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931.
Solid-phase extraction (SPE) of phenol and chlorophenols, their derivatization to methyl ethers, headspace single-drop microextraction (HS-SDME) of methyl ethers using 1-butanol as extraction solvent, and direct transfer of the drop into the injector for high performance liquid chromatography with diode array detection (HPLC-DAD) have been reported. A flanged-end polytetrafluoroethylene sleeve, 3 mm × 0.5 mm, placed at the tip of the syringe needle, allowed the use of 10 μL solvent drop for extraction. The procedure has been optimized for variables involved in SPE and HS-SDME. A rectilinear relationship was obtained between the amount of chlorophenols and peak area ratio of their methyl ethers/internal standard (4-methoxyacetophenone) in the range 0.01-10 mg L−1, correlation coefficient in the range 0.9956-0.9996, and limit of detection in the range 1.5-3.9 μg L−1 when HS-SDME alone was used for sample preparation. When using coupled SPE and HS-SDME, the linear range obtained was 0.1-500 μg L−1, correlation coefficient in the range 0.9974-0.9998, and the limit of detection in the range 0.04-0.08 μg L−1. Spiked real samples have been analyzed with adequate accuracy, and application of the method has been demonstrated for the analysis of chlorophenols formed upon bamboo pulp bleaching. 相似文献
932.
Basavaraju Srinivas Kannekanti Lalitha Police Anil Kumar Reddy Gajeelli Rajesh Valluri Durga Kumari Machiraju Subrahmanyam Bhudev Ranjan De 《Research on Chemical Intermediates》2011,37(8):1069-1086
Abstract
The liquid-phase selective dehydrogenation of cyclohexanol has been investigated using two classes of catalyst containing either Cu2O or CuO on TiO2 under solar light in deaerated conditions at room temperature using acetonitrile medium in a batch reactor. The effect on dehydrogenation of three conditions, cyclohexanol concentration, copper loading on TiO2, and amount of catalyst, were investigated. The maximum yield of cyclohexanone obtained was 40%. The catalysts were characterized by XRD, UV–DRS, TEM, SEM–EDAX, and XPS. It was found that 1% (w/w) Cu2O/TiO2 was 100% selective for photocatalytic dehydrogenation of cyclohexanol. 相似文献933.
Fabio?Lisi Davide?Carta Laura?Villanova Irene?Poli Dario?Buso Stefano?Costacurta Anita?J.?Hill Paolo?FalcaroEmail author 《Journal of Sol-Gel Science and Technology》2011,60(3):246-253
Functional coatings with amino groups are used in a wide range of biochemistry-related applications. A technological platform
that takes advantage of the affinity between amino-functionalized coatings and biomolecules is the DNA microarray methodology.
Reliability and reproducibility of the microarray data strongly depend on the quality of the substrate; therefore, a proper
awareness of how the storage conditions affect the amino-functionalized coatings is necessary. In this work we have studied
the influence of different relative humidity levels on amino-methyl-silane coatings prepared via sol–gel methodology. Drops
of a buffer solution containing a luminescent dye have been deposited (or spotted) on the coating; the dye molecules react with the amino-groups and leave circular luminescent marks (spots) on the substrate
surface. Shape and luminescence of the spots, as well as background signals, have been monitored using a microarray laser
scanner. With the proposed protocol we have measured the changes of these variables due to different storage conditions. FT-IR
measurements have been performed to investigate the related chemistry changes. 相似文献
934.
935.
Jonathan H. Hodgkin Ming S. Liu Buu N. Dao J. Mardel Anita J. Hill 《European Polymer Journal》2011,(3):394-400
Thermal treatments of hydroxyl-containing polyimide materials at high temperatures are believed to lead to unique structural and chemical changes to the polymer backbone and side groups. These rearrangements when applied to specific polymeric membranes improve both their permeability and selectivity over conventional materials and this development has been attributed to the formation of nanoporous cavities in the treated products. However, the mechanisms of the possible chemical reactions that take place and the structures of the end-products have been poorly understood. With validated evidence from experiments and virtual screening of different precursors and possible products by molecular simulation, we have determined that hydroxy-containing polyimides can be thermally rearranged into poly(biphenylene bisimide) polymers under designed conditions. The proposed reaction mechanism is novel and calls into question the previously reported polybenzoxazole mechanism of thermal rearrangement. The new results indicate that the exact conditions of synthesis and thermal treatment of the starting polyimides will be critical to the properties of the membranes produced. 相似文献
936.
Aranyi A Ilisz I Pataj Z Szatmári I Fülöp F Péter A 《Journal of chromatography. A》2011,1218(30):4869-4876
The stereoisomers of five 1-(phenylethylamino)methyl-2-naphthol analogs or 1-(naphthylethylamino)methyl-2-naphthol analogs containing two chiral centers were directly separated on chiral stationary phases containing the chiral selectors cellulose tris-(3,5-dimethylphenyl) carbamate (Lux Cellulose-1), cellulose tris-(3-chloro-4-methylphenyl) carbamate (Lux Cellulose-2) and amylose tris-(5-chloro-2-methylphenyl) carbamate (Lux Amylose-2). Experiments were performed in normal-phase mode in a wide temperature range -5 to 70°C. Thermodynamic parameters and T(iso) values were calculated from plots of lnk or lnα vs. 1/T. -Δ(ΔH°) ranged from 1.0 to 4.7 kJ mol(-1), -Δ(ΔS°) from 1.6 to 11.0 J mol(-1) K(-1) and -Δ(ΔG°) from 0.1 to 1.5 kJ mol(-1). The sequence of elution of the stereoisomers was determined in all cases and in one case a temperature-induced inversion of the elution sequence was observed. 相似文献
937.
