On-Chip Stochastic Detection of Silver Nanoparticles without a Reference Electrode.

We report the electrochemical detection of 20 nm silver nanoparticles at a chip-based microelectrode array (MEA) without the need for a conventional reference electrode. This is possible due to the system's open-circuit potential allowing the oxidation of silver nanoparticles in the presence of phosphate-buffered saline (PBS). The hypothesis is confirmed by modulating the open-circuit potential via addition of ascorbic acid in solution, effectively inhibiting the detection of silver nanoparticle events. Employing the reference-free detection concept, we observe a linear relationship between the nanoparticle impact frequency at the microelectrodes and the nanoparticle concentration. This allows for viable quantification of silver nanoparticle concentrations in situ. The presented concept is ideal for the development of simple lab-on-a-chip or point-of-use systems enabling fast and low-cost screening of nanoparticles.