Showing papers by "Sher Bahadar Khan published in 2013"

Preparation and characterization of poly(propylene carbonate)/exfoliated graphite nanocomposite films with improved thermal stability, mechanical properties and barrier properties

Abstract: Relatively high aspect ratio exfoliated graphite (EFG) particles with an average size of 7.4 mu m and a nanometer sized thickness of 30-50 nm were successfully prepared by thermal treatment at 1050 degrees C and subsequent ultrasonication for application as a filler to improve the physical properties of eco-friendly poly(propylene carbonate) (PPC). A series of poly(propylenecarbonate)/exfoliated graphite (PPC/EFG) nanocomposite films with different EFG contents were prepared via a solution blending method. The physical properties were strongly dependent upon the chemical and morphological structures originating from the differences in EFG composition. The morphological structures, thermal properties, mechanical properties and barrier properties of the nanocomposite films were investigated as a function of the EFG content. While all of the PPC/EFG nanocomposite films exhibited good dispersion of EFG to some extent, Fourier transform infrared and SEM results revealed that solution blending did not lead to strong interactions between PPC and EFG. As a result, poor dispersion occurred in composite films with a high EFG content. By loading EFG particles, the oxygen permeabilities, moisture permeabilities and water uptake at equilibrium decreased as the EFG content increased. Compared with pure PPC, PPC/EFG nanocomposite films have enhanced molecular ordering. Specifically, the 2% PPC/EFG composite film shows greater molecular ordering than the other composite films, which results in the highest mechanical strength. In future work, the compatibility and dispersion of the PPC matrix polymer and EFG filler particles should be increased by modifying the EFG surface or introducing additives

Synthesis, characterization of silver nanoparticle embedded polyaniline tungstophosphate-nanocomposite cation exchanger and its application for heavy metal selective membrane

Abstract: Utilizing the solution synthesis technique, polyaniline tungstophosphate (WP-PAni) was expediently obtained, which was allowed to react with silver to the formation of silver embedded polyaniline tungstophosphate (WP-PAni/Ag) nanocomposite. The polymerization of aniline into polyaniline was achieved by means of in situ oxidative polymerization of the monomers. The nanocomposite was characterized by FT-IR, X-ray powder diffraction, UV–Vis Spectrophotometry, SEM (Scanning Electron Microscopy), thermogravimetric analysis (TGA). On the basis of cation exchange capacity, this nanocomposite cation exchanger was used to develop heavy metal ion selective membrane for lead.

An assessment of zinc oxide nanosheets as a selective adsorbent for cadmium

Abstract: Zinc oxide nanosheet is assessed as a selective adsorbent for the detection and adsorption of cadmium using simple eco-friendly extraction method. Pure zinc oxide nanosheet powders were characterized using field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The zinc oxide nanosheets were applied to different metal ions, including Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III). Zinc oxide nanosheets were found to be selective for cadmium among these metal ions when determined by inductively coupled plasma-optical emission spectrometry. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on zinc oxide nanosheets.

Acetone sensor based on solvothermally prepared ZnO doped with Co3O4 nanorods.

Abstract: This paper describes a reliable and sensitive method for sensing dissolved acetone using doped nanomaterials. Large-scale synthesis of ZnO nanorods (NRs) doped with Co3O4 was accomplished by a solvothermal method at low temperature. The doped NRs were characterized in terms of their morphological, structural, and optical properties by using field-emission scanning electron microscopy coupled with energy-dispersive system, UV-Vis., Fourier transform IR, X-ray diffraction, and Xray photoelectron spectroscopy. The calcinated (at 400 °C) doped NRs are shown to be an attractive semiconductor nanomaterial for detecting acetone in aqueous solution using silver electrodes. The sensor exhibits excellent sensitivity, stability and reproducibility. The calibration plot is linear over a large concentration range (66.8 μM to 0.133 mM), displays high sensitivity (~3.58 μA cm−2 mM−1) and a low detection limit (~14.7 ± 0.2 μM; at SNR of 3).

