Salah Ud-Din Khan

Adsorption kinetic and isotherm of methylene blue, safranin T and rhodamine B onto electrospun ethylenediamine-grafted-polyacrylonitrile nanofibers membrane

AbstractEDA-g-PAN NFs membrane was prepared via electrospinning and chemical grafting techniques. Grafting (64%) with no change in the physical nature and colour was confirmed by FT-IR spectra. Adsorption kinetics of methylene blue (MB), rhodamine B (RB) and safranin T (ST) dyes onto PAN and EDA-g-PAN NFs membranes showed equilibrium time of around ~60 min. The adsorption kinetic followed pseudo-second-order model and intraparticle diffusion was not the only rate-limiting step. The adsorption data for the dyes fitted well to Langmuir and Freundlich equations. The order of adsorption capacity (qmax) obtained from Langmuir plot was: MB (94.07 mg/g) < ST (110.62 mg/g) < RB (138.69 mg/g). These values are more than most of the values reported in literature.

Detailed investigation of optimized alkali catalyzed transesterification of Jatropha oil for biodiesel production

Abstract The non-edible oils are believed to be one of the major feedstock for the production of biodiesel in future. In the present study, we investigated the production of Jatropha oil methyl esters (JOMEs) via alkali-catalyzed transesterification route. The biophysical characteristics of Jatropha oil were found within the optimal range in accordance with ASTM standards as a substitute diesel fuel. The chemical composition and production yield of as-synthesized biodiesel were confirmed by various analytical techniques such as FT-IR, 1 H NMR, 13 C NMR and gas chromatography coupled with mass spectrometry. A high percentage conversion, ∼96.09%, of fatty acids into esters was achieved under optimized transesterification conditions with 6: 1 oil to methanol ratio and 0.9 wt% NaOH for 50 min at ∼60 °C. Moreover, twelve fatty acids methyl esters (FAME) were quantified in the GC/MS analysis and it was interesting to note that the mass fragmentation pattern of saturated, monounsaturated and diunsaturated FAME was comparable with the literature reported values.

Synthesis, spectroscopic characterization and pH dependent photometric and electrochemical fate of Schiff bases.

A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms.

First-principles study of electronic, optical and thermoelectric properties in cubic perovskite materials AgMO3 (M = V,Nb,Ta)

In this paper, first-principles calculations of structural, electronic, optical and thermoelectric properties of AgMO3 (M = V, Nb and Ta) have been carried out using full potential linearized augmented plane wave plus local orbitals method (FP - LAPW + lo) and BoltzTraP code within the framework of density functional theory (DFT). The calculated structural parameters are found to agree well with the experimental data, while the electronic band structure indicates that AgNbO3 and AgTaO3 are semiconductors with indirect bandgaps of 1.60 eV and 1.64 eV, respectively, between the occupied O 2p and unoccupied d states of Nb and Ta. On the other hand, AgVO3 is found metallic due to the overlapping behavior of states across the Fermi level. Furthermore, optical properties, such as dielectric function, absorption coefficient, optical reflectivity, refractive index and extinction coefficient of AgNbO3 and AgTaO3, are calculated for incident photon energy up to 50 eV. Finally, we calculate thermo power for AgNbO3 and AgTaO3 at fixed doping 1019 cm-3. Electron doped thermo power of AgNbO3 shows significant increase over AgTaO3 with temperature.

A convenient method for the synthesis of (prop-2-ynyloxy)benzene derivatives via reaction with propargyl bromide, their optimization, scope and biological evaluation

A highly convenient method has been developed for the synthesis of (prop-2-ynyloxy) benzene and its derivatives. Differently substituted phenol and aniline derivatives were allowed to react with propargyl bromide in the presence of K2CO3 base and acetone as solvent. The compounds were synthesized in good yields (53–85%). Low cost, high yields and easy availability of compounds helped in the synthesis. Electron withdrawing groups favor the formation of stable phenoxide ion thus in turn favors the formation of product while electron donating groups do not favor the reaction. Phenol derivatives gave good yields as compared to that of aniline. As aprotic polar solvents favor SN2 type reactions so acetone provided best solvation for the reactions. K2CO3 was proved to be good for the synthesis. Antibacterial, Antiurease and NO scavenging activity of synthesized compounds were also examined. 4-bromo-2-chloro-1-(prop-2-ynyloxy)benzene 2a was found most active compound against urease enzyme with a percentage inhibition of 82.00±0.09 at 100 µg/mL with IC50 value of 60.2. 2-bromo-4-methyl-1-(prop-2-ynyloxy)benzene 2d was found potent antibacterial against Bacillus subtillus showing excellent inhibitory action with percentage inhibition of 55.67±0.26 at 100 µg/ml wih IC50 value of 79.9. Based on results, it can be concluded that some of the synthesized compounds may have potential antiurease and antibacterial effects against several harmful substances.

