Fabrication of silver nanoparticles in poly (N-isopropylacrylamide-co-allylacetic acid) microgels for catalytic reduction of nitroarenes

Abstract

Poly(N-isopropylacrylamide-co-allyl acetic acid) [p(NIPAM-co-AAAc)] microgels were synthesized in aqueous medium by free radical emulsion polymerization using N-isopropylacrylamide as monomer, allylacetic acid as comonomer, and N,N-methylene-bis-acrylamide as cross-linker. Silver nanoparticles were fabricated inside the microgels by in situ reduction of silver ions. Microgels were analyzed by UV-visible spectroscopy, FTIR, XRD, TEM, and DLS. The formation of silver nanoparticles was confirmed by UV-visible spectroscopy. UV-visible spectra of the Ag-poly(Nisopropylacrylamide-co-allyl acetic acid) hybrid microgels showed a prominent absorption peak at about 411 nm. This peak was due to the surface plasmon resonance effect of silver nanoparticles. The hybrid microgels were used as catalyst for the reduction of nitroarenes. The reduction reactions were found to be first order with respect to nitroarenes with the values of apparent rate constant (k app) equal to 0.248, 0.215, and 0.089 min −1 for 4-nitrophenol, 4-nitroaniline, and nitrobenzene respectively at 27 • C in aqueous medium. Silver nanoparticles were found to be a more effective and efficient catalyst for reduction of 4-nitrophenol and 4-nitroaniline as compared to nitrobenzene.

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

“…Our group has already reported recycling of silver nanoparticle‐containing hybrid microgel catalyst for reduction reaction. A very small decrease in catalytic activity with increasing number of cycles was observed which may be due to loss of catalyst during separation by centrifugation …”

“…A very small decrease in catalytic activity with increasing number of cycles was observed which may be due to loss of catalyst during separation by centrifugation. [23] We tried to reduce 4-NP using NaBH 4 in aqueous medium in the absence of the Ag-P(NIPAM-co-AAm) hybrid microgels but no change in the value of absorbance at 400 nm is observed which indicates that the reaction does not occur without catalyst. But in the presence of the Ag-P (NIPAM-co-AAm) hybrid microgels, the colour of the reaction mixture changes from yellow to colourless within 25 min, indicating the conversion of 4-NP into 4-AP.…”

“…N ‐isopropylacrylamide (NIPAM) based microgels are generally used for in situ fabrication of silver nanoparticles . The use of poly( N ‐isopropylacrylamide‐ co ‐acrylic acid), poly( N ‐isopropylacrylamide‐ co ‐methacrylic acid) and poly( N ‐isopropylacrylamide‐ co ‐allylacetic acid) microgels for the synthesis of silver nanoparticles has been reported in literature.…”

Synthesis and characterization of inorganic–organic polymer microgels for catalytic reduction of 4‐nitroaniline in aqueous medium

“…Farooqi et al also monitored catalytic reduction of p-nitrophenol by using Cu-p(NiPA-coAAc) hybrid microgels as catalyst [26]. According to best of our knowledge, there is no report on use of Agp(NiPA-co-AAc) hybrid microgels as catalyst for reduction of 4-nitroaniline (4-NA) in aqueous medium.…”

“…Functional group peaks in FTIR spectra of poly(N-isopropylacrylamide-co-acrylic acid) microgels and silver-poly(N-isopropylacrylamide-co-acrylic acid) hybrid microgels. [26]. The swelling of Ag-p(NiPA-co-AAc) hybrid microgels with increase of pH of the medium facilitates the mass transport of reactants and products.…”