PH-controlled construction of 2D and 3D micro-nano hybrid carbon architectures with fluorescence/phosphorescence dual-mode emission for white-emitting diodes

Abstract

Developing nanocarbon-based white-emitting diodes (WLEDs) with high energy conversion efficiency is still extremely challenging due to the issue of Kasha's rule and serious self-aggregation caused luminescent quenching of nanocarbon in a solid-state. Herein, the synergistic strategy of framework and intercalator between nanosheets and carbon dots (CDs) was adopted. Three novel 2D nanosheets, 3D nanoflowers and 3D parasa consocia-like micro-nano carbon architectures decorated with dispersive CDs were successfully fabricated through one-step hydrothermal reaction at different pH medium. The pH-regulated mechanisms of morphology and structure, via degree modulation of condensation and carbonization, were further proposed. All samples exhibited bright white emission, derived from fluorescence/phosphorescence dual-mode emission. The hybrid emission made sufficient utilization of single and triplet excitons with the quantum yield of 16%–30%. The superior white light with CIE coordinates of (0.331,0.334) was recorded for neutral sample (p-CNDs-N), ascribed to the multiple energy level transitions from polydisperse luminescence centers. The luminous efficiency was remarkably improved in HCl (p-CNDs-H) and NaOH treated samples (p-CNDs-OH), resulting from inner carbonization, external cross-linked network and the passivation of surface defect sites. This is the first example for pH-controlled fabrication of multi-dimension hybrid nanocarbon structures and pH-controlled fluorescence/phosphorescence dual-mode emission for highly efficient carbon-based WLEDs.