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1.
This paper reports the results of a variety of experiments carried out for understanding the solvation behavior of potassium thiocyanate in methanol–water mixtures. Electrical conductivity, speed of sound, viscosity, and FT-Raman spectra of potassium thiocyanate solutions in 5 and 10% methanol–water (w/w) mixtures were measured as functions of concentration and temperature. The conductivity and structural relaxation time suggest the ion–solvent and solvent-separated ion–ion associations increase as the salt concentration increases in the mixtures. The Raman band shifts due to the C–O stretching mode of methanol for the solvent mixtures reveal the formation of methanol–water complexes. The significant changes in the Raman bands for the C–N, C–S and O–H stretching modes indicate the presence of SCN−−solvent interactions through the N-end, “free” SCN− and the solvent-shared ion pairs as potassium thiocyanate is added to the methanol–water mixtures. The relative changes corresponding to H–O–H bending and C–O stretching frequencies indicate that K+ is preferentially solvated by water in these solvent mixtures. The appearance and increase of the intensity of a broad band at ≈940 cm−1 upon salt addition was attributed to the SCN−–H2O–K+ solvent-shared ion pairs. No Raman spectral evidence for K+(H2O)n species was observed. The preferential solvation of K+ and SCN− in the methanol−water mixtures was verified by the application of the Kirkwood−Buff theory of solutions. This theory confirms that K+ is strongly preferentially solvated by water, whereas SCN− is preferentially solvated by the methanol component. 相似文献
2.
Fathy Abdel‐Kader Amer Metwally Hammouda Abdel‐Aziz Sayed El‐Ahl Bakr Fathy Abdel‐Wahab 《中国化学会会志》2007,54(6):1543-1552
Treatment of heterocyclic β‐ketonitriles 1a,b with hydrazine hydrate and phenylhydrazine afforded the hydrazine derivatives 2a‐d which cyclized in PPA into pyrrolo[3,4‐c]pyrazoles 3a‐d. Reaction of 1a,b with cyanoacetohydrazide furnished the cyanoacetyl pyrrolo[3,4‐c]pyrazoles 4a,b. The hydrazine 2c reacted with β‐diketone and β‐ketoesters to afford pyrazolyl‐pyrrolines 5‐7. Also the later hydrazine reacted with some D‐aldoses and aceteophenone to give the corresponding hydrazones 10‐12 and hydrazine carboxamide derivatives 15a,b respectively. 相似文献
3.
4.
Elias Nursyafiqah Wahab Roswanira Abdul Jye Lau Woei Mahat Naji Arafat Chandren Sheela Jamalis Joazaizulfazli 《Cellulose (London, England)》2021,28(9):5669-5691
Cellulose - A greener processing route to replace the current environmentally-unfriendly esterification technique to produce biofuels such as pentyl valerate (PeVa) was explored. This study... 相似文献
5.
High-resolution three-dimensional atomic microscopy via double electromagnetically induced transparency
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Abdul Wahab 《中国物理 B》2021,30(9):94202-094202
We aim to present a new scheme for high-dimensional atomic microscopy via double electromagnetically induced transparency in a four-level tripod system. For atom–field interaction, we construct a spatially dependent field by superimposing three standing-wave fields(SWFs) in 3 D-atom localization. We achieve a high precision and high spatial resolution of an atom localization by appropriately adjusting the system variables such as field intensities and phase shifts. We also see the impact of Doppler shift and show that it dramatically deteriorates the precision of spatial information on 3 D-atom localization. We believe that our suggested scheme opens up a fascinating way to improve the atom localization that supplies some practical applications in atom nanolithography, and Bose–Einstein condensation. 相似文献
6.
Waleed A. El‐Said Mona A. Abdel‐Rahman Eman M. Sayed Aboel‐Magd A. Abdel‐Wahab 《Electroanalysis》2019,31(5):829-837
Here, we reported on a one‐step fabrication of magnetite Fe3O4 nanoparticles/indium tin oxide (ITO) electrode based on the direct growing of Fe3O4 nanoparticles on the ITO surface by using a solvothermal process. The modified electrode was used as electrochemical methotrexate (MTX) biosensor with high sensitivity based on cyclic voltammetry and square wave voltammetry techniques. The results demonstrated a linear relationship between the MTX concentration and its oxidation current peak over a wide range from 10?5 to 10?14 mole/L with a limit of detection of 0.4×10?15 M based on the square wave voltammetry (SWV) technique. In addition, Fe3O4/ITO electrode showed a good capability for measuring very low concentrations of MTX drug dissolved in human serum solution. Also, Fe3O4/ITO electrode was used for detecting MTX in blood serum samples collected from patients after their treatment with MTX. The prepared electrode showed the higher sensitivity that higher than the Viva‐E instrument, which opens the door for developing a cheap, simple and higher sensitive MTX sensor. 相似文献
7.
Temperature dependence of the turn-on time delay (ton) of uncooled semiconductor laser diodes biased below and above threshold is analyzed in presence of data pattern effect.
