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51.
Rui Chang Young Pyo Hong Stephanus Axnanda Baohua Mao Naila Jabeen Suidong Wang Renzhong Tai Zhi Liu 《Current Applied Physics》2012,12(5):1292-1296
We report Ambient pressure X-ray Photoelectron Spectroscopy Endstation with an integrated chemical analytical system that consists of a residual gas analyzer in the 2nd differential pumping stage and a new low-reactive sample holder heating assembly. This system has a linear response to the reaction chamber gas pressure. The sample heating assembly also has a low dark reaction rate up to 400 °C for H2 and CO oxidation. We expect this chemical analytical system will expand our capabilities in conducting in-operando catalysis research. 相似文献
52.
Shakeela Jabeen Alexander Greer Kathleen F. Edwards Joel F. Liebman 《Photochemistry and photobiology》2020,96(5):1140-1143
A unique approach is used to relate the HOMO-LUMO energy difference to the difference between the ionization potential (IP) and electron affinity (EA) to assist in deducing not only the colors, but also chromophores in elemental nonmetals. Our analysis focuses on compounds with lone pair electrons and σ electrons, namely X2 (X = F, Cl, Br, I), S8 and P4. For the dihalogens, the [IP – EA] energies are found to be: F2 (12.58 eV), Cl2 (8.98 eV), Br2 (7.90 eV), I2 (6.78 eV). We suggest that the interahalogen X–X bond itself is the chromophore for these dihalogens, in which the light absorbed by the F2, Cl2, Br2, I2 leads to longer wavelengths in the visible by a π → σ* transition. Trace impurities are a likely case of cyclic S8 which contains amounts of selenium leading to a yellow color, where the [IP – EA] energy of S8 is found to be 7.02 eV. Elemental P4 with an [IP – EA] energy of 9.09 eV contains a tetrahedral and σ aromatic structure. In future work, refinement of the analysis will be required for compounds with π electrons and σ electrons, such as polycyclic aromatic hydrocarbons (PAHs). 相似文献
53.
Shabnam Shahida Akbar Ali Muhammad Haleem Khan 《Journal of the Iranian Chemical Society》2014,11(1):1-8
A very sensitive, selective and simple flow injection time-based method was developed for on-line preconcentration and determination of thorium(IV) at micro g L–1 levels in environmental samples. The system operation was based on thorium(IV) ion retention at pH 4.0 in the minicolumn at a flow rate of 15.2 mL min–1. The trapped complex was then eluted with 3.6 mol L–1 HCl at a flow rate of 4.9 mL min–1. The amount of thorium(IV) in the eluate was measured spectrophotometrically at 651 nm using arsenazo-III solution (0.05 % in 3.6 mol L–1 HCl stabilized with 1 % triton X-100, 4.9 mL min–1) as colorimetric reagent. All chemical, and flow injection variables were optimized for the quantitative preconcentration of metal and a study of interference level of various ions was also carried out. The system offered low backpressure and improved sensitivity and selectivity. At a preconcentration time of 60 s and a sample frequency of 40 h–1, the enhancement factor was 97, the detection limit was 0.25 μg L–1, and the precision expressed as relative standard deviation was 1.08 % (at 50 μg L–1), whereas for 300 s of the preconcentration time and a sample frequency of 10 h–1, the enhancement factor of 357, the detection limit (3σ) of 0.069 μg L–1 and the precision of 1.32 % (at 10 μg L–1) was reported. The accuracy of the developed method was sufficient and evaluated by the analysis of certified reference material IAEA-SL-1 (Lake Sediment) and spiked water samples. 相似文献
54.
An attempt has been made to incorporate intercalation power of metal-flavonoids (metal-Fls) into ds.DNA for selective accumulation of heavy metal ions on DNA trapping water insoluble (3-aminopropyl)triethoxysilane (APTES) films. Three flavonoids (Fls) namely primuletin (prim), morin (mor) and quercetin (quer) were used to chelate heavy metal ions alone and through calf thymus DNA intercalation. Metal ion (M?=?Cu2+, Fe3+, Cr3+, As2+, Hg2+, Pb2+, Cd2+, Sb5+) captured from 10?µM solution of its salt over Fl-DNA-APTES film was found to be more efficient towards metal ion removal (99% removal) than M-Fl interaction into DNA-APTES (80% removal) which in turn was better than M-Fl-DNA trapping into APTES (60% removal). M-Fl chelation was 1:1 for all the complexes and binding strength (Kb in M?1) was of the order of 103–105 for different flavonoids (Fls) and the flavonoid-chelated metals (M-Fls). From the results, it was inferred that the nature of interaction between different constituents and metal chelation with the flavonoid are the key factors that affect the ion removal efficiency. It was also anticipated that any flavonoid can be used for ion removal process subject to its affinity strength towards the ion of interest. The work successfully demonstrated the usefulness of the method for ion removal in chemical, biological and environmental systems. 相似文献
55.
