A vacancy-engineered manganese nanosheet for the dual-channel sensing of catechol

Developing reliable and portable sensors for phenolic pollutants is crucial for environmental monitoring. Herein, catechol is used as a proof-of-concept to demonstrate a colorimetric sensing strategy based on vacancy-engineered manganese nanosheets (VE MNS). The VE MNS are synthesized via a simple and efficient method and exhibit dual enzyme-mimicking activities, including oxidase- and laccase-like functions, generating blue and red colorimetric responses with their respective chromogenic substrates. Notably, the oxidase-like activity of VE MNS exceeds its peroxidase-mimicking performance, which contrasts with most reported oxidase nanozymes. The laccase-like activity is approximately five times higher than that of natural laccase. By exploiting these dual catalytic properties, a dual-channel sensor array was constructed to identify six phenolic pollutants, enabling effective discrimination of catechol. In addition, a dual-channel colorimetric sensor was developed for visual catechol detection, exhibiting characteristic blue fading and red intensification with a detection limit of 0.68 μM. Furthermore, a portable hydrogel-based visual sensor was fabricated for naked-eye and smartphone-assisted detection. This work provides an efficient strategy for the reliable and on-site monitoring of phenolic pollutants and biosensing applications.