A facile synthesis and characterization of Ag, Au and Pt nanoparticles using a natural hydrocolloid gum kondagogu (Cochlospermum gossypium).

An environmentally benign method for the synthesis of noble metal nanoparticles has been reported using aqueous solution of gum kondagogu (Cochlospermum gossypium). Both the synthesis, as well as stabilization of colloidal Ag, Au and Pt nanoparticles has been accomplished in an aqueous medium containing gum kondagogu. The colloidal suspensions so obtained were found to be highly stable for prolonged period, without undergoing any oxidation. SEM-EDXA, UV-vis spectroscopy, XRD, FTIR and TEM techniques were used to characterize the Ag, Au and Pt nanoparticles. FTIR analysis indicates that -OH groups present in the gum matrix were responsible for the reduction of metal cations into nanoparticles. UV-vis studies showed a distinct surface plasmon resonance at 412 and 525 nm due to the formation of Au and Ag nanoparticles, respectively, within the gum network. XRD studies indicated that the nanoparticles were crystalline in nature with face centered cubic geometry. The noble metal nanoparticles prepared in the present study appears to be homogeneous with the particle size ranging between 2 and 10 nm, as evidenced by TEM analysis. The Ag and Au nanoparticles formed were in the average size range of 5.5±2.5 nm and 7.8±2.3 nm; while Pt nanoparticles were in the size range of 2.4±0.7 nm, which were considerably smaller than Ag and Au nanoparticles. The present approach exemplifies a totally green synthesis using the plant derived natural product (gum kondagogu) for the production of noble metal nanoparticles and the process can also be extended to the synthesis of other metal oxide nanoparticles.

Direct one-pot reductive amination of aldehydes with nitroarenes in a domino fashion: catalysis by gum-acacia-stabilized palladium nanoparticles.

This note describes the direct reductive amination of carbonyl compounds with nitroarenes using gum acacia-palladium nanoparticles, employing molecular hydrogen as the reductant. This methodology is found to be applicable to both aliphatic and aromatic aldehydes and a wide range of nitroarenes. The operational simplicity and the mild reaction conditions add to the value of this method as a practical alternative to the reductive amination of carbonyl compounds.