Used gold nano-particles as an on/off switch for response of a potentiometric sensor to Al(III) or Cu(II) metal ions

The potentiometric response of a carbon paste electrode modified with silica sol–gel and mercaptosuccinic acid (MSA) in the presence and absence of gold nano-particles was studied. The results showed that the electrode with gold nano-particles was responded to Al3+ ions as a hard metal ion. On the other hand, the electrode without gold nano-particles was responded to copper ions as a soft metal ion. The electrodes without and with gold nano-particles exhibits a Nernstian slope of 29.1 and 19.2 mV decade−1 for copper and aluminum ions over a wide concentration range of 4.3 × 10−7–1.0 × 10−2 and 4.5 × 10−7–1.6 × 10−3 mol L−1, respectively. The detection limits of electrodes were 4.0 × 10−7 and 1.6 × 10−7 mol L−1 for copper and aluminum ions, respectively.