Au Nanospheres@Ag Nanorods for Wide Linear Range Colorimetric Determination of Hypochlorite

In this study, we prepared Au nanospheres (NSs)@Ag nanorods (NRs) for colorimetric monitoring of hypochlorite (ClO–). The sensing strategy is based on the redox reaction between Ag and ClO–, which gives rise to the decrease in aspect ratio and a more than 180 nm blue-shift of the longitudinal localized surface plasmon resonance (LSPR) peak of Au NSs@Ag NRs. Meanwhile, a visible color change from yellow to green, blue, purple, and red was observed, which could be utilized for the qualitative determination of ClO– by the naked eyes. Moreover, the longitudinal LSPR peak showed a linear correlation with the length of Au NSs@Ag NRs, which agreed with the simulation results conducted by the FDTD method. Additionally, a good linear relationship between the blue-shift of the longitudinal LSPR peak and the concentration of ClO– over the range of 0.5–30 μM indicated that the Au NSs@Ag NRs could be used for quantitative detection of ClO–. And the limit of detection was calculated to be 0.24 μM. Most notably, this ClO– sensor exhibited good selectivity and excellent sensitivity. Finally, the proposed method was employed to detect ClO– in tap water and obtained satisfying results. Therefore, the proposed colorimetric assay provided a promising platform for determination of ClO– in real water samples.