Poly (N-isopropylacrylamide-acrylic acid) [p(NIPAM-AAc)] microgel was successfully fabricated using the precipitation polymerization method. Silver (Ag) nanoparticles and graphene oxide (G) were used to fabricate the following hybrid microgels: Ag-p(NIPAM-AAc) (Ag-HMG), Ag-G-p(NIPAM-AAc) (Ag-G-HMG), and G-p(NIPAM-AAc) (G-HMG). Ag-HMG, Ag-G-HMG, and G-HMG were characterized using a Zetasizer and UV-Vis spectroscopy. The reduction of a series of different compounds with comparable and distinct chemical structures was catalyzed by synthesized Ag-HMG, Ag-G-HMG, and G-HMG hybrid microgels. The average size of Ag nanoparticles was found to be ~50 nm. Ag nanoparticles were synthesized within microgels attached to G sheets. Ag-p(NIPAM-AAc), Ag-G-p(NIPAM-AAc), and G-p(NIPAM-AAc) hybrid microgels were used for the catalytic reduction of nitroarenes and dyes. By comparing their apparent rate constant (kapp), reduction duration, and percentage reduction, the activity of HMG (hybrid microgel) as a catalyst towards different substrates was investigated. Graphene sheets play role in electron relay among Ag nanoparticles and microgels.
It is first time reported that three phases (α, β, and γ) of manganese dioxide (MnO2) are successfully stabilized in a single entity. For this purpose, Citrullus colocynthis (bitter apple) extract is used as natural surfactant in green synthesis. MnO2 nanoparticles were synthesized in the presence and absence of plant extract under same conditions. The morphology of both products are analyzed by SEM and STEM to understand the role of plant extract in controlling the morphology of particles. The crystallinity and composition are analyzed by XRD and confirmed that product is comprised of multiple phases α, β, and γ. The reduction of dyes and nitroarenes are studied by using MnO2 nanoparticles (green and chemical products) as a catalyst. Apparent rate constant, percentage reduction, time reduction and reduced concentration are determined to compare the activity of both catalysts. After comparative data analysis, the catalytic reduction of picric acid is found fastest among all the substrates. All the results are analyzed on the basis of structure, functional group and affinity towards catalyst.
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