Fig. 18. (A) Schematic illustration for the biosensor fabrication process using graphene/gold nanoclusters (GR/AuNCs) modified GCE with exonuclease III (Exo III) supported target DNA recycling for detecting HIV DNA. (A) The initial signal obtained from the capture probe. (B) DPV of AuNCs/GR/GCE biosensor after incubation with 100 nM, 10 nM, 1 nM, 100 pM, 10 pM, 1 pM, 100 fM, 10 fM, 1 fM, and 0.1 fM concentrations of target HIV gene and Exo III. (C) The linear relationship showing current change as a function of the logarithmic value of the target DNA concentration within a 0.1 fM to 100 nM range. [Reprinted with permission from ref. 399, Y. Wang, X. Bai, W. Wen, X. Zhang and S. Wang, Ultrasensitive Electrochemical Biosensor for HIV Gene Detection Based on Graphene Stabilized Gold Nanoclusters with Exonuclease Amplification, ACS Appl. Mater. Interfaces, 2015, 7, 18872–18879. Copyright© American Chemical Society.].