Generation, Inversion, and Amplification of Intrinsic Circularly Polarized Room Temperature Phosphorescence in Chiral Carbon Dots

Chiral carbon dots (C-dots) with circularly polarized luminescence emission have attracted tremendous attention, but achieving circularly polarized room temperature phosphorescence (CPRTP) C-dots is still challenging. The present contribution reports the success in constructing C-dots with intrinsic CPRTP property through an eco-friendly solvent-free pyrolysis method using urea and (R/S)-1,1 '-binaphthyl-2,2 '-diamine as precursors. The obtained C-dots exhibit intrinsic circularly polarized fluorescence (CPF) and CPRTP dual emission with dissymmetric factors of 10-3, accompanied by long lifetime up to 400 ms. Detailed experimental characterizations and theoretical calculations show that the presence of carbonyl groups and nitrogen atoms as well as charge transfer excitation within the C-dots is crucial for the RTP emission. More importantly, upon the incorporation of achiral helical polyacetylene, chirality transfer from the nanoscale C-dots to achiral helical chains effectively occurs during the film formation process, resulting in amplified chiroptical performance. Significantly, based on the synergistic interaction of "circularly polarized excitation" and "re-polarization" mechanisms, inversion and amplification of CPF/CPRTP emissions with large dissymmetric factors up to 2.0 x 10-2/2.2 x 10-2 are observed in the resulting C-dots/polyacetylene composite films. This work provides a platform for the construction of novel CPRTP materials with significant potentials. Chiral C-dots with intrinsic circularly polarized fluorescence (CPF) and circularly polarized room temperature phosphorescence (CPRTP) property with dissymmetric factors (glum) of 10-3 are obtained. Significantly, based on the "circularly polarized excitation" and "re-polarization" mechanisms, inversion, and amplification of CPF/CPRTP emissions with large glum up to 2.0 x 10-2/2.2 x 10-2 are observed in the C-dots/polyacetylene composite films. image