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排序方式: 共有268条查询结果,搜索用时 15 毫秒
11.
CoFe2O4@SiO2‐CPTES‐Guanidine‐Cu(II) magnetic nanoparticles were synthesized and used as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of polyhydroquinolines and 2,3‐dihydroquinazoline‐4(1H)‐ones and for the oxidation of sulfides. The structure of this nanocatalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and inductively coupled plasma optical emission spectrometry. Simple preparation, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst are some of the advantages of this protocol. 相似文献
12.
Advanced Sensing of Antibiotics with Magnetic Gold Nanocomposite: Electrochemical Detection of Chloramphenicol 下载免费PDF全文
Dr. Petr Jakubec Dr. Veronika Urbanová Dr. Zdenka Medříková Prof. Dr. Radek Zbořil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14279-14284
The sensing and accurate determination of antibiotics in various environments represents a big challenge, mainly owing to their widespread use in medicine, veterinary practice, and other fields. Therefore, a new, simple electrochemical sensor for the detection of antibiotic chloramphenicol (CAP) has been developed in this work. The amplification strategy of the sensor is based on the application of magnetite nanostructures stabilized with carboxymethyl cellulose (Fe3O4‐CMC) and decorated with nanometer‐sized Au nanoparticles (NPs) (Fe3O4‐CMC@Au). In this case, CMC serves as a stabilizing agent, preventing the aggregation of Fe3O4 NPs, and hence, enabling the kinetic barrier for electron transport to be overcome, and the Au NPs serve as an electron‐conducting tunnel for better electron transport. As a proof of concept, the developed nanosensor is used for the detection of CAP in human urine samples, giving a recovery value of around 97 %, which indicates the high accuracy of the as‐prepared nanosensor. 相似文献
13.
14.
Tarak Saied Nourchaine Jelaiel Mohamed Lotfi Efrit Yves Fort Corinne Comoy 《Tetrahedron》2017,73(11):1489-1494
We report herein a short and efficient synthesis of benz[e][1,2,4]- or [d][1,2,6]oxadiazepines and benzo[f][1,3,5]triazocines from easily prepared N-aryl iminoesters. The strategy involves a bis-nucleophile reagent (hydroxylamine or guanidine) that promotes a one-step ring closure from the starting functionalized iminoesters. 相似文献
15.
N,N,N',N'-Tetrabromobenzene-1,3-disulfonamide (TBBDA)/triphenylphosphine and N,N,N',N'-tetra- chlorobenzene-1,3-disulfonamide (TCBDA)/triphenylphosphine have been introduced as highly efficient systems for the versatile conversion of aldoxime derivatives into nitriles. The process reported here is operationally simple and reactions have been mildly performed in dichloromethane at room temperature. 相似文献
16.
Influences of nanoparticles and chain length on thermodynamic and electrical behavior of fluorine liquid crystals 下载免费PDF全文
Ines Ben Amor Lotfi Saadaoui Abdulaziz N. Alharbi Talal M. Althagafi and Taoufik Soltani 《中国物理 B》2022,31(10):104202-104202
Hydrogen-bonded polar nematic liquid crystal series with the general formula nOBAF (n = 7—12) is studied. The mesomorphic characterization is demonstrated through differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The complexes with short alkyl chains (n=7, 8) present a wide nematic range and monotropic smectic F mesophase, whereas the longer alkyl chain (n=10—12) analogues show high melting and low clearing mesomorphic liquid crystals. The thermal range of the mesophase and the birefringence increase with chain length decreasing. Furthermore, the effect of the nanoparticles (LiNbO3) on the thermal and the electrical behavior of 8OBAF are investigated. The presence of LiNbO3 nanoparticles increases the conductivity and reduces the resistivity of the complex. 相似文献
17.
