Fabrication of a sensor chip containing Au and Ag electrodes and its application for sensitive Hg(II) determination using chronocoulometry Original Research Article

In this work, we explored a novel fabrication method to construct Au and Ag electrodes on chip, utilizing the different solubility of gold and silver in different etching solutions. KI-I2 etching solution and 50% HNO3 were chosen to dissolve the metal layers alternatively. Planar electrodes with gold and silver could be simultaneously and accurately patterned on chip using photolithographic technique. The as-prepared electrode could be directly served as integrated three-electrode system for electrochemical measurement. Based on it, a sensing strategy has been carried out using home-made electrochemical sensing (ECS) chip, which depended on the competition of double strand DNA and Hg(II)-mediated T–T base pairs (T-Hg(II)-T). Actually, a mercury specific oligonucleotide (MSO) was immobilized onto the thus-fabricated gold working electrode and employed as the sensing element. Chronocoulometry (CC) was chosen to monitor the differences of surface charge volume and quantify the concentrations of Hg(II) ions with a low detection limit down to 1 nM. Therefore, a facile method to fabricate Au and Ag electrodes has been demonstrated to simplify the production of ECS chip. The ECS chip was finally used for constructing an effective sensing platform for sensitive Hg(II) determination, which held promising potential for designing ECS chip in lab-on-a-chip device or point-of-care diagnosis.