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571.
MnO2/TiO2-ZrO2, which was synthesized by the adsorption method, demonstrated very high catalytic activity in the selective oxidation of benzyl alcohols to benzaldehydes with excellent yields and selectivity in short reaction times. The physical and chemical properties of MnO2/TiO2-ZrO2 were investigated by XRD, XRF, BET, FT-IR and SEM techniques. The influence of the catalyst support (SBA-15, ZSM-5, TiO2-ZrO2 and Y), type of metal oxide supported, method of loading and amount of manganese nitrate loading have been thoroughly investigated. Moreover, the catalyst has shown excellent reusability in the process. 相似文献
572.
573.
Javad Safari Sayed Hossein Banitaba Shiva Dehghan Khalili 《Arabian Journal of Chemistry》2011,4(1):11-15
Silica sulfuric acid was found to be an efficient, reusable and environment-friendly catalyst for fast hydrolysis of various isobenzofuranone to corresponding 2-ketomethylquinoline derivatives in a high yield under solvent-free using microwave irradiation. As the activator of silica sulfuric acid the wet SiO2 was chosen. The reactions in conventional conditions were compared with the microwave assisted reactions. This approach can prove beneficial since the recovery of solvents from conventional reaction systems always results in some losses. 相似文献
574.
Graphene quantum dots were synthesized by control carbonization of citric acid and utilized for selective determination of dopamine in the presence of ascorbic and uric acids. The prepared graphene quantum dots were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared, ultraviolet–visible and fluorescence spectroscopy. The results revealed that dopamine could quench the fluorescence of graphene quantum dots through a dynamic quenching mechanism. Under the optimized conditions, the linear concentration range was obtained within 0.01–50.0 µM, with the correlation coefficient of 0.9983 and a limit of detection of 8.2 nM. This method does not show any interference with respect to coexisting foreign substances, even at the presence of 500-fold of ascorbic acid and uric acid. 相似文献
575.
Gholam Reza Mahdavinia Javad Hasanpour Zeinab Rahmani Shiva Karami Hossein Etemadi 《Cellulose (London, England)》2013,20(5):2591-2604
Hydrogel nanocomposites were synthesized from grafting of acrylamide onto hydroxypropyl methylcellulose using methylenebisacrylamide crosslinker and sodium montmorillonite (Na-MMt) nanoclay. The effect of nanoclay content on the swelling of nanocomposites was investigated and an optimum swelling capacity was obtained at 12.7 wt% of Na-MMt. The effect of salt solutions on the swelling of nanocomposites revealed that the degree of swelling of samples depends only slightly on the salinity. The structure of nanocomposites was characterized by XRD, SEM, FTIR, and TEM techniques. The XRD and TEM results confirmed the exfoliation of Na-MMt nanoclay in nanocomposite matrix. The morphology of the nanocomposites was characterized by SEM technique and according to the results a loose surface was observed. The nanocomposite hydrogels were evaluated to remove cationic crystal violet dye from water. The investigation of the dye adsorption capacity and rate of nanocomposite hydrogels as a function of Na-MMt content revealed that the both adsorption capacity and rate is enhanced as the nanoclay content is increased in nanocomposite composition. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The best fit to the experimental data was obtained with the Langmuir model. 相似文献
576.
A robust ionic liquid-based method for dispersive liquid-liquid microextraction was developed for the determination of cobalt in saline samples. Its robustness was increased by introducing a common ion of the IL into the sample solution. The concentration of cobalt in the settled phase of the ionic liquid was determined by the FAAS using a homemade microsample injection valve. Under the optimized conditions, the calibration graph was linear in the concentration range from 0.4 to 120 ??g L?1 with the detection limit of 0.1 ??g L?1. Accuracy was checked against the ISO standard method. The method was successfully applied to the determination of cobalt in water and saline samples. 相似文献
577.
Ternary mixtures of thiamin, riboflavin and pyridoxal have been simultaneously determined in synthetic and real samples by applications of spectrophotometric and least-squares support vector machines. The calibration graphs were linear in the ranges of 1.0 - 20.0, 1.0 - 10.0 and 1.0 - 20.0 microg ml(-1) with detection limits of 0.6, 0.5 and 0.7 microg ml(-1) for thiamin, riboflavin and pyridoxal, respectively. The experimental calibration matrix was designed with 21 mixtures of these chemicals. The concentrations were varied between calibration graph concentrations of vitamins. The simultaneous determination of these vitamin mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. The partial least squares (PLS) modeling and least-squares support vector machines were used for the multivariate calibration of the spectrophotometric data. An excellent model was built using LS-SVM, with low prediction errors and superior performance in relation to PLS. The root mean square errors of prediction (RMSEP) for thiamin, riboflavin and pyridoxal with PLS and LS-SVM were 0.6926, 0.3755, 0.4322 and 0.0421, 0.0318, 0.0457, respectively. The proposed method was satisfactorily applied to the rapid simultaneous determination of thiamin, riboflavin and pyridoxal in commercial pharmaceutical preparations and human plasma samples. 相似文献
578.
579.
Mitra Ghassemzadeh Samira Bahemmat Javad Malakootikhah Bernhard Neumüller Alexander Rothenberger 《无机化学与普通化学杂志》2007,633(8):1178-1182
The reactions of AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one (AMTTO, 1 ) with 2‐hydroxybenzaldehyde (salicylaldehyde) and 4‐hydroxybenzaldehyde in methanol under reflux conditions led to the corresponding Schiff‐bases ( H2L1 and H2L2 ). The reaction of H2L1 with palladium acetate in ethanol and additional recrystallization from toluene gave the tetrameric complex [Pd(L)]4·2C7H8 ( 2 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for H2L1 at ?80 °C: space group P21/c with a = 1285.4(1), b = 707.7(1), c = 1348.2(1) pm, β = 109.32(1)°, Z = 4, R1 = 0.0328, H2L2 at ?80 °C: space group P43212 with a = 762.5(1), b = 762.5(1), c = 4038.9(2) pm, Z = 8, R1 = 0.025 and for 2 at ?103 °C: space group C2/c with a = 2862.5(6), b = 2847.6(6), c = 1727.8(4) pm, β = 105.18(3)°, Z = 8, R1 = 0.0704. 相似文献
580.
Javad Azizian Ali Reza Karimi Zahra Kazemizadeh Ali A. Mohammadi Mohammad R. Mohammadizadeh 《Tetrahedron letters》2005,46(36):6155-6157
11H-Indeno[1,2-b]quinoxalin-11-ones generated in situ from ninhydrin and various 1,2-phenylenediamines, catalysed by montmorillonite K10 under microwave irradiation, condense with 4-hydroxyproline to produce 11-(1H-pyrrol-1-yl)-11H-indeno[1,2-b]quinoxaline derivatives in good yields. 相似文献