Sher Bahadar Khan

Exploration of CeO2 nanoparticles as a chemi-sensor and photo-catalyst for environmental applications

CeO₂ nanoparticles were synthesized hydrothermally and utilized as redox mediator for the fabrication of efficient ethanol chemi-sensor. The developed chemi-sensor showed an excellent performance for electrocatalytic oxidization of ethanol by exhibiting higher sensitivity (0.92 μA∙cm⁻²∙mM⁻¹) and lower limit of detection (0.124±0.010 mM) with the linear dynamic range of 0.17 mM-0.17 M. CeO₂ nanoparticles have been characterized by field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), Raman spectrum, Fourier transform infrared spectroscopy (FTIR), and UV-visible absorption spectrum which revealed that the synthesized CeO₂ is an aggregated form of optically active spherical nanoparticles with the range of 15-36 nm (average size of ~25±10 nm) and possessing well crystalline cubic phase. Additionally, CeO₂ performed well as a photo-catalyst by degrading amido black and acridine orange.

Low-temperature growth of ZnO nanoparticles: photocatalyst and acetone sensor.

Well-crystalline ZnO nanoparticles (NPs) were synthesized in large-quantity via simple hydrothermal process using the aqueous mixtures of zinc chloride and ammonium hydroxide. The detailed structural properties were examined using X-ray diffraction pattern (XRD) and field emission scanning electron microscope (FESEM) which revealed that the synthesized NPs are well-crystalline and possessing wurtzite hexagonal phase. The NPs are almost spherical shape with the average diameters of ∼ 50 ± 10 nm. The quality and composition of the synthesized NPs were obtained using Fourier transform infrared (FTIR) and electron dispersed spectroscopy (EDS) which confirmed that the obtained NPs are pure ZnO and made with almost 1:1 stoichiometry of zinc and oxygen, respectively. The optical properties of ZnO NPs were investigated by UV-vis absorption spectroscopy. Synthesized ZnO NPs were extensively applied as a photocatalyst for the degradation of acridine orange (AO) and as a chemi-sensor for the electrochemical sensing of acetone in liquid phase. Almost complete degradation of AO has taken place after 80 min of irradiation time. The fabricated acetone sensor based on ZnO NPs exhibits good sensitivity (∼ 0.14065 μA cm(-2) mM(-1)) with lower detection limit (0.068 ± 0.01 mM) in short response time (10s).

Role of ZnO-CeO2 Nanostructures as a Photo-catalyst and Chemi-sensor

ZnO-CeO 2 nanostructures were synthesized by simple and efficient low temperature method. The structure and morphology of the ZnO-CeO 2 nanostructures were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM), which revealed elongated shaped CeO 2 nanoparticles with diameters of 40–90 nm distributed on the surface of elongated ZnO nanostructures with diameters of 50–200 nm (edge-centre). Further the structure of the synthesized ZnO-CeO 2 nanostructure was supported by Raman spectra and Fourier transform infrared spectroscopy (FTIR). UV-vis absorption spectrum was used to confirm the optical properties of the CeO 2 doped ZnO nanostructures. Photo-catalytic activity of CeO 2 doped ZnO nanostructure was evaluated by degradation of acridine orange and methylene blue which degraded 84.55% and 48.65% in 170 min, respectively. ZnO-CeO 2 nanostructures also showed good sensitivity (0.8331 μA·cm −2 ·(mol/l) −1 ) in short response time (10 s) by applying to chemical sensing using ethanol as a target compound by I – V technique. These degradation and chemical sensing properties of ZnO-CeO 2 nanostructures are of great importance for the application of ZnO-CeO 2 system as a photo-catalyst and chemical sensor.

Special susceptive aqueous ammonia chemi-sensor: extended applications of novel UV-curable polyurethane-clay nanohybrid.

In this contribution, chemical sensor for the detection of aqueous ammonia has been fabricated using UV-curable polyurethane acrylate (PU) and nanohybrids (NH-1, NH-3 and NH-5). PU has been prepared by reacting polycaprolactone triol (PCLT) and isophorone diisocyanate (IPDI) while the nanohybrids, NH-1, NH-3, and NH-5 have been synthesized by solution blending method using PU with 1, 3, and 5 wt% loading levels of C-20B. PU and their nanohybrids showed higher sensitivity investigated by I-V technique using aqueous ammonia as a target chemical. All the nanohybrids showed higher sensitivity as compared to neat PU. The sensitivity increased with increase in clay content and the nanohybrid containing 5 wt% of clay showed the highest sensitivity (8.5254 μA cm(-2) mM(-1)) with the limit of detection (LOD) of 0.0175 ± 0.001 μM, being 7.8 times higher than pure PU. The calibration plot for all the sensors was linear over the large range of 0.05 μM to 0.05 M. The response time of the fabricated sensor was <10.0 s. Therefore, one can fabricate efficient aqueous ammonia sensor by utilization of nanohybrid as an efficient electron mediator.

Bond-Based 2D Quadratic Fingerprints in QSAR Studies. Virtual and In Vitro Tyrosinase Inhibitory Activity Elucidation

In this report, we show the results of quantitative structure–activity relationship (QSAR) studies of tyrosinase inhibitory activity, by using the bond‐based quadratic indices as molecular descriptors (MDs) and linear discriminant analysis (LDA), to generate discriminant functions to predict the anti‐tyrosinase activity. The best two models [Eqs (6) and (12)] out of the total 12 QSAR models developed here show accuracies of 93.51% and 91.21%, as well as high Matthews correlation coefficients (C) of 0.86 and 0.82, respectively, in the training set. The validation external series depicts values of 90.00% and 89.44% for these best two equations (6) and (12), respectively. Afterwards, a second external prediction data are used to perform a virtual screening of compounds reported in the literature as active (tyrosinase inhibitors). In a final step, a series of lignans is analysed using the in silico‐developed models, and in vitro corroboration of the activity is carried out. An issue of great importance to remark here is that all compounds present greater inhibition values than Kojic Acid (standard tyrosinase inhibitor: IC50u2003=u200316.67u2003μm). The current obtained results could be used as a framework to increase the speed, in the biosilico discovery of leads for the treatment of skin disorders.

2-(2-Methyl-5-nitro-1H-imidazol-1-yl)ethyl 2-nitro­benzoate

In the title compound, C13H12N4O6, the mean plane through the nitrobenzene forms a dihedral angle of 37.38u2005(15)° with the plane through the imidazole ring. The crystal packing is stabilized by weak intermolecular C—H⋯O and C—H⋯N interactions together with π–π stacking interactions between nitrobenzene rings [centroid–centroid distance = 3.788u2005(3)u2005Å] and between imidazole rings [centroid–centroid distance = 3.590u2005(2)u2005Å].