Gold nanoparticles (AuNPs) were prepared from HAuCl 4 using gum kondagogu, by adopting green synthesis, which is a simple, low cost and ecofriendly technique. The gum kondagogu (Cochlospermum gossypium) serves as both reducing agent and stabilizer. The formation of the AuNPs was identified through the change in the color of the solution from yellow to red. The synthesized AuNPs were characterized by various techniques. The green synthesized AuNPs were found to be stable in the pH range pH 2-12 and up to the concentration of 5 M NaCl. The stabilized AuNPs demonstrated the excellent catalytic activity in reducing p-nitrophenol to p-aminophenol in the presence of a reducing agent, NaBH 4 . The effects of catalyst dose and temperature were studied. The synthesized, new gum-based catalyst was very efficient, easy to prepare, stable, cost-effective and ecofriendly. The synthesized AuNPs showed good antibacterial activity.

A green method for the solvothermal synthesis of copper sulphide nanoparticles (CuS NPs) using xanthan gum as a capping agent was developed. The CuS NPs were characterised by scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, BrunauerÀEmmentÀTeller, zeta analysis, thermal gravimetricÀ differential thermal analysis, Fourier transform infrared and UVÀvisible absorption spectra. These characterisations together determine the composition, structural, thermal and optical properties. The UVÀvisible spectrum had a broad absorption in the visible range. The particle size of the products was observed by TEM in the range of 8À20 nm. The photocatalytic performance of the CuS NPs was evaluated for the degradation of organic dyes (methylene blue, rhodamine B, eosin Y and congo red) under irradiation of solar, visible and UV lights. The CuS NPs showed good photocatalytic activity. Kinetic analyses indicate that the photodegradation rates of dyes usually follow pseudofirst-order kinetics for degradation mechanisms.

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