A selective pink-to-purple colorimetric sensor for aluminium via the aggregation of gold nanoparticles

Herein, the synthesis and characterization of N-lauroyltryramine capped gold nanoparticles (NLTA-AuNPs) colorimetric sensor for selective and sensitive determination of Al3+ ions was reported. The color of NLTA-AuNPs changes visually from pink to purple from 6 mu M Al3+, which is below the permissible level of Al3+ for drinking water (7.4 mu M) described by world health orgainsation. The surface plasmon resonance (SPR) maximum of NLTA-AuNPs at 538 nm was selectively affected by the addtion of Al3+. Transmission electron microscopy revelaed that Al3+ ions induce the aggregation of NLTA-AuNPs. The mechanistic study suggests that Al3+ reduce the interparticle distance through chelation effect between NLTA and Al3+ ions. The absorbance ratio (A670/ A538) of NLTA-AuNPs follows a linear correlation with the Al3+ concentration range from 1 to 12 mu M and the spectroscopy detection limit was as low as 1.15 mu M. The interference study indicates that NLTA-AuNPs detects Al3+ ions even in the presence of environmentally dominant metal ions. The application of the proposed sensor was demonstrated through estimating Al3+ ions in ground water and sewage water with good recovery. The simplicity, rapid detection of Al3+ may allow the NLTA-AuNPs sensor beyond routine lab testing for on-site exploration.