A pH-Dependent Colorimetric Probe Based on Sodium Dodecyl Sulfate Silver Nanoparticles for Cadmium(II) and Aluminum(III) Determination

A novel pH-dependent sensitive and convenient assay was proposed for the determination of Cd2+ and Al3+ in aqueous medium using the sodium dodecyl sulfate (SDS) modified AgNPs as signal probes. In different pH values, the probe showed a visually detectable color change based on the strong interaction of Cd2+ and Al3+ with SDS. The color of SDS-AgNPs solution would change from bright yellow to purple red in the presence of Cd2+ at pH 9.8, and to reddish brown in the presence of Al3+ at pH 5.5. Under the optimum experimental conditions, the ratio of A(580 nm)/A(390 nm) of SDS-AgNPs gradually increased with increasing of Cd2+, and a good linear relationship was achieved when Cd2+ concentration ranging from 4.2x10(-8) M to 3.0x10(-6) M. Linear decreasing of A(390 nm) related to Al3+ concentration was over the range of 3.6x10(-8) M to 2.0x10(-6) M. The limit of detection was as low as 11.2 nM Cd2+ and 7.2 nM Al3+, respectively. Importantly, it has been successfully applied to detect Cd2+ and Al3+ in real samples.