A sonochemical synthesis of cyclodextrin functionalized Au-FeNPs for colorimetric detection of Cr6+ in different industrial waste water

[Display omitted] •A sonochemical synthesis of cyclodextrin functionalized Au-FeNPs.•The β-CD/Au-FeNPs act as an excellent selective and sensitive colorimetric sensing of Cr6+.•The lowest detection limit is found to be 2.6 nM. This paper describes a simple, selective and sensitive colorimetric sensing of Cr6+ ions using β-Cyclodextrin (β-CD) functionalized gold-iron nanoparticles (β-CD/Au-FeNPs). The sonochemically synthesized nanoparticles are winered in colour due to the SPR band of β-CD functionalized bimetalic nanoparticles Au-FeNPs. The capping and stabilizing of Au-FeNPs by redox β-CD is confirmed by FT-IR. The particles are spherical in shape and it posses the effective diameter of 18–20 nm. Under optimized conditions, in the presence of Cr6+ the wine red Au-FeNPs solution was turned to colourless, accompanying the broadening and red shifting of SPR band. The ratio between the absorbance wavelength at 573 nm to 535 nm (A573/A535) is linearly correlated with the Cr6+ concentrations ranging from 50 nM to 500 nM, with a detection limit of Cr6+ of 2.5 nM was achieved for the first time using β-CD/Au-FeNPs by spectrophotometry. The selectivity of the β-CD/Au-FeNPs towards other interfering metal ions. Finally the proposed method has been successfully employed for the determination of Cr6+ ion in various industrial waste water with good recoveries.