The effect of solvent on the crystal structure and size distribution of cadmium sulfide nanocrystals
R. Lotfi Orimi N. Shahtahmasebi N. Tajabor A. Kompany 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2894-2898
CdS nanocrystals with different structures were synthesized by the method of solution precipitation using thiourea and cadmium acetate as starting materials in different solvents: water, methanol and N,N-dimethylformamide (DMF). Our results show that the solvent has direct effect on the structure and size of the final nanoparticles. It was found that using DMF, as a solvent, results in producing smaller nanoparticles with the cubic structures, while using the other solvents gives rise to larger nanoparticles with the hexagonal structure. It was also found that using heat during washing the precipitate results in a more homogenous size distribution of CdS nanocrystals. On the basis of our experimental results we also suggest a critical structure transformation size. 相似文献
18.
Fluorimetric Determination of Histamine in Fish Using Micellar Media and Fluorescamine as Labelling Reagent 总被引:1,自引:0,他引:1
Adamou R Coly A Douabalé SE Saleck ML Gaye-Seye MD Tine A 《Journal of fluorescence》2005,15(5):679-688
An analytical method based on the use of fluorescamine to produce a fluorescent derivative with histamine and combined with
micellar-enhanced fluorescence detection of the formed complex is developed for the sensitive and rapid determination of histamine
in fishes. The fluorescence properties of the obtained complex in water and micellar solutions of sodium dodecyl sulfate (SDS),
cetyltrimethylammonium chloride (CTAC) and brij-700 are reported. Physicochemical variables influencing the sensitivity of
the method (pH, micellar, fluorescamine and NaCl relative concentrations) have been optimized. The stability of the formed
complex, as shown by kinetic study, depends on the pH of the solution. Linear calibration curves allowing an effective histamine
determination were established with large linear dynamic range (LDR), and low limits of detection (LOD) between 0.5 and 33
ng mL−1, according to the solvent. Application to the analysis of fish samples (sardines) yielded satisfactory results. The method
seems to be suitable for environmental fish quality control.
Presented in part, at the 39th IUPAC Congress and the 86th Conference of the Canadian Society for Chemistry, August, 10–15,
2003, Ottawa (Canada). 相似文献
19.
This paper describes a new magnetic resonance spectroscopic imaging (MRSI) technique based upon the discrete wavelet transform to reduce acquisition time and cross voxel contamination. Prototype functions called wavelets are used in wavelet encoding to localize defined regions in localized space by dilations and translations. Wavelet encoding in MRSI is achieved by matching the slice selective RF pulse profiles to a set of dilated and translated wavelets. Single and dual band slice selective excitation and refocusing pulses, with profiles resembling Haar wavelets, are used in a spin-echo sequence to acquire 2D-MRSI wavelet encoding data. The 2D space region is spanned up to the desired resolution by a proportional number of dilations (increases in the localization gradients) and translations (frequency shift) of the Haar wavelets (RF pulses). Acquisition time is reduced by acquiring successive MR signals from regions of space with variable size and different locations with no requirement for a TR waiting time between acquisitions. An inverse wavelet transform is performed on the data to produce the correct spatial MR signal distribution. 相似文献
20.
Ines Ben Rejeb Lotfi Monser Mohamed Gargouri 《Applied biochemistry and biotechnology》2010,162(6):1536-1546
A new, simple, and original method is described for specific measurement of polyunsaturated fatty acid content in olive oil. This analytical system uses coupled enzymes, lipase and lipoxygenase. The system consists of lipase-catalyzed hydrolysis of triacylglycerol and subsequent lipoxygenation of liberated polyunsaturated fatty acids. The hydroperoxy-fatty acids formed were easily monitored by spectrophotometry at 234 nm. After being optimized, the method was validated in terms of linearity, precision sensitivity, and recovery. Linear calibration graph was obtained in the range 50–500 µg mL?1, with a correlation coefficient higher than 0.921 and a detection limit (S/N?=?3) of 15 µg mL?1. The precision of the method (relative standard deviation) for within and between days is better than 7% and 12%, respectively. The proposed method was successfully applied to the estimation of polyunsaturated fatty acids level in olive oil samples and results obtained were in excellent agreement with those obtained by the classical official method. The proposed method is accurate, simple, cheap, and can be satisfactorily used for routine analysis of edible oils. 相似文献