Vibronic fingerprints in the luminescence of graphene quantum dots at cryogenic temperature

Atomically precise graphene quantum dots synthesized by bottom-up chemistry are promising versatile single emitters with potential applications forquantum photonic technologies. Towards a better understanding and control of GQDs' optical properties, we report on single-molecule spectroscopy at cryogenictemperature. We investigate the effect of temperature on GQDs' spectral linewidth and vibronic replica which we interpret building on DFTcalculations. Finally, we highlight that the vibronic signatures are specific to the GQDs geometry and can be used as a fingerprint for identification purposes.