Determination of Ag[I] and NADH Using Single-Molecule Conductance Ratiometric Probes

The sensing platform based on single-molecule measurements provides a new perspective for constructing ultrasensitive systems. However, most of these sensing platforms are unavailable for the accurate determination of target analytes. Herein, we demonstrate a conductance ratiometric strategy combing with the single-molecule conductance techniques for ultrasensitive and precise determination. A single-molecule sensing platform was constructed with the 3,3',5,5'-tetramethylbenzidine (TMB) and oxidized TMB (oxTMB) as the conductance ratiometric probes, which was applied in the detection of Ag[I] and nicotinamide adenine dinucleotide (NADH). It was found that the charge transport properties of TMB and oxTMB were distinct with more than an order of magnitude change of the conductance, thus enabling conductance ratiometric analysis of the Ag[I] and NADH in the real samples. The proposed method is ultrasensitive and has an anti-interference ability in the complicated matrix. The limit of detection can be as low as attomolar concentrations (∼34 aM). We believe that the proposed conductance ratiometric approach is generally enough to have a promising potential for broad and complicated analysis.