Highly sensitive and stable phenyl hydrazine chemical sensors based on CuO flower shapes and hollow spheres

Abstract: Chemical sensors are needed to develop efficient sensing systems with high flexibility, and low capital cost for controlled recognition of analytes. Herein, we report a highly sensitive, low cost, simple chemical sensor based on flower shape and hollow sphere CuO. Following the precipitation process, FESEM images revealed that CuO nanosheets are grown in high density and organized in a proper manner to give a flower shape structure; however, following the hydrothermal method in the presence of urea, the cage like micro structures CuO hollow spheres have been discovered. XRD revealed that the grown CuO has a single-crystalline phase of a monoclinic system. The resistivity of CuO hollow spheres (1.93 × 106 Ω m) is ∼100 times higher than flower shape CuO (2.2 × 104 Ω m). The prepared CuO flower shapes and hollow spheres have been evaluated for the detection and quantification of phenyl hydrazine. The findings indicate that CuO hollow spheres and flowers exhibited good sensitivity (0.578 and 7.145 μA cm−2 mM−1) and a lower limit of detection (LOD = 2.4 mM) with a linear dynamic range (LDR) of 5.0 μM to 10.0 mM and rapid assessment of the reaction kinetics (in the order of seconds). The designed flower shape CuO sensing system is 12 times more sensitive than CuO hollow spheres. To the best of our knowledge, the measured sensitivity ∼ 7.145 μA cm−2 mM−1 of CuO flower shapes is found to be among the highest sensitivity values reported for phenyl hydrazine up to now.

Synthesis and environmental applications of cellulose/ZrO2 nanohybrid as a selective adsorbent for nickel ion

Abstract: Cellulos/ZrO2 nanohybrid has been synthesized by simple growth of ZrO2 on cellulose matrix and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transforms infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Interestingly, FESEM showed nanoparticles with an average size of 50 nm. The analytical potential of the newly prepared nanohybrid was studied for a selective extraction of nickel prior to its determination by inductively coupled plasma-optical emission spectrometry. The selectivity of nanohybrid was investigated toward eight metal ions, including Cd2+, Co2+, Cr3+, Cu2+, Fe3+, Ni2+, Zn2+ and Zr4+. Data obtained from the selectivity study showed that nanohybrid was the most selective toward Ni2+. The uptake capacity for Ni2+ was experimentally calculated and found to be 79 mg g(-1). Moreover, adsorption isotherm data of Ni2+ on nanohybrid was well fit with the Langmuir adsorption isotherm, strongly supporting that the adsorption process was mainly monolayer on homogeneous adsorbent surfaces. Finally, data of Ni2+ adsorption on nanohybrid as a function of contact time displayed that equilibrium kinetics are very fast

Chemo-sensors development based on low-dimensional codoped Mn2O3-ZnO nanoparticles using flat-silver electrodes

Abstract: Semiconductor doped nanostructure materials have attained considerable attention owing to their electronic, opto-electronic, para-magnetic, photo-catalysis, electro-chemical, mechanical behaviors and their potential applications in different research areas. Doped nanomaterials might be a promising owing to their high-specific surface-area, low-resistances, high-catalytic activity, attractive electro-chemical and optical properties. Nanomaterials are also scientifically significant transition metal-doped nanostructure materials owing to their extraordinary mechanical, optical, electrical, electronic, thermal, and magnetic characteristics. Recently, it has gained significant interest in manganese oxide doped-semiconductor materials in order to develop their physico-chemical behaviors and extend their efficient applications. It has not only investigated the basic of magnetism, but also has huge potential in scientific features such as magnetic materials, bio- & chemi-sensors, photo-catalysts, and absorbent nanomaterials. The chemical sensor also displays the higher-sensitivity, reproducibility, long-term stability, and enhanced electrochemical responses. The calibration plot is linear (r2 = 0.977) over the 0.1 nM to 50.0 μM 4-nitrophenol concentration ranges. The sensitivity and detection limit is ~4.6667 μA cm-2 μM-1 and ~0.83 ± 0.2 nM (at a Signal-to-Noise-Ratio, SNR of 3) respectively. To best of our knowledge, this is the first report for detection of 4-nitrophenol chemical with doped Mn2O3-ZnO NPs using easy and reliable I-V technique in short response time. As for the doped nanostructures, NPs are introduced a route to a new generation of toxic chemo-sensors, but a premeditate effort has to be applied for doped Mn2O3-ZnO NPs to be taken comprehensively for large-scale applications, and to achieve higher-potential density with accessible to individual chemo-sensors. In this report, it is also discussed the prospective utilization of Mn2O3-ZnO NPs on the basis of carcinogenic chemical sensing, which could also be applied for the detection of hazardous chemicals in ecological, environmental, and health care fields.

