacokinetics studies of drugs. The sensor was used for the direct assay of amoxicillin antibiotic in commercial pharmaceutical preparations.     

Anti-angiogenic activity of Morinda citrifolia extracts and its chemical constituents

Morinda citrifolia L. has been used for the treatment of a wide variety of diseases, including cancer. This study was undertaken to evaluate the anti-angiogenic effect of M. citrifolia fruits and leaves. Anti-angiogenic activity was evaluated in?vivo using the chick chorioallantoic membrane assay. Bioactivity-guided fractionation and isolation were performed to identify the active constituent, and high-performance liquid chromatography analysis was then used to quantify the amount of this active constituent in the active extracts and fraction. The methanol extracts of fruits and leaves of M. citrifolia and the subsequent chloroform fraction of the fruit methanolic extract were found to have potential anti-angiogenic activity and were more potent compared to suramin. Scopoletin was identified as one of the chemical constituents that may be partly responsible for the anti-angiogenic activity of M. citrifolia fruits. The present findings further support the use of M. citrifolia in cancer or other pathological conditions related to angiogenesis.     

Phytochemical analysis, cytotoxic activity and constituents-activity relationships of the leaves of Cinnamomum iners (Reinw. ex Blume-Lauraceae)

The leaves of Cinnamomum iners (Reinw. ex Blume-Lauraceae) have been refluxed successively with chloroform and alcohol to get chloroform extract and alcoholic extract. Both the extracts have been assayed for cytotoxicity against human colorectal tumour cells. The chloroform extract exhibited significant cytotoxicity with IC(50) 31?μg mL(-1) (p??200?μg mL(-1). The chloroform extract has been further proceeded for chemical analysis by GC-TOFMS and 178 components were identified including acids, amines, amides, aldehydes, alcohols, esters, benzene derivatives, bicyclic compounds, terpenes, hydrocarbons, naphthalene derivatives, furan derivatives, azulenes, etc. Nine components representing 51.73% of the total chloroform extract were detected as major components. Caryophyllene (14.41%) and Eicosanoic acid ethyl ester (12.17%) are the most prominent components of the chloroform extract. β-Caryophyllene (14.41%) as most abundant compound supports potent cytotoxicity as shown by chloroform extract.     

Determination of catecholamine in human serum by a fluorescent quenching method based on a water-soluble fluorescent conjugated polymer-enzyme hybrid system

In this paper, a sensitive water-soluble fluorescent conjugated polymer biosensor for catecholamine (dopamine DA, adrenaline AD and norepinephrine NE) was developed. In the presence of horse radish peroxidase (HRP) and H(2)O(2), catecholamine could be oxidized and the oxidation product of catecholamine could quench the photoluminescence (PL) intensity of poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylethynylenealt-1,4-poly(phenylene ethynylene)) (PPESO(3)). The quenching PL intensity of PPESO(3) (I(0)/I) was proportional to the concentration of DA, AD and NE in the concentration ranges of 5.0 × 10(-7) to 1.4 × 10(-4), 5.0 × 10(-6) to 5.0 × 10(-4), and 5.0 × 10(-6) to 5.0 × 10(-4) mol L(-1), respectively. The detection limit for DA, AD and NE was 1.4 × 10(-7) mol L(-1), 1.0 × 10(-6) and 1.0 × 10(-6) mol L(-1), respectively. The PPESO(3)-enzyme hybrid system based on the fluorescence quenching method was successfully applied for the determination of catecholamine in human serum samples with good accuracy and satisfactory recovery. The results were in good agreement with those provided by the HPLC-MS method.