Hybridization and Characterization of Carboxylate-Rich Graphene Quantum Dots (GQDs)/TiO2 Nanotubes for UV Detectors

Abstract

Hybrid ultraviolet (UV) detectors were fabricated based on two-dimensional TiO₂ nanotubes coated with carboxylate-rich graphene quantum dots (CGQDs). TiO₂ nanotubes (TNTs) were synthesized by simple electrochemical process. CGQDs were synthesized by the liquid-phase extraction technique. CGQDs were characterized by TEM to image lattice arrangement and UV-vis to ensure their predominant properties. The structure and morphology of TNTs coated with CGQDs were characterized by SEM for surface morphology. To fabricate hybrid UV detectors, CGQDs were coated on TNTs surfaces by repeating the numbers of coatings. The two electronic probes were employed to measure electronic properties under the radiation of 365 nm UV light. The photocurrent density peaks are increased when the numbers of coatings are increased. The external quantum efficiency and spectral responsivity (R_s) were calculated from the illuminated time-dependent photocurrent density peaks. The spectral responsivity value (R_s) of CGQDs/TNTs which were coated with 15 times showed the highest of 95.50 mA W^-1 corresponding to the external quantum efficiency (EQE) of 0.32.