Electrochemical detection of silver ions by using sulfur quantum dots modified gold electrode

Sensitive and low-cost determination of Ag+ is important due to the potential risk of Ag+ increasingly applied in various fields. In this work, we report an extremely simple electrochemical sensor for the Ag+ determination based on the sulfur quantum dots (SQDs) modified Au electrode. The SQDs were synthesized by a top-down method through alkali etching of bulk sulfur powder, which were then directly used for Au electrode surface modification due to the high affinity between Au and S atoms. The strong binding between Ag and S makes the modified electrode highly sensitive for Ag+ sensing. The theoretical investigation was carried out by calculating the bond length and binding strength between Ag and S. Since the non-conductive nature of the SQDs, the amount of modifier is a crucial factor for the sensing performance. Under optimum condition, the proposed sensor showed a linear detection range of 0.1 nM to 3 mu M with a detection limit of 71 pM.