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 NSspAg 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 mu M 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 mu M. 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.