Catalytic reduction of 4‐nitrophenol using silver nanoparticles‐engineered poly(N‐isopropylacrylamide‐co‐acrylamide) hybrid microgels

• Published in: Applied organometallic chemistry 2017-02, Vol.31 (2), p.np-n/a
• Main Authors: Begum, Robina, Farooqi, Zahoor H., Ahmed, Ejaz, Naseem, Khalida, Ashraf, Sania, Sharif, Ahsan, Rehan, Rida
• Format: Article
• Language: English
• Subjects: Acrylamide; Catalysis; Catalysts; Catalytic activity; catalytic reduction; Chemical reduction; Chemical synthesis; Chemistry; Cobalt; Differential scanning calorimetry; Dosage; Fourier analysis; Fourier transforms; Heat measurement; Hybrid systems; Infrared analysis; Infrared spectroscopy; Isopropylacrylamide; Microgels; Nanoparticles; Networks; Photon correlation spectroscopy; Polymerization; Reducing agents; Reduction; Scanning electron microscopy; Silver; Spectrophotometry; Thermal analysis; Thermogravimetric analysis; Transmission electron microscopy; X-ray diffraction
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.3563

Nearly monodisperse poly(N‐isopropylacrylamide‐co‐acrylamide) [P(NIPAM‐co‐AAm)] microgels were synthesized using precipitation polymerization in aqueous medium. These microgels were used as microreactors to fabricate silver nanoparticles by chemical reduction of silver ions inside the polymer network. The pure and hybrid microgels were characterized using Fourier transform infrared and UV–visible spectroscopies, dynamic light scattering, X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry and transmission electron microscopy. Results revealed that spherical silver nanoparticles having diameter of 10–20 nm were successfully fabricated in the poly(N‐isopropylacrylamide‐co‐acrylamide) microgels with hydrodynamic diameter of 250 ± 50 nm. The uniformly loaded silver nanoparticles were found to be stable for long time due to donor–acceptor interaction between amide groups of polymer network and silver nanoparticles. Catalytic activity of the hybrid system was tested by choosing the catalytic reduction of 4‐nitrophenol as a model reaction under various conditions of catalyst dose and concentration of NaBH4 at room temperature in aqueous medium to explore the catalytic process. The progress of the reaction was monitored using UV–visible spectrophotometry. The pseudo first‐order kinetic model was employed to evaluate the apparent rate constant of the reaction. It was found that the apparent rate constant increased with increasing catalyst dose due to an increase of surface area as a result of an increase in the number of nanoparticles. Silver nanoparticles were successfully fabricated in poly(N‐isopropylacrylamide‐co‐acrylamide) hybrid microgels. The silver nanoparticles are stabilized inside the polymeric network due to metal–organic interaction and can be effectively used as catalyst for reduction of 4‐nitrophenol into 4‐aminophenol in the presence of a mild reducing agent. The catalytic activity can be controlled by varying the ratio of concentration of reducing agent to that of substrate and catalyst dose.