Controlling the optimum surfactants concentrations for dispersing carbon nanofibers in aqueous solution

As a new nano-scale functional material, it is necessary to achieve a uniform distribution in the composites for gaining the CNFs’ excellent reinforcing effect. In this paper, CNFs were purified by the method of high temperature annealing treatment. Six surfactants, methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), sodium dodecyl sulfate (SDS), dodecylamine (DDA), N, N-dimethyl formamide (DMF) and cetyltrimethyl ammonium bromide (CTAB) were used individually and combinatorially in a certain concentration to disperse the CNFs in aqueous solution. To achieve a good dispersion of the CNFs, a method utilizing ultrasonic processing was employed. The CNFs treated by the method of high temperature annealing treatment were characterized by differential thermal analysis (DTA) and thermogravimetry analysis (TGA), and the ultrasonication-driven dispersion of CNFs in aqueous solutions were monitored by UVvis spectroscopy and transmission electron microscopy (TEM). The experiments reveal that the method of high temperature annealing treatment purified the CNFs and the maximum achievable dispersion of CNFs corresponds to the maximum UV absorbance of the solution. All results show that the surfactants mixture of MC and SDS in a certain concentration of 0.4 and 2.0 g/L has the maximum dispersion effect on CNFs in aqueous solution, the optimum concentration ratio of MC, SDS, and CNFs was 2: 10: 1.     

Cu(OTf)2-Catalyzed 1,2,3-triazole-ring-controlled selective phenolic O–H bond methylthiomethylation

Copper-catalyzed selective methylthiomethylation of 1,4-disubstituted 1,2,3-triazole phenols using DMSO as a methylthiomethylation reagent was achieved. Controlled by the triazole ring, the ortho-phenolic hydroxyl in N(1) aryl can be selectively methylthiomethylated, generating functionalized 1,4-disubstituted 1,2,3-triazoles bearing aryl methylthiomethyl ether fragment.     

L ‐Proline‐Promoted CuI‐Catalyzed C‐S Bond Formation between Aryl Iodides and Thiols

An improved, mild procedure for the CuI‐catalyzed coupling reactions of aryl iodides with aliphatic and aromatic thiols, using L ‐proline as the ligand, is reported. This procedure is noteworthy given its high generality and exceptional level of functional group toleration.     

Direct Pyridazine Ring Synthesis from β-Cyano Esters. A Facile Synthesis of the Derivatives of Tetrahydro-3,6-pyridazinedione 3-Hydrazone

4-Substituted tetrahydro-3,6-pyridazinedione 3-hydrazones (2) (or their 3-hydrazino tautomers 3), useful intermediates in the synthesis of bicyclic pyridazine derivatives, were prepared in satisfactory yields in the reaction of the corresponding alkyl 3-substituted 3-cyanopropionates with hydrazine hydrate.     

An Improving Method For the Preparation of Ethynylferrocene

Ethynylferrocene was prepared in satisfactory yield by reaction of formylferrocene with triphenylphosphine and carbon tetrachloride followed by dehydrohalogenation in presence of n-butyllithum. The reaction condition is mild and the reaction time is much shorter. The method is convenient and economical.     

Synthesis of [1,2,3]Triazolo[5,1-a]isoquinoline Derivatives via a Selective Cascade Cyclization Sequence of 1,2-bis(Phenylethynyl)benzene Derivatives

A direct, concise, synthetic method for the generation of [1,2,3]triazolo[5,1-a]isoquinoline derivatives, using a selective cascade cyclization of unsymmetrical substituted 1,2-bis(phenylethynyl)benzene derivatives with NaN₃, has been developed. The reaction gave different substituted [1,2,3]triazolo[5,1-a]isoquinolines in moderate to good yields. It was found that the substituents on the alkynes were important for the selectivities of the cascade cyclization sequences.     

A New Taraxastane‐Type Triterpene from Vitex trifolia var. simplicifolia

3‐Oxotaraxer‐14‐en‐30‐al ( 1 ), a new taraxastane‐type triterpene, together with 14 known compounds, taraxerone ( 2 ), 3‐epiursolic acid ( 3 ), 2α,3β‐dihydroxyurs‐12‐en‐28‐oic acid ( 4 ), lupeol ( 5 ), betulinic acid ( 6 ), casticin ( 7 ), artemetin ( 8 ), luteolin ( 9 ), 4‐hydroxybenzoic acid ( 10 ), docosanoic acid ( 11 ), tetracosanoic acid ( 12 ), cerotic acid ( 13 ), β‐sitosterol ( 14 ), and β‐daucosterol ( 15 ), was isolated from the leaves and twigs of Vitex trifolia var. simplicifolia . Compounds 2 – 6 were found for the first time in this plant. Their structures were established by spectroscopic analysis, including 2D‐NMR techniques. Cytotoxic activities of compounds 3 , and 5 – 10 were tested on the three cancer cell lines, PANC‐1, K562, and BxPC‐3. Results revealed that 7 exhibited cytotoxicity against PANC‐1, K562, and BxPC‐3, with IC₅₀ values of 4.67, 0.72, and 4.01 μg/ml, respectively, whereas 8 was inactive against these cancer cell lines. The structure? activity relationship of compound 7 and 8 indicated that the 3′‐OH group in polymethoxyflavonoids is essential for antitumor activity.     

DNAzyme based electrochemical sensors for trace uranium

We have developed a uranyl-specific DNAzyme that was immobilized on the surface of a gold electrode to give a highly sensitive and selective biosensor for uranyl ion. The typical DNAzyme system consisted of the RNA (rA) as the substrate (ADNA), and the other strand is the enzyme (TDNA) with a ferrocene (Fc). The presence of uranyl ion induces the cleavage of the DNA substrate strand at the rA position to form two fragments. The Fc unit thereby is released from the surface of the electrode, and this results in a decreased peak current. This electrochemical biosensor has a dynamic range from 2 nM to 14 nM of uranyl ion, with a detection limit at 1 nM. It exhibits high sensitivity and excellent selectivity over other metal ions, and thus represents a promising technique for simple, fast, on-site, and real-time electrochemical sensing of UO₂(II) ion. It also serves as a guide in choosing different methods for designing electrochemical sensors for other metal ions.