Cyclodextrin encapsulated monometallic and inverted core–shell bimetallic nanoparticles as efficient free radical scavengers
An effective method for the synthesis of monometallic and inverted core–shell bimetallic nanoparticles of silver and gold using four different cyclodextrins (α-CD, β-CD, γ-CD or HP β-CD) in aqueous alkaline medium at room temperature, stable for several months and having radical scavenging activity is reported. UV-visible absorbance spectra showed surface plasmon absorption maxima at 407 and 528 nm, for silver and gold respectively. The inverted core–shell bimetallic nanoparticles showed absorption maxima between the peaks corresponding to pure silver and pure gold nanoparticles & changed linearly with increasing concentration of shell metal precursor in the bimetallic nanoparticles. TEM showed the presence of uniform spherical particles in the range of 12–14 nm size and incase of bimetallic nanoparticles shows the inverted core–shell nanostructures in the range of 15–17 nm. All the encapsulated nanoparticles showed radical scavenging behavior as observed from the rapid quenching of the DPPH light absorption.