The photophysical properties of a series of 3-(1′H-Indol-3′-yl)-1-phenylprop-2-en-1-one and its derivatives (indole chalcones) were studied in different solvents. Solvent effects
on the absorption and fluorescence spectra were quantified using Reichardt’s and bulk solvent polarity parameters and were
complemented by the results of the Kamlet-Taft treatment. The observed excited state dipole moment was found to be larger
than the ground state dipole moment of these chalcones. The correlation of the solvatochromic Stokes-shifts with the microscopic
solvent polarity parameter (ETN E_T^N ) was found to be superior to that obtained using bulk solvent polarity functions. 相似文献
938.
Sunil Kumar Zinki Jindal Nitu Kumari Narendra Kumar Verma 《Journal of nanoparticle research》2011,13(10):5465-5471
To exploit the photoluminescent behavior of CdS at nanoscale with different doping concentration of europium—a rare earth
element, we report the synthesis of Eu-doped CdS nanorods by using low temperature solvothermal process by using ethylenediamine.
The outcomes can have future applications as phosphors, photovoltaic cells, lasers, light emitting diodes, bio-imaging, and
sensors. The doping was confirmed by electron dispersive spectroscopy supported by X-ray diffraction. From scanning electron
microscopy and transmission electron microscopy analysis it was observed that the average diameter of the Cd1−x
Eu
x
S nanorods is about 10–12 nm having lengths in the range of 50–100 nm. UV–Visible spectroscopy study was carried out to determine
the band gap of the nanorods and the absorbance peaks showed blue shift with respect to the bulk CdS. The blue shift was also
observed as the doping concentration of Eu increases. From photoluminescence (PL) studies at λex = 450 nm, peaks at 528 and 540 nm were observed due to CdS, peak at 570 nm is due to defects related transitions, while the
peak at 613 nm is due to Eu. As the doping concentration of Eu is increased the intensity of the luminescent peak at 613 nm
is increased. Thermogravimetric analysis showed the nanorods are thermally stable up to 300 °C. The traces of impurities adsorbed
on the nanorods were confirmed by Fourier transform infrared spectroscopy. 相似文献
939.
Jiménez AJ Marcos ML Hausmann A Rodríguez-Morgade MS Guldi DM Torres T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(50):14139-14146
Phthalocyanine (Pc) dimers connected through trans-platinum(II) diacetylide linkers have been prepared by reaction of the corresponding ethynylphthalocyanines with trans-bis(triethylphosphine)platinum(II) chloride. Special emphasis was placed on the analysis of the ground- and excited-state features of these compounds in relation to butadiyne-bridged Pc dimers and the corresponding monomers. Both Zn(II)-containing Pc dimers exhibit long-lived triplet excited states. The insertion of σ-bonded trans-platinum(II) diacetylide spacers decoupled the two Pc groups and led to an appreciable acceleration (by a factor of up to 10) of the radiative and nonradiative decay rate of the singlet and triplet excited states. 相似文献
940.
Kamini Venkatesh Vadlamani Ravi Anita Prinzie Dirk Van den Poel 《European Journal of Operational Research》2014
To improve ATMs’ cash demand forecasts, this paper advocates the prediction of cash demand for groups of ATMs with similar day-of-the week cash demand patterns. We first clustered ATM centers into ATM clusters having similar day-of-the week withdrawal patterns. To retrieve “day-of-the-week” withdrawal seasonality parameters (effect of a Monday, etc.) we built a time series model for each ATMs. For clustering, the succession of seven continuous daily withdrawal seasonality parameters of ATMs is discretized. Next, the similarity between the different ATMs’ discretized daily withdrawal seasonality sequence is measured by the Sequence Alignment Method (SAM). For each cluster of ATMs, four neural networks viz., general regression neural network (GRNN), multi layer feed forward neural network (MLFF), group method of data handling (GMDH) and wavelet neural network (WNN) are built to predict an ATM center’s cash demand. The proposed methodology is applied on the NN5 competition dataset. We observed that GRNN yielded the best result of 18.44% symmetric mean absolute percentage error (SMAPE), which is better than the result of Andrawis, Atiya, and El-Shishiny (2011). This is due to clustering followed by a forecasting phase. Further, the proposed approach yielded much smaller SMAPE values than the approach of direct prediction on the entire sample without clustering. From a managerial perspective, the clusterwise cash demand forecast helps the bank’s top management to design similar cash replenishment plans for all the ATMs in the same cluster. This cluster-level replenishment plans could result in saving huge operational costs for ATMs operating in a similar geographical region. 相似文献