Highly sensitive, selective, and reusable nanofibrous membrane-based carbon polymer dots sensors for detection of Cr(VI) in water

• Core-shell structured fluorescent carbon polymer dots were prepared by hydrothermal method. • The carbon polymer dots were covalently incorporated onto poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers to fabricate novel nanofibrous membrane sensors. • The sensor exhibited excellent fluorescent property, selective and sensitive to trace amounts of Cr(VI) ions. And the sensor could be reused for many times with stable detection performance. • The results could be detected by naked eyes or smartphone, which is facile and safe to operate. Core-shell structured fluorescent carbon polymer dots (CPDs) were covalently incorporated onto poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers to fabricate novel nanofibrous membrane sensors to detect trace amount of heavy metal ions in drinking water systems. The membrane sensor was assembled in a syringe filter cell as a sensor unit together with a volumetric syringe, and fluorescent color changes of the sensors responding to concentrations of Cr(VI) can be identified by naked eyes. The sensor system possesses features of instant detection, low cost, environment-friendliness, and high sensitivity to quantitative measure Cr(VI) in a concentration range of 1–50 ppb, which is much lower than federal permissible limit of Cr(VI) in drinking water. Moreover, the used sensor could be refreshed and reused for many times without obvious fluorescence loss and nanofibrous membrane damage by simply exposing to a 20 μM Vitamin C (VC) solution. The fluorescent color changes of the sensors could be read by an App on a smartphone, which is facile, convenient and suitable for more accurate household operation, showing great prospect for instant on-site detection of Cr(VI) in drinking water.