Single-step multiplex detection of toxic metal ions by Au nanowires-on-chip sensor using reporter elimination.

We have developed a Au nanowires (NWs)-on-chip surface-enhanced Raman scattering (SERS) multiplex sensor that can sensitively detect multiple toxic metal ions. Most importantly, the reporter elimination method simplified the detection procedure to a single step, which has been much desired for remote environmental monitoring. This sensor has several notable features. First, it shows high reproducibility based on well-defined single-crystalline Au NWs. Second, single-NW-sensors that can detect a specific metal ion are combined for multiplex sensing of metal ions. Third, when a sample solution is put onto the NWs-on-chip sensor, a decrease in the SERS signal of a specific NW-sensor identifies the target metal ion. Simple, rapid, sensitive and quantitative detection of metal ions becomes possible through the measurement of the SERS signals. We successfully detected ions of mercury (Hg(2+)), silver (Ag(+)), and lead (Pb(2+)) coexisting in the same solution by using this sensor.