A novel triangular silver nanoprisms-based surface plasmon resonance assay for free chlorine

In this study, a novel assay for the detection of free chlorine is proposed for the first time. It is based on a redox reaction that occurs between triangular silver nanoprisms and free chlorine, which results in a morphological transformation and a change of the localized surface plasmon resonance (SPR) of the triangular silver nanoprisms. In the assay, the presence of free chlorine would etch triangular silver nanoprisms from triangle to round, leading to a significant blue-shift SPR absorption band of triangular silver nanoprisms. The wavelength shift was used for facile and reliable free chlorine quantification in the range of 0.1-20 μM. The obtained detection limit was as low as 0.07 μM, which was about one and half orders of magnitude lower than that of the most widely used N-N-diethyl-p-phenylenediamine (DPD) colorimetric methods. Moreover, this assay was employed to determine the free residual chlorine in local tap water samples. The obtained results were in accordance with those obtained by the DPD colorimetric method.