Non-aggregation based label free colorimetric sensor for the detection of Cr (VI) based on selective etching of gold nanorods

Gold nanorods (GNRs) exhibit strong longitudinal surface plasmon resonance absorption (LPA), which is highly dependent on its aspect ratio (length/width). The strong oxidization of Cr (VI) enables it to etch GNRs selectively at tips. The redox etching causes the aspect ratio of GNRs to decrease, resulting in the LPA blue shifts and the color of GNRs distinctly changes. Besides, the blue shift is linear to the concentration of Cr (VI) in the range of 0.1–20 μM. Thus, a non-aggregation based label free colorimetric sensor for the detection of Cr (VI) has been developed based on the selective etching of GNRs. The proposed colorimetric sensor is responsive, simple, sensitive (detection limit is 8.8 × 10 −8 M) and selective, and it has been successfully applied to the detection of Cr (VI) in drinking water and sea water. Moreover, the mechanism of colorimetric sensor for the detection of Cr (VI) was also discussed.