Facile Synthesis Strategy from Sludge-Derived Extracellular Polymeric Substances to Nitrogen-Doped Graphene...

Extracellular polymeric substances (EPS) are microbial aggregates derived from waste sewage sludge accumulated in sewage treatment plants, which provides natural, renewable, and abundant carbon, nitrogen, oxygen sources for the development of carbon materials to achieve the value-added utilization of waste sewage sludge resources. In this work, a nitrogen-doped graphene oxide (GO)-like material (N-GO) was simply produced using EPS as starting materials. A facile H₂O₂ oxidation-assisted method (room temperature) was developed to synthesize nitrogen-doped GO-like quantum dots (N-GOQDs) with strong tunable fluorescence from N-GO for the first time. This approach eliminates the conventional use of toxic chemicals, concentrated acids as well as expensive equipment, and strict condition requirements, which provides new insights into the synthesis of N-GO and N-GOQDs. In addition, this H₂O₂-assisted method was further demonstrated to prepare yellow fluorescent GO quantum dots (GOQDs) from GO successfully. The as-prepared N-GO shows excellent adsorption capacity for removing organic matters (malachite green, rhodamine B, and methylene blue) from water in 10 min. The water-soluble N-GOQDs were demonstrated to be a low toxicity and good biocompatibility fluorescence probe for bioimaging.