A signal-on electrochemical biosensor for sensitive detection of silver ion based on alkanethiol–carbon nanotube-oligonucleotide modified electrodes

• DOI: 10.1016/j.snb.2014.06.061
• Publication Date: 2014-06-22T05:45:17Z
• Authors: Ziping Zhang; Jing Yan
• Keywords: 01 natural sciences; 0104 chemical sciences

Abstract A simple, signal-on electrochemical biosensor for sensitive detection of Ag + was developed based on the three components of alkanethiol, single-walled carbon nanotube (SWNT) and silver ion-specific oligonucleotide (SSO) layer-by-layer modified electrode where square wave voltammetry (SWV) response of K 3 [Fe(CN) 6 ] at the modified electrode was used for signal transduction. A gold electrode was first assembled with 1-dodecanethiol (C 12 H 25 SH) monolayer to which SWNTs were attached. The SWNT surfaces were further noncovalently bound with SSO probes to obtain the sensor interface. The negatively charged SSO probe acts as a physical obstacle and electrostatic repulsion barrier to block the SWNT-mediated long-distance electron transfer of K 3 [Fe(CN) 6 ] across the –SC 12 H 25 monolayer. Upon Ag + binding, the SWNT surface-bound SSO probe forms an unimolecular duplex through C–Ag + –C interaction-mediated intramolecular hybridization and departs from the SWNT surface, resulting in decreased electron transfer resistance and increased SWV current of K 3 [Fe(CN) 6 ] at the modified electrode. This current enhancement effect provides a signal-on mechanism for sensitive transduction of Ag + recognition and the resulted current increase is linear with the logarithmic concentration of Ag + from 2.0 nM to 100 nM. The developed biosensor was highly selective and its practical applicability in tap water was also tested with a satisfactory result.