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

•Sulfur quantum dots modified gold electrode were used to fabricate an efficient electrochemical detection of silver ions.•The proposed sensor showed a linear detection range of 0.1 nM to 3 μM with detection limit of 32 pM.•Due to the low-cost and simple preparation process, the proposed DNA-free sensor suitable for practicle detection. 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 μM with a detection limit of 71 pM.