Electrospun 1,4-DHAQ-Doped Cellulose Nanofiber Films for Reusable Fluorescence Detection of Trace Cu2+ and Further for Cr3+

1,4-Dihydroxyanthraquinone (1,4-DHAQ a fluorophore) doped cellulose (CL) (denoted as 1,4-DHAQ@CL) microporous nanofiber film has been achieved via simple electrospinning and subsequent deacetylating, and used for highly sensitive and selective fluorescence detection of Cu2+ in aqueous solution. As the resultant byproduct of Cu2+-contaminated 1,4-DHAQ@CL nanofiber film showed recovered fluorescence by extra addition of Cu3+ nitrate solution, 1,4-DHAQ and Cu2+ codoped CL (denoted as (1,4-DHAQ)-Cu2+@CL)) microporous nanofiber film has been further fabricated for the detection of Cr3+ in aqueous solution. It was found that the fluorescence intensity of the 1,4-DHAQ@CL microporous nanofiber film linearly decreases with Cu2+ concentration ranging from 2.5 X 10(-9) to 3.75 X 10(-8) M, while that of the codoped (1,4-DHAQ)-Cu2+@CL nanofiber film linearly increases with Cr3+ concentration from 2.5 x 10(-9) to 2.5 X 10(-8) M, both with high selectivity over many other common heavy metal ions. The sensing mechanism for Cu2+ is ascribed to the formation of phenolate between 1,4-DIAQ and Cu2+, while that for Cr3+ is attributed to the reversing reaction from Cu2+-based phenolate to Cu2+ and Cr3+-based excited complex with recovered fluorescence. The sensitive and selective detection of Cu2+ and Cr3+ by using the 1,4-DHAQ@CL and the (1,4-DHAQ)-Cu2+@CL nanofiber films was further demonstrated in polluted lake waters, thus indicating their potential applications in environmental monitoring of Cu2+ and Cr3+ in polluted water. Additionally, both the 1,4-DHAQ@CL and (1,4-DHlAQ)-Cu2+@CL microporous nanofiber films are reusable for the detection of Cu2+ and Cr3+, respectively, after simple treatment. The design concept in this work might also open a door to the design of effective fluorescence probes for other heavy metal ions.