Chemical sensing based on catalytic nanomotors: motion-based detection of trace silver

Abstract

A motion-based chemical sensing involving fuel-driven nanomotors is demonstrated. The new protocol relies on the use of an optical microscope for tracking changes in the speed of nanowire motors in the presence of the target analyte. Selective and sensitive measurements of trace silver ions are illustrated based on the dramatic and specific acceleration of bimetal nanowire motors in the presence of silver. Such nanomotor-based measurements would lead to a wide range of novel and powerful chemical and biological sensing protocols.

Figure 1

Motion of Au-Pt catalytic nanomotors in a 5% H₂O₂ solution containing 11 common cations. (A) Image displaying 3-sec track lines for the movement of 5 randomly selected nanomotors in 11 different 100 µM metal-nitrate salt solutions (of K⁺, Pd²⁺, Ni²⁺, Mn²⁺, In³⁺, Ag⁺, Cd²⁺, Ca²⁺, Cu²⁺, Pb²⁺ and Bi³⁺). (B) Corresponding bar graph comparing the average nanomotors speed (conditions, as in A). Error bars for n=20.

Figure 2

Track lines of nanomotors illustrating the distances traveled by five Au-Pt nanowires in the presence of different Ag(I) concentrations: 0 (A), 1 (B), 10 (C) and 100 (D) µM, along with 5 wt% H₂O₂ fuel solution. (E) A calibration curve for Ag(I) over the micromolar range (0.5–100 µM). Other conditions, as in Figure 1.