One-step hydrothermal synthesis of a flexible nanopaper-based Fe3+ sensor using carbon quantum dot grafted cellulose nanofibrils

Photoluminescent flexible nanopaper-based Fe3+ sensors were fabricated by carbon quantum dot (CQD) grafted oxidized cellulose nanofibrils (OCNF). Transparent and tunable luminescent CQD–OCNF nanopapers were facilely synthesized from citric acid, ethanediamine and an OCNF suspension using a one-pot hydrothermal method without catalysts. The morphology and chemical structures of the CQD–OCNF nanopapers were investigated by TEM, SEM, XRD, FT-IR spectroscopy, XPS and CP/MAS 13C NMR spectroscopy. The carboxyl groups of OCNF were covalently bonded to the amino groups of the newly-formed CQDs. The resultant CQD–OCNF nanopapers presented high transparency in bright field imaging and strong blue emission under ultraviolet excitation. The CQD–OCNF nanopaper was used as a highly sensitive and selective fluorescent sensor for Fe3+ ions. This study provides a facile and effective method for fabricating luminescent CQD–OCNF nanopapers with high selectivity for the detection of Fe3+.