Colorimetric detection of pollutant aromatic amines isomers with p-sulfonatocalix[6]arene-modified gold nanoparticles

This paper reports the synthesis of p-sulfonatocalix[6]arene-modified gold nanoparticles (pSC6-Au NPs) in aqueous media, which were characterized by IR spectroscopy, ultraviolet–visible spectroscopy (UV–vis), transmission electron microscopy (TEM), etc. The pSC6-Au NPs were employed as colorimetric probes to detect diaminobenzenes (DABs) isomer. In solution the pSC6-Au NPs are red in color due to the intense surface plasmon absorption band centered at 520 nm. DABs bridge the nanoparticles via electrostatic interaction and host–guest interaction, which induces aggregation of the nanoparticles. Upon aggregation, the surface plasmon absorption band broadens and red-shifts so that the nanoparticle solution appears a deep purple color. However, the sensitivity of pSC6-Au NPs towards other amines, including o-diaminobenzene, o-nitroaniline, m-nitroaniline, p-nitroaniline, o-chloroaniline, p-chloroaniline, o-toluidine, m-toluidine, p-toluidine and aniline, are negligible. The possible underlying mechanism is discussed.