We show that even when the laser is biased at or slightly above threshold, the increase in temperature of operation will lead
to increase in the threshold carrier (Nth) and consequently the laser diode will be biased below the threshold again and a significant value of ton will be produced. Thus, knowledge about a value of dc-bias current required to achieve zero ton within wide range of temperature degrees is important when considering uncooled laser diode in high-speed optical communication
systems. The temperature dependence of ton is calculated according to the temperature dependence of Nth and Auger recombination coefficient (C) and not by the well-know exponentional relationship of threshold current with temperature.
The temperature dependence of Nth is calculated according to the temperature dependence of laser cavity parameters. Advanced analytical model is derived in
term of carrier density, recombination coefficients and the injection current (Iinj). The validity of proposed model is confirmed by a numerical method. In addition, approximated models are included where
under specified assumptions the proposed model reduces to the well-known approximate models of ton. According to our typical values and at a specified value of modulation current, the dc-bias one (Iib) should be increased from Iib = Ith to Iib ≈ 1.25 and 1.5Ith in order to achieve approximately zero ton when the temperature increases from 25°C to 55°C and 85°C, respectively. 相似文献
8.
Hanieh Ghadimi Ramin M.A.TehraniAbdussalam Salhin Mohamed Ali Norita MohamedSulaiman Ab Ghani 《Analytica chimica acta》2013
A novel glassy carbon electrode (GCE) modified with a composite film of poly (4-vinylpyridine) (P4VP) and multiwalled carbon nanotubes (P4VP/MWCNT GCE) was used for the voltammetric determination of paracetamol (PCT). This novel electrode displayed a combined effect of P4VP and MWCNT on the electro-oxidation of PCT in a solution of phosphate buffer at pH 7. Hence, conducting properties of P4VP along with the remarkable physical properties of MWCNTs might have combined effects in enhancing the kinetics of PCT oxidation. The P4VP/MWCNT GCE has also demonstrated excellent electrochemical activity toward PCT oxidation compared to that with bare GCE and MWCNT GCE. The anodic peak currents of PCT on the P4VP/MWCNT GCE were about 300 fold higher than that of the non-modified electrodes. By applying differential pulse voltammetry technique under optimized experimental conditions, a good linear ratio of oxidation peak currents and concentrations of PCT over the range of 0.02–450 μM with a limit of detection of 1.69 nM were achieved. This novel electrode was stable for more than 60 days and reproducible responses were obtained at 99% of the initial current of PCT without any influence of physiologically common interferences such as ascorbic acid and uric acid. The application of this electrode to determine PCT in tablets and urine samples was proposed. 相似文献
9.
Dadan Hermawan Izdiani Mohd Yatim Khaulah Ab Rahim Mohd Marsin Sanagi Wan Aini Wan Ibrahim Hassan Y. Aboul-Enein 《Chromatographia》2013,76(21-22):1527-1536
A simple solid phase extraction (SPE) method coupled with high performance liquid chromatography (HPLC) using UV detector and microemulsion electrokinetic chromatography (MEEKC) has been developed and compared for the quantitative determination of miconazole nitrate in pharmaceutical formulation. For HPLC method, two parameters were optimized, namely, the wavelength and the mobile phases. The optimized condition was at the 225 nm wavelength and the mobile phase of ACN:MeOH (90:10 v/v). There are seven MEEKC parameters that were optimized, in this research, which were applied to voltage, temperature, wavelength, sodium dodecyl sulfate (SDS) concentration, buffer pH, buffer concentration and butan-1-ol concentration. The optimum MEEKC condition was obtained using 86.35 % (w/w) 2.5 mM borate buffer pH 9, 0.25 % (w/w) SDS, 0.8 % (w/w) ethyl acetate, 6.6 % w/w butan-1-ol and 6.0 % (w/w) acetonitrile. The combination of SPE using a diol column with HPLC–UV and the MEEKC methods were successfully applied for the determination of miconazole nitrate in a pharmaceutical formulation with the recovery percentage of 98.35 and 92.50 %, respectively. 相似文献
10.
Anish Khan Abdullah M. Asiri Aftab Aslam Parwaz Khan Malik Abdul Rub Naved Azum Mohammed M. Rahman Sher Bahadar Khan Khalid A. Alamry Sulaiman Ab Ghani 《Journal of Sol-Gel Science and Technology》2013,65(2):160-169
Nano tetrapod based on conducting polythiophene (PTh) and tin-phosphate (SnP) were synthesized by in situ chemical oxidative polymerization. The morphology of the resulting polythiophene tinphosphate composite was characterized by elemental analysis, fourier transform infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The physico-chemical characterization carried out on the composite showed that SnP was modified by conducting PTh with an enhancement of various properties. On the basis of highest distribution coefficient values for Hg(II), the composite was also used for the preparation of Hg(II) selective membrane electrode. The electrode showed working concentration range of 1 × 10?1 to 1 × 10?7 with Nernstian slope of 29.29 mV per decade change in concentration and the electrode may be used for wide working pH range of 4–8 having quick response time about 23 s. The life of electrode is 4 months without any notable drift in potential. 相似文献