Najrul Hussain

A green approach for the decoration of Pd nanoparticles on graphene nanosheets: An in situ process for the reduction of C–C double bonds and a reusable catalyst for the Suzuki cross-coupling reaction

A new strategy for in situ synthesis of palladium nanoparticles (Pd NPs) decorated on reduced graphene oxide (rGO) nanosheets with controlled size and shape is reported. This strategy was designed as three processes in one pot, namely, (a) reduction of graphene oxide, (b) formation of Pd NPs on the rGO nanosheets and (c) simultaneous reduction of olefin. In this synthesis process, a hydrogen atmosphere was used to develop the Pd NPs–rGO nanocatalyst, which is reusable and easily separable. The influence of the size and morphology of the Pd–rGO–H2 catalyst on the catalytic activity in the Suzuki cross-coupling reaction was investigated by comparing with other catalysts, Pd–rGO–As and Pd–rGO–Gl, and they were synthesized by different reducing agents, ascorbic acid and glucose, respectively. The catalysts were characterized by electron microscopy (HRTEM, SEM), FT-IR, XRD and XPS. The Pd–rGO–H2 catalyst was found to possess excellent catalytic activity and recyclability in the Suzuki cross-coupling reaction under mild reaction conditions.

Nickel nanoparticles supported on reduced graphene oxide sheets: a phosphine free, magnetically recoverable and cost effective catalyst for Sonogashira cross-coupling reactions

In this study, we have developed a cost effective and one-pot strategy for the synthesis of a heterogeneous catalyst consisting of a Ni nanoparticle–reduced graphene oxide composite for Sonogashira cross-coupling reactions. Several characterization tools were employed to characterize the Ni nanoparticle–reduced graphene oxide composite, which indicated that magnetic Ni nanoparticles of a size range of 1–4 nm were uniformly anchored on the reduced graphene oxide nanosheets without using any surfactant or stabilizing agent. Different types of aryl halides and phenylacetylenes were coupled under the optimized reaction conditions with excellent yields to give biphenylacetylenes. The ferromagnetic behaviour of the Ni nanoparticle–graphene composite resulted in it being easily separable from the reaction mixture and the composite was reusable, up to six times, without losing its catalytic activity. The fresh as well as the reused catalyst for the Sonogashira cross-coupling reaction was well characterized using analytical techniques which showed that the Ni nanoparticles were well dispersed on the reduced graphene oxide nanosheets without agglomeration, and the size and morphology of the catalyst remained unchanged after use in the catalytic reaction.

Bio-derived ZnO nanoflower: a highly efficient catalyst for the synthesis of chalcone derivatives

The green, eco-friendly synthesis of ZnO nanoparticles using the peel of Musa balbisiana and their use as nanocatalysts in the synthesis of chalcones derivatives is reported here. Bio-derived ZnO nanoparticles were characterized by XRD, XPS, FTIR, SEM, BET and TEM techniques. The single step condensation of substituted aryl carbonyls is an attractive feature to obtain substituted chalcones in 88–98% yields in less than 2 min under microwave irradiation in solvent free conditions. A short reaction time with excellent yields of chalcones is the main advantage of our study.

Magnetically recoverable graphene-based nanocomposite material as an efficient catalyst for the synthesis of propargylamines via A3 coupling reaction

The magnetically separable Au NPs–Fe3O4–rGO catalyst provides a robust and efficient route for the A3 coupling reaction of secondary amines, terminal alkynes and aldehyde with tolerance of diverse functional groups for the synthesis of propargylamine in high yields. Further, the catalyst could be reused several times without losing significant activity due to the stability of the NPs onto reduced graphene oxide sheets (rGO). The synthesized catalyst was characterized by different instrumental techniques before as well as after the catalytic reaction and it was observed that the catalyst retained its size and surface morphology after the reaction. The advantages of using the Au NPs–Fe3O4–rGO catalyst for the synthesis of pharmaceutically important compounds, propargylamines, over those in previous reports include its magnetically separable nature, additive-free characteristic, functional group tolerance and recyclability. The enhanced catalytic activity of the Au NPs–Fe3O4–rGO composite material results from the synergistic effect among Au NPs, Fe3O4 NPs and rGO sheets.