Green synthesis and applications of Au–Ag bimetallic nanoparticles

• Alloy as well as core–shell nanostructures are synthesized.
• Study of catalytic degradation of 2-, 3-, 4-nitrophenols and methyl orange.
• Alloy nanoparticles are found to form efficient nanofluid.
• The radical scavenging activity is a promise in biomedical field.

This paper reports for the first time the synthesis of bimetallic nanoparticles at room temperature using the fruit juice of pomegranate. Simultaneous reduction of gold and silver ions in different molar ratios leads to the formation of alloy as well as core–shell nanostructures. The nanoparticles have been characterized using UV–vis spectroscopy, transmission electron microscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction. The synthesized alloy particles are used as catalysts in the reduction of 2-, 3-, 4-nitrophenols to the corresponding amines and in the degradation of methyl orange. The reduction kinetics for all the reactions follows pseudo-first order. The rate constants follow the order k4-nitrophenol < k2-nitrophenol < k3-nitrophenol. Thermal conductivity is measured as a function of volume fraction and it is observed that the incorporation of the alloy nanoparticles enhances the thermal conductivity of the base fluid (water) showing nanofluid application. The nitric oxide and hydroxyl radical scavenging activity shown by the nanoparticles promise the potential application in biomedical field.

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