Green synthesis of blue-fluorescent carbon nanospheres from the pith of tapioca (Manihot esculenta) stem for Fe(III) detection

Blue-light emitting fluorescent carbon nanospheres (CNs) were synthesized from the biological precursor, the pith of tapioca (Manihot esculenta) stem, by simple and facile hydrothermal carbonization method. The extracted CNs were amorphous, having an average dimension of 23.6 nm and are surface-functionalized with hydroxyl, carbonyl, carboxyl, and ether groups. The hydrophilic functional groups provide the uniform dispersed nature and stability to the CNs in the aqueous medium. Moreover, these groups act as charge trapping centers and result in an enhanced blue fluorescence with a high quantum yield of 19%, which is relatively high compared to those reported for CNs derived from other biological precursors. The luminescence quenching of these functionalized CNs was highly selective to the Fe(III) ions. The static quenching mechanism involved in the system is employed for Fe(III) detection in the aqueous medium, and the limit of detection obtained is 26.5 µM.