Highly selective and sensitive colorimetric probes for hypochlorite anion based on azo derivatives

Two oxime-based colorimetric probes for the hypochlorite anion (ClO−) have been rationally designed and synthesized on basis of the mechanism of intramolecular charge transfer (ICT). Upon addition of ClO−, the probes displayed around 20 nm redshift in the absorption maximum, accompanied with the color change from orange to pink, which were attributed to the reaction of the oxime groups with ClO− to form aldehyde groups. The probes were highly selective for ClO− detection without the interference of other ions and oxidants.