Selective detection of toxic Pb(II) ions based on wet-chemically prepared nanosheets integrated CuO–ZnO nanocomposites

Abstract: The present study describes a selective detection methodology for hazardous metal ions based on low-dimensional nanosheets (NSs) integrated CuO-ZnO composite materials. A large-scale synthesis of NSs by wet-chemical process is performed using alkaline reducing agents at higher pH medium. The prepared NSs are characterized in terms of their morphological, structural and optical properties, and efficiently applied for the toxic metal ions detection. The detailed structural, compositional, and optical characterization of NSs are evaluated by XRD, FT-IR, XPS, EDS, and UV-vis spectroscopy, which confirmed that the obtained NSs are well-crystalline CuO-ZnO and possessed good optical properties. The CuO-ZnO NS morphology is investigated by FE-SEM, which confirmed that the NS possesses microstructure shape and growth in large-quantity. The analytical application of CuO-ZnO NSs is studied for a selective extraction of toxic lead-divalent [Pb(II)] ions prior to its determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of doped NSs phase is investigated for eight different metal ions, including Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III) under similar experimental conditions. From the selectivity study, it is confirmed that the composite CuO-ZnO NS phase is the most toward Pb(II) ions according to the magnitude of distribution coefficient (K-d) values, such as Pb(II) > Y(III) > Cd(II) > La(III) > Hg(II) > Cu(II) > Mn(II) > Pd(II). The uptake capacity for Pb(II) is experimentally calculated to be similar to 82.66 mg g(-1).

Co3O4 co-doped TiO2 nanoparticles as a selective marker of lead in aqueous solution

Abstract: Co3O4 co-doped TiO2 nanoparticles were prepared by a low temperature thermal method and their functional relationships with metal ions was investigated using solid phase extraction. The analytical potential of Co3O4 co-doped TiO2 nanoparticles was studied for the selective extraction of lead using inductively coupled plasma-optical emission spectrometry. The selectivity of Co3O4 co-doped TiO2 nanoparticles was investigated toward different metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(II and III), Hg(II), La(III), Mn(II), Ni(II), Pb(II), Pd(II) and Y(III). Data obtained from the selectivity study showed that Co3O4 co-doped TiO2 nanoparticles have the highest selectivity toward Pb(II). The uptake capacity for Pb(II) was experimentally calculated to be 114.05 mg g−1. Moreover, adsorption isotherm data of Pb(II) on Co3O4 co-doped TiO2 nanoparticles fit well with the Langmuir adsorption isotherm, strongly supporting that the adsorption process was mainly as a monolayer on Co3O4 co-doped TiO2 nanoparticle surfaces.

A facile route to cage-like mesoporous silica coated ZSM-5 combined with Pt immobilization

Abstract: Uniform core–shell composites with cage-like mesoporous silica (CmesoSiO2) shells and zeolite HZSM-5 cores have been synthesized by a facile acid-catalyzed sol–gel coating process. The mesoporous silica shells are uniform and coated on the anisotropic HZSM-5 crystal faces, and the shell-thicknesses can be tuned from 25 to 70 nm. The core–shell composites possess a high surface area (∼862 m2 g−1) and pore volume (∼0.66 cm3 g−1), large pore sizes (3.2–8.2 nm) and unchanged zeolite micropore properties. The silica shells are composed of cage-like mesopores and entrances (ranging from 3.2 to 8.2 nm) as well as a plenty of micropores. Pt nanocatalysts with an average particle size of ∼3.2 nm have been successfully encapsulated into the micropores and partial mesopores of the cage-like silica shells. The catalytic oxidation of toluene shows that the Pt/HZ@CmesoSiO2 composite presents an equivalent activity for toluene combustion at the light-off temperature of ∼195 °C (T50%) relative to the mixture catalyst (198 °C of T50%), but more excellent catalytic durability without activity loss (193 °C of T50%) after a 100 h test.

