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RISS 인기검색어
- 검색키워드
- 저자 : Zahoor Hussain Farooqi (검색결과 3 건)
- 무료
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Zahoor Hussain Farooqi,Shanza Rauf Khan,Tajamal Hussain,Robina Begum,Kiran Ejaz,Shumaila Majeed,Muhammad Ajmal,Farah Kanwal,Mohammad Siddiq 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.9
We investigated the effect of crosslinking density of poly(N-isopropyl acrylamide-co-acrylic acid) micro-gels on catalytic activity of silver nanoparticles fabricated hybrid microgels. Multiresponsive poly(N-isopropyl acryla-mide-co-acrylic acid) microgels with 2, 4, 6 and 8 mole percentage of N,N-methylene-bis-acrylamide were synthesizedby emulsion polymerization. These microgels were characterized by dynamic light scattering and were used as mi-croreactors to synthesize silver nanoparticles. Hybrid system was characterized by ultraviolet-visible spectroscopy. Thecatalytic activity of hybrid microgels with different crosslinker content was compared by studying the reduction of p-nitrophenol as a model reaction. Kinetics of reaction was monitored by spectrophotometry. The value of the apparentrate constant decreases from 0.568 to 0.313 min−1, when content of crosslinker are increased from 2 to 8 mole percent-age respectively. This decreases in value of apparent rate constant is due to increase in diffusional barrier offered byhigh crosslinking of polymer network at high mole percentages of N,N-methylene-bis-acrylamide.
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Muhammad Shahid,Zahoor Hussain Farooqi,Robina Begum,Khalida Naseem,Muhammad Ajmal,Ahmad Irfan 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.5
Poly(N-isopropylacrylamide-acrylamide-methacrylic acid) [p(NIPa-AAm-Ma)] polymer microgels were prepared by free radical precipitation polymerization method. AgNPs were fabricated in the sieves of polymer network by chemical reduction using AgNO3 salt as a precursor of silver ions. Various techniques like dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared microscopy (FTIR), and UV-Visible spectroscopy were used for characterization of pure and composite microgels. The diameter of AgNPs fabricated in polymeric network was found to be in the range of 10-15 nm. Stimuli responsive behavior of hybrid microgels was same as that of pure microgels. Catalytic efficiency of the hybrid microgels was investigated by reducing 4-Nitroaniline (4-NA) into 4-Aminoaniline (4-AA) using NaBH4 as reducing agent under different conditions of temperature of the medium, concentration of reducing agent, 4-Nitroaniline and hybrid microgels to explore the catalysis process. Kinetic and thermodynamic aspects of reduction of 4-Nitroaniline in the presence of catalyst were also discussed on the basis of values of Arrhenius and Eyring parameters like pre-exponential factor, activation energy, enthalpy of activation and entropy of activation. Catalytic activity of the hybrid microgels was found to be thermally tunable in the temperature range of 25- 70 oC. The value of rate constant (kapp) for reduction of 4-NA was minimum at 55 oC, which can be attributed to volume phase transition of the hybrid microgels.
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Mohammad Siddiq,Muhammad Ajmal,Zahoor Hussain Farooqi 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.11
Multi-responsive poly(N-isoprpylacrlamide-methacrylic acid-acrylamide) [P(NIPAM-MAA-AAm)] copolymer microgel was prepared by free radical emulsion polymerization. Silver nanoparticles were fabricated inside the microgel network by in-situ reduction of silver nitrate. Swelling and deswelling behavior of the pure microgels was studied under various conditions of pH and temperature using dynamic light scattering. A red shift was observed in surface plasmon resonance wavelength of Ag nanoparticles with pH induced swelling of hybrid microgel. The catalytic activity of the hybrid system was investigated by monitoring the reduction of p-nitrophenol under different conditions of temperature and amount of catalysts. For this catalytic reaction a time delay of 8 to 10min was observed at room temperature,which was reduced to 2 min at high temperature due to swelling of microgels, which facilitated diffusion of reactants to catalyst surface and increased rate of reaction.
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