Mohsan Nawaz

Chitosan/CNTs green nanocomposite membrane: Synthesis, swelling and polyaromatic hydrocarbons removal

Carbon nanotubes (CNTs) were irradiated in air at 100 kGy under gamma radiations. The Raman spectroscopy of γ-treated CNTs showed distinctive changes in the absorption bands. The CNTs were mixed with blend of chitosan (Cs)/poly (vinyl alcohol) (PVA) and crosslinked with silane. The chemical reactions between the components affected the position and intensities of the infrared bands. Scanning electron micrograph of Cs/CNTs nanocomposite membrane showed the homogeneous dispersion of CNTs in the polymer matrix. The addition of CNTs lowered its swelling in water. Naphthalene (NAPH) was selected as a model compound and its removal was studied using HPLC technique. This membrane showed fast uptake of NAPH and 87% was removed from water within 30 min. The NAPH loaded membrane showed strong chemical interactions and cannot be desorbed. The fast uptake of PAHs and the green nature of this membrane made them suitable candidates for clean-up purposes.

Synthesis and in vitro acetylcholinesterase and butyrylcholinesterase inhibitory potential of hydrazide based Schiff bases

To discover multifunctional agents for the treatment of Alzheimers disease, a series of hydrazide based Schiff bases were designed and synthesized based on multitarget-directed strategy. We have synthesized twenty-eight analogs of hydrazide based Schiff bases, characterized by various spectroscopic techniques and evaluated in vitro for acetylcholinesterase and butyrylcholinesterase inhibition. All compounds showed varied degree of acetylcholinesterase and butyrylcholinesterase inhibition when compared with standard Eserine. Among the series, compounds 10, 3 and 24 having IC50 values 4.12±0.01, 8.12±0.01 and 8.41±0.06μM respectively showed potent acetylcholinesterase inhibition when compared with Eserine (IC50=0.85±0.0001μM). Three compounds 13, 24 and 3 having IC50 values 6.51±0.01, 9.22±0.07 and 37.82±0.14μM respectively showed potent butyrylcholinesterase inhibition by comparing with eserine (IC50=0.04±0.0001μM). The remaining compounds also exhibited moderate to weak inhibitory potential. Structure activity relationship has been established. Through molecular docking studies the binding interaction was confirmed.

Synthesis, association and surface morphology of poly (ethylene oxide)-polystyrene block copolymer

Synthesis of block copolymers is of great interest due to their abilities to self-assemble into a variety of structured, ordered, or partially ordered morphologies, and because they have number of applications. Three samples of poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) were synthesized by employed atom transfer radical polymerization (ATRP) technique and using monofunctional PEO-macroinitiator (mPEO-F) as starting material. The composition of the copolymer was obtained through NMR spectroscopy, whereas the molecular mass and degree of dispersity from light scattering and GPC/SEC. The CMC was obtained from the dependence of hydrodynamic radius (RH) over the concentration and found that it was decreased with contents of polystyrene and temperature. The RH dependence also indicated that shape of micelles change after certain concentration of copolymer. The reduced viscosity data plotted against concentration did not show a simple straight line as expected in case of polymers; rather, its slope was changed at a particular concentration, indicating sudden variation in the self-assembling behavior of the copolymers. The transmission electron microscopic (TEM) results of the material indicated the morphology pattern of two-dimensional arrays of hexagons with holes.

Synthesis, in vitro α-glucosidase inhibitory potential and molecular docking study of thiadiazole analogs

α-Glucosidase is a catabolic enzyme that regulates the bodys plasma glucose levels by providing energy sources to maintain healthy functioning. 2-Amino-thiadiazole (1-13) and 2-amino-thiadiazole based Schiff bases (14-22) were synthesized, characterized by 1H NMR and HREI-MS and screened for α-glucosidase inhibitory activity. All twenty-two (22) analogs exhibit varied degree of α-glucosidase inhibitory potential with IC50 values ranging between 2.30 ± 0.1 to 38.30 ± 0.7 μM, when compare with standard drug acarbose having IC50 value of 39.60 ± 0.70 μM. Among the series eight derivatives 1, 2, 6, 7, 14, 17, 19 and 20 showed outstanding α-glucosidase inhibitory potential with IC50 values of 3.30 ± 0.1, 5.80 ± 0.2, 2.30 ± 0.1, 2.70 ± 0.1, 2.30 ± 0.1, 5.50 ± 0.1, 4.70 ± 0.2, and 5.50 ± 0.2 μM respectively, which is many fold better than the standard drug acarbose. The remaining analogs showed good to excellent α-glucosidase inhibition. Structure activity relationship has been established for all compounds. The binding interactions of these compounds were confirmed through molecular docking.

Eco-friendly synthesis and catalytic application of chitosan/gold/carbon nanotube nanocomposite films

Novel eco-friendly chitosan nanocomposite membranes containing gold nanoparticles and carbon nanotubes (CNTs) have been synthesized. The catalytic activity of the nanocomposites was explored using a model reduction reaction of 4-nitrophenol to 4-aminophenol. Kinetic studies demonstrated that the presence of CNTs increased the rate of the reaction, mainly by reducing the induction time. TEM images confirmed the uniform distribution of gold and CNTs in the chitosan matrices. Scanning electron microscopy micrographs revealed that the inclusion of CNTs led to a more compact and less porous network structure which improved the mechanical properties of the films. Catalytically active membranes prepared from the nanocomposites could be reused at least ten times with no loss of mechanical integrity or catalytic effect, opening up the possibility of using this new, environmentally-friendly catalyst support in a continuous flow system.

