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 (pSC(6)-Au NPs) in aqueous media, which were characterized by IR spectroscopy, ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), etc. The pSC(6)-Au NPs were employed as colorimetric probes to detect diaminobenzenes (DABs) isomer. In solution the pSC(6)-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 pSC(6)-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. (C) 2009 Elsevier B.V. All rights reserved.