TiGa–VN complexes in GaN: a new prospect of carrier mediated ferromagnetism

First principle investigations exploring the effects of nitrogen vacancies on ferromagnetism in Ti doped wurtzite GaN are reported. The presence of nitrogen vacancies demonstrated no noticeable effect in the case of pure GaN but exhibited ferromagnetism in the case of Ti doped GaN. The magnetic moment however ceased upon doubling the concentration of dopant and vacancies in the host which points towards possible antiferromagnetic coupling. The conventional double exchange ordering observed in the case of the vacancy-added Ti:GaN switched to a carrier mediated exchange for the TiGa–VN complex in Ti:GaN. For Ti doped GaN, the energy difference calculated with and without N vacancies is found to be relatively smaller than that of other 3d transition metal (Cr, Mn, Fe, Co, Ni, Cu) doped GaN. The results calculated for different configurations to explore the effects of nitrogen vacancies on the electronic and magnetic properties of Ti:GaN are discussed in detail.

Regioselective synthesis of 2-(bromomethyl)-5-aryl-thiophene derivatives via palladium (0) catalyzed suzuki cross-coupling reactions: as antithrombotic and haemolytically active molecules

BackgroundIt is seen that the regioselective functionalizations of halogenated heterocycles play an important role in the synthesis of several types of organic compounds. In this domain, the Suzuki-Miyaura reaction has emerged as a convenient way to build carbon-carbon bonds in synthesizing organic compounds. Some of the most important applications of these reactions can be seen in the synthesis of natural products, and in designing targeted pharmaceutical compounds. Herein, we present the regioselective synthesis of the novel series of 2-(bromomethyl)-5-aryl-thiophenes 3a-i,via Suzuki cross-coupling reactions of various aryl boronic acids with 2-bromo-5-(bromomethyl)thiophene (2).ResultsThe synthesized compounds were screened for their haemolytic and antithrombolytic activities. The novel compounds 3f, 3i showed highest 69.7, 33.6% haemolysis of blood cells, respectively. The antithrombolytic activity of the compounds was found to be within low to moderate against human blood clot. The compound 3i showed potent clot lysis (31.5%).ConclusionsConsidering these results, it is concluded that the synthesized compounds can be used as a promising source of therapeutic agents.

Utilization of electron‐deficient thiadiazole derivatives as π-spacer for the red shifting of absorption maxima of diarylamine-fluorene based dyes

This study is carried out to design diarylamine-fluorene dyes by incorporating electron‐deficient thiadiazole derivatives. Quantum chemical calculations are performed to study the geometries, electronic structures and absorption spectra of the dyes. Interaction of dyes with TiO2 cluster is also studied. The effects of the electron‐deficient units on the spectra and electrochemical properties have been investigated. Dyes D1–D4 display remarkably enhanced spectral response in the red portion of the solar spectrum as compared with reference compound D0. The newly designed dyes demonstrate desirable energetic and spectroscopic parameters and may lead to efficient metal‐free organic dye sensitizers for DSSCs.

Thermodynamic and spectroscopic investigation of interactions between reactive red 223 and reactive orange 122 anionic dyes and cetyltrimethyl ammonium bromide (CTAB) cationic surfactant in aqueous solution.

The present study describes the conductometric and spectroscopic study of the interaction of reactive anionic dyes, namely, reactive red 223 and reactive orange 122 with the cationic surfactant cetyltrimethyl ammonium bromide (CTAB). In a systematic investigation, the electrical conductivity data was used to calculate various thermodynamic parameters such as free energy (ΔG), enthalpy (ΔH), and the entropy (ΔS) of solubilization. The trend of change in these thermodynamic quantities indicates toward the entropy driven solubilization process. Moreover, the results from spectroscopic data reveal high degree of solubilization, with strong interactions observed in the cases of both dyes and the CTAB. The spontaneous nature of solubilization and binding was evident from the observed negative values of free energies (ΔG p and ΔG b).

Performance Evaluation of Tandem Bladed Centrifugal Compressor

Abstract A tandem-bladed centrifugal compressor which may have better performance than the conventional designs has not yet been studied for its potential turbocharger application. In addition, no numerical study of the entire stage (including tandem impeller and volute) has been performed to fully exploit the benefits of such design with variation in axial clearance levels, circumferential clocking fractions, blade geometries/angles, number of inducer blades and the thickness of inducer blades. This paper presents a thorough experimental and numerical study on the performance of a moderate pressure ratio, unshrouded, tandem-bladed centrifugal compressor in comparison to a conventional compressor of commercial use in china for turbocharger application. The characteristics of a tandem compressor are investigated and compared for various parameters. Conventional impeller was first modified into tandem-bladed design but with no modifications in backsweep angle, meridional gas passage and camber distributions in order to have a true comparison. The tandem design was further modified and investigated by (1) narrowing down the meridional gas passage, (2) using straight or concave leading edge of exducer, (3) reducing the thickness and (4) the number of inducer blades. CFD and experimental results were found to be in good agreement. The study reveals a shift of surge point towards lower mass flow rate in all cases of tandem designs. A maximum of 25% increase in the range of operation is observed. All in all there is little influence of the different circumferential clocking fractions and axial spacings of the inducer. Computational investigations of a modified tandem compressor with 20% reduction in inducer thickness have shown better performance than the conventional design. Use of fourteen inducer blades with reduced blade thickness can further enhance the performance.