Nonlinear optical response of graphene oxide quantum dots fabricated from electrospun polyacrylonitrile fibers

The nonlinear optical response of graphene oxide quantum dots (GOQDs) fabricated by the carbonization and exfoliation of electrospun polyacrylonitrile (PAN) fibers is reported. Electrospun and carbonized fibers were characterized by SEM and XPS. SEM micrograph confirmed the formation of PAN fibers of 153.44 ± 6.44 nm, while by XPS the binding energies associated with sp² and sp³ carbon hybridizations were found, after the carbonization process. On the other hand, the GOQDs obtained were characterized by photoluminescence (PL), UV–Vis, Raman spectroscopy, and High-Resolution Transmission Electron Microscopy (HRTEM). The GOQDs size of 10 nm was estimated by HRTEM. Raman spectroscopy showed the D and G bands associated with the sp² and sp³ hybridizations of the GOQDs, by PL two energy values of 2.67 and 2.97 eV were calculated. The UV–Vis spectrum showed two absorption bands confirming the presence of GOQDs. The nonlinear characterization was carried out using the P-scan technique, previously photodepositing GOQDs onto an optical fiber, using a coherent radiation source at a wavelength of 1550 nm. The results obtained showed a saturable absorption behavior with a value of β=−2.474×10⁻⁴m/W and a nonlinear susceptibility of χ⁽³⁾≈−7.749×10⁻⁴(esu). The results of this work showed that GOQDs obtained can be used for optical switching applications.