Encapsulation of silver nanoparticles into graphite grafted with hyperbranched poly(amidoamine) dendrimer and their catalytic activity towards reduction of nitro aromatics

Hyperbranched polyamidoamine (PAMAM) dendrimer have been successfully grafted on the graphite surface and silver nanoparticles (AgNPs) were readily synthesized within the graphite grafted PAMAM dendrimer templates and applied as nanocatalysts in the reduction of nitro aromatics. Three generations of PAMAM dendrimers with varying chain branches have been utilized in order to serve this purpose. The grafting of PAMAM dendrimer on graphite surface has been monitored using TGA, Raman and FT-IR spectra and the AgNPs/GR-G1.0PAMAM, AgNPs/GR-G2.0PAMAM, AgNPs/GR-G3.0PAMAM nanocatalysts were characterized using XRD, UV–visible spectra, SEM, TEM and EDX spectral analysis. The prepared catalysts were found to exhibit enhanced catalytic activity towards the reduction of 4-nitrophenol and the reaction rate constant for our third generation catalyst was estimated to be 21.7 × 10−3 s−1, which is the highest reported heterogeneous system so far. The efficiency of the system has been further demonstrated through the reduction of halonitroarenes without dehalogenation in the halo-substituted nitro benzenes and reduction of nitro groups in the presence of imine functionalities under mild condition.

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► Successfully synthesized heterogeneous AgNPs/GR-G1.0, 2.0, 3.0PAMAM.
► Ag/GR-G3.0PAMAM shows highest rate 21.7 × 10−3 s−1 in the reduction of 4-nitro phenol.
► Selectivity determined by reduction of halonitroarenes without dehalogenations.