Non-aggregation colorimetric sensor for detecting vitamin C based on surface plasmon resonance of gold nanorods

In this sensing system, vitamin C (Vc) could reduce Hg2+ to Hg0, which selectively deposited on the tips of gold nanorods (AuNRs) to form gold amalgamation due to the shielding effect of the surfactant cetyltrimethylammonium bromide (CTAB) on the transverse site of AuNRs. As a result, the aspect ratio (length/width) of AuNRs was decreased and the morphology of AuNRs was changed. When the concentration of Vc was in the range of 0.11–85.0 μM, the longitudinal plasmon absorption wavelength (LPAW, λL) blue shifted (ΔλL); while in the range of 85.0–385 μM, the transversal plasmon absorption wavelength (TPAW, λT) red shifted (ΔλT) gradually, as well as the color of the solution changed obviously. Thus, a non-aggregation colorimetric sensor for rapid determination of Vc has been developed. The detection limit (LD) of this sensor is 3.5 × 10−9 g Vc mL−1 for λL and 5.1 × 10−6 g Vc mL−1 for λT, respectively, which is much lower than that of aggregation colorimetric sensor, showing its great sensitivity. What's more, the sensor has been applied to the detecting of Vc in real samples with the results agreeing well with aggregation colorimetric sensor using λL, showing its great practicality. At the same time, the structures of AuNRs were characterized by transmission electron microscope (TEM), and the sensing mechanism for the detection of Vc has been discussed.