Unraveling the β-Cyclodextrin-Driven Inclusion Complexation with Phenylalanine-Capped AuNPs for Colorimetric Detection of Cr(III) and Fe(III)

Here, we highlight the synthesis of microwave-assisted monodisperse phenylalanine-capped AuNPs (F-AuNPs) in a one-step facile, cost-effective, eco-friendly process. The interaction of synthesized NPs was studied in the presence of macrocyclic supramolecule β-cyclodextrin (β-CD). Here, phenylalanine functions as both a reducing and capping agent, whereas β-CD forms an inclusion complex with phenylalanine, resulting in a ternary system, i.e., βCDF-AuNPs. The reaction parameters such as power, time, temperature, and concentrations of phenylalanine and HAuCl 4 for the synthesis of F-AuNPs were optimized and studied using UV–visible spectroscopy. The synthesized βCDF-AuNPs were found to be highly stable for more than a month The estimated average size of βCDF-AuNPs were found to be around 28 nm. These βCDF-AuNPs were employed to develop a highly selective and sensitive colorimetric sensor for Fe(III) and Cr(III) ions. With the addition of Fe(III) and Cr(III), the βCDF-AuNPs show a significant redshift, which resulted from the coordination between βCDF-AuNPs and metal ions [Fe(III) and Cr(III)]. The developed colorimetric sensor is ultrafast and has a limit of detection of 105 nM for Cr(III) and 152 nM for Fe(III). Moreover, selectivity experiments revealed that the colorimetric sensor is specific to Fe(III) and Cr(III) ions, even with the interference of other metal ions at very high concentrations.