Synthesis, molecular docking study and in vitro thymidine phosphorylase inhibitory potential of oxadiazole derivatives

We have synthesized oxadiazole derivatives (1-16), characterized by 1H NMR, 13C NMR and HREI-MS and screened for thymidine phosphorylase inhibitory potential. All derivatives display varied degree of thymidine phosphorylase inhibition in the range of 1.10 ± 0.05 to 49.60 ± 1.30 μM when compared with the standard inhibitor 7-Deazaxanthine having an IC50 value 38.68 ± 1.12 μM. Structure activity relationships (SAR) has been established for all compounds to explore the role of substitution and nature of functional group attached to the phenyl ring which applies imperious effect on thymidine phosphorylase activity. Molecular docking study was performed to understand the binding interaction of the most active derivatives with enzyme active site.

Preparation of gold nanoparticles in polystyrene–PEO block copolymers: the role of ultrasound

This work reports the preparation of ordered arrays of gold nanoparticles by sonochemically enhanced borohydride reduction of precursor lithium tetrachloroaurate (LiAuCl4) incorporated into the core of polymeric micelles formed from amphiphilic copolymers of polystyrene (PS) and poly(ethylene oxide) (PEO). The copolymers were prepared with varying styrene block lengths from a PEO macroinitiator by atom transfer radical polymerization (ATRP). UV/visible spectroscopy was used to confirm the formation of elemental gold. The effect of sonication time on the appearance of the gold nanoparticles was determined and showed that the absorbance first increased as the nanoparticles formed but decreased at longer times, presumably as a result of a degree of agglomeration. Transmission electron microscopy revealed the morphology of the nanocomposites which confirmed that micellar polystyrene-block-polyethylene oxide is an excellent vehicle for the formation of well-defined films containing nanoparticulate gold. However, we report for the first time that care must be taken to optimize the preparation time to obtain the desired particle sizes because this parameter is very sensitive to the duration over which sonication is carried out.

Ag-loaded thermo-sensitive composite microgels for enhanced catalytic reduction of methylene blue

In this work, we report the synthesis of composite system pNAC, composed of silver nanoparticles embedded in pure thermo-sensitive crosslinked polymer network of poly(N-isopropylacrylamide-co-acrylamide) (pNA), using as a catalyst for the reduction of methylene blue (MB) dye by sodium borohydride (NaBH4). The pNA was prepared by conventional free radical polymerization technique using sodium dodecyl sulfate as stabilizing agent, followed by in situ reduction of AgNO3 inside the polymer network by NaBH4 for the synthesis of composite systems pNACs. The synthesized pNA and pNACs were characterized by FTIR, dynamic light scattering, thermo-gravimetric analysis, scanning electron microscopy and UV–visible spectroscopy techniques. The materials were found sensitive toward temperature change of the medium. The entrapment ability of pNA toward different amounts of AgNO3 solution was studied, and effect of metal content on particle size of pNACs was analyzed. The pNACs were applied as a catalyst for the reduction of MB in which they exhibit high catalytic activity and reusability toward the reaction.

Adsorption of Cd2+ ions on plant mediated SnO2 nanoparticles

Plant mediated SnO2 nanoparticles were synthesized by using SnCl4.5H2O as a precursor material. The nanoparticles were then characterized for BET surface area measurements, energy dispersive x-rays (EDX), scanning electron microscopy (SEM), UV–vis diffuse reflectance (DRS) spectra and x-rays diffraction (XRD) analysis. The successful synthesis of SnO2 nanoparticles was confirmed by EDX analysis. The particle sizes were in the range 19–27 nm whereas the crystallite size computed from XRD measurement was found to be 19.9 nm. Batch adsorption technique was employed for the removal of Cd2+ ions from aqueous solution. The sorption studies of Cd2+ ions were performed at pHs 4 and 6. The equilibrium concentration of Cd2+ ions was determined by atomic absorption spectrometer (flame mode). The uptake of Cd2+ ions was affected by initial concentration, pH and temperature of the electrolytic solution. It was observed that the adsorption of Cd2+ ions enhanced with increase in the initial concentration of Cd2+ ions whereas a decrease in the percent adsorption was detected. From the thermodynamic parameters, the adsorption process was found spontaneous and endothermic in nature. The n values confirmed 2:1 exchange mechanism between surface protons and Cd2+ ions.

In situ formation of copper nanoparticles in a p(NIPAM-VAA-AAm) terpolymer microgel that retains the swelling behavior of microgels

Abstract Copper nanoparticles (CuNPs) are formed inside a microgel assembly by an in situ reduction method, confirmed by changes observed in the absorption spectra of CuNPs at different pH values. The presence of CuNPs has been also confirmed by X-ray diffraction (XRD) studies. The terpolymer microgel p(N-isopropylacrylamide-vinyl acetic acid-acrylamide) (p[NIPAM-VAA-AAm]), which is reported for the first time, was synthesized by free radical emulsion polymerization of a temperature-sensitive NIPAM monomer, pH sensitive VAA monomer and a hydrophilic AAm monomer. The effect of temperature below and above the pKa of VAA and the effect of pH at 20°C in the absence and presence of CuNPs on the hydrodynamic radius of microgel was studied. Size of microgel particles is a function of temperature due to the presence of NIPAM, and a function of pH due to the presence of VAA. The presence of CuNPs has little or no effect on the size of microgels by varying pH, which allows these gels to retain their properties with added benefits of CuNPs for possible drug delivery applications.