Fluorescent carbon dots have attracted great attention due to their good luminescence and low toxicity. Here, blue fluorescent core-shell structured carbon polymer dots (CPDs) with high stability in a wide pH range, long storage time, and excellent fluorescence in various solvents and even in polymers were prepared by hydrothermal synthesis of dendritic tris(2-aminoethyl)amine (TAEA) and citric acid. The CPDs core structure provides strong fluorescent luminescence, a shell structure of the core possesses high amount of dendritic primary amino groups connected by ethylene groups to the core. This unique structure prevents aggregation of the cores and self-quenching effect of CPDs. As a result, the CPDs have high fluorescence in both aqueous and hydrophobic solutions and even as pure solid-state powder. In addition, the CPDs are also insensitive to pH of solutions, and the fluorescence intensity of the solution was stable in the pH range of 4-14. The 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 used together with a volumetric syringe, and fluorescent color changes of the sensors responding to concentrations of Cr6+ can be differentiated by naked eyes. The sensor system possesses features of instant detection, low cost, environment-friendliness, and high sensitivity to quantitatively measure Cr6+ in a concentration range of 1-50 ppb, which is much lower than federal permissible limit of Cr6+ in drinking water. Moreover, the used sensor could be refreshed and reused 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 using an app on a smartphone, which is simple, convenient and suitable for more accurate household operation, showing great application prospect for on-site instant detection of Cr6+ in drinking water.

Fabrication of core-shell carbon polymer dots with stable fluorescence in polymers and potential applications as a sensor of chromium(VI)

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.