Ultrasensitive colorimetric detection of Cu2+ using gold nanorods.

We utilized Cu(2+) induced gold nanorod shortening in the presence of Na2S2O3 and NH3 for colorimetric sensing of copper ions. Compared with conventional methods, this method has good reproducibility, fast response time and very high sensitivity to Cu(2+). The sensor has a large dynamic range for Cu(2+) covering 5 nM to 500 mM with a detection limit of 1.6 nM, which is lower than previously reported for the colorimetric detection of copper ions.