Muhammad H. Sultan Shamama Javed Osama Ali Madkhali Mohammad Intakhab Alam Yosif Almoshari Mohammad Ali Bakkari Durgaramani Sivadasan Ahmad Salawi Ameena Jabeen Waquar Ahsan 《Molecules (Basel, Switzerland)》2022,27(6)
The present study aimed to develop a local dental nanoemulgel formulation of Nigella sativa oil (NSO) for the treatment of periodontal diseases. NSO purchased from a local market was characterized using a GC–MS technique. A nanoemulsion containing NSO was prepared and incorporated into a methylcellulose gel base to develop the nanoemulgel formulation. The developed formulation was optimized using a Box–Behnken statistical design (quadratic model) with 17 runs. The effects of independent factors, such as water, oil, and polymer concentrations, were studied on two dependent responses, pH and viscosity. The optimized formulation was further evaluated for droplet size, drug release, stability, and antimicrobial efficacy. The developed formulation had a pH of 7.37, viscosity of 2343 cp, and droplet size of 342 ± 36.6 nm. Sustained release of the drug from the gel for up to 8 h was observed, which followed Higuchi release kinetics with non-Fickian diffusion. The developed nanoemulgel formulation showed improved antimicrobial activity compared to the plain NSO. Given the increasing emergence of periodontal diseases and antimicrobial resistance, an effective formulation based on a natural antibacterial agent is warranted as a dental therapeutic agent. 相似文献
56.
Abbasi Y. A. Shahida S. Ali A. Khan M. H. 《Journal of Radioanalytical and Nuclear Chemistry》2019,319(3):1029-1036
Journal of Radioanalytical and Nuclear Chemistry - A simple, efficient and economical liquid–liquid extraction method has been developed for quantitative extraction of mercury(II) from... 相似文献
57.
Sumaira Qayyum Tasawar Hayat Sumaira Jabeen Ahmed Alsaedi 《Mathematical Methods in the Applied Sciences》2020,43(9):5657-5672
Research on optimization of entropy generation in nanofluid flow gained much interest. In this study, the Walter's-B nanofluid flow is considered to analyze the irreversibility in cubic autocatalysis. Fluid motion is considered in presence of viscous dissipation, magnetohydrodynamics (MHD), radiation, and heat generation absorption. Homotopy analysis method (HAM) is employed to solve nonlinear ordinary differential system. Results show that fluid flow reduces for larger Weissenberg and Hartman numbers. Temperature gradually enhances for larger Weissenberg number and radiation parameter. For higher estimation of thermophoresis parameter, the temperature and concentration are enhanced. Opposite impact of Hartman and Weissenberg numbers is noticed for entropy generation and Bejan number. Disorderedness and Bejan number are reduced near the sheet, while the opposite trend is seen away from the sheet. 相似文献
58.
M. Rasul Jan Farah Jabeen Jasmin Shah Fazal Mabood 《Journal of Thermal Analysis and Calorimetry》2010,101(1):303-308
An environment friendly method, thermal catalytic pyrolysis of used isobutyl isoprene rubber was investigated. In this method,
the used inner butyl tube rubbers were catalytically pyrolyzed into valuable hydrocarbons and carbon black. In this method,
the tube rubber was pyrolyzed both thermally (with out catalyst) and catalytically in a batch reactor under atmospheric pressure.
The effect of temperature, the amount of catalyst, and the reaction time on the yields of the pyrolyzed products were investigated.
Char yield decreased with increase of pyrolysis temperature while total gas and liquid yields increased. The liquid fraction
was obtained with boiling point up to 478 K. At optimum conditions, the liquid product was collected and analyzed for different
fuel properties. Typical analysis of the used isobutyl isoprene rubber oil for both the cases of parent and refluxed oil has
been performed. Phenols and carbonyls were quantitatively determined by spectrophotometric methods using folin-denis and phenyl
hydrazine reagents, respectively. The distillation data showed that ~100% of oil has boiling point <473 K which is the boiling
point for 80% of distilled product in commercial kerosene. Its specific gravity, viscosity, freezing point, Cetane number,
and diesel index were also within the limits of kerosene. 相似文献
59.