Sol–gel synthesis and characterization of conducting polythiophene/tin phosphate nano tetrapod composite cation-exchanger and its application as Hg(II) selective membrane electrode

Abstract: 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.

Preparation and properties of poly(urethane acrylate) (PUA) and tetrapod ZnO whisker (TZnO‐W) composite films

Abstract: Tetrapod zinc oxide whiskers (TZnO-Ws) were successfully synthesized via a thermal oxidation method and confirmed using Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. A series of poly(urethane acrylate) (PUA)/TZnO-W composite films with various TZnO-W contents were prepared via a UV curing method and their physical properties were investigated to understand their possible use as packaging materials. The morphological, thermal, mechanical, antibacterial and barrier properties of the PUA/TZnO-W composite films were interpreted as a function of TZnO-W content. The thermal stability, barrier properties and antibacterial properties of the composite films, which were strongly dependent upon their chemical and morphological structure, were enhanced as the TZnO-W content increased. The oxygen transmission rate and water vapor transmission rate decreased from 614 to 161 cm3 m−2 per day and 28.70 to 28.16 g m−2 per day, respectively. However, the mechanical strength of the films decreased due to the low interfacial interaction and poor dispersion with high TZnO-W loading. The enhanced barrier properties and good antibacterial properties of the PUA/TZnO-W composite films indicate that these materials are potentially suitable for many packaging applications. However, further studies are needed to increase the compatibility of polymer matrix and filler. © 2012 Society of Chemical Industry

Crystallographic Studies of Dehydration Phenomenon in Methyl 3-hydroxy-2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1 λ 6 -benzo[ e ][1,2]thiazine-3-carboxylate

Abstract: Methyl 3-hydroxy-2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1λ6-benzo[e][1,2]thiazine-3-carboxylate was synthesized in single step through in situ bromination of methyl 2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1λ6-benzo[e][1,2]thiazine-3-carboxylate using dibenzoyl peroxide & N-bromosuccinamide and was crystallized in acetone-ethyl acetate mixture (1:1) However, crystallization in methanol converted the title compound to methyl 3-methoxy-2-methyl-1,1,4-trioxo-1,2,3,4-tetrahydro-1λ6-benzo[e][1,2]thiazine-3-carboxylate, an unsymmetrical ether The titled compound C11H11NO6S (3) crystallized in nonoclinic space group P21/c whereas, the compound C12H13NO6S (4) crystallized in triclinic space group P-1 X-ray studies shows that the molecules of 1 are linked into a one-dimensional framework structure by C–H···O and O–H···O hydrogen bonds, while in 4, intermolecular C–H···O and C–H···π hydrogen bonds and a π···π interaction result in the formation of infinite chains running along the [010] and [001] directions

Investigation of Micellar and Phase Separation Phenomenon of the Amphiphilic Drug Amitriptyline Hydrochloride with Cationic Hydrotropes

Abstract: Micellization and phase separation of the amphiphilic drug amitriptyline hydrochloride (AMT) in the absence and presence of cationic hydrotropes (aniline hydrochloride, para-toluidine hydrochloride, and ortho-toluidine hydrochloride) have been investigated in the present study. The experimental critical micelle concentration (cmc) values are lower than cmc id values (cmc id is the cmc value at ideal mixing state), indicating attractive interactions between the two components (drug and hydrotrope) in mixed micelles. The bulk behaviors were investigated using the different theoretical models of Clint, Rubingh, Motomura, and Rodenas for comparison of the results of different binary combinations of the drug and hydrotropes. Synergistic interactions were confirmed in all binary combinations at all temperatures, which increase with increasing concentration of hydrotropes. Activity coefficients (f 1 and f 2) were found to be consistently less than unity indicating nonideality in the systems. At a fixed drug concentration (50 mmol·dm−3) and pH (6.7), the hydrotropes showed a continuous increase in the cloud point. Thermodynamic parameters were also evaluated and discussed in detail.

