Benzene-1,3-disulfonate capped gold nanoparticles: DFT computations in support of particles-capping agent and nano-sensing interactions

Abstract

We have successfully synthesized water-dispersible gold (Au) nanoparticles (NPs) using benzene disulfonate anions (BDS2−) as a capping agent and applied them for the colorimetric recognition of Pb2+ and Cu2+ ions in aqueous solutions. The synthetic method for the BDS-AuNPs is very simple, one-pot and rapid. The particles are stable in a wide pH range of 5 to 10 over a month and are small in size (dTEM=8.9nm and dDLS=17nm). They selectively bind Pb2+ and Cu2+ ions over 14 other metal ions. This makes the particles an efficient optical dual-nanosensor. The limit of detection (LOD) values for Pb2+(0.469 μM) and Cu2+ (0.645 μM) ions are quite low. The association constant values for the Pb2+----BDS-AuNPs and Cu2+-----BDS-AuNPs complexes are found to be 1.612 × 106 M−1 (R2 adj. 0.9603) and 8.12 × 105 M−1 (R2 adj 0.9947), respectively, indicating strong interactions between the particles and the metal ions. A DFT computational study reveals that the binding affinity of BDS to the Aun cluster increases with the increase of Au atoms in the Aun cluster, supporting the experimental findings. The practical acceptance of the sensor was tested with real samples, where the sensor showed excellent recovery results. So, the BDS-AuNPs could be treated as an easy-to-develop dual-nanosensor for Pb2+ and Cu2+ metal ions.