Saima Jabeen Trevor J. Dines Stephen A. Leharne Robert Withnall Babur Z. Chowdhry 《Journal of Raman spectroscopy : JRS》2010,41(10):1306-1317
Raman and infrared spectra are reported for rhodanine, 3‐aminorhodanine and 3‐methylrhodanine in the solid state. Comparisons of the spectra of non‐deuterated/deuterated species facilitate discrimination of the bands associated with N H, NH2, CH2 and CH3 vibrations. DFT calculations of structures and vibrational spectra of isolated gas‐phase molecules, at the B3‐LYP/cc‐pVTZ and B3‐PW91/cc‐pVTZ level, enable normal coordinate analyses in terms of potential energy distributions for each vibrational normal mode. The cis amide I mode of rhodanine is associated with bands at ∼1713 and 1779 cm−1, whereas a Raman and IR band at ∼1457 cm−1 is assigned to the amide II mode. The thioamide II and III modes of rhodanine, 3‐aminorhodanine and 3‐methylrhodanine are observed at 1176 and 1066/1078; 1158 and 1044; 1107 and 984 cm−1 in the Raman and at 1187 and 1083; 1179 and 1074; 1116 and 983 cm−1 in the IR spectra, respectively. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
60.
Saima Jabeen Rex A. Palmer Brian S. Potter Madeleine Helliwell Trevor J. Dines Babur Z. Chowdhry 《Journal of chemical crystallography》2009,39(2):151-156
Abstract Rhodanines (2-thio-4-oxothiazolidines) are synthetic small molecular weight organic molecules with diverse applications in
biochemistry, medicinal chemistry, photochemistry, coordination chemistry and industry. The X-ray crystal structure determination
of two rhodanine derivatives, namely (I), 3-aminorhodanine [3-amino-2-thio-4-oxothiazolidine], C3H4N2OS2, and (II) 3-methylrhodanine [3-methyl-2-thio-4-oxothiazolidine], C4H5NOS2, have been conducted at 100 K. I crystallizes in the monoclinic space group P21/n with unit cell parameters a = 9.662(2), b = 9.234(2), c = 13.384(2) ?, β = 105.425(3)°, V = 1151.1(3) ?3, Z = 8 (2 independent molecules per asymmetric unit), density (calculated) = 1.710 mg/m3, absorption coefficient = 0.815 mm−1. II crystallizes in the orthorhombic space group Iba2 with unit cell a = 20.117(4), b = 23.449(5), c = 7.852(2) ?, V = 3703.9(12)
?3, Z = 24 (three independent molecules per asymmetric unit), density (calculated) = 1.584 mg/m3, absorption coefficient 0.755 mm−1. For I in the final refinement cycle the data/restraints /parameter ratios were 2639/0/161, goodness-of-fit on F2 = 0.934, final R indices [I > 2sigma(I)] were R1 = 0.0299, wR2 = 0.0545 and R indices (all data) R1 = 0.0399, wR2 = 0.0568.
The largest difference peak and hole were 0.402 and −0.259 e ?−3. For II in the final refinement cycle the data/restraints/parameter ratios were 3372/1/221, goodness-of-fit on F2 = 0.950, final R indices [I > 2sigma(I)] were R1 = 0.0407, wR2 = 0.1048 and R indices (all data) R1 = 0.0450, wR2 = 0.1088.
The absolute structure parameter = 0.19(9) and largest difference peak and hole 0.934 and −0.301 e ?−3. Details of the geometry of the five molecules (two for I and three for II) and the crystal structures are fully discussed. Corresponding features of the molecular geometry are highly consistent and
firmly establish the geometry of the rhodanine ring.
Index Abstract Low temperature X-ray structures of (I) 3-aminorhodanine [3-amino-2-thio-4-oxothiazolidine] and (II) 3-methylrhodanine3-methyl-2-thio-4-oxothiazolidine are presented. Crystals of I are monoclinic and occupy space group P21/n with eight molecules (2 per asymmetric unit cell) and (II) is orthorhombic in space group Iba2 with 24 molecules (3 per asymmetric unit). This study has provided five highly consistent
copies of the rhodanine ring at high resolution thus enabling its geometry to be established with confidence.
The two independent molecules in the asymmetric unit of 3-aminorhodanine (left) and the three independent molecules in the
asymmetric unit of 3-methylrhodanine (right) showing space filling and van der Waals contacts (drawn with MERCURY [Bruno et al.
Acta Cryst B58:389, 2002]). 相似文献