Nonlinear optical properties of DPO and DMPO: a theoretical and computational study

Abstract: The gas phase properties of the Z- and E-isomers of 4-(p-N,N-dimethyl-aminophenylmethylene)-2-phenyl-5-oxazolone (DPO) and 4-(2,5-dimethoxyphenylmethylene)-2-phenyl-5-oxazolone (DMPO) are studied using traditional hybrid and long-range-corrected density functional theories (LC-DFT). Excellent agreement is found between the optimized molecular geometries and the experimental crystal structures. Our calculations predict both DPO and DMPO to have significant nonlinear optical (NLO) susceptibilities. These results are compared with data for the prototypical NLO chromophore p-nitroaniline, and the effect of the range separation parameter on LC-DFT hyperpolarizabilities is also analyzed.

Interaction of the Amphiphilic Drug Amitriptyline Hydrochloride with Gemini and Conventional Surfactants: A Physicochemical Approach

Abstract: Pyrene fluorescence measurements were carried out on various binary mixtures of the antidepressant amphiphilic drug amitriptyline hydrochloride (AMT) with conventional (TTAB and CTAB) and gemini surfactants (14-4-14 and 16-4-16). In all cases mixed micellar aggregates were formed and the mixed critical micelle concentration (cmc) of various mixtures was computed from the I 1/I 3 versus total surfactant concentration plots. In the region where mixed micelles are formed, the interaction of the amphiphlic drug and four surfactants showed synergistic behavior. The results were analyzed using an interaction parameter, β, which characterize the interaction in the mixed micelle and is introduced by a regular solution theory. The β values are negative in all binary mixtures, and their magnitudes increase with increasing hydrophobicity of the amphiphile. The micellar mole fraction of AMT in the mixed micelle (x 1) and in the ideal sate (x ideal) were evaluated and their values (x 1 > x ideal) suggest that the contribution of the AMT component is greater in binary mixtures as compared to that in the ideal state. Activity coefficients (f 1 and f 2) and excess Gibbs energy (G ex) were also calculated. The values of micelle aggregation numbers (N agg) and various other parameters like the Stern–Volmer constant (K sv), micropolarity and dielectric constant of mixed systems have also been evaluated from the ratios of respective peak intensities (I 1/I 3 or I 0/I 1).

Fuel cell based on novel hyper-branched polybenzimidazole membrane

Abstract: A novel hyper-branched polybenzimidazole (HB-PBI) has been synthesized and efficiently utilized as a conducting polymer for the fabrication of an efficient high temperature fuel cell. The developed fuel cell showed outstanding proton conductivity (0.168 Scm(-1) at 150 A degrees C) along with excellent single cell performance, displaying a maximum power density of 0.346 Wcm(-2). The HB-PBI has been synthesized by polymerization of bibenzimidazole diterephthalic acid (BBIDTA) and 3,3'-diaminobenzene in the presence of poly phosphoric acid while the BBIDTA was synthesized by treating trimellitic anhydride with 3,3'-diaminobenzene. Both HB-PBI and BBIDTA were structurally characterized by nuclear magnetic resonance (H-1 and C-13 NMR). HB-PBI showed high thermal stability and mechanical properties, findings that were corroborated by thermogravimetric analysis and use of a universal testing machine. Additionally, proton conduction and the thermal and mechanical properties of HB-PBI were compared with polybenzene imidazole (m-PBI), and found that HB-PBI has higher proton conducting, thermal and mechanical properties.

Aluminium phthalocyanine chloride thin films for temperature sensing

Abstract: This study presents the fabrication and temperature sensing properties of sensors based on aluminium phthalocyanine chloride (AlPcCl) thin films. To fabricate the sensors, 50-nm-thick electrodes with 50-mu m gaps between them are deposited on glass substrates. AlPcCl thin films with thickness of 50-100 nm are deposited in the gap between electrodes by thermal evaporation. The resistance of the sensors decreases with increasing thickness and the annealing at 100 degrees C results in an increase in the initial resistance of sensors up to 24%. The sensing mechanism is based on the change in resistance with temperature. For temperature varying from 25 degrees C to 80 degrees C, the change in resistance is up to 60%. Simulation is carried out and results obtained coincide with experimental data with an error of +/-1%.